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Hurricane Maria Forecast Discussion Number 12
2017-09-19 04:55:15| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Mon Sep 18 2017 000 WTNT45 KNHC 190255 TCDAT5 Hurricane Maria Discussion Number 12 NWS National Hurricane Center Miami FL AL152017 1100 PM AST Mon Sep 18 2017 The Air Force Hurricane Hunters were able to fly a single pass from northwest to southeast through the eye of Maria just prior to 0000 UTC. The aircraft found a peak SFMR wind of 139 kt in the northwest eyewall, i.e. category 5 intensity. Raw objective T-numbers from UW/CIMSS reached as high as T7.3 just before the center moved over land. Based on these data, the initial wind speed was increased to 140 kt on the earlier special advisory, and that intensity is maintained for this advisory, although some slight weakening may have occurred as the small core of the hurricane passed over Dominica. Since the center has moved over land, the aircraft has not been able to make a second pass through the eye. The aircraft will be in the storm a few more hours and should be able to provide additional center fixes once the eye moves west of Dominica. Maria is forecast to remain within an environment of low wind shear and over warm water during the next couple of days. Given these favorable atmospheric and oceanic conditions, Maria is expected to remain a Category 4 or 5 hurricane when it approaches the Virgin Islands and Puerto Rico, however some fluctuations in intensity are possible due during the next 24 to 36 h due to eyewall cycles. Land interaction and a slight increase in shear are likely to cause some gradual weakening after Maria moves over the southwestern Atlantic in 3 to 4 days. Maria is moving west-northwestward or 300/8 kt. A weak ridge located over the western Atlantic is expected to steer the hurricane west-northwestward through 48 hours, and on this track the center of Maria is forecast to pass near or over the Virgin Islands and Puerto Rico on Wednesday. After that time, the western portion of the ridge is forecast to weaken, which should allow Maria to turn northwestward, then north-northwestward by day 5. The track guidance is in good agreement and little change was required to the NHC track forecast through 72 hours. At days 4 and 5, the global model envelope has shifted slightly eastward and the NHC forecast was adjusted accordingly to be in better agreement with the HFIP correct consensus and ECMWF model. KEY MESSAGES: 1. Maria will affect portions of the Leeward Islands and the British and U.S. Virgin Islands as an extremely dangerous major hurricane during the next couple of days, and hurricane warnings are in effect for many of these islands. 2. Maria is likely to affect Puerto Rico as an extremely dangerous major hurricane, and a hurricane warning is in effect for that island. Preparations to protect life and property should be rushed to completion. 3. The potential for a life-threatening storm surge, accompanied by large and destructive waves, has increased for the Leeward Islands, the Virgin Islands, and Puerto Rico. 4. Life-threatening flash floods and mudslides from heavy rainfall are expected across the Leeward Islands, including Puerto Rico and the U.S. and British Virgin Islands. FORECAST POSITIONS AND MAX WINDS INIT 19/0300Z 15.5N 61.4W 140 KT 160 MPH 12H 19/1200Z 16.1N 62.6W 140 KT 160 MPH 24H 20/0000Z 17.0N 64.0W 140 KT 160 MPH 36H 20/1200Z 17.9N 65.4W 135 KT 155 MPH 48H 21/0000Z 18.7N 66.9W 125 KT 145 MPH 72H 22/0000Z 20.5N 69.6W 120 KT 140 MPH 96H 23/0000Z 22.8N 71.5W 110 KT 125 MPH 120H 24/0000Z 25.5N 72.5W 100 KT 115 MPH $$ Forecaster Brown
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