Preliminary assessment of the utility of ASCAT wind vector retrievals at the Tropical Prediction Center/National Hurricane Center

Europe's first polar-orbiting operational meteorological satellite system, METOP-A, was successfully launched on October 19, 2006. The METOP-A satellite carries as part of its payload the Advanced Scatterometer (ASCAT). ASCAT is the first officially operational active microwave sensor capable of providing near-surface ocean wind field measurements. ASCAT is designed to retrieve the wind speed and direction near the ocean surface and builds upon the experience gained from the C-band scatterometers onboard the European ERS-1 and ERS-2 research satellites. ASCAT therefore represents a successful transition of a research capability to operations.

Ocean surface vector wind (OSVW) retrievals from the ASCAT instrument have been available in near real time at the Tropical Prediction Center/National Hurricane Center (TPC/NHC) since late June 2007. ASCAT does not duplicate the capabilities of the NASA QuikSCAT, due to ASCAT's narrower data swaths, coarser resolution (and therefore lesser sensitivity to high wind speeds), and reduced sensitivity to rain. Therefore, while though TPC/NHC forecasters have become quite familiar with the strengths and weaknesses of QuikSCAT, an evaluation of the utility of ASCAT at TPC/NHC is ongoing to determine its particular strengths and weaknesses. The most obvious difference with ASCAT is the significantly fewer passes over tropical cyclones and other weather features of interest due to the lesser data coverage. The ASCAT processing by NOAA/NESDIS and the display capabilities at TPC/NHC have been evolving since the data first became available in near real time, and these changes have greatly affected the utility of ASCAT when its data swath does contain the center of a tropical cyclone. An assessment of ASCAT retrievals in cool season gap wind events near the coast of Central America, within the marine forecast and warning area of responsibility of TPC's Tropical Analysis and Forecast Branch (TAFB), is also underway. At the conference we will present quantitative results regarding overpass frequencies and ASCAT-derived maximum wind speed estimates for tropical cyclones and gap wind events. In addition, we will present statistical comparisons between winds derived from ASCAT, QuikSCAT, conventional surface observations, and model analyses.