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Hurricane Sam Forecast Discussion Number 38
2021-10-02 04:41:43| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Fri Oct 01 2021 000 WTNT43 KNHC 020241 TCDAT3 Hurricane Sam Discussion Number 38 NWS National Hurricane Center Miami FL AL182021 1100 PM AST Fri Oct 01 2021 The satellite appearance of Sam has degraded slightly during the past few hours, with the eye becoming more cloud filled and the eyewall cloud tops become a little less symmetric. Various subjective and objective satellite intensity estimates are in the 115-130 kt range, and based on the slight decay the initial intensity is lowered to 125 kt. An Air Force Reserve Hurricane Hunter aircraft is currently enroute to investigate Sam. Sam is making its forecast turn toward the north-northeast with the initial motion now 020/15 kt. There is no change to the track forecast philosophy and little change to the forecast track from the previous advisory. The steering flow between a deep-layer ridge to the northeast and east of Sam and a large mid-latitude low pressure system centered over Atlantic Canada should cause Sam to turn northeastward during the next 24 h, followed by a continued northeastward motion as the system become entrained in southwesterly mid-latitude flow. The models are in fairly good agreement, although there is some spread in both the track and the speed due to model differences in the cyclone's evolution as it becomes extratropical. The new forecast track lies close to the center of the guidance envelope and the various consensus models. Slow weakening is expected to continue during the next 2-3 days as Sam moves over cooler sea surface temperatures and begins extratropical transition. This is likely to be complete by 72 h, with the global models suggesting that Sam will evolve into a warm-core seclusion extratropical low. Based on this and the guidance, it is likely that the cyclone will maintain hurricane strength until after the transition is done. By the end of the forecast period, the extratropical low is expected to be decaying over the far north Atlantic. The new intensity forecast lies at the upper edge of the intensity guidance. Key Messages: 1. Swells generated by Sam will impact the northern Leeward Islands the Greater Antilles, the Bahamas, and Bermuda during the next couple of days. Swells are expected to reach the United States east coast and Atlantic Canada on Saturday. These swells could cause life-threatening surf and rip current conditions. Please consult products from your local weather office. 2. Tropical storm conditions are possible on Bermuda during the next several hours, and a Tropical Storm Warning is in effect for the island. FORECAST POSITIONS AND MAX WINDS INIT 02/0300Z 31.4N 61.2W 125 KT 145 MPH 12H 02/1200Z 33.5N 60.2W 120 KT 140 MPH 24H 03/0000Z 35.8N 58.3W 110 KT 125 MPH 36H 03/1200Z 37.7N 55.6W 100 KT 115 MPH 48H 04/0000Z 39.6N 52.2W 95 KT 110 MPH 60H 04/1200Z 43.0N 47.3W 90 KT 105 MPH 72H 05/0000Z 47.2N 43.2W 80 KT 90 MPH...POST-TROP/EXTRATROP 96H 06/0000Z 50.5N 38.0W 65 KT 75 MPH...POST-TROP/EXTRATROP 120H 07/0000Z 54.5N 27.5W 50 KT 60 MPH...POST-TROP/EXTRATROP $$ Forecaster Beven
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