Satellite and Model Layer Precipitable Water Products to Support Forecasting of Heavy Precipitation Events

The Cooperative Institute for Research in the Atmosphere (CIRA) CIRA has developed an advected layered precipitable water (ALPW) product that allows forecasters to see the vertical distribution of water vapor in near real-time. The ALPW product is created for four atmospheric layers (surface-850, 850-700, 700-500, and 500-300 hPa), and is currently updated every three hours. ALPW is commonly used by the NOAA Weather Prediction Center (WPC) in Mesoscale Precipitation Discussions to alert forecasters to flooding and National Hurricane Center (NHC) for tropical wave analysis. ALPW is created by using NOAA investments in polar orbiting satellite sounding retrievals from passive microwave radiances, in particular, the Microwave Integrated Retrieval System (MiRS). Data from the Suomi-NPP, NOAA-18 and -19, Metop-A and –B, and Defense Meteorological Program (DMSP) F17 and F18 spacecraft are merged with model winds to create the LPW product. NOAA-20 products may be incorporated by the time of the meeting. The NOAA JPSS Proving Ground and Risk Reduction program supports the development of advanced blending algorithms and the distribution of the product to NOAA national centers and select Weather Forecast Offices. The NASA Short-term Prediction Research and Transition Center (SPoRT) assists CIRA with ALPW distribution to users.

The question of how the satellite-derived ALPW compares to model water vapor fields is being investigated via the NOAA Hydrometeorology Testbed. LPW is derived from both the Global Forecast System (GFS) and High Resolution Rapid Refresh (HRRR) models to match the ALPW product time and grid. Does ALPW provide any guidance on whether the model water vapor is too high or low and is this reflected in model precipitation forecasts? User feedback from the Flash Flood and Intense Rainfall (FFaIR) experiment at WPC in the summer of 2018 will be presented. Validation of the different water vapor products against radiosondes will be shown.