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Hurricane Maria Forecast Discussion Number 21
2017-09-21 10:43:29| National Hurricane Center (Atlantic)
Issued at 500 AM AST Thu Sep 21 2017 000 WTNT45 KNHC 210843 TCDAT5 Hurricane Maria Discussion Number 21 NWS National Hurricane Center Miami FL AL152017 500 AM AST Thu Sep 21 2017 Although the large, 40 n mi diameter, eye of the hurricane is still a little ragged-looking, it is gradually becoming better defined, and a ring of cold cloud tops is intensifying around the eye. The current intensity estimate is 100 kt based on earlier Air Force Hurricane Hunter data and recent Dvorak classifications from TAFB and SAB. Maria is likely to move over warm waters with moderate southwesterly vertical shear for the next couple of days. Maria's well-developed upper-level outflow suggests that shear is probably not having much influence over the hurricane at this time. Although the numerical guidance is not very aggressive about intensification, based on the current trends of the cloud pattern, some strengthening seems likely over the next day or so. Later in the forecast period, shear will probably cause gradual weakening. The official intensity forecast is a little above the latest model consensus. Maria continues its northwestward motion, at about 315/8 kt. The hurricane is expected to turn north-northwestward and northward around a subtropical ridge over the Atlantic for the next 2 to 3 days. Late in the forecast period, a mid-level high over the northeastern U.S. could slow the forward motion somewhat. This high is forecast by the global models to subsequently weaken however, which should allow Maria to turn north-northeastward in the flow on the northwestern edge of a subtropical ridge over the west-central Atlantic. The official track forecast lies between the corrected consensus guidance and the latest ECMWF prediction. This is quite similar to the previous NHC track. KEY MESSAGES: 1. Heavy rainfall is expected to continue, and catastrophic flash flooding is occurring in Puerto Rico, especially in areas of mountainous terrain. Everyone in Puerto Rico should continue to follow advice from local officials to avoid these life-threatening flooding conditions. 2. A Hurricane Warning is in effect for the northern coast of the Dominican Republic, the Turks and Caicos Islands, and the southeastern Bahamas, where Maria is expected to bring dangerous wind, storm surge, and heavy rainfall. FORECAST POSITIONS AND MAX WINDS INIT 21/0900Z 19.6N 68.4W 100 KT 115 MPH 12H 21/1800Z 20.5N 69.3W 105 KT 120 MPH 24H 22/0600Z 21.6N 70.4W 110 KT 125 MPH 36H 22/1800Z 22.9N 71.1W 105 KT 120 MPH 48H 23/0600Z 24.3N 71.7W 100 KT 115 MPH 72H 24/0600Z 27.4N 72.3W 100 KT 115 MPH 96H 25/0600Z 30.0N 72.0W 90 KT 105 MPH 120H 26/0600Z 32.5N 70.5W 80 KT 90 MPH $$ Forecaster Pasch
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