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Tropical Storm Paulette Forecast Discussion Number 6
2020-09-08 10:35:33| National Hurricane Center (Atlantic)
Issued at 500 AM AST Tue Sep 08 2020 000 WTNT42 KNHC 080835 TCDAT2 Tropical Storm Paulette Discussion Number 6 NWS National Hurricane Center Miami FL AL172020 500 AM AST Tue Sep 08 2020 GOES-16 Proxy-VIS and enhanced BD-curve infrared imagery reveals that Paulette's cloud pattern has continued to improve during the past several hours. Specifically, the developing inner core is much more symmetric with new bursts of deep convection (-76C cloud tops) near the surface circulation center. Subsequently, subjective and objective satellite intensity estimates support an initial intensity of 45 kt. The global models and the statistical-dynamical intensity guidance indicate increasing southwesterly shear commencing later today. So, only modest strengthening is shown in the NHC foreast during next 24 hours. On Friday, the shear stiffens and becomes less diffluent as the cyclone approaches the high amplitude mid-Atlantic TUTT. Therefore, Gradual weakening is expected to occur at that time. Beyond day 3, there are some mixed signals, specifically in the GFS/FV3 and ECMWF SHIPS output. The GFS/FV3 continues to indicate strong southwesterly shear through day 5 further weakening Paulette to a depression around day 4. The ECMWF SHIPS, however, shows a more southerly and diffluent upper wind pattern supporting reintensification after day 4. The intensity forecast sides with that latter solution and also agrees with the HCCA intensity multi-model indicating the same intensity trend. The initial motion is estimated to be northwestward, or 325/5 kt. The rather weak synoptic steering pattern consists of a large mid- to upper-level low just west of the Canary Islands and ridging to the northwest of the cyclone. During the next couple of days, the large-scale models show the upper low filling and lifting northeastward, allowing the subtropical ridge to build in behind the departing upper low from the western Atlantic. This change in the pattern should cause Paulette to turn west-northwestward on Wednesday and continue moving in this general motion through early Saturday. Through the remaining portion of the period, the global models indicate a major shortwave trough moving off of the northeast coast of the U.S. and breaking down the western extent of the subtropical ridge/Bermuda high. This growing weakness in the ridge should cause Paulette to turn toward the northwest early Sunday. The official track forecast is a little bit slower and to the right of the previous forecast after day 3, and is close to the various consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 08/0900Z 18.1N 42.8W 45 KT 50 MPH 12H 08/1800Z 18.6N 43.6W 50 KT 60 MPH 24H 09/0600Z 19.5N 45.0W 55 KT 65 MPH 36H 09/1800Z 20.2N 46.9W 55 KT 65 MPH 48H 10/0600Z 20.5N 48.9W 55 KT 65 MPH 60H 10/1800Z 20.8N 50.4W 50 KT 60 MPH 72H 11/0600Z 21.3N 51.9W 50 KT 60 MPH 96H 12/0600Z 22.9N 54.9W 45 KT 50 MPH 120H 13/0600Z 25.4N 57.8W 50 KT 60 MPH $$ Forecaster Roberts
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