FLASH Case Study on the Blanco River

On the evening of May 23rd into the early morning of May 24th, 2015 the Blanco River in Texas experienced a significant flooding event resulting in the closure of I-35 north & southbound near the city of San Marcos, TX. There were also multiple high-water rescues in the area including helicopter rescues of victims trapped in houses. The Hays County jail in Texas was also evacuated due to threatening flood waters. The FLASH development system was running for this event producing products forecasting & monitoring the flooding in near real time.

The storm total MRMS QPE shows 6-8” over the headwaters of the Blanco River catchment. The MRMS QPE to FFG ratio product shows exceedance of 160-180%.

FLASH products from May 24th, 2015 02 UTC over the Blanco River catchment. The storm total MRMS QPE shows 6-8” over the headwaters of the Blanco River catchment. The MRMS QPE to FFG ratio product shows exceedance of 160-180%.

Traditional rainfall based products including the rainfall accumulation and the ratio of rainfall to flash flood guidance highlight a large area northwest of San Marcos for flooding impacts. The storm system produced 6-8″ of rain over the region to the northwest resulting in exceedance of flash flood guidance by 160-180%.

FLASH CREST Maximum Streamflow and Maximum Unit Streamflow for May 24th, 2015 02 UTC.

FLASH CREST maximum streamflow and maximum unit streamflow for May 24th, 2015 02 UTC over the Blanco River catchment.

The FLASH hydrologic model based products correctly show the heavy rainfall being concentrated into the rivers and the downstream flooding impacts in San Marcos resulting from the heavy rainfall to the northwest of the region.

FLASH QPE to FFG ratio and CREST unit streamflow for May 24th, 2015 07 UTC.

FLASH QPE to FFG ratio and CREST unit streamflow for May 24th, 2015 07 UTC over the Blanco River catchment.


  1. This was a very heavy rainfall event that was captured well by MRMS radar-only estimates
  2. The flash flood guidance product indicated significant exceedance over threshold values, but the areas of concern were limited to the headwaters of the Blancos river
  3. The distributed hydrologic model forecasts better refined the threat area to the Blancos river and provided several hours of lead time
  4. This event clearly highlights the need to account for overland flow and routing, displacing the impacts well downstream of the causative rainfall

FLASH Performance with Recent Flood Events in Oklahoma & Texas

The MRMS-FLASH system, running in a real-time demonstration mode for several years now, performed admirably for the recent flash flooding events in Oklahoma and Texas. The MRMS-FLASH system runs in a completely automated fashion ingesting quantitative precipitation estimates every 5-minutes from the MRMS mosaic of NEXRAD data. The FLASH hydrologic modeling system subsequently produces 6-hour forecast hydrographs for everywhere across the CONUS.

On evening of May 25th, 2015 the city of Houston, Texas experienced a serious flash flooding event. MRMS precipitation estimates indicate that the western portions of the city experienced 6-8″ of rainfall.

MRMS QPE for May 25th Houston Flash Flood

MRMS QPE for May 25th, 2015 Houston Flash Flood

The ratio of precipitation to flash flood guidance shows exceedance values of 100-140% over this area, however some of the USGS stream gauges reporting flash flooding (blue triangles) and the flash flood local storm reports (brown circles) fall outside of this region. This product is important because it is equivalent to the main tool operational NWS forecasters have available for flash flood monitoring and prediction.
MRMS QPE to FFG Ratio for the May 25th Houston flash flood.

MRMS QPE to FFG Ratio for the May 25th, 2015 Houston flash flood. Blue triangles are USGS stream gauges reported flash flooding, brown circles are NWS flash flood local storm reports.

The Coupled Routing and Excess Storage (CREST) distributed hydrologic model, a part of the MRMS-FLASH hydrologic modeling suite, generates maps of streamflow and unit streamflow (cubic meters per second per square kilometer) every 15 minutes. Comparisons between the observations of flash flooding and the maps of unit streamflow show a good correspondence between areas of high unit streamflows and flash flooding.
Animation of unit streamflow from the May 25th, 2015 Houston Flash Flood

Animation of unit streamflow from the May 25th, 2015 Houston Flash Flood. Blue triangles are USGS stream gauges reported flash flooding, brown circles are NWS flash flood local storm reports.

The MRMS-FLASH suite of hydrologic models are able to correctly identify areas of flash flooding thanks to the incorporation of

  1. Stream & overland routing
  2. Modeling of impervious surfaces

New Book – Radar Hydrology: Principles, Models, and Applications

Radar-HydrologyPublished: December 23, 2014 by CRC Press
Radar Hydrology: Principles, Models, and Applications provides graduate students, operational forecasters, and researchers with a theoretical framework and practical knowledge of radar precipitation estimation. The only text on the market solely devoted to radar hydrology, this comprehensive reference:

  • Begins with a brief introduction to radar
  • Focuses on the processing of radar data to arrive at accurate estimates of rainfall
  • Addresses advanced radar sensing principles and applications
  • Covers radar technologies for observing each component of the hydrologic cycle
  • Examines state-of-the-art hydrologic models and their inputs, parameters, state variables, calibration procedures, and outputs
  • Discusses contemporary approaches in data assimilation
  • Concludes with methods, case studies, and prediction system design
  • Includes downloadable MATLAB® content

Flooding is the #1 weather-related natural disaster worldwide. Radar Hydrology: Principles, Models, and Applications aids in understanding the physical systems and detection tools, as well as designing prediction systems.

Editorial Reviews
“This is the first book on radar hydrology written by hydrologists. Whereas the excellent knowledge of radar technology by the authors permits an adequate coverage of the principles of rainfall rate estimation by radar, their hydrological background allows them to provide a unique message on the benefits (and on the remaining challenges) in exploiting radar techniques in hydrology. … In a clear and concise manner, the book combines topics from different scientific disciplines into a unified approach aiming to guide the reader through the requirements, strengths, and pitfalls of the application of radar technology in hydrology—mostly for flood prediction. Chapters include excellent discussion of theory, data analysis, and applications, along with several cross references for further review and useful conclusions.”

2014 HWT-Hydro Final Report

The final report on the inaugural Hazardous Weather Testbed Hydro experiment has been released. The report details how the experiment was run, configuration details for AWIPS2, conclusions from the experiment and recommendations for future iterations of the experiment. Thanks again to all of our participants!

2014 HWT-Hydro Final Report

FLASH team participates in the Integrated Precipitation and Hydrology Experiment (IPHEx)

The NSSL NOXP Radar on location for iPHEX

The NSSL NOXP Radar on location for iPHEX

Members of the FLASH team have been involved in the Integrated Precipitation and Hydrology Experiment (IPHEx) to study warm season precipitation and hydrologic response in the complex terrain of western North Carolina. The team has been with NSSL’s NOXP radar to coordinate operations with several other ground-based platforms as well as NASA’s ER-2 and UND’s Citation aircraft. Further, a number of developmental radar-based (MRMS) and hydrologic model-based (FLASH) products are being supplied to the experimental team for research and evaluation. The experiment runs from May 1 – June 15, 2014.

Website hosting MRMS, FLASH, and NOXP products: http://wdssii.nssl.noaa.gov/web/wdss2/products/radar/iphex.shtml
More information about IPHEX can be found here: http://iphex.pratt.duke.edu
And here: http://pmm.nasa.gov/IPHEx

FLASH Students Conduct CREST Training Workshop with Namibia’s Department of Hydrology

Race Clark & Jill Hardy with members of Namibia’s Department of Hydrology

Race Clark & Jill Hardy with members of Namibia’s Department of Hydrology

HyDROS students Jill Hardy and Race Clark recently taught a three-day CREST training workshop in Windhoek, Namibia. Participants were mainly drawn from members of Namibia’s Department of Hydrology, though others from the Polytechnic of Namibia, the Regional Center for Mapping and Resources for Development (Nairobi, Kenya), the South African National Space Agency (Pretoria, South Africa), NAMWater, and NASA also participated in the workshop. The workshop is part of a larger, ongoing effort to build capacity for flood and drought monitoring in the African nation. The NSF (via the Open Science Data Cloud PIRE program) funded Ms. Hardy and Mr. Clark’s travel, along with a grant to the University of Oklahoma from the NASA SERVIR program. Several workshop participants also got the chance to take part in field visits to three separate stream gauge stations on the Kuiseb River basin. CREST (Coupled Routing and Excess STorage) is a distributed hydrologic model used at varying scales across the globe and was jointly developed by OU and NASA. For more information, visit hydro.ou.edu/research/crest.
Namibia stream gauge located on the Kuiseb River basin.

Namibia stream gauge located on the Kuiseb River basin.

Race Clark Wins Graduate Student Poster Competition at NWA Meeting

Race Clark and Poster

Race Clark and Poster

Race Clark (CIMMS at NSSL) was awarded first place in the graduate student poster competition at the 38th Annual National Weather Association (NWA) meeting in Charleston, SC. Clark is a Ph.D. student in the OU School of Meteorology and works with advisors J.J. Gourley (NSSL) and Yang Hong (OU Civil and Environmental Engineering).

The award is selected by the NWA Weather Analysis and Forecasting Committee. The poster, A CONUS-wide analysis of flash flooding: simulations, warnings, and observations, identifies regional trends in the frequency of flash flood observations in NWS Storm Data, flash flood warnings, and flash flood guidance. His co-authors are J.J. Gourley (NOAA/OAR/NSSL), Yang Hong (OU), Zac Flamig (OU), and Ed Clark (NOAA/NWS). The recognition includes $125 and complimentary membership in the NWA for 2014.

Bon Voyage!

Bon Voyage!

Bon Voyage!

Prof. Céline Lutoff from the Universite de Grenoble, France has completed her 6-month visit with the FLASH team at the National Weather Center. While in Norman, she and her family experienced two EF5 tornadoes that were very near (Moore and El Reno), as well as the deadly Oklahoma City flash flood. Céline assisted in many flash flood-related studies with the team. In particular, she helped launch the “social component” of the Flood Observations – Citizens As Scientists using Technology (FLOCAST) project (http://flash.ou.edu/flocast/). Her expertise was invaluable in developing the interview questions that will be used to understand societal perceptions, responses, and behavior of victims impacted by flash floods. Céline helped in the development of a photography guideline, which is presently being used to collect unique and informative photographs of flash flooding. Lastly, she co-supervised a study that is aimed at understanding the characteristics of deadly and injurious flash flooding events vs. those that have little impact on lives. Although she will be missed, we anticipate many more fruitful collaborations with her and her team in France in the future! Céline was hosted at the University of Oklahoma by the Cooperative Institute for Mesoscale Meteorological Studies.

Flamig awarded 2013 Chateaubriand Fellowship

NSSL’s Zachary Flamig has been awarded the prestigious 2013 Chateaubriand Fellowship. The merit-based grant is offered by the Embassy of France in the United States and aims to encourage collaborations, partnerships or joint projects between France and the U.S. Flamig is a Ph.D. student in the School of Meteorology at The University of Oklahoma and works at NSSL with advisor J.J. Gourley.

Flamig will conduct his fellowship at the University Joseph Fourier in Grenoble, France and will work with the Hydrometeorology, Climate and Impacts (HCMI) team at the Laboratoire d’etude des Transferts en hydrologie et Environnement (LTHE). His mission will be to explore a variety of hydrologic models with various physics representations, including the French Cevennes (CVN) distributed hydrologic model, to determine the surface runoff generation and routing mechanisms that are needed to yield accurate simulations of flash floods. Results from his research topic will be incorporated in the U.S. Flooded Locations and Simulated Hydrographs (FLASH) project at NSSL, which capitalizes on the high-resolution (1km/5min) radar-based inputs from the NMQ/Q2 system. The four-month fellowship begins in January, 2014.

NSSL collaborated with the French team during HyMeX (Fall 2012) and used the NOAA X-Pol mobile radar to complement the research radar network. NSSL/CIMMS previously hosted an LTHE graduate intern, Martin Calianno, and is presently hosting Prof. Celine Lutoff, a social scientist. Flamig’s fellowship will strengthen collaboration between the teams to advance the state-of-the-science of flash flood prediction and societal impacts.

The 2013 Flash Flood and Intense Rainfall experiment (FFaIR)

A team from NSSL will partner with the NOAA Hydrometeorological Testbed at the Weather Prediction Center to host the 1st annual Flash Flood and Intense Rainfall Experiment (FFaIR). FFaIR will explore using high-resolution atmospheric and hydrologic models to improve short-term forecasts of both precipitation amounts and flash flooding. The project runs from July 8-26, 2013.

NSSL’s Flooded Locations And Simulated Hydrographs (FLASH) system will be one of several modeling systems evaluated during FFaIR. The FLASH system uses radar-estimated rainfall from NSSL’s National Mosaic and QPE System (NMQ/Q2) as input into the CREST (Coupled Routing and Excess STorage) hydrologic model. FLASH then creates real-time 6-hour forecasts on a 1km grid that is updated every 15 minutes.

The 2013 FFaIR experiment will provide, for the first time, a pseudo-real time environment where participants from across the weather enterprise can explore the interface of meteorology and hydrology. Working together through the forecast process will foster collaboration between National Centers for Environmental Prediction, National Weather Service Forecast Offices, NOAA labs, and the academic community.