000 WTNT44 KNHC 100252 TCDAT4 Hurricane Michael Discussion Number 14 NWS National Hurricane Center Miami FL AL142018 1000 PM CDT Tue Oct 09 2018 Data from Air Force Reserve and NOAA Hurricane Hunter aircraft this afternoon and evening indicate that Michael has been undergoing a rapid deepening phase with the pressure having dropped to 947 mb, a decrease of 20 mb between 1800Z and 0200Z with most of those pressures falls occurring during the past few hours. Michael's eye has become more distinct in GOES-16 high-resolution infrared satellite imagery, with a solid ring of cloud top temperatures colder than -75 deg C surrounding the warming eye. Some cloud tops in the eyewall have been as cold as -88C, which is very impressive for a Gulf system. The peak 8000-ft flight-level winds measured by the NOAA aircraft thus far has been 130 kt and the strongest SFMR surface wind speed observed has been 110 kt in the same location as the peak flight-level winds. Based on these wind data, along with a central pressure of 947 mb, Michael's intensity has been increased to 110 kt. Satellite intensity estimates from TAFB and SAB, along with objective estimates from UW-CIMSS ADT and NHC, support an intensity of 115-127 kt. However, those also estimates also would support a central pressure of about 935 mb, which the aircraft has not measured thus far. The initial motion estimate is due north, or 360/10 kt. Michael is essentially on the previous advisory track, and there is no significant change to the previous track forecast discussion. The models have settled in a stable forecast pattern, which calls for Michael to remain embedded within deep southerly flow for the next 24 hours between a substantial ridge to the east and a highly amplified mid-latitude trough moving eastward across the western and central U.S. and northern Mexico. As a result, the dangerous hurricane is expected to move northward to north-northeastward and make landfall along the coast of the central panhandle of Florida by late Wednesday afternoon. After landfall, increasing southwesterly flow ahead of the approaching deep-layer trough is expected to accelerate Michael toward the northeast through 48 h, with the cyclone moving across the southeastern U.S. late Wednesday and Thursday, and emerging over the western Atlantic by early Friday. A continued northeastward motion at forward speeds of 30-40 kt is forecast at 72-120 h when Michael is expected to be an extratropical cyclone. The new NHC forecast track is essentially just an update of the previous advisory track, and lies close to the tightly packed consensus models TVCN, TVCX, TCON, and NOAA-HCCA. Similar to the previous advisory, the environment ahead of Michael is expected to remain conducive for additional strengthening until landfall occurs due to SSTs of at least 85 deg F beneath the hurricane, combined with decreasing vertical wind shear along with the shear vector shifting from current west-northwesterly to a less hostile southwesterly component, which will be more along Michael's forecast track. As a result, Michael is now explicitly forecast to become a category 4 hurricane before landfall occurs. After landfall, significant weakening is expected while Michael moves over the southeastern United States, but the cyclone is forecast to re-strengthen over the western Atlantic due to baroclinic forcing after it merges with a front and becomes extratropical on Friday. The new intensity forecast closely follows a blend of the IVCN, HCCA, and FSSE consensus models throughout the 120-h period. Tropical storm conditions are expected to reach the hurricane warning area by Wednesday morning, so all preparations should be rushed to completion. Key Messages: 1. Life-threatening storm surge is likely along portions of the coasts of the Florida Panhandle, Big Bend, and Nature Coast, where a storm surge warning is in effect. The worst storm surge is expected between Mexico Beach and Keaton Beach, where 9 to 13 feet of inundation is possible. Water levels will rise well in advance of the center of Michael, and residents within the storm surge warning area should finish preparations to protect life and property today. 2. Everyone in the hurricane warning area along the Florida Gulf Coast should prepare for life-threatening major hurricane winds associated with the core of Michael. Hurricane force winds will also extend well inland across portions of the Florida Panhandle, southern Georgia, and southeast Alabama as Michael moves inland. 3. Heavy rainfall from Michael could produce life-threatening flash flooding from the Florida Panhandle and Big Bend region into portions of Georgia, the Carolinas, and southeast Virginia. 4. Tropical storm conditions will likely affect portions of the southeast U.S. coast from northeast Florida through North Carolina, and tropical storm watches and warnings are in effect for these areas...NHC
