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Tropical Storm Paulette Forecast Discussion Number 17
2020-09-11 04:51:20| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Thu Sep 10 2020 000 WTNT42 KNHC 110251 TCDAT2 Tropical Storm Paulette Discussion Number 17 NWS National Hurricane Center Miami FL AL172020 1100 PM AST Thu Sep 10 2020 Paulette has been fighting off intense vertical wind shear, which is analyzed by UW-CIMSS to be on the order of 35-40 kt out of the southwest. Deep convection with cold cloud tops of -70 to -80 degrees C have persisted near and to the northeast of the center throughout the evening. A late arriving ASCAT overpass revealed that Paulette is stronger than previously analyzed, with believable wind vectors of 50-55 kt in the northeastern quadrant. There were some values even higher than these. However, the ASCAT ambiguities and satellite imagery suggest most of those are either rain contaminated or too close to the edge of the ASCAT pass to be trustworthy. Nonetheless, the other values indicate that the initial intensity is now at least 55 kt. The SHIPS guidance suggests that the current shear over Paulette will begin to gradually decrease tomorrow and continue to decrease into the weekend. By late Saturday the guidance indicates the shear could fall to 10 kt or less. By that time, the cyclone is forecast to be traversing over waters with SSTs near 29 C. The only negative environmental factor could be some dry air in the vicinity of the system. However that same dry air has not seemed to have that much of an effect on Paulette as of late. With shear expected to remain fairly strong the next 24 h, no strengthening is anticipated during that time. After 24 h, Paulette should gradually intensify into early next week. The NHC intensity forecast for this advisory has been increased across the board. In the near term this change is due to the adjusted initial intensity. Beyond 24 h, the latest NHC forecast is close to a blend of the multi-model consensus values, including the HFIP corrected consensus and the Florida State Superensemble. Paulette is now moving northwest, or 305/09 kt. There is no change to the forecast track reasoning from the previous advisory. The forecast models are in good agreement between a generally northwest to west-northwestward motion over the next 3-4 days as the cyclone is steered around a subtropical ridge to its north. Around day 4, about the same time the system would be making its closest approach to Bermuda, a turn to the northeast is expected as the system rounds the western periphery of the ridge. The latest NHC track forecast is little changed from the previous one, and is near the tracks of the various consensus aids. It should be noted that there is sufficient spread in the track guidance such that it is too soon to know what types of impacts Paulette could have on Bermuda early next week. Key Messages: 1. Paulette is expected to approach Bermuda as a hurricane this weekend and make its closest approach to the island on Monday and Tuesday. While the exact details of Paulette's track and intensity near the island are not yet known, the risk of strong winds, storm surge, and heavy rainfall on Bermuda continues to increase. 2. Swells produced by Paulette are expected to affect portions of the Leeward Islands, the Greater Antilles, the Bahamas, Bermuda, and the southeastern United States into the weekend. These swells could cause life-threatening surf and rip current conditions. FORECAST POSITIONS AND MAX WINDS INIT 11/0300Z 22.7N 50.9W 55 KT 65 MPH 12H 11/1200Z 23.4N 52.4W 55 KT 65 MPH 24H 12/0000Z 24.6N 54.1W 55 KT 65 MPH 36H 12/1200Z 26.1N 55.8W 60 KT 70 MPH 48H 13/0000Z 27.6N 57.6W 65 KT 75 MPH 60H 13/1200Z 28.9N 59.9W 70 KT 80 MPH 72H 14/0000Z 30.0N 62.3W 80 KT 90 MPH 96H 15/0000Z 32.6N 65.0W 85 KT 100 MPH 120H 16/0000Z 35.0N 62.5W 90 KT 105 MPH $$ Forecaster Latto
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