Evaluation of Operational National Weather Service Gridded Flash Flood Guidance over the Arkansas Red River Basin

Abstract

National Oceanic and Atmospheric Administration's National Weather Service (NWS) flash flood warnings are issued by Weather Forecast Offices and are underpinned by information from the Flash Flood Guidance (FFG) system operated by the River Forecast Centers (RFCs). This study focuses on the quantitative evaluation and limitations of the FFG system using reported flash flood cases in 2010 and 2011. The flash flood reports were obtained from the NWS Storm Event database for the Arkansas‐Red Basin RFC (ABRFC). The current FFG system at the ABRFC provides gridded flash flood guidance (GFFG) system using the NWS Hydrology Laboratory‐Research Distributed Hydrologic Model to translate the upper zone soil moisture to estimates of Soil Conservation Service Curve Numbers. Comparisons of the GFFG and real‐time Multisensor Precipitation Estimator‐derived Quantitative Precipitation Estimate for the same duration and location were used to analyze the success of the system. Typically, the six‐hour duration was characterized by higher probability of detection values than the three‐hour duration, which highlights the difficulty of hydrologic process estimation for shorter time scales. The current system does not take into account physical characteristics such as land use, including irrigated agricultural farm and urban areas, hence, overly dry soil moisture estimates over these areas can lower the success rate of the GFFG product.

Towards Real‐Time Continental Scale Streamflow Simulation in Continuous and Discrete Space

“…https://www.weather.gov/media/news/ WRN_Pilot_Projects_Final.pdf, accessed July 31, 2017). This operation is carried out daily by 122 local WFOs and 13 regional RFCs (McEnery et al, 2005;Seo et al, 2013;Clark et al, 2014). Using a suite of hydrologic datasets, observations and models, NWS personnel assimilate the best available information in near real-time and issue flood forecasts at approximately 3,600 locations or forecast points across the country (including Alaska but not Hawaii).…”

“…In the U.S., the National Weather Service (NWS) is operationally responsible for issuing flood forecasts and warnings to the public (McEnery et al, 2005;Seo et al, 2013;Clark et al, 2014). This service is supported by local Weather Forecast Offices (WFOs) and regional River Forecast Centers (RFCs) that rely on myriad observations, numerical weather prediction (NWP) models, hydrologic and hydraulic models, and peer-to-peer communication.…”

Establishing a rainfall threshold for flash flood warnings in China’s mountainous areas based on a distributed hydrological model

“…Thus, unlike the US NWS's FFG, which regularly applies a lumped hydrological model to catchments on a scale of 1000 km 2 (Gourley et al, 2012), this study takes advantage of distributed hydrological models in flood simulations at ungauged locations and uses the threshold frequency method to determine the rainfall threshold for flash flood warnings in China's mountainous areas. The rainfall threshold value of the US NWS's FFG is usually updated one to three times per day (Gourley et al, 2012), while the GFFG is updated three to four times per day (Seo et al, 2013). This process requires the systems to frequently calculate the rainfall threshold.…”

Flash Flood Prediction by Coupling KINEROS2 and HEC-RAS Models for Tropical Regions of Northern Vietnam

“…However, they have been categorized into fatal and costly natural disasters [3][4][5]. Northern Vietnam is one of the regions most affected by FF in Vietnam and likely to suffer more frequently due to the impacts of climate change [6].…”