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Tropical Storm Victor Forecast Discussion Number 11

2021-10-02 04:46:02| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Fri Oct 01 2021 000 WTNT45 KNHC 020245 TCDAT5 Tropical Storm Victor Discussion Number 11 NWS National Hurricane Center Miami FL AL202021 1100 PM AST Fri Oct 01 2021 The structure of Victor this evening continues to degrade with the low-level center becoming decoupled from the mid- to upper-level circulation associated with the deeper convection. While the tropical storm does continue to produce a region of deep convection with cloud tops colder than -70 C, this activity is organized in a linear band that is now more than 150 n mi northeast of the exposed low-level center as seen on Proxy-Vis satellite imagery. Both ASCAT-B/C clipped the western half of Victor's circulation, showing peak winds of 40 kt on the far edge of the pass. In addition, the latest subjective and objective satellite intensity estimates have been falling this evening. The latest intensity for this advisory has been lowered to 50 kt this advisory, assuming the scatterometer data missed higher wind values to the northeast of Victor closer to the convection. However, given Victor's current structure, this estimate may still be generous. Now that the low-level cloud swirl is readily apparent on satellite imagery, it is somewhat easier to track Victor this evening, with the estimated motion still west-northwest at 290/11 kt. Because the cyclone is also becoming more vertically shallow, the primarily steering feature will be a large low-level subtropical ridge centered to the north, which should guide Victor on a general west-northwestward to northwestward heading for the next 2-3 days at a similar forward motion. The latest track guidance has shifted westward this cycle, likely in response to Victor being a weaker cyclone less coupled to the deep convection. The latest NHC track forecast was also shifted a bit west over the forecast period, staying closer to the consensus aids HCCA and TVCA, though it is worth nothing this is still not as far west as the latest GFS or ECMWF runs. While the deep-layer 200-850 hPa vertical wind shear has not been prohibitively strong today (15-20 kt), more substantial mid-level shear underneath the outflow layer (25-30 kt) appears to be responsible for the current disheveled appearance of Victor. This shear is related to a large upper-level cutoff low upstream of the tropical storm. Even though the current shear is not expected to increase much more in the short-term, the mid-level environment over Victor is expected to continue drying as the existing shear will import very dry air upstream into the core of the cyclone. All of the guidance responds to these unfavorable conditions by gradually weakening Victor over the next few days, and the latest NHC intensity forecast has been lowered a bit more compared to the previous advisory. While pulses of deep convection are likely to continue north of Victor over the next several days, the circulation is expected to gradually lose definition, and the global and high-res regional hurricane models now open up the system into a trough between 72-96 hours. The latest NHC intensity forecast now follows suit, showing dissipation by 96 hours. FORECAST POSITIONS AND MAX WINDS INIT 02/0300Z 12.3N 35.3W 50 KT 60 MPH 12H 02/1200Z 13.2N 36.9W 45 KT 50 MPH 24H 03/0000Z 14.6N 38.7W 40 KT 45 MPH 36H 03/1200Z 16.5N 40.6W 40 KT 45 MPH 48H 04/0000Z 18.5N 42.6W 35 KT 40 MPH 60H 04/1200Z 20.6N 44.7W 35 KT 40 MPH 72H 05/0000Z 22.2N 46.5W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 06/0000Z...DISSIPATED $$ Forecaster Papin

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Tropical Storm Victor Forecast Advisory Number 11

2021-10-02 04:42:30| National Hurricane Center (Atlantic)

Issued at 0300 UTC SAT OCT 02 2021 000 WTNT25 KNHC 020242 TCMAT5 TROPICAL STORM VICTOR FORECAST/ADVISORY NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL AL202021 0300 UTC SAT OCT 02 2021 THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT. TROPICAL STORM CENTER LOCATED NEAR 12.3N 35.3W AT 02/0300Z POSITION ACCURATE WITHIN 25 NM PRESENT MOVEMENT TOWARD THE WEST-NORTHWEST OR 290 DEGREES AT 11 KT ESTIMATED MINIMUM CENTRAL PRESSURE 999 MB MAX SUSTAINED WINDS 50 KT WITH GUSTS TO 60 KT. 50 KT....... 50NE 0SE 0SW 0NW. 34 KT.......120NE 60SE 0SW 120NW. 12 FT SEAS..210NE 120SE 150SW 210NW. WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT. REPEAT...CENTER LOCATED NEAR 12.3N 35.3W AT 02/0300Z AT 02/0000Z CENTER WAS LOCATED NEAR 12.1N 35.0W FORECAST VALID 02/1200Z 13.2N 36.9W MAX WIND 45 KT...GUSTS 55 KT. 34 KT...120NE 40SE 0SW 80NW. FORECAST VALID 03/0000Z 14.6N 38.7W MAX WIND 40 KT...GUSTS 50 KT. 34 KT...120NE 0SE 0SW 90NW. FORECAST VALID 03/1200Z 16.5N 40.6W MAX WIND 40 KT...GUSTS 50 KT. 34 KT...100NE 0SE 0SW 60NW. FORECAST VALID 04/0000Z 18.5N 42.6W MAX WIND 35 KT...GUSTS 45 KT. 34 KT... 80NE 0SE 0SW 60NW. FORECAST VALID 04/1200Z 20.6N 44.7W MAX WIND 35 KT...GUSTS 45 KT. 34 KT... 80NE 0SE 0SW 0NW. FORECAST VALID 05/0000Z 22.2N 46.5W...POST-TROP/REMNT LOW MAX WIND 30 KT...GUSTS 40 KT. EXTENDED OUTLOOK. NOTE...ERRORS FOR TRACK HAVE AVERAGED NEAR 150 NM ON DAY 4 AND 175 NM ON DAY 5...AND FOR INTENSITY NEAR 15 KT EACH DAY OUTLOOK VALID 06/0000Z...DISSIPATED REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 12.3N 35.3W NEXT ADVISORY AT 02/0900Z $$ FORECASTER PAPIN

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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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Hurricane Sam Forecast Advisory Number 38

2021-10-02 04:40:05| National Hurricane Center (Atlantic)

Issued at 0300 UTC SAT OCT 02 2021 000 WTNT23 KNHC 020239 TCMAT3 HURRICANE SAM FORECAST/ADVISORY NUMBER 38 NWS NATIONAL HURRICANE CENTER MIAMI FL AL182021 0300 UTC SAT OCT 02 2021 CHANGES IN WATCHES AND WARNINGS WITH THIS ADVISORY... NONE. SUMMARY OF WATCHES AND WARNINGS IN EFFECT... A TROPICAL STORM WARNING IS IN EFFECT FOR... * BERMUDA A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 36 HOURS. HURRICANE CENTER LOCATED NEAR 31.4N 61.2W AT 02/0300Z POSITION ACCURATE WITHIN 15 NM PRESENT MOVEMENT TOWARD THE NORTH-NORTHEAST OR 20 DEGREES AT 15 KT ESTIMATED MINIMUM CENTRAL PRESSURE 940 MB MAX SUSTAINED WINDS 125 KT WITH GUSTS TO 150 KT. 64 KT....... 50NE 45SE 35SW 35NW. 50 KT....... 80NE 90SE 70SW 70NW. 34 KT.......150NE 180SE 130SW 130NW. 12 FT SEAS..270NE 315SE 300SW 270NW. WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT. REPEAT...CENTER LOCATED NEAR 31.4N 61.2W AT 02/0300Z AT 02/0000Z CENTER WAS LOCATED NEAR 30.7N 61.5W FORECAST VALID 02/1200Z 33.5N 60.2W MAX WIND 120 KT...GUSTS 145 KT. 64 KT... 50NE 45SE 35SW 35NW. 50 KT... 80NE 90SE 60SW 60NW. 34 KT...150NE 180SE 130SW 130NW. FORECAST VALID 03/0000Z 35.8N 58.3W MAX WIND 110 KT...GUSTS 135 KT. 64 KT... 50NE 45SE 35SW 35NW. 50 KT... 80NE 90SE 70SW 70NW. 34 KT...150NE 180SE 140SW 140NW. FORECAST VALID 03/1200Z 37.7N 55.6W MAX WIND 100 KT...GUSTS 120 KT. 64 KT... 40NE 50SE 40SW 35NW. 50 KT... 80NE 80SE 70SW 70NW. 34 KT...170NE 200SE 150SW 150NW. FORECAST VALID 04/0000Z 39.6N 52.2W MAX WIND 95 KT...GUSTS 115 KT. 64 KT... 40NE 50SE 40SW 30NW. 50 KT... 80NE 80SE 70SW 70NW. 34 KT...170NE 200SE 160SW 150NW. FORECAST VALID 04/1200Z 43.0N 47.3W MAX WIND 90 KT...GUSTS 110 KT. 50 KT... 90NE 90SE 80SW 70NW. 34 KT...180NE 200SE 180SW 150NW. FORECAST VALID 05/0000Z 47.2N 43.2W...POST-TROP/EXTRATROP MAX WIND 80 KT...GUSTS 100 KT. 50 KT...100NE 100SE 100SW 80NW. 34 KT...200NE 220SE 200SW 180NW. EXTENDED OUTLOOK. NOTE...ERRORS FOR TRACK HAVE AVERAGED NEAR 150 NM ON DAY 4 AND 175 NM ON DAY 5...AND FOR INTENSITY NEAR 15 KT EACH DAY OUTLOOK VALID 06/0000Z 50.5N 38.0W...POST-TROP/EXTRATROP MAX WIND 65 KT...GUSTS 80 KT. OUTLOOK VALID 07/0000Z 54.5N 27.5W...POST-TROP/EXTRATROP MAX WIND 50 KT...GUSTS 60 KT. REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 31.4N 61.2W INTERMEDIATE PUBLIC ADVISORY...WTNT33 KNHC/MIATCPAT3...AT 02/0600Z NEXT ADVISORY AT 02/0900Z $$ FORECASTER BEVEN

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Tropical Storm Victor Forecast Discussion Number 10

2021-10-01 22:43:32| National Hurricane Center (Atlantic)

Issued at 500 PM AST Fri Oct 01 2021 000 WTNT45 KNHC 012043 TCDAT5 Tropical Storm Victor Discussion Number 10 NWS National Hurricane Center Miami FL AL202021 500 PM AST Fri Oct 01 2021 Victor is looking disorganized. Deep convection has decreased in organization and coverage this afternoon. No recent microwave imagery has been available to assess the structure of the storm, but visible images from MET-11 and GOES-17 suggest that the circulation of the tropical storm is still elongated southwest-to-northeast. The intensity estimate remains 55 kt for this advisory, but this is on the high end of the recent estimates and could be generous. Compared to the large changes made this morning, almost no change was made to the official track forecast this afternoon. The model consensus has shifted substantially back to the right, and now lies very near the previous NHC forecast. Victor is forecast to turn northwestward tomorrow, and then continue on that heading through early next week, steered by ridging to the northeast. The new NHC forecast is very near the model consensus through the end of the forecast. Despite the recent agreement between the NHC forecast and the consensus, confidence in the forecast will remain low until we see better run-to-run consistency in the track model guidance. Shear and dry air may already be taking a toll on Victor, and SHIPS diagnostics from the GFS and ECMWF suggest that the environment will get worse with time. All of the intensity models forecast that Victor will weaken over the next several days in response to the hostile environment, and this is reflected in the NHC forecast, which is heavily based on the IVCN multi-model consensus. By day 5, all of the dynamical models indicate that Victor will likely degenerate into a trough of low pressure, so dissipation is shown. Several models, including the HWRF, GFS, and ECMWF indicate dissipation could occur sooner than that. FORECAST POSITIONS AND MAX WINDS INIT 01/2100Z 12.0N 34.3W 55 KT 65 MPH 12H 02/0600Z 12.7N 35.5W 50 KT 60 MPH 24H 02/1800Z 13.9N 37.2W 45 KT 50 MPH 36H 03/0600Z 15.6N 39.0W 45 KT 50 MPH 48H 03/1800Z 17.6N 40.9W 40 KT 45 MPH 60H 04/0600Z 19.7N 42.9W 40 KT 45 MPH 72H 04/1800Z 21.5N 44.5W 35 KT 40 MPH 96H 05/1800Z 24.5N 47.5W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 06/1800Z...DISSIPATED $$ Forecaster D. Zelinsky

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