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Tropical Depression Victor Forecast Discussion Number 15
2021-10-03 04:46:48| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Sat Oct 02 2021 000 WTNT45 KNHC 030246 TCDAT5 Tropical Depression Victor Discussion Number 15 NWS National Hurricane Center Miami FL AL202021 1100 PM AST Sat Oct 02 2021 Victor remains a tropical cyclone this evening, with pulsing deep convection occuring primarily north of the well-defined low-level center. However, this convection lacks much organization and is continually being stripped away by around 20 kt of south-southwesterly vertical wind shear. Earlier this evening, there was an ASCAT-A pass valid at 2238 UTC which had peak wind retrievals of 25-30 kt to the northeast of the center. There was also a nearby moored ocean buoy that at 0000 UTC reported sustained winds of 28 kt with a pressure of 1006.7 mb also just northeast of Victor. The latest advisory intensity is thus being maintained at 30 kt but the minimum pressure was lowered a bit due to this in-situ buoy data. The 30 kt intensity also agrees with most recent TAFB Dvorak CI estimate from 0000 UTC. Ultimately the combination of southwesterly vertical wind shear and the associated entrainment of dry air will prove victorious against Victor, with the depression forecast to gradually weaken during the forecast period. The latest NHC intensity forecast still shows Victor becoming a remnant low by tomorrow evening, though 27 to 28 C sea surface temperatures could still support sheared convective bursts to the north of the low center into early next week. Victor's low-level wind field will also continue to spin down over the subsequent days, and the circulation is forecast to open up into a trough by Tuesday. The latest forecast is essentially unchanged from the previous one and is in good agreement with the consensus aids and deterministic model output. The depression continues to move to the northwest at 310/12 kt though with the occasional tug poleward by the convection on its northern side. This northwestward motion is expected to continue as Victor remains embedded in the flow around a low-level subtropical anticyclone to its northeast. The NHC track forecast continues to be in general agreement with the track guidance consensus, maintaining Victor on a similar forward motion until the system opens up into a trough in 2-3 days. FORECAST POSITIONS AND MAX WINDS INIT 03/0300Z 14.8N 38.9W 30 KT 35 MPH 12H 03/1200Z 16.3N 40.5W 30 KT 35 MPH 24H 04/0000Z 18.4N 42.4W 30 KT 35 MPH...POST-TROP/REMNT LOW 36H 04/1200Z 20.3N 44.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 05/0000Z 21.8N 46.4W 25 KT 30 MPH...POST-TROP/REMNT LOW 60H 05/1200Z 23.2N 48.3W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 06/0000Z...DISSIPATED $$ Forecaster Papin
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Tropical Depression Victor Forecast Discussion Number 14
2021-10-02 22:40:01| National Hurricane Center (Atlantic)
Issued at 500 PM AST Sat Oct 02 2021 000 WTNT45 KNHC 022039 TCDAT5 Tropical Depression Victor Discussion Number 14 NWS National Hurricane Center Miami FL AL202021 500 PM AST Sat Oct 02 2021 Victor was about out of time as a tropical cyclone, but a recent burst of deep convection about 60 n mi northeast of its center saved it from being declared a remnant low this afternoon. The cyclone continues to struggle with dry air and strong southwesterly shear. Scatterometer overpasses missed Victor today, so the initial advisory intensity of 30 kt is based on the latest CI-value from the TAFB Dvorak estimate. The depression is moving northwest, or 310/12 kt in the flow to the southwest of a subtropical ridge. This general motion is forecast to continue until Victor dissipates in a few days. The latest NHC track forecast is little changed from the previous one, and is near the various multimodel track consensus solutions. Victor refused to succumb to the strong shear and dry air over the past 24 h. However, these hostile conditions are not forecast to abate over the cyclone for the foreseeable future. Therefore, the depression should struggle to maintain persistent deep convection, and the cyclone could degenerate to a remnant low at any time over the next couple of days. The global model guidance is in good agreement that Victor should gradually weaken early this week, and open into a tough of low pressure by Tuesday. The latest NHC intensity forecast is unchanged from the previous one, except for the timing of the system becoming a remnant low. FORECAST POSITIONS AND MAX WINDS INIT 02/2100Z 13.7N 38.0W 30 KT 35 MPH 12H 03/0600Z 14.9N 39.5W 30 KT 35 MPH 24H 03/1800Z 16.8N 41.6W 30 KT 35 MPH...POST-TROP/REMNT LOW 36H 04/0600Z 18.9N 43.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 04/1800Z 20.7N 45.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 60H 05/0600Z 22.5N 47.3W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 05/1800Z...DISSIPATED $$ Forecaster Latto
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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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Hurricane Sam Forecast Discussion Number 40
2021-10-02 16:51:40| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Sat Oct 02 2021 000 WTNT43 KNHC 021451 TCDAT3 Hurricane Sam Discussion Number 40 NWS National Hurricane Center Miami FL AL182021 1100 AM AST Sat Oct 02 2021 Sam has been an impressive hurricane during the past several days. The latest satellite imagery shows it remains a powerful system, with a well-defined eye and symmetric cloud pattern. In fact, since the plane left overnight, the eye has actually warmed, with little change in the eyewall convection. Thus the initial intensity will stay 115 kt, above the latest satellite classifications, but consistent with the earlier aircraft data and low bias of the Dvorak technique for much of the this storm. Sam is now in the top 10 for consecutive days as a category 4 hurricane or greater in the historical record, about the same as Matthew 2016. The hurricane is forecast to gradually lose strength during the next 36 hours or so while it remains over marginally warm waters, but in fairly light shear. In fact, some of the guidance decrease the shear overnight, which should allow Sam to keep much of its strength, provided it doesn't undertake an eyewall cycle. The new intensity forecast is higher in the first day or so, consistent with the latest model solutions. In about 2 days, Sam will cross the north wall of the Gulf Stream, and in 3 days is expected to spectacularly transition into a large hurricane-force post-tropical cyclone over the far north Atlantic. No changes were made to the end of the intensity forecast. Sam has turned northeastward at about 15 kt. The hurricane should accelerate later this weekend due to increasing flow between a deep-layer ridge to the east and a large mid- to upper-level low over Atlantic Canada. By midweek the system is forecast to turn more to the north-northeast as it becomes a spoke in a very large extratropical low over the far North Atlantic. The new forecast has shifted somewhat eastward during the first couple of days but ends up very near the last advisory by day 5. Key Messages: 1. Swells generated by Sam will impact the northern Leeward Islands, the Greater Antilles, the Bahamas, Bermuda, the eastern United States coast 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 02/1500Z 33.9N 59.3W 115 KT 130 MPH 12H 03/0000Z 35.6N 57.8W 105 KT 120 MPH 24H 03/1200Z 37.4N 55.3W 100 KT 115 MPH 36H 04/0000Z 39.2N 52.0W 95 KT 110 MPH 48H 04/1200Z 41.8N 47.3W 85 KT 100 MPH 60H 05/0000Z 46.0N 42.0W 80 KT 90 MPH 72H 05/1200Z 50.0N 38.5W 75 KT 85 MPH...POST-TROP/EXTRATROP 96H 06/1200Z 53.0N 33.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 120H 07/1200Z 59.0N 26.0W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Blake
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Hurricane Sam Forecast Discussion Number 39
2021-10-02 10:44:03| National Hurricane Center (Atlantic)
Issued at 500 AM AST Sat Oct 02 2021 000 WTNT43 KNHC 020843 TCDAT3 Hurricane Sam Discussion Number 39 NWS National Hurricane Center Miami FL AL182021 500 AM AST Sat Oct 02 2021 The Air Force Reserve Hurricane Hunters conducted their final mission into Sam a few hours ago and found that the hurricane is still of category 4 intensity, but the maximum winds have decreased some. The crew reported a peak 700-mb flight-level wind of 130 kt (equating to surface winds of 115-120 kt) and unflagged SFMR winds of 110-115 kt. Based on these wind data, Sam's intensity is now estimated to be 115 kt. This value is at the upper end of the latest satellite estimates, which range from 100-115 kt. The hurricane's central pressure has also risen to 945 mb. Sam is still moving toward the north-northeast with a motion of 020/15 kt. The hurricane is entering the area between a deep-layer ridge to the east and a large mid- to upper-level low over Atlantic Canada, and this flow should cause Sam to turn toward the northeast by tonight and then maintain that general heading for much of the forecast period. The storm is also expected to accelerate, reaching a peak forward speed of more than 25 kt in 60-72 hours. The track guidance is tightly clustered through day 3, but there is significantly more spread on days 4 and 5 due to uncertainty on exactly how Sam will interact with the aforementioned mid-/upper-level low. The NHC forecast has been placed near a blend of the GFS-ECMWF mean and the HCCA consensus aid, which necessitated a northward shift from the previous forecast only on days 4 and 5. Deep-layer southerly shear of 15-20 kt appears to be contributing to Sam's current weakening. Continued shear and cooler waters along Sam's path should lead to additional weakening in the coming days, although not at a rapid rate due to some baroclinic forcing. Global models suggest that Sam will begin extratropical transition in about 48 hours, with that process completing by 72 hours. The NHC intensity forecast closely follows the HCCA and IVCN consensus aids during Sam's tropical phase, but then transitions to a blend of the GFS and ECMWF global model guidance on days 3 through 5 during its extratropical phase. Sam is expected to continue producing hurricane-force winds through at least day 3, with more significant weakening occurring on days 4 and 5 once it is a vertically stacked occluded low. 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 today. These swells could cause life-threatening surf and rip current conditions. Please consult products from your local weather office. 2. Although the Tropical Storm Warning for Bermuda has been discontinued, a few wind gusts to tropical storm force will still be possible on the island during the morning. FORECAST POSITIONS AND MAX WINDS INIT 02/0900Z 32.8N 60.5W 115 KT 130 MPH 12H 02/1800Z 34.6N 59.3W 100 KT 115 MPH 24H 03/0600Z 36.6N 57.1W 95 KT 110 MPH 36H 03/1800Z 38.4N 54.2W 90 KT 105 MPH 48H 04/0600Z 40.7N 50.0W 85 KT 100 MPH 60H 04/1800Z 44.4N 44.8W 80 KT 90 MPH 72H 05/0600Z 48.9N 40.7W 75 KT 85 MPH...POST-TROP/EXTRATROP 96H 06/0600Z 53.4N 34.7W 55 KT 65 MPH...POST-TROP/EXTRATROP 120H 07/0600Z 58.7N 26.4W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Berg
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