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Journal articles on the topic 'Flash Flood Warnings'
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1
Martinaitis, Steven M., Jonathan J. Gourley, Zachary L. Flamig, Elizabeth M. Argyle, Robert A. Clark, Ami Arthur, Brandon R. Smith, Jessica M. Erlingis, Sarah Perfater, and Benjamin Albright. "The HMT Multi-Radar Multi-Sensor Hydro Experiment." Bulletin of the American Meteorological Society 98, no. 2 (February 1, 2017): 347–59. http://dx.doi.org/10.1175/bams-d-15-00283.1.
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Abstract There are numerous challenges with the forecasting and detection of flash floods, one of the deadliest weather phenomena in the United States. Statistical metrics of flash flood warnings over recent years depict a generally stagnant warning performance, while regional flash flood guidance utilized in warning operations was shown to have low skill scores. The Hydrometeorological Testbed—Hydrology (HMT-Hydro) experiment was created to allow operational forecasters to assess emerging products and techniques designed to improve the prediction and warning of flash flooding. Scientific goals of the HMT-Hydro experiment included the evaluation of gridded products from the Multi-Radar Multi-Sensor (MRMS) and Flooded Locations and Simulated Hydrographs (FLASH) product suites, including the experimental Coupled Routing and Excess Storage (CREST) model, the application of user-defined probabilistic forecasts in experimental flash flood watches and warnings, and the utility of the Hazard Services software interface with flash flood recommenders in real-time experimental warning operations. The HMT-Hydro experiment ran in collaboration with the Flash Flood and Intense Rainfall (FFaIR) experiment at the Weather Prediction Center to simulate the real-time workflow between a national center and a local forecast office, as well as to facilitate discussions on the challenges of short-term flash flood forecasting. Results from the HMT-Hydro experiment highlighted the utility of MRMS and FLASH products in identifying the spatial coverage and magnitude of flash flooding, while evaluating the perception and reliability of probabilistic forecasts in flash flood watches and warnings. NSSL scientists and NWS forecasters evaluate new tools and techniques through real-time test bed operations for the improvement of flash flood detection and warning operations.
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Huang, Wei, Zhixian Cao, Minghai Huang, Wengang Duan, Yufang Ni, and Wenjun Yang. "A New Flash Flood Warning Scheme Based on Hydrodynamic Modelling." Water 11, no. 6 (June 11, 2019): 1221. http://dx.doi.org/10.3390/w11061221.
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Flash flooding is one of the most severe natural hazards and commonly occurs in mountainous and hilly areas. Due to the rapid onset of flash floods, early warnings are critical for disaster mitigation and adaptation. In this paper, a flash flood warning scheme is proposed based on hydrodynamic modelling and critical rainfall. Hydrodynamic modelling considers different rainfall and initial soil moisture conditions. The critical rainfall is calculated from the critical hazard, which is based on the flood flow depth and velocity. After the critical rainfall is calculated for each cell in the catchment, a critical rainfall database is built for flash flood warning. Finally, a case study is presented to show the operating procedure of the new flash flood warning scheme.
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Créton-Cazanave, L. "Warning! The use of meteorological information during a flash-flood warning process." Advances in Science and Research 3, no. 1 (May 26, 2009): 99–103. http://dx.doi.org/10.5194/asr-3-99-2009.
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Abstract. Warning is a key issue to reduce flash floods impacts. But, despite many studies, local and national authorities still struggle to issue good flash floods warnings. We will argue that this failure results from a classical approach of warnings, based on a strict separation between the assessment world and the action world. We will go further than the previous criticisms (Pielke and Carbone, 2002) and show that forecasters, decision makers, emergency services and local population have quite similar practices during a flash-flood warning. Focusing on the use of meteorological information in the warning process, our case study shows that more research about the real practices of stakeholders would be another step towards integrated studies.
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Ma, Meihong, Huixiao Wang, Pengfei Jia, Guoqiang Tang, Dacheng Wang, Ziqiang Ma, and Haiming Yan. "Application of the GPM-IMERG Products in Flash Flood Warning: A Case Study in Yunnan, China." Remote Sensing 12, no. 12 (June 17, 2020): 1954. http://dx.doi.org/10.3390/rs12121954.
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NASA’s Integrated Multi-Satellite Retrievals for Global Precipitation Measurement (IMERG) is a major source of precipitation data, having a larger coverage, higher precision, and a higher spatiotemporal resolution than previous products, such as the Tropical Rainfall Measuring Mission (TRMM). However, there rarely has been an application of IMERG products in flash flood warnings. Taking Yunnan Province as the typical study area, this study first evaluated the accuracy of the near-real-time IMERG Early run product (IMERG-E) and the post-real-time IMERG Final run product (IMERG-F) with a 6-hourly temporal resolution. Then the performance of the two products was analyzed with the improved Rainfall Triggering Index (RTI) in the flash flood warning. Results show that (1) IMERG-F presents acceptable accuracy over the study area, with a relatively high hourly correlation coefficient of 0.46 and relative bias of 23.33% on the grid, which performs better than IMERG-E; and (2) when the RTI model is calibrated with the gauge data, the IMERG-F results matched well with the gauge data, indicating that it is viable to use MERG-F in flash flood warnings. However, as the flash flood occurrence increases, both gauge and IMERG-F data capture fewer flash flood events, and IMERG-F overestimates actual precipitation. Nevertheless, IMERG-F can capture more flood events than IMERG-E and can contribute to improving the accuracy of the flash flood warnings in Yunnan Province and other flood-prone areas.
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Song, Park, Lee, Park, and Song. "Flood Forecasting and Warning System Structures: Procedure and Application to a Small Urban Stream in South Korea." Water 11, no. 8 (July 29, 2019): 1571. http://dx.doi.org/10.3390/w11081571.
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The runoff from heavy rainfall reaches urban streams quickly, causing them to rise rapidly. It is therefore of great importance to provide sufficient lead time for evacuation planning and decision making. An efficient flood forecasting and warning method is crucial for ensuring adequate lead time. With this objective, this paper proposes an analysis method for a flood forecasting and warning system, and establishes the criteria for issuing urban-stream flash flood warnings based on the amount of rainfall to allow sufficient lead time. The proposed methodology is a nonstructural approach to flood prediction and risk reduction. It considers water level fluctuations during a rainfall event and estimates the upstream (alert point) and downstream (confluence) water levels for water level analysis based on the rainfall intensity and duration. We also investigate the rainfall/runoff and flow rate/water level relationships using the Hydrologic Engineering Center’s Hydrologic Modeling System (HEC-HMS) and the HEC’s River Analysis System (HEC-RAS) models, respectively, and estimate the rainfall threshold for issuing flash flood warnings depending on the backwater state based on actual watershed conditions. We present a methodology for issuing flash flood warnings at a critical point by considering the effects of fluctuations in various backwater conditions in real time, which will provide practical support for decision making by disaster protection workers. The results are compared with real-time water level observations of the Dorim Stream. Finally, we verify the validity of the flash flood warning criteria by comparing the predicted values with the observed values and performing validity analysis.
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Li, Zhehao, Hongbo Zhang, Vijay Singh, Ruihong Yu, and Shuqi Zhang. "A Simple Early Warning System for Flash Floods in an Ungauged Catchment and Application in the Loess Plateau, China." Water 11, no. 3 (February 27, 2019): 426. http://dx.doi.org/10.3390/w11030426.
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Under climate change, flash floods have become more frequent and severe, and are posing a danger to society, especially in the ungauged catchments. The objective of this paper, is to construct a simple and early warning system, serving for flash floods risk management in the ungauged catchments of the Loess Plateau in China, and offer a reference for flash flood warning in other areas in the world. Considering the absence of hydrological data in the ungauged catchments, the early warning system for flash floods is established by combining the regional or watershed isograms of hydrological parameters and local empirical formulas. Therein, rainfall and water stage/flow are used as warning indices for real-time risk estimation of flash flood. For early warning, the disaster water stage was first determined according to the protected objects (e.g., residents and buildings), namely the critical water stage. The critical flow (flow threshold), was calculated based on the water stage, and the established relationship between water stage and flow using the cross-sectional measured data. Then, according to the flow frequency curve of the design flood, the frequency of critical flow was ascertained. Assuming that the rainfall and the flood have the same frequency, the critical rainfall threshold was calculated through the design rainstorm with the same frequency of the design flood. Due to the critical rainfall threshold being sensitive with different soil conditions, the design flood and frequency curve of flood flow were calculated under different soil conditions, and thus the rainfall threshold was given under different soil condition for early warning of the flash flood disaster. Taking two sections in Zichang County (within the Loess Plateau) as an example, we set the rainfall and water stage/flow thresholds to trigger immediate or preparation signals for the migration of the population along the river. The application of this method to the 7.26 flood events in 2017 in China, shows that the early warning system is feasible. It is expected that this simple early warning system can provide early warnings of flash floods in ungauged catchments in the Loess Plateau and other similar areas.
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Pan, Tsung-Yi, Hsuan-Tien Lin, and Hao-Yu Liao. "A Data-Driven Probabilistic Rainfall-Inundation Model for Flash-Flood Warnings." Water 11, no. 12 (November 30, 2019): 2534. http://dx.doi.org/10.3390/w11122534.
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Owing to their short duration and high intensity, flash floods are among the most devastating natural disasters in metropolises. The existing warning tools—flood potential maps and two-dimensional numerical models—are disadvantaged by time-consuming computation and complex model calibration. This study develops a data-driven, probabilistic rainfall-inundation model for flash-flood warnings. Applying a modified support vector machine (SVM) to limited flood information, the model provides probabilistic outputs, which are superior to the Boolean functions of the traditional rainfall-flood threshold method. The probabilistic SVM-based model is based on a data preprocessing framework that identifies the expected durations of hazardous rainfalls via rainfall pattern analysis, ensuring satisfactory training data, and optimal rainfall thresholds for validating the input/output data. The proposed model was implemented in 12 flash-flooded districts of the Xindian River. It was found that (1) hydrological rainfall pattern analysis improves the hazardous event identification (used for configuring the input layer of the SVM); (2) brief hazardous events are more critical than longer-lasting events; and (3) the SVM model exports the probability of flash flooding 1 to 3 h in advance.
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N. Mbau, Stella, and Vinesh Thiruchelvam. "Flash Flood Warning Sub-Systems for Rural Africa." International Journal of Engineering & Technology 7, no. 3.32 (August 26, 2018): 47. http://dx.doi.org/10.14419/ijet.v7i3.32.18389.
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This paper aims to present the need for sub-systems in rural Africa for real-time warning delivery. It has been reported in previous studies, that Sub-Sahara Africa lacks weather radars. This means that there are no real-time early warnings presenting a gap in knowledge that this study aims to address. This is done through the following objective; to examine the relationship between variables in the study and therefore, establish whether sub-systems are a significant variable in flash flood warning systems for rural Africa. The variables to be examined are; the independent variable (existing warning system), the dependent variable (early warnings), the moderator variable (ancillary elements) and the mediator variable (sub-systems). This is investigated through a closed-ended questionnaire that is administered to a sample of meteorologists whose email addresses are available on the World Meteorological Organization’s expert database. The target sample is determined through the G*Power application. The data is analyzed on SPSS. Variables in the study are found to be correlated after conducting a Pearson’s correlation test. Using PROCESS allows for the testing of various models where moderation is confirmed. A moderated mediation model is also confirmed. The results confirm that sub-systems are significant enough to be developed for rural Africa.
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Martinaitis, Steven M., Benjamin Albright, Jonathan J. Gourley, Sarah Perfater, Tiffany Meyer, Zachary L. Flamig, Robert A. Clark, Humberto Vergara, and Mark Klein. "The 23 June 2016 West Virginia Flash Flood Event as Observed through Two Hydrometeorology Testbed Experiments." Weather and Forecasting 35, no. 5 (October 1, 2020): 2099–126. http://dx.doi.org/10.1175/waf-d-20-0016.1.
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AbstractThe flash flood event of 23 June 2016 devastated portions of West Virginia and west-central Virginia, resulting in 23 fatalities and 5 new record river crests. The flash flooding was part of a multiday event that was classified as a billion-dollar disaster. The 23 June 2016 event occurred during real-time operations by two Hydrometeorology Testbed (HMT) experiments. The Flash Flood and Intense Rainfall (FFaIR) experiment focused on the 6–24-h forecast through the utilization of experimental high-resolution deterministic and ensemble numerical weather prediction and hydrologic model guidance. The HMT Multi-Radar Multi-Sensor Hydro (HMT-Hydro) experiment concentrated on the 0–6-h time frame for the prediction and warning of flash floods primarily through the experimental Flooded Locations and Simulated Hydrographs product suite. This study describes the various model guidance, applications, and evaluations from both testbed experiments during the 23 June 2016 flash flood event. Various model outputs provided a significant precipitation signal that increased the confidence of FFaIR experiment participants to issue a high risk for flash flooding for the region between 1800 UTC 23 June and 0000 UTC 24 June. Experimental flash flood warnings issued during the HMT-Hydro experiment for this event improved the probability of detection and resulted in a 63.8% increase in lead time to 84.2 min. Isolated flash floods in Kentucky demonstrated the potential to reduce the warned area. Participants characterized how different model guidance and analysis products influenced the decision-making process and how the experimental products can help shape future national and local flash flood operations.
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Ir Vinesh Thiruchelvam, Prof Dr, and Mbau Stella Nyambura. "A Flash Flood Early Warning System for Rural Kenya: A Pilot Study." International Journal of Engineering & Technology 7, no. 4.38 (December 3, 2018): 810. http://dx.doi.org/10.14419/ijet.v7i4.38.27550.
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The cost of climate change has increased phenomenally in recent years. Therefore, understanding climate change and its impacts, that are likely to get worse and worse into the future, gives us the ability to predict scenarios and plan for them. Flash floods, which are a common result of climate change, follow increased precipitation which then increases risk and associated vulnerability due to the unpredictable rainfall patterns. Developing countries suffer grave consequences in the event that weather disasters strike because they have the least adaptive capacity. At the equator where the hot days are hotter and winds carrying rainfall move faster, Kenya’s Tana River County is noted for its vulnerability towards flash floods. Additionally, this county and others that are classified as rural areas in Kenya do not receive short term early warnings for floods. This county was therefore selected as the study area for its vulnerability. The aim of the study is therefore to propose a flash flood early warning system framework that delivers short term early warnings. Using questionnaires, information about the existing warning system will be collected and analyzed using SPSS. The results will be used to interpret the relationships between variables of the study, with a particular interest in the moderation effect in order to confirm that the existing system can be modified; that is, if the moderation effect is confirmed.
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Ir Vinesh Thiruchelvam, Prof Dr, and Mbau Stella Nyambura. "A Flash Flood Early Warning System for Rural Kenya: A Pilot Study." International Journal of Engineering & Technology 7, no. 4.38 (December 3, 2018): 1310. http://dx.doi.org/10.14419/ijet.v7i4.38.27812.
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The cost of climate change has increased phenomenally in recent years. Therefore, understanding climate change and its impacts, that are likely to get worse and worse into the future, gives us the ability to predict scenarios and plan for them. Flash floods, which are a common result of climate change, follow increased precipitation which then increases risk and associated vulnerability due to the unpredictable rainfall patterns. Developing countries suffer grave consequences in the event that weather disasters strike because they have the least adaptive capacity. At the equator where the hot days are hotter and winds carrying rainfall move faster, Kenya’s Tana River County is noted for its vulnerability towards flash floods. Additionally, this county and others that are classified as rural areas in Kenya do not receive short term early warnings for floods. This county was therefore selected as the study area for its vulnerability. The aim of the study is therefore to propose a flash flood early warning system framework that delivers short term early warnings. Using questionnaires, information about the existing warning system will be collected and analyzed using SPSS. The results will be used to interpret the relationships between variables of the study, with a particular interest in the moderation effect in order to confirm that the existing system can be modified; that is, if the moderation effect is confirmed.
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Ntelekos, Alexandros A., Konstantine P. Georgakakos, and Witold F. Krajewski. "On the Uncertainties of Flash Flood Guidance: Toward Probabilistic Forecasting of Flash Floods." Journal of Hydrometeorology 7, no. 5 (October 1, 2006): 896–915. http://dx.doi.org/10.1175/jhm529.1.
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Abstract Quantifying uncertainty associated with flash flood warning or forecast systems is required to enable informed decision making by those responsible for operation and management of natural hazard protection systems. The current system used by the U.S. National Weather Service (NWS) to issue flash-flood warnings and watches over the Unites States is a purely deterministic system. The authors propose a simple approach to augment the Flash Flood Guidance System (FFGS) with uncertainty propagation components. The authors briefly discuss the main components of the system, propose changes to improve it, and allow accounting for several sources of uncertainty. They illustrate their discussion with examples of uncertainty quantification procedures for several small basins of the Illinois River basin in Oklahoma. As the current FFGS is tightly coupled with two technologies, that is, threshold-runoff mapping and the Sacramento Soil Moisture Accounting Hydrologic Model, the authors discuss both as sources of uncertainty. To quantify and propagate those sources of uncertainty throughout the system, they develop a simple version of the Sacramento model and use Monte Carlo simulation to study several uncertainty scenarios. The results point out the significance of the stream characteristics such as top width and the hydraulic depth on the overall uncertainty of the Flash Flood Guidance System. They also show that the overall flash flood guidance uncertainty is higher under drier initial soil moisture conditions. The results presented herein, although limited, are a necessary first step toward the development of probabilistic operational flash flood guidance forecast-response systems.
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Bae, Deg-Hyo, Moon-Hwan Lee, and Sung-Keun Moon. "Development of a precipitation–area curve for warning criteria of short-duration flash flood." Natural Hazards and Earth System Sciences 18, no. 1 (January 12, 2018): 171–83. http://dx.doi.org/10.5194/nhess-18-171-2018.
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Abstract. This paper presents quantitative criteria for flash flood warning that can be used to rapidly assess flash flood occurrence based on only rainfall estimates. This study was conducted for 200 small mountainous sub-catchments of the Han River basin in South Korea because South Korea has recently suffered many flash flood events. The quantitative criteria are calculated based on flash flood guidance (FFG), which is defined as the depth of rainfall of a given duration required to cause frequent flooding (1–2-year return period) at the outlet of a small stream basin and is estimated using threshold runoff (TR) and antecedent soil moisture conditions in all sub-basins. The soil moisture conditions were estimated during the flooding season, i.e., July, August and September, over 7 years (2002–2009) using the Sejong University Rainfall Runoff (SURR) model. A ROC (receiver operating characteristic) analysis was used to obtain optimum rainfall values and a generalized precipitation–area (P–A) curve was developed for flash flood warning thresholds. The threshold function was derived as a P–A curve because the precipitation threshold with a short duration is more closely related to basin area than any other variables. For a brief description of the P–A curve, generalized thresholds for flash flood warnings can be suggested for rainfall rates of 42, 32 and 20 mm h−1 in sub-basins with areas of 22–40, 40–100 and > 100 km2, respectively. The proposed P–A curve was validated based on observed flash flood events in different sub-basins. Flash flood occurrences were captured for 9 out of 12 events. This result can be used instead of FFG to identify brief flash flood (less than 1 h), and it can provide warning information to decision-makers or citizens that is relatively simple, clear and immediate.
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Ibarreche, José, Raúl Aquino, R. M. Edwards, Víctor Rangel, Ismael Pérez, Miguel Martínez, Esli Castellanos, et al. "Flash Flood Early Warning System in Colima, Mexico." Sensors 20, no. 18 (September 14, 2020): 5231. http://dx.doi.org/10.3390/s20185231.
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This paper presents a system of sensors used in flash flood prediction that offers critical real-time information used to provide early warnings that can provide the minutes needed for persons to evacuate before imminent events. Flooding is one of the most serious natural disasters humans confront in terms of loss of life and results in long-term effects, which often have severely adverse social consequences. However, flash floods are potentially more dangerous to life because there is often little or no forewarning of the impending disaster. The Emergency Water Information Network (EWIN) offers a solution that integrates an early warning system, notifications, and real-time monitoring of flash flood risks. The platform has been implemented in Colima, Mexico covering the Colima and Villa de Alvarez metropolitan area. This platform consists of eight fixed riverside hydrological monitoring stations, eight meteorological stations, nomadic mobile monitoring stations called “drifters” used in the flow, and a sniffer with data muling capability. The results show that this platform effectively compiles and forwards information to decision-makers, government officials, and the general public, potentially providing valuable minutes for people to evacuate dangerous areas.
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Cools, J., P. Vanderkimpen, G. El Afandi, A. Abdelkhalek, S. Fockedey, M. El Sammany, G. Abdallah, M. El Bihery, W. Bauwens, and M. Huygens. "An early warning system for flash floods in hyper-arid Egypt." Natural Hazards and Earth System Sciences 12, no. 2 (February 27, 2012): 443–57. http://dx.doi.org/10.5194/nhess-12-443-2012.
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Abstract. An early warning system (EWS) for flash floods has been developed for part of the Sinai peninsula of Egypt, an hyper-arid area confronted with limited availability of field data, limited understanding of the response of the wadi to rainfall, and a lack of correspondence between rainfall data and observed flash flood events. This paper shows that an EWS is not a "mission impossible" when confronted with large technical and scientific uncertainties and limited data availability. Firstly, the EWS has been developed and tested based on the best available information, this being quantitative data (field measurements, simulations and remote sensing images) complemented with qualitative "expert opinion" and local stakeholders' knowledge. Secondly, a set of essential parameters has been identified to be estimated or measured under data-poor conditions. These are: (1) an inventory of past significant rainfall and flash flood events, (2) the spatial and temporal distribution of the rainfall events and (3) transmission and infiltration losses and (4) thresholds for issuing warnings. Over a period of 30 yr (1979–2010), only 20 significant rain events have been measured. Nine of these resulted in a flash flood. Five flash floods were caused by regional storms and four by local convective storms. The results for the 2010 flash flood show that 90% of the total rainfall volume was lost to infiltration and transmission losses. Finally, it is discussed that the effectiveness of an EWS is only partially determined by technological performance. A strong institutional capacity is equally important, especially skilled staff to operate and maintain the system and clear communication pathways and emergency procedures in case of an upcoming disaster.
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Luong, Thanh Thi, Judith Pöschmann, Rico Kronenberg, and Christian Bernhofer. "Rainfall Threshold for Flash Flood Warning Based on Model Output of Soil Moisture: Case Study Wernersbach, Germany." Water 13, no. 8 (April 12, 2021): 1061. http://dx.doi.org/10.3390/w13081061.
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Convective rainfall can cause dangerous flash floods within less than six hours. Thus, simple approaches are required for issuing quick warnings. The flash flood guidance (FFG) approach pre-calculates rainfall levels (thresholds) potentially causing critical water levels for a specific catchment. Afterwards, only rainfall and soil moisture information are required to issue warnings. This study applied the principle of FFG to the Wernersbach Catchment (Germany) with excellent data coverage using the BROOK90 water budget model. The rainfall thresholds were determined for durations of 1 to 24 h, by running BROOK90 in “inverse” mode, identifying rainfall values for each duration that led to exceedance of critical discharge (fixed value). After calibrating the model based on its runoff, we ran it in hourly mode with four precipitation types and various levels of initial soil moisture for the period 1996–2010. The rainfall threshold curves showed a very high probability of detection (POD) of 91% for the 40 extracted flash flood events in the study period, however, the false alarm rate (FAR) of 56% and the critical success index (CSI) of 42% should be improved in further studies. The proposed adjusted FFG approach has the potential to provide reliable support in flash flood forecasting.
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Clark, Colin. "Saving Lives: Timely Flash Flood Warnings in the UK." Journal of Geoscience and Environment Protection 05, no. 02 (2017): 60–74. http://dx.doi.org/10.4236/gep.2017.52005.
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Hofmann, Julian, and Holger Schüttrumpf. "Risk-Based Early Warning System for Pluvial Flash Floods: Approaches and Foundations." Geosciences 9, no. 3 (March 14, 2019): 127. http://dx.doi.org/10.3390/geosciences9030127.
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In times of increasing weather extremes and expanding vulnerable cities, a significant risk to civilian security is posed by heavy rainfall induced flash floods. In contrast to river floods, pluvial flash floods can occur anytime, anywhere and vary enormously due to both terrain and climate factors. Current early warning systems (EWS) are based largely on measuring rainfall intensity or monitoring water levels, whereby the real danger due to urban torrential floods is just as insufficiently considered as the vulnerability of the physical infrastructure. For this reason, this article presents a concept for a risk-based EWS as one integral component of a multi-functional pluvial flood information system (MPFIS). Taking both the pluvial flood hazard as well as the damage potential into account, the EWS identifies the urban areas particularly affected by a forecasted heavy rainfall event and issues object-precise warnings in real-time. Further, the MPFIS performs a georeferenced documentation of occurred events as well as a systematic risk analysis, which at the same time forms the foundation of the proposed EWS. Based on a case study in the German city of Aachen and the event of 29 May 2018, the operation principle of the integrated information system is illustrated.
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Créton-Cazanave, L., and C. Lutoff. "Stakeholders' issues for action during the warning process and the interpretation of forecasts' uncertainties." Natural Hazards and Earth System Sciences 13, no. 6 (June 11, 2013): 1469–79. http://dx.doi.org/10.5194/nhess-13-1469-2013.
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Abstract. This article considers the socio-geographical approach carried out as part of the MedUp program. It presents a study of the ways that the French "actors" manage forecast uncertainties during a flash flood warning process. In order to better understand the role of forecasts' uncertainties in decision making, we focused on the actions people took and how what they say explains their actions. The practices of actors involved in warnings for the Vidourle watershed (Gard, France), in particular, are analyzed using a practice-based approach. A set of categories of the "actors" was developed based on their descriptions of the problems they faced during the flash flood warning, independent of their socio-professional status and position in the warning chain. Five actor profiles result from this: Translators, Managers, Committed, Navigators and Vulnerable. For each profile, specific action contexts are defined, determining how each deals with uncertainty.
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Cumiskey, Lydia, Micha Werner, Karen Meijer, S. H. M. Fakhruddin, and Ahmadul Hassan. "Improving the social performance of flash flood early warnings using mobile services." International Journal of Disaster Resilience in the Built Environment 6, no. 1 (February 9, 2015): 57–72. http://dx.doi.org/10.1108/ijdrbe-08-2014-0062.
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Purpose – The purpose of this study is to provide recommendations for improving the social performance of warnings using mobile services in flash flood prone communities. A warning cannot be considered effective until it is received, understood and responded to by those at risk. This is defined as the social performance of warning communication techniques. Mobile services offer opportunities for improving this, particularly in Bangladesh, but have been underutilised. In this research, characteristics of the warning, mobile services and community are found to influence the social performance. Design/methodology/approach – A framework on the factors affecting the social performance was developed and applied using data collected through interviews at the national and regional level along with focus-group discussions (FGDs) and key informant interviews at the local level in the Sunamganj District, Bangladesh. Findings – The study demonstrated that mobile services are the preferred means of warning communication. Communities strongly preferred voice short messaging service (SMS) and interactive voice response (IVR) because of easier accessibility and understanding of the message. Text-based services [SMS and cell broadcasting service (CBS)] were still found to be acceptable. These should be simple, use symbols and refer to additional sources of information. Further recommendations include mixing push (e.g. SMS and CBS) and pull-based (e.g. IVR) mobile services, utilising local social networks, decentralising the dissemination process and raising awareness. Research limitations/implications – A limited sample of interviews and FGDs were used. Practical implications – Concrete recommendations are made for overcoming obstacles related to the effective use of mobiles services. Social implications – The suggestions made can contribute to improving the social performance of flood early warning communication. Originality/value – The conceptualisation of mobile services’ contribution to social performance of flood warning and field-level application.
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Ivanescu, Veronica, and Radu Drobot. "Deriving Rain Threshold for Early Warning Based on a Coupled Hydrological-Hydraulic Model." Mathematical Modelling in Civil Engineering 12, no. 4 (December 1, 2016): 10–21. http://dx.doi.org/10.1515/mmce-2016-0014.
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Abstract Flash floods are highly variable phenomena in both time and space. Therefore, tools with the potential to provide early warning are needed to analyse them. In Europe, flash floods often occur on small catchments; it has already been shown that the spatial variability of rainfall has a great impact on the catchment response. The aim of this paper is to use a coupled hydrological-hydraulic model (MIKE SHE/MIKE 11) to determine the rainfall thresholds and transformation coefficients from hourly rain to other durations, which will lead to flooding of the inhabited areas to the ungauged Ungureni catchment. The model was calibrated and validated using a reference discharge previously obtained by UTCB at the downstream gauge section of Teleorman River (Tatarastii de Sus) using MIKE 11 UHM module. Once the rainfall thresholds are determined, they can be used in flood forecasting and issuing warning with lead time for the inhabitants of the two villages located in Ungureni watershed. The method proposed in this paper can be used for other watersheds prone to flooding, so warnings can be issued with lead time.
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Herman, Gregory R., and Russ S. Schumacher. "Flash Flood Verification: Pondering Precipitation Proxies." Journal of Hydrometeorology 19, no. 11 (November 1, 2018): 1753–76. http://dx.doi.org/10.1175/jhm-d-18-0092.1.
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Abstract Quantitative precipitation estimate (QPE) exceedances of numerous different heavy precipitation thresholds—including spatially varying average recurrence interval (ARI) and flash flood guidance (FFG) thresholds—are compared among each other and against reported and warned flash floods to quantify existing deficiencies with QPEs and to identify best practices for using QPE for flash flood forecasting and analysis. QPEs from three different sources—NCEP Stage IV Precipitation Analysis (ST4), Climatology Calibrated Precipitation Analysis (CCPA), and Multi-Radar Multi-Sensor (MRMS) QPE—are evaluated across the United States from January 2015 to June 2017. In addition to evaluating different QPE sources, threshold types, and magnitudes, QPE accumulation interval lengths from hourly to daily are considered. Systematic errors with QPE sources are identified, including a radar distance dependence on extreme rainfall frequency in MRMS, spurious occurrences of locally extreme precipitation in the complex terrain of the West in ST4, and insufficient QPEs for many legitimate heavy precipitation events in CCPA. Overall, flash flood warnings and reports corresponded to each other far more than any QPE exceedances. Correspondence between all sources was at a maximum in the East and worst in the West, with ST4, CCPA, and MRMS QPE exceedances locally yielding maximal correspondence in the East, Plains, and West, respectively. Surprisingly, using a fixed 2.5 in. (24 h)−1 proxy outperformed shorter accumulation exceedances and the use of ARIs and FFGs. On regional scales, different ARI exceedances achieved superior performance to the selection of any fixed threshold; FFG exceedances were consistently too rare to achieve optimal correspondence with observed flash flooding.
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Gourley, Jonathan J., and Humberto Vergara. "Comments on “Flash Flood Verification: Pondering Precipitation Proxies”." Journal of Hydrometeorology 22, no. 3 (March 2021): 739–47. http://dx.doi.org/10.1175/jhm-d-20-0215.1.
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AbstractNew operational tools for monitoring flash flooding based on radar quantitative precipitation estimates (QPEs) have become available to U.S. National Weather Service forecasters. Herman and Schumacher examined QPE exceedance thresholds for several tools and compared them to each other, to flash flood reports (FFRs), and to flash flood warnings. The Next Generation Radar network has been updated with dual-polarization capabilities since the publication of Herman and Schumacher, which has changed the characteristics of the derived QPEs. Updated thresholds on Multi-Radar Multi-Sensor version 12 products that are associated to FFRs are provided and thus can be used as guidance by the operational forecasting community and other end-users of the products.
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Flamig, Zachary L., Humberto Vergara, and Jonathan J. Gourley. "The Ensemble Framework For Flash Flood Forecasting (EF5) v1.2: description and case study." Geoscientific Model Development 13, no. 10 (October 16, 2020): 4943–58. http://dx.doi.org/10.5194/gmd-13-4943-2020.
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Abstract. The Ensemble Framework For Flash Flood Forecasting (EF5) was developed specifically for improving hydrologic predictions to aid in the issuance of flash flood warnings by the US National Weather Service. EF5 features multiple water balance models and two routing schemes which can be used to generate ensemble forecasts of streamflow, streamflow normalized by upstream basin area (i.e., unit streamflow), and soil saturation. EF5 is designed to utilize high-resolution precipitation forcing datasets now available in real time. A study on flash-flood-scale basins was conducted over the conterminous United States using gauged basins with catchment areas less than 1000 km2. The results of the study show that the three uncalibrated water balance models linked to kinematic wave routing are skillful in simulating streamflow.
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Roux, Hélène, Arnau Amengual, Romu Romero, Ernest Bladé, and Marcos Sanz-Ramos. "Evaluation of two hydrometeorological ensemble strategies for flash-flood forecasting over a catchment of the eastern Pyrenees." Natural Hazards and Earth System Sciences 20, no. 2 (February 7, 2020): 425–50. http://dx.doi.org/10.5194/nhess-20-425-2020.
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Abstract. This study aims at evaluating the performances of flash-flood forecasts issued from deterministic and ensemble meteorological prognostic systems. The hydrometeorological modeling chain includes the Weather Research and Forecasting Model (WRF) forcing the rainfall-runoff model MARINE dedicated to flash floods. Two distinct ensemble prediction systems accounting for (i) perturbed initial and lateral boundary conditions of the meteorological state and (ii) mesoscale model physical parameterizations have been implemented on the Agly catchment of the eastern Pyrenees with three subcatchments exhibiting different rainfall regimes. Different evaluations of the performance of the hydrometeorological strategies have been performed: (i) verification of short-range ensemble prediction systems and corresponding streamflow forecasts, for a better understanding of how forecasts behave; (ii) usual measures derived from a contingency table approach, to test an alert threshold exceedance; and (iii) overall evaluation of the hydrometeorological chain using the continuous rank probability score, for a general quantification of the ensemble performances. Results show that the overall discharge forecast is improved by both ensemble strategies with respect to the deterministic forecast. Threshold exceedance detections for flood warning also benefit from large hydrometeorological ensemble spread. There are no substantial differences between both ensemble strategies on these test cases in terms of both the issuance of flood warnings and the overall performances, suggesting that both sources of external-scale uncertainty are important to take into account.
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Spyrou, Christos, George Varlas, Aikaterini Pappa, Angeliki Mentzafou, Petros Katsafados, Anastasios Papadopoulos, Marios N. Anagnostou, and John Kalogiros. "Implementation of a Nowcasting Hydrometeorological System for Studying Flash Flood Events: The Case of Mandra, Greece." Remote Sensing 12, no. 17 (August 27, 2020): 2784. http://dx.doi.org/10.3390/rs12172784.
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Severe hydrometeorological hazards such as floods, droughts, and thunderstorms are expected to increase in the future due to climate change. Due to the significant impacts of these phenomena, it is essential to develop new and advanced early warning systems for advance preparation of the population and local authorities (civil protection, government agencies, etc.). Therefore, reliable forecasts of extreme events, with high spatial and temporal resolution and a very short time horizon are needed, due to the very fast development and localized nature of these events. In very short time-periods (up to 6 h), small-scale phenomena can be described accurately by adopting a “nowcasting” approach, providing reliable short-term forecasts and warnings. To this end, a novel nowcasting system was developed and presented in this study, combining a data assimilation system (LAPS), a large amount of observed data, including XPOL radar precipitation measurements, the Chemical Hydrological Atmospheric Ocean wave System (CHAOS), and the WRF-Hydro model. The system was evaluated on the catastrophic flash flood event that occurred in the sub-urban area of Mandra in Western Attica, Greece, on 15 November 2017. The event was one of the most catastrophic flash floods with human fatalities (24 people died) and extensive infrastructure damage. The update of the simulations with assimilated radar data improved the initial precipitation description and led to an improved simulation of the evolution of the phenomenon. Statistical evaluation and comparison with flood data from the FloodHub showed that the nowcasting system could have provided reliable early warning of the flood event 1, 2, and even to 3 h in advance, giving vital time to the local authorities to mobilize and even prevent fatalities and injuries to the local population.
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Nguyen, Hong T., Trung Q. Duong, Liem D. Nguyen, Tram Q. N. Vo, Nhat T. Tran, Phuong D. N. Dang, Long D. Nguyen, Cuong K. Dang, and Loi K. Nguyen. "Development of a Spatial Decision Support System for Real-Time Flood Early Warning in the Vu Gia-Thu Bon River Basin, Quang Nam Province, Vietnam." Sensors 20, no. 6 (March 17, 2020): 1667. http://dx.doi.org/10.3390/s20061667.
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Vu Gia-Thu Bon (VGTB) river basin is an area where flash flood and heavy flood events occur frequently, negatively impacting the local community and socio-economic development of Quang Nam Province. In recent years, structural and non–structural solutions have been implemented to mitigate damages due to floods. However, under the impact of climate change, natural disasters continue to happen unpredictably day by day. It is, therefore, necessary to develop a spatial decision support system for real-time flood warnings in the VGTB river basin, which will support in ensuring the area’s socio-economic development. The main purpose of this study is to develop an online flood warning system in real-time based on Internet-of-Things (IoT) technologies, GIS, telecommunications, and modeling (Soil and Water Assessment Tool (SWAT) and Hydrologic Engineering Center’s River Analysis System (HEC–RAS)) in order to support the local community in the vulnerable downstream areas in the event of heavy rainfall upstream. The structure of the designed system consists of these following components: (1) real-time hydro-meteorological monitoring network, (2) IoT communication infrastructure (Global System for Mobile Communications (GSM), General Packet Radio Service (GPRS), wireless networks), (3) database management system (bio-physical, socio-economic, hydro-meteorological, and inundation), (4) simulating and predicting model (SWAT, HEC–RAS), (5) automated simulating and predicting module, (6) flood warning module via short message service (SMS), (7) WebGIS, application for providing and managing hydro-meteorological and inundation data, and (8) users (citizens and government officers). The entire operating processes of the flood warning system (i.e., hydro-meteorological data collecting, transferring, updating, processing, running SWAT and HEC–RAS, visualizing) are automated. A complete flood warning system for the VGTB river basin has been developed as an outcome of this study, which enables the prediction of flood events 5 h in advance and with high accuracy of 80%.
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Šaur, David, and Kateřina Víchová. "Forecasting of flash floods by Algorithm of Storm Prediction." MATEC Web of Conferences 210 (2018): 04033. http://dx.doi.org/10.1051/matecconf/201821004033.
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This article focuses on the forecasting of flash floods using the Algorithm of Storm Prediction as a new tool to predict convective precipitation, severe phenomena and the risk of flash floods. The first part of the article contains information on methods for predicting dangerous severe phenomena. This algorithm uses mainly data from numerical weather prediction models (NWP models), database of historic weather events and relief characteristics describing the influence of orography on the initiation of atmospheric convection. The result section includes verification of predicted algorithm outputs, selected NWP models and warnings of CHMI and ESTOFEX on three events related to the floods that hit the Zlín Region between years of 2015 - 2017. The main result is a report with prediction outputs of the algorithm visualized in maps for the territory of municipalities with extended competence and their regions. The outputs of the algorithm will be used primarily to increase the effectiveness of preventive measures against flash floods not only by the Fire Rescue Service of Czech Republic but also by the flood and crisis management authorities.
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Flack, David, Christopher Skinner, Lee Hawkness-Smith, Greg O’Donnell, Robert Thompson, Joanne Waller, Albert Chen, et al. "Recommendations for Improving Integration in National End-to-End Flood Forecasting Systems: An Overview of the FFIR (Flooding From Intense Rainfall) Programme." Water 11, no. 4 (April 8, 2019): 725. http://dx.doi.org/10.3390/w11040725.
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Recent surface-water and flash floods have caused millions of pounds worth of damage in the UK. These events form rapidly and are difficult to predict due to their short-lived and localised nature. The interdisciplinary Flooding From Intense Rainfall (FFIR) programme investigated the feasibility of enhancing the integration of an end-to-end forecasting system for flash and surface-water floods to help increase the lead time for warnings for these events. Here we propose developments to the integration of an operational end-to-end forecasting system based on the findings of the FFIR programme. The suggested developments include methods to improve radar-derived rainfall rates and understanding of the uncertainty in the position of intense rainfall in weather forecasts; the addition of hydraulic modelling components; and novel education techniques to help lead to effective dissemination of flood warnings. We make recommendations for future advances such as research into the propagation of uncertainty throughout the forecast chain. We further propose the creation of closer bonds to the end users to allow for an improved, integrated, end-to-end forecasting system that is easily accessible for users and end users alike, and will ultimately help mitigate the impacts of flooding from intense rainfall by informed and timely action.
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Salgueiro Donato Bacelar, Luiz Carlos, Aliana Maciel, Carlos Frederico de Angelis, and Javier Tomasella. "Limiares de chuva deflagradores de inundações bruscas: metodologia, aplicação e avaliação em ambiente operacional." Revista DAE 221, no. 68 (December 10, 2019): 71–86. http://dx.doi.org/10.36659/dae.2020.007.
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The present technical article refers to the methodology, application and evaluation of the first computational tool for diagnosis and prognosis of flash floods, based on rain thresholds, which was implemented in the platform of the National Center for Monitoring and Early Warning of Natural Disasters (Cemaden). From historical series of river levels and rainfall data, a procedure was developed to construct relationships that indicate the amount of rain necessary to increase the probability of flash floods occurring in up to twentyfour hours. Rainfall data from rain gauges, weather radars, satellites and atmospheric modeling are used for real-time monitoring of the pre-es- tablished critical rainfall thresholds, integrated into the monitoring and operation. Three cases of flash flood risk warnings sent after the implementation of the tool were analyzed, which demonstrated a good performance in the anticipation of flash floods hazard situations. O presente artigo refere-se à apresentação da metodologia, aplicação e avaliação da primeira ferramenta computacional para diagnóstico e prognóstico para inundações bruscas, baseada em limiares de chuva, que foi implementada na plataforma do Centro Nacional de Monitoramento e Alerta de Desastres Naturais (Cemaden). A partir de séries históricas de níveis dos rios e dados pluviométricos, um procedimento foi ela- borado para construir relações que indicam a quantidade de chuva necessária para aumento da probabilidade de ocorrência de inundações bruscas em até vinte e quatro horas. Os dados de precipitação provenientes de pluviômetros, radares meteorológicos, satélites e modelagem atmosférica por conjunto são utilizados para acompanhamento em tempo real dos níveis críticos de chuva pré-estabelecidos, integrados ao monitoramen- to e operação. Foram analisados três casos de alertas de risco às inundações bruscas, enviados após a implementação da ferramenta, que demonstrou um bom desempenho na antecipação de situações de perigo devido às inundações bruscas
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HAYDEN, M., S. DROBOT, S. RADIL, C. BENIGHT, E. GRUNTFEST, and L. BARNES. "Information sources for flash flood warnings in Denver, CO and Austin, TX." Environmental Hazards 7, no. 3 (2007): 211–19. http://dx.doi.org/10.1016/j.envhaz.2007.07.001.
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Di Paola, Francesco, Elisabetta Ricciardelli, Domenico Cimini, Filomena Romano, Mariassunta Viggiano, and Vincenzo Cuomo. "Analysis of Catania Flash Flood Case Study by Using Combined Microwave and Infrared Technique." Journal of Hydrometeorology 15, no. 5 (September 25, 2014): 1989–98. http://dx.doi.org/10.1175/jhm-d-13-092.1.
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Abstract In this paper, the analysis of an extreme convective event atypical for the winter season, which occurred on 21 February 2013 on the east coast of Sicily and caused a flash flood over Catania, is presented. In just 1 h, more than 50 mm of precipitation was recorded, but it was not forecast by numerical weather prediction (NWP) models and, consequently, no severe weather warnings were sent to the population. The case study proposed is first examined with respect to the synoptic situation and then analyzed by means of two algorithms based on satellite observations: the Cloud Mask Coupling of Statistical and Physical Methods (MACSP) and the Precipitation Evolving Technique (PET), developed at the National Research Council of Italy. Both of the algorithms show their ability in the near-real-time monitoring of convective cell formation and their rapid evolution. As quantitative precipitation forecasts by NWP could fail, especially for atypical convective events like in Catania, tools like MACSP and PET shall be adopted by civil protection centers to monitor the real-time evolution of deep convection events in aid to the severe weather warning service.
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Nielsen, Erik R., Gregory R. Herman, Robert C. Tournay, John M. Peters, and Russ S. Schumacher. "Double Impact: When Both Tornadoes and Flash Floods Threaten the Same Place at the Same Time." Weather and Forecasting 30, no. 6 (November 23, 2015): 1673–93. http://dx.doi.org/10.1175/waf-d-15-0084.1.
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Abstract While both tornadoes and flash floods individually present public hazards, when the two threats are both concurrent and collocated (referred to here as TORFF events), unique concerns arise. This study aims to evaluate the climatological and meteorological characteristics associated with TORFF events over the continental United States. Two separate datasets, one based on overlapping tornado and flash flood warnings and the other based on observations, were used to arrive at estimations of the instances when a TORFF event was deemed imminent and verified to have occurred, respectively. These datasets were then used to discern the geographical and meteorological characteristics of recent TORFF events. During 2008–14, TORFF events were found to be publicly communicated via overlapping warnings an average of 400 times per year, with a maximum frequency occurring in the lower Mississippi River valley. Additionally, 68 verified TORFF events between 2008 and 2013 were identified and subsequently classified based on synoptic characteristics and radar observations. In general, synoptic conditions associated with TORFF events were found to exhibit similar characteristics of typical tornadic environments, but the TORFF environment tended to be moister and have stronger synoptic-scale forcing for ascent. These results indicate that TORFF events occur with appreciable frequency and in complex meteorological scenarios. Furthermore, despite these identified differences, TORFF scenarios are not easily distinguishable from tornadic events that fail to produce collocated flash flooding, and present difficult challenges both from the perspective of forecasting and public communication.
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Henderson, Jen, Erik R. Nielsen, Gregory R. Herman, and Russ S. Schumacher. "A Hazard Multiple: Overlapping Tornado and Flash Flood Warnings in a National Weather Service Forecast Office in the Southeastern United States." Weather and Forecasting 35, no. 4 (August 1, 2020): 1459–81. http://dx.doi.org/10.1175/waf-d-19-0216.1.
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AbstractThe U.S. weather warning system is designed to help operational forecasters identify hazards and issue alerts to assist people in taking life-saving actions. Assessing risks for separate hazards, such as flash flooding, can be challenging for individuals, depending on their contexts, resources, and abilities. When two or more hazards co-occur in time and space, such as tornadoes and flash floods, which we call TORFFs, risk assessment and available actions people can take to stay safe become increasingly complex and potentially dangerous. TORFF advice can suggest contradictory action—that people get low for a tornado and seek higher ground for a flash flood. The origin of risk information about such threats is the National Weather Service (NWS) Weather Forecast Office. This article contributes to an understanding of the warning and forecast system though a naturalistic study of the NWS during a TORFF event in the southeastern United States. Drawing on literature for the Social Amplification of Risk Framework, this article argues that during TORFFs, elements of the NWS warning operations can unintentionally amplify or attenuate one threat over the other. Our results reveal three ways this amplification or attenuation might occur: 1) underlying assumptions that forecasters understandably make about the danger of different threats; 2) threat terminology and coordination with national offices that shape the communication of risks during a multihazard event; and 3) organizational arrangements of space and forecaster expertise during operations. We conclude with suggestions for rethinking sites of amplification and attenuation and additional areas of future study.
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Rogelis, María Carolina, and Micha Werner. "Streamflow forecasts from WRF precipitation for flood early warning in mountain tropical areas." Hydrology and Earth System Sciences 22, no. 1 (February 1, 2018): 853–70. http://dx.doi.org/10.5194/hess-22-853-2018.
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Abstract. Numerical weather prediction (NWP) models are fundamental to extend forecast lead times beyond the concentration time of a watershed. Particularly for flash flood forecasting in tropical mountainous watersheds, forecast precipitation is required to provide timely warnings. This paper aims to assess the potential of NWP for flood early warning purposes, and the possible improvement that bias correction can provide, in a tropical mountainous area. The paper focuses on the comparison of streamflows obtained from the post-processed precipitation forecasts, particularly the comparison of ensemble forecasts and their potential in providing skilful flood forecasts. The Weather Research and Forecasting (WRF) model is used to produce precipitation forecasts that are post-processed and used to drive a hydrologic model. Discharge forecasts obtained from the hydrological model are used to assess the skill of the WRF model. The results show that post-processed WRF precipitation adds value to the flood early warning system when compared to zero-precipitation forecasts, although the precipitation forecast used in this analysis showed little added value when compared to climatology. However, the reduction of biases obtained from the post-processed ensembles show the potential of this method and model to provide usable precipitation forecasts in tropical mountainous watersheds. The need for more detailed evaluation of the WRF model in the study area is highlighted, particularly the identification of the most suitable parameterisation, due to the inability of the model to adequately represent the convective precipitation found in the study area.
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Javelle, Pierre, Julie Demargne, Dimitri Defrance, Jean Pansu, and Patrick Arnaud. "Evaluating flash-flood warnings at ungauged locations using post-event surveys: a case study with the AIGA warning system." Hydrological Sciences Journal 59, no. 7 (June 6, 2014): 1390–402. http://dx.doi.org/10.1080/02626667.2014.923970.
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Kong, Fanzhe, Wei Huang, Zhilin Wang, and Xiaomeng Song. "Effectof Unit Hydrographs and Rainfall Hyetographs on Critical Rainfall Estimates of Flash Flood." Advances in Meteorology 2020 (June 10, 2020): 1–15. http://dx.doi.org/10.1155/2020/2801963.
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To obtain critical rainfall (CR) estimates similar to the rainfall value that causes minor basin outlet flooding, and to reduce the flash flood warning missed/false alarm rate, the effect of unit hydrographs (UHs) and rainfall hyetographs on computed threshold rainfall (TR) values was investigated. The Tanjia River basin which is a headwater subbasin of the Greater Huai River basin in China was selected as study basin. Xin’anjiang Model, with subbasins as computation units, was constructed, and time-variant distributed unit hydrographs (TVUHs) were used to route the channel network concentration. Calibrated Xin’anjiang Model was employed to derive the TVUHs and to obtain the maximum critical rainfall duration (Dmax) of the study basin. Initial soil moisture condition was represented by the antecedent precipitation index (Pa). Rainfall hyetographs characterized by linearly increasing, linearly decreasing, and uniform hyetographs were used. Different combinations of the three hyetographs and UHs including TVUHs and time-invariant unit hydrographs (TIVUHs) were utilized as input to the calibrated Xin’anjiang Model to compute the relationships between TR and Pa (TR-Pa curves) by using trial and error methodology. The computed TR-Pa curves reveal that, for given Pa and UH, the TR corresponding to linearly increasing hyetograph is the minimum one. So, the linearly increasing hyetograph is the optimum hyetograph type for estimating CR. In the linearly increasing hyetograph context, a comparison was performed between TR-Pa curves computed from different UHs. The results show that TR values for different TIVUHs are significantly different and the TR-Pa curve gradient of TVUHs is lower than that of TIVUHs. It is observed that CR corresponds to the combination of linearly increasing hyetograph and TVUHs. The relationship between CR and Pa (CR-Pa curves) and that between CR and duration (D) (CR-D curves) were computed. Warnings for 12 historical flood events were performed. Warning results show that the success rate was 91.67% and that the critical success index (CSI) was 0.91. It is concluded that the combination of linearly increasing hyetograph and TVUHs can provide the CR estimate similar to the minimum rainfall value necessary to cause flash flooding.
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Claudia, Fara Diva, Cecylia Putri Mawarni, Kadek Krisna Yulianti, and Paulus Agus Winarso. "Utilization of estimated rainfall as an early warning system before flash flood event." Journal of Physics: Theories and Applications 2, no. 2 (September 30, 2018): 73. http://dx.doi.org/10.20961/jphystheor-appl.v2i2.30670.
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<p class="Abstract">On October 10, 2018 there has been extreme weather in the form of heavy rain accompanied by lightning in Tanah Datar District, West Sumatra. This extreme weather caused flash floods and landslides that killed many people. Therefore, by using remote sensing data in the form of radar and satellite as well as WRF modeling (Weather Research and Forecasting) the authors conducted analysis of heavy rainfall events to determine the estimated rainfall and atmospheric dynamics during the occurrence of flash floods and landslides. WRF modeling is used to determine the condition of atmospheric lability. For the calculation of rainfall estimation, the method used is the Convective Stratiform Technique (CST) method that utilizes satellite data and the Z-R relation selection method that utilizes radar data. Then the calculation results from each method are verified using observation data. Relative bias shows the CST method and the selection of Z-R relations tend to be overestimate, but has a very high correlation value with observation data. Information on rainfall estimation and atmospheric dynamics is expected to be used to provide early warnings aimed at minimizing losses from the impact of disasters.</p>
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Montesarchio, V., E. Ridolfi, F. Russo, and F. Napolitano. "Rainfall threshold definition using an entropy decision approach and radar data." Natural Hazards and Earth System Sciences 11, no. 7 (July 27, 2011): 2061–74. http://dx.doi.org/10.5194/nhess-11-2061-2011.
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Abstract. Flash flood events are floods characterised by a very rapid response of basins to storms, often resulting in loss of life and property damage. Due to the specific space-time scale of this type of flood, the lead time available for triggering civil protection measures is typically short. Rainfall threshold values specify the amount of precipitation for a given duration that generates a critical discharge in a given river cross section. If the threshold values are exceeded, it can produce a critical situation in river sites exposed to alluvial risk. It is therefore possible to directly compare the observed or forecasted precipitation with critical reference values, without running online real-time forecasting systems. The focus of this study is the Mignone River basin, located in Central Italy. The critical rainfall threshold values are evaluated by minimising a utility function based on the informative entropy concept and by using a simulation approach based on radar data. The study concludes with a system performance analysis, in terms of correctly issued warnings, false alarms and missed alarms.
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Moser, Ben A., William A. Gallus, and Ricardo Mantilla. "An Initial Assessment of Radar Data Assimilation on Warm Season Rainfall Forecasts for Use in Hydrologic Models." Weather and Forecasting 30, no. 6 (November 18, 2015): 1491–520. http://dx.doi.org/10.1175/waf-d-14-00125.1.
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Abstract The effect of introducing radar data assimilation into the WRF Model to improve high-resolution rainfall forecasts that are used for flash flood forecasting is analyzed. The authors selected 12 heavy rainfall events and performed two WRF 24-h simulations that produced quantitative precipitation forecasts (QPFs) for each, one using the standard configuration in forecast mode (QPF-Cold) and one using radar data assimilated at initialization (QPF-Hot). Simulation outputs are compared with NWS stage IV QPEs for storm placement, area over threshold coverage, and equitable threat scores. The two QPF products and stage IV data are used to force the distributed hydrological model CUENCAS for the same 800 km × 800 km domain centered over Iowa (and to calculate peak flows across the river network). The hydrological model responses to the three products are compared in terms of spatial location and flood intensity. In general, QPF-Hot outperformed QPF-Cold in replicating stage IV QPE statistics. However, QPF-Hot was too wet in the first 2 h of the event, and storms created by the radar-assimilation techniques dissipated quickly, with rainfall forecasts resembling QPF-Cold after 12 h. Flash flooding predicted by CUENCAS using QPF-Hot was more consistent with stage IV in terms of placement and intensity; however, results were not consistent for all events evaluated. The most encouraging result is that expected flash flooding was indeed predicted in all 12 cases using QPF-Hot and not QPF-Cold even though placement and intensity were not a perfect match. The initial results of this study indicate that radar assimilation improves WRF’s ability to capture the character of storms, promising more accurate guidance for flash flood warnings.
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Yang, Tsun-Hua, Sheng-Chi Yang, Jui-Yi Ho, Gwo-Fong Lin, Gong-Do Hwang, and Cheng-Shang Lee. "Flash flood warnings using the ensemble precipitation forecasting technique: A case study on forecasting floods in Taiwan caused by typhoons." Journal of Hydrology 520 (January 2015): 367–78. http://dx.doi.org/10.1016/j.jhydrol.2014.11.028.
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Burow, Daniel, Kelsey Ellis, and Liem Tran. "Simultaneous and collocated tornado and flash flood warnings associated with tropical cyclones in the contiguous United States." International Journal of Climatology 41, no. 8 (March 23, 2021): 4253–64. http://dx.doi.org/10.1002/joc.7071.
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Dietrich, J., S. Trepte, Y. Wang, A. H. Schumann, F. Voß, F. B. Hesser, and M. Denhard. "Combination of different types of ensembles for the adaptive simulation of probabilistic flood forecasts: hindcasts for the Mulde 2002 extreme event." Nonlinear Processes in Geophysics 15, no. 2 (March 19, 2008): 275–86. http://dx.doi.org/10.5194/npg-15-275-2008.
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Abstract. Flood forecasts are essential to issue reliable flood warnings and to initiate flood control measures on time. The accuracy and the lead time of the predictions for head waters primarily depend on the meteorological forecasts. Ensemble forecasts are a means of framing the uncertainty of the potential future development of the hydro-meteorological situation. This contribution presents a flood management strategy based on probabilistic hydrological forecasts driven by operational meteorological ensemble prediction systems. The meteorological ensemble forecasts are transformed into discharge ensemble forecasts by a rainfall-runoff model. Exceedance probabilities for critical discharge values and probabilistic maps of inundation areas can be computed and presented to decision makers. These results can support decision makers in issuing flood alerts. The flood management system integrates ensemble forecasts with different spatial resolution and different lead times. The hydrological models are controlled in an adaptive way, mainly depending on the lead time of the forecast, the expected magnitude of the flood event and the availability of measured data. The aforementioned flood forecast techniques have been applied to a case study. The Mulde River Basin (South-Eastern Germany, Czech Republic) has often been affected by severe flood events including local flash floods. Hindcasts for the large scale extreme flood in August 2002 have been computed using meteorological predictions from both the COSMO-LEPS ensemble prediction system and the deterministic COSMO-DE local model. The temporal evolution of a) the meteorological forecast uncertainty and b) the probability of exceeding flood alert levels is discussed. Results from the hindcast simulations demonstrate, that the systems would have predicted a high probability of an extreme flood event, if they would already have been operational in 2002. COSMO-LEPS showed a reasonably good performance within a lead time of 2 to 3 days. Some of the deterministic very short-range forecast initializations were able to predict the dynamics of the event, but others underpredicted rainfall. Thus a lagged average ensemble approach is suggested. The findings from the case study support the often proposed added value of ensemble forecasts and their probabilistic evaluation for flood management decisions.
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Forte, F., L. Pennetta, and R. O. Strobl. "Historic records and GIS applications for flood risk analysis in the Salento peninsula (southern Italy)." Natural Hazards and Earth System Sciences 5, no. 6 (November 2, 2005): 833–44. http://dx.doi.org/10.5194/nhess-5-833-2005.
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Abstract. The occurrence of calamitous meteoric events represents a current problem of the Salento peninsula (Southern Italy). In fact, flash floods, generated by very intense rainfall, occur not only in autumn and winter, but at the end of summer as well. These calamities are amplified by peculiar geological and geomorphological characteristics of Salento and by the pollution of sinkholes. Floodings affect often large areas, especially in the impermeable lowering zones. These events cause warnings and emergency states, involving people as well as socio-economic goods. A methodical investigation based on the historic flood records and an analysis of the geoenvironmental factors have been performed, using a Geographic Information System (GIS) methodology for database processing in order to identify the distribution of areas with different risk degrees. The data, referring to events that occurred from 1968 to 2004, have been collected in a database, the so-called IPHAS (Salento Alluvial PHenomena Inventory), extracted in an easily consultable table. The final goal is the development of a risk map where the areas that are affected by floodings are included between small ridges, the so-called "Serre". More than 50% of the Salento peninsula shows high or very high risk values. The numerous maps that were utilized and generated represent an important basis in order to quantify the flood risk, according to the model using historic records.
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Miao, Qinghua, Dawen Yang, Hanbo Yang, and Zhe Li. "Establishing a rainfall threshold for flash flood warnings in China’s mountainous areas based on a distributed hydrological model." Journal of Hydrology 541 (October 2016): 371–86. http://dx.doi.org/10.1016/j.jhydrol.2016.04.054.
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Moore, Angelyn W., Ivory J. Small, Seth I. Gutman, Yehuda Bock, John L. Dumas, Peng Fang, Jennifer S. Haase, Mark E. Jackson, and Jayme L. Laber. "National Weather Service Forecasters Use GPS Precipitable Water Vapor for Enhanced Situational Awareness during the Southern California Summer Monsoon." Bulletin of the American Meteorological Society 96, no. 11 (November 1, 2015): 1867–77. http://dx.doi.org/10.1175/bams-d-14-00095.1.
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Abstract During the North American Monsoon, low-to-midlevel moisture is transported in surges from the Gulf of California and Eastern Pacific Ocean into Mexico and the American Southwest. As rising levels of precipitable water interact with the mountainous terrain, severe thunderstorms can develop, resulting in flash floods that threaten life and property. The rapid evolution of these storms, coupled with the relative lack of upper-air and surface weather observations in the region, make them difficult to predict and monitor, and guidance from numerical weather prediction models can vary greatly under these conditions. Precipitable water vapor (PW) estimates derived from continuously operating ground-based GPS receivers have been available for some time from NOAA’s GPS-Met program, but these observations have been of limited utility to operational forecasters in part due to poor spatial resolution. Under a NASA Advanced Information Systems Technology project, 37 real-time stations were added to NOAA’s GPS-Met analysis providing 30-min PW estimates, reducing station spacing from approximately 150 km to 30 km in Southern California. An 18–22 July 2013 North American Monsoon event provided an opportunity to evaluate the utility of the additional upper-air moisture observations to enhance National Weather Service (NWS) forecaster situational awareness during the rapidly developing event. NWS forecasters used these additional data to detect rapid moisture increases at intervals between the available 1–6-h model updates and approximately twice-daily radiosonde observations, and these contributed tangibly to the issuance of timely flood watches and warnings in advance of flash floods, debris flows, and related road closures.
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Grams, Heather M., Jian Zhang, and Kimberly L. Elmore. "Automated Identification of Enhanced Rainfall Rates Using the Near-Storm Environment for Radar Precipitation Estimates." Journal of Hydrometeorology 15, no. 3 (June 1, 2014): 1238–54. http://dx.doi.org/10.1175/jhm-d-13-042.1.
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Abstract Reliable and timely flash flood warnings are critically dependent on the accuracy of real-time rainfall estimates. Precipitation is not only the most vital input for basin-scale accumulation algorithms such as the Flash Flood Monitoring and Prediction (FFMP) program used operationally by the U.S. National Weather Service, but it is the primary forcing for hydrologic models at all scales. Quantitative precipitation estimates (QPE) from radar are widely used for such a purpose because of their high spatial and temporal resolution. However, converting the native radar variables into an instantaneous rain rate is fraught with challenges and uncertainties. This study addresses the challenge of identifying environments conducive for tropical rain rates, or rain rates that are enhanced by highly productive warm rain growth processes. Model analysis fields of various thermodynamic and moisture parameters were used as predictors in a decision tree–based ensemble to generate probabilities of warm rain–dominated drop growth. Variable importance analysis from the ensemble training showed that the probability accuracy was most dependent on two parameters in particular: freezing-level height and lapse rates of temperature. The probabilities were used to assign a tropical rain rate for hourly QPE and were evaluated against existing Z–R–based QPE products available to forecasters. The probability-based delineations showed improvement in QPE over the existing methods, but the two predictands tested had varying levels of performance for the storm types evaluated and require further study.
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Ishihara, Masahito. "Radar Echo Population of Air-Mass Thunderstorms and Nowcasting of Thunderstorm-Induced Local Heavy Rainfalls Part II: A Feasibility Study on Nowcasting." Journal of Disaster Research 8, no. 1 (February 1, 2013): 69–80. http://dx.doi.org/10.20965/jdr.2013.p0069.
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Many air-mass thunderstorms were generated in the Tokyo metropolitan area on August 5, 2008, when a severe local rainstorm caused a flash flood in the center of Tokyo. Using three-dimensional radar reflectivity data from the Japan Meteorological Agency (JMA), nowcasting was examined concerning the peak time and peak rainfall intensity of thunderstorms. Four qualitative forecastmethods – precipitation cores aloft, time changes in vertically integrated liquid water, time changes in echo-top height, lightning activity – and three quantitative forecast methods using three parameters were adopted in eight thunderstorms related to heavy-rainfall warnings issued by the JMA on August 5, 2008. While there is much worth further examination in the method using precipitation core aloft, the other methods are not in the stage of operational use in order to forecast time and rainfall intensity at the rainfall peak of each thunderstorm.
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Moy de Vitry, Matthew, Simon Dicht, and João P. Leitão. "floodX: urban flash flood experiments monitored with conventional and alternative sensors." Earth System Science Data 9, no. 2 (September 4, 2017): 657–66. http://dx.doi.org/10.5194/essd-9-657-2017.
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Abstract. The data sets described in this paper provide a basis for developing and testing new methods for monitoring and modelling urban pluvial flash floods. Pluvial flash floods are a growing hazard to property and inhabitants' well-being in urban areas. However, the lack of appropriate data collection methods is often cited as an impediment for reliable flood modelling, thereby hindering the improvement of flood risk mapping and early warning systems. The potential of surveillance infrastructure and social media is starting to draw attention for this purpose. In the floodX project, 22 controlled urban flash floods were generated in a flood response training facility and monitored with state-of-the-art sensors as well as standard surveillance cameras. With these data, it is possible to explore the use of video data and computer vision for urban flood monitoring and modelling. The floodX project stands out as the largest documented flood experiment of its kind, providing both conventional measurements and video data in parallel and at high temporal resolution. The data set used in this paper is available at https://doi.org/10.5281/zenodo.830513.
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Jury, Mark R. "Weather–Climate Interactions in the Eastern Antilles and the 2013 Christmas Storm." Earth Interactions 18, no. 19 (November 1, 2014): 1–20. http://dx.doi.org/10.1175/ei-d-14-0011.1.
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Abstract This study considers eastern Antilles (11°–18°N, 64°–57°W) weather and climate interactions in the context of the 2013 Christmas storm. This unseasonal event caused flash flooding in Grenada, St. Vincent, St. Lucia, Martinique, and Dominica from 24 to 25 December 2013, despite having winds <15 m s−1. The meteorological scenario and short-term forecasts are analyzed. At the low level, a convective wave propagated westward while near-equatorial upper westerly winds surged with eastward passage of a trough. The combination of tropical moisture, cyclonic vorticity, and uplift resulted in rain rates greater than 30 mm h−1 and many stations reporting 200 mm. Although forecast rainfall was low and a few hours late, weather services posted flood warnings in advance. At the climate scale, the fresh Orinoco River plume brought into the region by the North Brazil Current together with solar radiation greater than 200 W m−2, enabled sea temperatures to reach 28°C, and supplied convective available potential energy greater than 1800 J kg−1. Climate change model simulations are compared with reference fields and trends are analyzed in the eastern Antilles. While temperatures are set to increase, the frequency of flood events appears to decline in the future.