Extended Abstract (16K)P1.62
Climatological study of the gulf stream's impact on tropical cyclone intensity
Robert J. Bright, North Carolina State University, Raleigh, NC; and L. Xie and L. J. Pietrafesa
Tropical cyclone (TC) intensity prediction remains one of the most challenging problems facing scientists and forecasters. This is mainly due to our lack of understanding of the complex coupling between the ocean-atmosphere system as well as a shortage of data over the open oceans. The importance of air-sea interaction in affecting the intensity changes of TCs has been well documented. Warm ocean currents such as the Gulf Stream (GS) provide TCs with abundant heat and moisture. This study utilized historical storm data and satellite imagery to analyze the intensity changes and storm-related characteristics (type of track over GS, intensity prior to GS, and month of occurrence) of 45 coastal and landfalling TCs from Florida to North Carolina from 1951 to 2000. It was found that 76% of the TCs intensified based on minimum central pressure (MCP) and 82% either intensified or maintained their intensity based on maximum wind speed (MWS) over the GS. Thirty-one of the cases were further classified as either intensifying (24) or weakening (7) according to a criteria combining both MCP and MWS changes. The strengthening cases were further categorized according to their intensification rates and of these, 14 and six were found to have moderately and rapidly intensified respectively. When the 28 TCs that intensified according to either MCP and MWS or MWS only were normalized to the 42 cases that could either be classified as either intensifying, maintaining, or weakening, 76% were Category 2 strength or weaker. Also, when normalized to the 42 non-contradictory cases, 83% crossed the GS between May and July. Thus, it appears that weaker TCs (Category 2 or lower) and those occurring earlier in the season are more positively influenced by the GS. However, major (Category 3, 4, and 5) hurricanes are more likely to intensify rapidly once intensification over the GS is triggered.
Poster Session 1, Tropical Cyclones, Large-scale Dynamics and Convection
Monday, 29 April 2002, 11:00 AM-12:30 PM
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