THE IMPACT OF MULTISPECTRAL GOES-8 WIND INFORMATION ON ATLANTIC TROPICAL CYCLONE TRACK FORECASTS IN 1995 - PART II - NOGAPS FORECASTS

Experimental wind datasets were derived for two time periods (13-20 Ju ly and 24 August-10 September 1995) from GOES-8 observations processed at the University of Wisconsin Cooperative institute for Meteorologic al Satellite Studies (UW CIMSS). The first dataset was focused on Trop ical Storm Chantal, and the second dataset was focused on the multiple -storm environment that included Hurricanes Humberto, Iris, and Luis. Both datasets feature a processing and quality control strategy design ed to optimize the quantity and content of geostationary satellite-der ived winds in the vicinity of tropical cyclones. Specifically, the win ds were extracted from high-density targets obtained from multispectra l imagery, which included three water vapor bands (6.7, 7.0, and 7.3 m u m), infrared, and visible. The Navy Operational Global Atmospheric P rediction System (NOGAPS) was used as the vehicle to determine the imp act of these winds upon tropical cyclone track forecasts. During the 1 995 Atlantic hurricane season the NOGAPS forecasts were found to be qu ite skillful, displaying relative improvement of tropical cyclone posi tion error with respect to CLIPER (climate and persistence) of 20% at 24 h, 35% at 48 h, and 33% at 72 h. The NOGAPS data assimilation syste m was run with and without the high density GOES-8 winds for the two a forementioned time periods. The assimilation of these winds resulted i n significant improvements in the NOGAPS forecasts for Tropical Storm Chantal and Hurricane Iris and mixed results for Hurricanes Humberto a nd Luis. Overall, for all four cyclones, tie NOGAPS forecasts made wit h the use of the UW CIMSS winds displayed relative improvement of fore cast position error with respect to those made without the use of the UW CIMSS winds of 14% at 24 h, and 12% at both 48 and 72 h.