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| #982803 (Received by flhurricane at: 10:44 AM 18.Sep.2019) TCDAT4 Hurricane Humberto Discussion Number 24 NWS National Hurricane Center Miami FL AL092019 1100 AM AST Wed Sep 18 2019 An Air Force Reserve Hurricane Hunter aircraft conducting a reconnoiter of Humberto this morning found that the intensity of the major hurricane had increased slightly, but that the inner-core 64- and 50-kt wind fields had expanded significantly, now extending outward up to at least 90 n mi and 110 n mi, respectively, in the southeastern quadrant. During their pass through the southeastern quadrant, the aircraft measured 700-mb flight-level winds of 120 kt, but peak SFMR winds of only 97 kt. Given that convection is minimal in that quadrant, the normal downward mixing is likely not occurring, the intensity has only been increased to 105 kt. The aircraft also measured a central pressure of 952 mb with a dropsonde, which is close to the pressure of 954.2 mb with 30-kt winds that NOAA buoy 41048 measured in the eye around 0930 UTC. The initial motion estimate remains 065/14 kt. Humberto is beginning to feel the effects of a deep-layer trough approaching from the west, and the hurricane should continue to accelerate toward the east-northeast through tonight, passing just north and northwest of Bermuda, followed by a turn toward the northeast by early Thursday afternoon. By 48 hours or so, Humberto is forecast to turn back toward the east-northeast and maintain that motion through day 5 as a ridge to the east of the cyclone weakens and flattens out. The new NHC track forecast is very similar to the previous one for the first 36 hours, and then is a little faster and to the left of the previous advisory thereafter, closer to the tightly packed consensus track model guidance. Humberto may have peaked in intensity based on the cloud pattern in satellite imagery beginning to take on the appearance of an extratropical cyclone. Thus, some fluctuations in strength could occur during the next 12 hours or so. Thereafter, very strong southwesterly vertical wind shear and cold upwelling beneath the hurricane should disrupt the inner-core convection and organization, resulting in steady weakening. By 72 hours, the global models continue to show Humberto merging with a frontal system, and the NHC intensity forecast calls for extratropical transition by that time. The official intensity forecast follows the corrected- consensus models HCCA and FSSE through the next 12-24 hours, and then is above that guidance through the remainder of the forecast period, closer to an average of the global models. Key Messages: 1. A prolonged period of dangerous winds is expected on Bermuda from late this afternoon through Thursday morning, with hurricane-force winds expected overnight tonight. Preparations to protect life and property should be rushed to completion. 2. Storm surge and dangerous breaking waves could cause coastal flooding tonight and Thursday along the southern coast of Bermuda. 3. Swells will continue to affect the northwestern Bahamas and the southeastern coast of the United States from east-central Florida to North Carolina during the next couple of days, creating life- threatening surf and rip current conditions. FORECAST POSITIONS AND MAX WINDS INIT 18/1500Z 32.2N 68.1W 105 KT 120 MPH 12H 19/0000Z 33.5N 65.4W 100 KT 115 MPH 24H 19/1200Z 36.1N 62.1W 90 KT 105 MPH 36H 20/0000Z 38.6N 60.5W 75 KT 85 MPH 48H 20/1200Z 40.7N 59.5W 60 KT 70 MPH 72H 21/1200Z 43.3N 50.4W 45 KT 50 MPH...POST-TROP/EXTRATROP 96H 22/1200Z 47.2N 33.4W 45 KT 50 MPH...POST-TROP/EXTRATROP 120H 23/1200Z 54.0N 20.0W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Stewart |
