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Hurricane Larry Forecast Discussion Number 40
2021-09-10 16:48:30| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Fri Sep 10 2021 000 WTNT42 KNHC 101448 TCDAT2 Hurricane Larry Discussion Number 40 NWS National Hurricane Center Miami FL AL122021 1100 AM AST Fri Sep 10 2021 Larry remains a well organized hurricane at a high latitude, and it is quickly approaching southeastern Newfoundland. Satellite images show a fairly tight inner core and large curved bands surrounding that feature. However, there are some notable dry slots between the core and bands that have developed during the past several hours. The latest Dvorak numbers have nudged downward, with the CI values ranging between 65 kt and 72 kt. Based on these estimates, and a very recent ASCAT pass that showed peak winds near 65 kt, the initial intensity is set at 70 kt for this advisory. The cyclone remains quite large, with hurricane-force winds and tropical-storm-force winds estimated to extend outward up to 80 and 210 n mi from the center, respectively. The hurricane is in the process of turning to the right, with the latest initial motion estimated to be a fairly quick 015/25 kt. An even faster north-northeast to northeast motion is expected during the next day or two as the hurricane moves in the fast flow between a mid- to upper-level trough over the northeastern U.S./eastern Canada and a mid-level ridge over the central Atlantic. This motion should take Larry across southeastern Newfoundland tonight. Larry is then expected to merge with a large extratropical low over the Labrador Sea on Sunday. The NHC track forecast is similar to the previous one and near the middle of the guidance envelope. Although Larry will be moving over cooler waters north of the Gulf Stream Current later today, the hurricane will likely hold its strength or weaken just a little before landfall. After landfall, the models show the inner core dissipating, and the combination of land interaction, cooler waters, and an increase in shear should cause weakening and lead to extratropical transition by early Saturday. The NHC intensity forecast is close to the GFS model, which often performs well for hurricanes that transition to extratropical cyclones. Key Messages: 1. Larry is forecast to move over portions of southeastern Newfoundland tonight as it undergoes transition to a hurricane-force post-tropical cyclone. Hurricane conditions, a dangerous storm surge, and heavy rainfall are expected in portions of southeastern Newfoundland where a Hurricane Warning in effect. 2. Large swells generated by Larry will continue to affect the Bahamas, Bermuda, and the east coast of the United States and Atlantic Canada through Saturday night. These swells will cause life-threatening surf and rip current conditions, and beachgoers and other interests along these coasts are urged to follow the guidance of lifeguards and local officials. FORECAST POSITIONS AND MAX WINDS INIT 10/1500Z 40.0N 60.5W 70 KT 80 MPH 12H 11/0000Z 45.1N 56.4W 70 KT 80 MPH 24H 11/1200Z 52.0N 49.4W 60 KT 70 MPH...POST-TROP/EXTRATROP 36H 12/0000Z 57.5N 44.0W 60 KT 70 MPH...POST-TROP/EXTRATROP 48H 12/1200Z 61.1N 38.7W 55 KT 65 MPH...POST-TROP/EXTRATROP 60H 13/0000Z...DISSIPATED $$ Forecaster Cangialosi
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Hurricane Larry Forecast Discussion Number 39
2021-09-10 10:44:31| National Hurricane Center (Atlantic)
Issued at 500 AM AST Fri Sep 10 2021 000 WTNT42 KNHC 100844 TCDAT2 Hurricane Larry Discussion Number 39 NWS National Hurricane Center Miami FL AL122021 500 AM AST Fri Sep 10 2021 Larry's satellite presentation has remained largely unchanged overnight. Deep convection continues to persist over and to the northeast of the center, with a larger outer band around the eastern portion of the circulation. Subjective Dvorak intensity estimates from TAFB and SAB have lowered slightly, and the initial intensity has been adjusted downward to 75 kt. This lies between the lower subjective satellite estimates and the higher UW/CIMSS ADT and SATCON values. Larry is forecast to remain over warm waters and in low vertical wind shear conditions this morning, therefore little overall change in intensity is expected in the short term. The hurricane will cross the north wall of the Gulf Stream over much cooler SSTs this afternoon, but the increasingly fast forward speed of the system and baroclinic forcing from a mid-latitude trough approaching from the west is likely to help Larry maintain hurricane strength as is passes over southeastern Newfoundland tonight. Larry is forecast to become extratropical shortly thereafter, and some slight weakening should occur before the post-tropical cyclone is absorbed by a larger extratropical low near southern Greenland in a couple of days. The NHC intensity forecast is similar to the HCCA and IVCN consensus aids and also follows the trends of the latest global model guidance. Larry has turned north-northeastward or 015/23 kt. The track guidance is once again in excellent agreement that Larry should turn northeastward today and continue to accelerate ahead of the aforementioned trough. The center of Larry should pass over southeastern Newfoundland tonight, but users are reminded to not focus on the exact details of the track forecast as strong winds, heavy rainfall, and a dangerous storm surge will extend far from the center of the cyclone. The updated official forecast lies near the center of the track guidance envelope, but is slightly faster than the previous forecast during the first 36 hours. Key Messages: 1. Larry is forecast to move over portions of southeastern Newfoundland tonight as it undergoes transition to a hurricane-force post-tropical cyclone. Hurricane conditions, a dangerous storm surge, and heavy rainfall are expected in portions of southeastern Newfoundland where a Hurricane Warning in effect. 2. Large swells generated by Larry will continue to affect the Bahamas, Bermuda, and the east coast of the United States and Atlantic Canada through Saturday. These swells will cause life-threatening surf and rip current conditions, and beachgoers and other interests along these coasts are urged to follow the guidance of lifeguards and local officials. FORECAST POSITIONS AND MAX WINDS INIT 10/0900Z 37.7N 61.8W 75 KT 85 MPH 12H 10/1800Z 41.9N 59.2W 75 KT 85 MPH 24H 11/0600Z 48.6N 53.0W 70 KT 80 MPH 36H 11/1800Z 55.0N 46.8W 60 KT 70 MPH...POST-TROP/EXTRATROP 48H 12/0600Z 60.0N 42.0W 60 KT 70 MPH...POST-TROP/EXTRATROP 60H 12/1800Z...DISSIPATED $$ Forecaster Brown
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Post-Tropical Cyclone Mindy Forecast Discussion Number 6
2021-09-10 04:48:23| National Hurricane Center (Atlantic)
Issued at 1100 PM EDT Thu Sep 09 2021 483 WTNT43 KNHC 100248 TCDAT3 Post-Tropical Cyclone Mindy Discussion Number 6 NWS National Hurricane Center Miami FL AL132021 1100 PM EDT Thu Sep 09 2021 The structure of Mindy this evening has become quite diffuse, with a linear band of convection mostly associated with a prominent outflow boundary emanating away from the system. The last-light visible low-level cloud motions gave the impression that Mindy was opening up into a trough, with southwesterly flow ahead and northeasterly flow immediately behind the estimated center. Indeed, a ASCAT-A pass valid at 0002 UTC suggested that Mindy no longer has closed cyclonic flow on its northeast side, with a lack of easterly wind vectors in this sector of the system. In addition, a rapidly advancing frontal boundary has already moved off of the Carolina coast and will soon be merging with the leftover vort-max associated with Mindy. The accumulation of all this evidence indicates that Mindy no longer meets the definition of a tropical cyclone, and this will be the final advisory on the system. The post-tropical remains of Mindy have continued to accelerate to the east-northeast this evening at 070/25 kt, moving almost as quickly as the the maximum sustained winds, which is another reason why the circulation is likely no longer closed. This motion should continue for the next 12-24 hours with a gradual slowdown until what remains of the circulation becomes indistinguishable from the frontal boundary it is becoming embedded in. FORECAST POSITIONS AND MAX WINDS INIT 10/0300Z 32.5N 75.0W 30 KT 35 MPH...POST-TROP/EXTRATROP 12H 10/1200Z 33.2N 71.6W 25 KT 30 MPH...POST-TROP/EXTRATROP 24H 11/0000Z 34.1N 67.8W 25 KT 30 MPH...POST-TROP/EXTRATROP 36H 11/1200Z...DISSIPATED $$ Forecaster Papin
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Hurricane Olaf Forecast Discussion Number 10
2021-09-10 04:48:23| National Hurricane Center (East Pacific)
Issued at 900 PM MDT Thu Sep 09 2021 482 WTPZ45 KNHC 100248 TCDEP5 Hurricane Olaf Discussion Number 10 NWS National Hurricane Center Miami FL EP152021 900 PM MDT Thu Sep 09 2021 Imagery from the Mexican radar at Cabo San Lucas, along with satellite imagery, indicates that the eye of Olaf is about to make landfall near San Jose del Cabo, and that hurricane conditions in the northwestern eyewall have already spread onshore. The eyewall cloud tops have cooled during the past few hours, and the objective intensity estimate from the CIMSS ADT technique has increased to 90 kt. Based on this and an increase in the organization of the eyewall on the Cabo radar imagery, the initial intensity is increased to 85 kt. The initial motion is 325/10. Olaf should continue moving northwestward to north-northwestward for the next 12-24 h, with the center moving near or over the southern portion of the Baja California peninsula during this time. After that, a mid-level ridge extending westward from the southwestern United States should cause Olaf to turn westward, and this should be followed by a southwestward motion as the weakening cyclone becomes steered by low-level northeasterly flow. The forecast guidance has changed little since the previous advisory, and the new forecast track has only minor adjustments from the previous forecast. A gradual weakening is expected during the first 24 h as Olaf interacts with the Baja California peninsula. When the cyclone turns westward after 24 h, it should move over colder water and into a drier air mass. This combination should cause the convection to decay, with the system becoming a post-tropical low by 60 h and a remnant low by 72 h. The new intensity forecast has some minor changes from the previous forecast, and it lies in the middle of the intensity guidance envelope. Key Messages: 1. Olaf is forecast to move very near or over the southern portion of Baja California Sur tonight and Friday. Hurricane conditions have begun within the southern portion of the hurricane warning area tonight and will spread northward through Friday. 2. Heavy rains associated with Olaf are expected across portions of southern Baja California Sur through Friday. This will pose a threat of significant and life-threatening flash flooding and mudslides. FORECAST POSITIONS AND MAX WINDS INIT 10/0300Z 23.0N 109.6W 85 KT 100 MPH 12H 10/1200Z 23.9N 110.7W 75 KT 85 MPH...INLAND 24H 11/0000Z 24.6N 112.3W 65 KT 75 MPH...OVER WATER 36H 11/1200Z 24.8N 113.6W 55 KT 65 MPH 48H 12/0000Z 24.4N 114.8W 45 KT 50 MPH 60H 12/1200Z 23.7N 115.9W 35 KT 40 MPH...POST-TROPICAL 72H 13/0000Z 23.0N 117.2W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 14/0000Z 21.6N 120.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 15/0000Z 21.0N 122.0W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Beven
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Hurricane Larry Forecast Discussion Number 38
2021-09-10 04:44:46| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Thu Sep 09 2021 249 WTNT42 KNHC 100244 TCDAT2 Hurricane Larry Discussion Number 38 NWS National Hurricane Center Miami FL AL122021 1100 PM AST Thu Sep 09 2021 There is not much new to report in the satellite structure with Larry this evening. The hurricane consists of a small core region of cold convective cloud tops near and just north of the center with a much larger concentric band of more moderate convective activity encircling the smaller core. Radar from Bermuda also shows this structure well even as the hurricane pulls away from the island. The most recent subjective Dvorak satellite intensity estimates from SAB and TAFB were unchanged from this afternoon, and the initial intensity will remain at 80 kt for this advisory. Larry is now moving to the north and beginning to accelerate at 360/20 kt. The track guidance remains in good agreement that Larry should soon turn to the northeast and continue accelerating quickly ahead of a large mid-latitude trough. On the current track, Larry should pass near or over southeastern Newfoundland tomorrow night or Saturday morning, becoming post-tropical shortly after it passes by. The post-tropical cyclone Larry should continue to move rapidly to the northeast until it is absorbed by the aforementioned mid-latitude trough after 48 hours. The official track forecast again lies close to the various consensus model predictions, and is just a touch faster than the previous forecast. Larry has another 12 hours or so over warm Gulf Stream waters, and most of the guidance is in agreement that the hurricane should maintain its intensity in the short-term. However, more gradual weakening should begin thereafter once Larry moves over much cooler waters. Unfortunately, there is not much time for Larry to weaken before the hurricane impacts Newfoundland, and it also is possible the rapidly approaching mid-latitude trough will provide some baroclinic forcing that could expand the wind field of the hurricane further. The NHC intensity forecast remain close to the latest HCCA guidance which is quite similar to the previous forecast. After 24 hours, the latest forecast GFS and ECMWF simulated IR brightness temperature suggest that Larry's convection should quickly shear off after passing by Newfoundland, with the hurricane becoming a powerful post-tropical cyclone by 36 hours. Both of these models now also suggest the post-tropical cyclone will quickly be stretched and then absorbed as its captured by an even larger extratropical cyclone produced by the upstream trough after 48 hours. Key Messages: 1. Larry is forecast to move near or over portions of southeastern Newfoundland Friday night or early Saturday morning as it undergoes transition to a hurricane-force post-tropical cyclone. Hurricane conditions and dangerous storm surge are expected in portions of southeastern Newfoundland where a Hurricane Warning in effect. 2. Large swells generated by Larry will continue to affect the Leeward Islands, portions of the Greater Antilles, the Bahamas, Bermuda, and the east coast of the United States and Atlantic Canada through the end of the week. These swells will cause life-threatening surf and rip current conditions, and beachgoers and other interests along these coasts are urged to follow the guidance of lifeguards and local officials. FORECAST POSITIONS AND MAX WINDS INIT 10/0300Z 35.5N 62.3W 80 KT 90 MPH 12H 10/1200Z 39.0N 60.9W 80 KT 90 MPH 24H 11/0000Z 45.1N 56.1W 75 KT 85 MPH 36H 11/1200Z 52.0N 49.3W 65 KT 75 MPH...POST-TROP/EXTRATROP 48H 12/0000Z 58.1N 44.0W 60 KT 70 MPH...POST-TROP/EXTRATROP 60H 12/1200Z...DISSIPATED $$ Forecaster Papin
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