NOAA Deploys 2006 Hydrometeorological Testbed In Flood-Prone Western Watershed

December 28, 2005

NOAA's Weather and Water Mission includes goals for improving the predictability of floods to better protect the public from losses of life and property. Yet, the accuracy of quantitative precipitation estimation (QPE) and short range forecasts of precipitation (QPF) and flooding have shown disappointingly slow improvement over the last decade. The Hydrometeorological Testbed (HMT) is a concept designed to accelerate the testing and infusion of new technologies, models, and scientific results from the research community into daily forecasting operations of the National Weather Service, including NCEP, WFOs and River Forecast Centers.

HMT is a national effort (Ralph et al. 2005, Bulletin of the American Meteorological Society, pages 1619-1632), with partners throughout NOAA (, that will be implemented in different regions of the U.S. over the next decade. The first full-scale implementation of HMT, called HMT-West, targets California's flood-vulnerable American River Basin (ARB) near Sacramento. Experts consider Sacramento to be the Nation's foremost candidate to incur a New Orleans-level flood catastrophe ("Tempting fate: Are we next? --- Sacramento's flood peril highest in U.S.", Sacramento Bee, 30 October 2005). NOAA has been engaged in research addressing water management issues regarding this watershed for the past several years (e.g., " NOAA Advises California Water Managers on Improving QPF for Folsom Dam Operation").

Field activities for HMT-West will occur over the next 3-4 winter seasons. This report focuses on FY06 activities, which began on 1 December 2005 and will continue through 23 March 2006. Several research observing systems from NOAA's Earth System Research Laboratory/Physical Sciences Division (ESRL/PSD) and National Severe Storms Laboratory (NSSL) have been deployed to the region to support the HMT-West 2006 effort. Transportable and mobile scanning precipitation radars (polarimetric and Doppler) have been deployed to complement and fill gaps in the operational network. Additional remote sensors that have been deployed include wind profiling radars, precipitation profiling radars, and GPS sensors for measuring precipitable water vapor. Precipitation gauges, raindrop disdrometers, surface meteorological stations, soil moisture/temperature probes and stream level loggers are operating within the coverage areas of the scanning radars. Also, radiosondes are being released serially upwind of the area during storm episodes. In addition to the field observations, several high-resolution weather prediction models are being run by NOAA ESRL's Global Systems Division (GSD) to supplement the operational model guidance already available to the NWS.

HMT-West 2006 activities are being coordinated with several NWS partners such as the Hydrometeorological Prediction Center, the Office of Hydrology, the California/Nevada River Forecast Center, Western Region Headquarters and several Weather Forecast Offices in the region (Sacramento, Reno, Monterey). A daily conference call involving the NWS partners, as well as ESRL and NSSL staff, is conducted to discuss status and forecast issues associated with the project.

Precipitation totals in the ARB from 1 December through 28 December have been large, exceeding 25 inches of liquid. The early-season storms that produced this precipitation did not lead to any serious flooding but did serve to moisten the soils in the basin to the point that runoff from subsequent storms will increase, therefore heightening the threat of serious flooding. HMT-West 2006 is poised to sample these storms and aid in the forecasts of precipitation and warnings of flooding.

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