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Chill falls over the Atlantic as the official season heads towards close
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| #1016388 (Received by flhurricane at: 4:57 AM 13.Sep.2020) TCDAT2 Hurricane Paulette Discussion Number 26 NWS National Hurricane Center Miami FL AL172020 500 AM AST Sun Sep 13 2020 Over the past 6 hours, conventional and passive microwave satellite data indicate that very little change to Paulette`s overall convective cloud pattern and inner-core structure has occurred. A recent GMI pass indciated that the inner-core convection remains somewhat disheveled due to a narrow but pronounced band of dry air having penetrated the mid-levels of the cyclone. However, the low-level eye feature remains intact with a diameter of at least 30 nmi. Given the little change in structure since the previous reconnaissance mission, the intensity is being maintained at 65 kt. Another Air Force Reserve Hurricane Hunter aircraft will be investigating Paulette later this morning to provide a better estimate of the hurricane`s intensity. The initial motion estimate remains west-northwestward or 300/12 kt. Overall, there is no significant change to the previous track forecast or reasoning. The global and regional models are in excellent agreement on Paulette passing over or near Bermuda during the 24-36 hour period as the cyclone rounds a sharp east-to-west oriented subtropical ridge located near and due east of Bermuda. After passing Bermuda and moving north of the ridge in about 36 hours, Paulette is forecast to accelerate northeastward ahead of an approaching deep-layer trough and associated surface cold front. There is one important feature to mention -- the official forecast track is west of the latest 0600 UTC interpolated models due to the interpolated model tracks taking the center of Paulette at least 30 nmi east of Bermuda. In contrast, the GFS, UKMET, and ECMWF are less than 6 nmi apart at 12-48 hours, and that consensus brings the hurricane across or just west of Bermuda in about 30 hours. Therefore, the new NHC official track forecast is essentially just an update and extension of the previous advisory track, and lies just west of the tightly packed NHC guidance envelope. Environmental conditions appear favorable to Paulette to strengthen during the next 72 hours or so, with only occasional intrusions of dry mid-level air briefly interrupting the intensification process. The ragged inner core structure will likely delay intensification this morning, but by the this afternoon and continuing into Monday, the vertical shear is forecast by the global models to decrease to near zero, which should allow for significant strengthening to occur. In fact, it highly probable that Paulette will continue to intensify as the hurricane passes over Bermuda. By 48 hours when the hurricane is expected to be north of Bermuda, baroclinic interaction with the aforementioned deep-layer trough is forecast to aid in the intensification process with Paulette possibly becoming a major hurricane around 72 hours. Thereafter, increasing vertical wind shear in excess of 25 kt should gradually weaken the cyclone. It is possible that by 96 hours or so, Paulette could merge with a frontal system and become a powerful extratropical low. For now, however, Paulette is forecast to remain just ahead of the front within the warm sector of a flat frontal wave. The official intensity forecast is similar to the previous advisory, and is near the upper end of intensity guidance throughout the 120-h forecast period. Key Messages: 1. Paulette is expected to approach Bermuda as a hurricane on Sunday and will be near the island Sunday night and Monday. A prolonged period of strong winds, storm surge, and heavy rainfall is expected on Bermuda beginning Sunday evening, and a hurricane warning is in effect for the island. Preparations to protect life and property should be rushed to completion. 2. Swells produced by Paulette are affecting portions of the Leeward Islands, the Greater Antilles, the Bahamas, Bermuda, and the east coast of the United States. These swells could cause life-threatening surf and rip current conditions. FORECAST POSITIONS AND MAX WINDS INIT 13/0900Z 29.4N 60.8W 65 KT 75 MPH 12H 13/1800Z 30.2N 62.5W 70 KT 80 MPH 24H 14/0600Z 31.8N 64.4W 80 KT 90 MPH 36H 14/1800Z 34.0N 65.0W 90 KT 105 MPH 48H 15/0600Z 35.9N 62.4W 95 KT 110 MPH 60H 15/1800Z 37.8N 57.9W 95 KT 110 MPH 72H 16/0600Z 39.3N 54.0W 90 KT 105 MPH 96H 17/0600Z 42.0N 46.0W 80 KT 90 MPH 120H 18/0600Z 43.8N 40.0W 65 KT 75 MPH $$ Forecaster Stewart |
