Development and Testing of a Layer Precipitable Water Product to Aid Forecasting of Heavy Precipitation and Flooding

Forecasters have long used precipitable water products to aid forecasting of heavy precipitation and flooding, especially along the west coast of continents, where atmospheric rivers make landfall. Two of the most common products are GOES water vapor imagery, which shows mid- to upper-level water vapor, and total precipitable water products from polar-orbiting microwave sensors, which allow the detection of total column water vapor through clouds. A deficiency of these products is that they contain little information about the vertical distribution of the water vapor. Recent instruments and techniques, such as NOAA's Microwave Integrated Retrieval System (MIRS) and NASA's Atmospheric Infrared Sounder (AIRS), allow the retrieval of water vapor profiles. We have developed a four-layer precipitable water product (surface to 850 hPa, 850 hPa to 700 hPa, 700 hPa to 500 hPa, and 500 hPa to 300 hPa), which we call Layer Precipitable Water. The product is produced at 3 h intervals from MIRS and AIRS retrievals; it covers the Earth from 71°N to 71°S. It is available in real time in AWIPS format, so that forecasters can easily access the product. The product has undergone testing and evaluation in 2013 by NWS forecasters on the U.S. west coast, in Alaska, and in Puerto Rico via transition activities with the NASA/SPoRT program. At the conference, details of the product's development will be presented along with forecaster evaluations of the usefulness of the product in forecasting heavy rain and flooding.