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Hurricane Sam Forecast Discussion Number 41
2021-10-02 22:37:19| National Hurricane Center (Atlantic)
Issued at 500 PM AST Sat Oct 02 2021 000 WTNT43 KNHC 022037 TCDAT3 Hurricane Sam Discussion Number 41 NWS National Hurricane Center Miami FL AL182021 500 PM AST Sat Oct 02 2021 The hurricane is gradually losing strength. Satellite images show that the eye has become more cloud filled, with Sam's ring of deep convection becoming less intense and two main towers in the southeast and northwest quadrants. Still, the tropical cyclone is quite a sight even on full-disk images with a large distinctive cloud pattern. The latest intensity estimates have decreased, so the initial wind speed is set to 110 kt, with higher uncertainty than average in this figure due to recent recon/satellite differences. Sam wisely has avoided much shear during its 10-day journey across the Atlantic, and it could remain a major hurricane for another day or so. However, in 36 hours or so, the system should move north of the Gulf Stream, which would normally cause a dramatic weakening. But in this case, a favorable mid-latitude trough interaction should cause Sam to transition into a large and powerful extratropical low by 60 hours. After that, it loses its baroclinic forcing and should gradually spin down over the far North Atlantic southwest of Iceland. Guidance is in fairly solid agreement on this scenario, and the new intensity forecast is mostly just an update of the previous one, remaining close to the consensus. The system continues moving northeastward at about 15 kt. Sam should move faster to the northeast by Monday as it encounters stronger wind flow between a deep-layer ridge to the east and a large mid- to upper-level low over Atlantic Canada. The track will weave leftward a bit at longer ranges due to the upper trough pulling the extratropical system north-northeastward at times, and eventually another trough has a similar tug by day 5. There are no significant changes to the previous forecast with guidance in close agreement. Key Messages: 1. Swells generated by Sam will impact the northern Leeward Islands, the Greater Antilles, the Bahamas, Bermuda, the eastern United States and Atlantic Canada for the next couple of days. These swells could cause life-threatening surf and rip current conditions. Please consult products from your local weather office. FORECAST POSITIONS AND MAX WINDS INIT 02/2100Z 35.4N 58.2W 110 KT 125 MPH 12H 03/0600Z 36.8N 56.5W 100 KT 115 MPH 24H 03/1800Z 38.6N 53.6W 95 KT 110 MPH 36H 04/0600Z 40.8N 49.5W 90 KT 105 MPH 48H 04/1800Z 44.7N 44.0W 85 KT 100 MPH 60H 05/0600Z 49.3N 40.2W 75 KT 85 MPH...POST-TROP/EXTRATROP 72H 05/1800Z 51.6N 38.5W 65 KT 75 MPH...POST-TROP/EXTRATROP 96H 06/1800Z 53.0N 32.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 120H 07/1800Z 60.0N 28.0W 40 KT 45 MPH...POST-TROP/EXTRATROP $$ Forecaster Blake
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