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Tropical Storm Michael Forecast Discussion Number 7
2018-10-08 10:58:42| National Hurricane Center (Atlantic)
Issued at 400 AM CDT Mon Oct 08 2018 000 WTNT44 KNHC 080858 TCDAT4 Tropical Storm Michael Discussion Number 7 NWS National Hurricane Center Miami FL AL142018 400 AM CDT Mon Oct 08 2018 Michael has become better organized this morning, with the deep convection migrating westward on top of the low-level center and upper-level outflow beginning to increase within the western semicircle. An Air Force Reserve Hurricane Hunter aircraft made several passes through the system during the past few hours, and somewhat surprisingly, found that the central pressure has fallen to about 983 mb and maximum winds have increased to near 60 kt. This increase in intensity indicates that despite the shear which has been affecting Michael, the system has, by definition, rapidly intensified during the past 24 hours. With the increase in the initial wind speeds, the official intensity forecast is higher than in the previous forecast. Decreasing vertical shear and very warm sea surface temperatures are expected to support continued strengthening, and due to the favorable conditions, the NHC intensity forecast follows a blend of the IVCN consensus and the HCCA model. This new official forecast brings the intensity to just below major hurricane strength in 48 hours, and since the storm will still be over water for a time between 48 and 72 hours, there is a real possibility that Michael will strengthen to a major hurricane before landfall. Weakening is expected after landfall, but the system will likely maintain tropical storm strength after day 4 when it moves off the east coast of the United States. Michael should then become an extratropical low by day 5. The reconnaissance fixes indicate that Michael's center is moving northward, or 360 degrees at 6 kt. A general northward motion with some increase in forward speed is expected during the next 48 hours as Michael enters the southerly flow between high pressure over the western Atlantic and a deep-layer trough over the western and central United States. After 48 hours, Michael is expected to turn northeastward toward and across the southeastern United States, exiting over the western Atlantic between days 4 and 5. Nearly all of the track models have shifted westward after 24 hours, which left the previous forecast near the eastern edge of the guidance envelope. Due to this shift, the new NHC track forecast has also been adjusted westward close to the consensus aids. Overall the track guidance is in fairly good agreement up until landfall along the Florida Panhandle or Florida Big Bend, which has yielded a fairly confident track forecast. Key Messages: 1. Hurricane conditions are expected over portions of western Cuba, where a hurricane warning is now in effect. Tropical storm conditions are expected over the northeastern Yucatan Peninsula and the Isle of Youth today. 2. Michael is expected to produce heavy rainfall and flash flooding over portions of western Cuba and the northeastern Yucatan Peninsula of Mexico during the next couple of days. 3. Michael is forecast to be a hurricane, and possibly a major hurricane, when it reaches the northeastern Gulf Coast by mid-week, and storm surge and hurricane watches are now in effect for portions of the area. Some areas along the Florida Gulf Coast are especially vulnerable to storm surge, regardless of the storm's exact track or intensity. Residents in the watch areas should monitor the progress of this system and follow any advice given by local officials. FORECAST POSITIONS AND MAX WINDS INIT 08/0900Z 20.6N 85.5W 60 KT 70 MPH 12H 08/1800Z 21.7N 85.6W 70 KT 80 MPH 24H 09/0600Z 23.5N 86.1W 85 KT 100 MPH 36H 09/1800Z 25.2N 86.7W 90 KT 105 MPH 48H 10/0600Z 27.2N 86.7W 95 KT 110 MPH 72H 11/0600Z 31.2N 84.5W 55 KT 65 MPH...INLAND 96H 12/0600Z 35.5N 77.5W 50 KT 60 MPH...INLAND 120H 13/0600Z 40.5N 64.5W 50 KT 60 MPH...POST-TROP/EXTRATROP $$ Forecaster Berg
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