83rd Annual

Tuesday, 11 February 2003: 8:45 AM
From Satellite Quantitative Precipitation Estimates (QPE) to Nowcasts for extreme precipitation events
Roderick A. Scofield, NOAA/NESDIS, Camp Springs, MD; and R. J. Kuligowski and C. Davenport
Poster PDF (235.7 kB)
The Satellite Analysis Branch (SAB) of NESDIS provides satellite derived QPEs for heavy rain or snow (including Lake Effect) over the contiguous U.S. and Puerto Rico. SAB's efforts concentrate primarily on locations where there is a potential for or occurrence of flash floods or heavy precipitation. The estimates are sent via the Advanced Weather Interactive Processing System (AWIPS) as part of the satellite-derived precipitation message (SPENES). The SPENES message also contains manually produced guidance on satellite analysis, trends, and short range forecasts (Nowcasts). SAB's Home Page that contains graphics products of these estimates is located at: " http://www.ssd.noaa.gov ". Heavy rainfall estimates from the Automatic Hydro- Estimator (H-E) have replaced many of the estimates computed interactively on the Interactive Flash Flood Analyzer (IFFA). An advantage of the H-E is its ability to vastly improve the spatial and temporal coverage of satellite precipitation estimates while improving timeliness. The H-E should be on AWIPS by the time of this 2003 Amercan Meteorological Society Conference.

A natural extension of the H-E is its evolution into an automatic H-E Nowcaster. However, this is not an easy task since one of the greatest challenges of an operational meteorologist is the short term prediction of the direction and speed of movement of Mesoscale Convective Systems (MCS). Propagation is the controlling influence on the movement of MCSs. At this time, the mechanisms of storm propagation are minimally understood. Any 3 hour Nowcast algorithm must take into account propagation characteristics of MCSs. In the spirit of NCAR's (National Center for Atmospheric Research) radar-driven Auto-nowcast system, an initial attempt at developing a satellite-driven H-E Nowcaster is presented. The following briefly describes the H- E Nowcaster process: (a) the speed and direction of the coldest portions (or most active) of the convective systems are measured on the latest satellite imagery; (b) this speed and direction are used to extrapolate the current estimated rainfall rates from the H-E out to 3 hours; (c) in forward propagating events, heaviest rainfall areas are correlated best to the mean cloud-layer shear vector (i.e., moves in the direction of 850-300 thickness isopleths, (d) for regenerative convective systems (e.g. back building, quasi-stationary, forward moving meso beta) (Corfidi et al, Chappell, Shi and Scofield) the growth and movement of individual clusters must be considered in the computation process, and (5) trend and expectancy guidelines are used to anticipate the evolution of the convective systems for the next 3 hours and are used to adjust the extrapolated rainfall. In addition to the GOES (Geostationary Operational environmental Satellite) infrared (IR) and visible (VIS) imagery and various POES (polar orbiting environmental satellite) microwave data, the H-E Nowcaster will make use of 6.7 um GOES Water Vapor imagery, GOES derived products and Sounder data, SSM/I data, the NOAA 15/16 AMSU, and TRMM data, and blends of various satellite data. WSR-88D data will assist in the diagnostics of storm evolution and be used as a boundary detector to help determine where MCS will propagate.

Home pages that contain automatic Flash flood estimates (around the world) and future Nowcasts are on the NESDIS Flash Flood Home Page: "http://orbit35i.nesdis.noaa.gov/arad/ht/ff".

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