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Hurricane Maria Forecast Discussion Number 17
2017-09-20 10:58:22| National Hurricane Center (Atlantic)
Issued at 500 AM AST Wed Sep 20 2017 000 WTNT45 KNHC 200858 TCDAT5 Hurricane Maria Discussion Number 17 NWS National Hurricane Center Miami FL AL152017 500 AM AST Wed Sep 20 2017 Radar observations from the San Juan WSR-88D and wind data from an Air Force Reserve Unit Hurricane Hunter aircraft indicate that Maria has just about completed an eyewall replacement. Based on the now-dominant outer eyewall, the eye diameter has increased from 10 n mi to 30 n mi. This has likely contributed to some weakening, and based on the latest observations from the Hurricane Hunters, the intensity is set at 135 kt which is at the top of category 4 range. Although there has been a slight reduction of intensity, Maria remains an extremely dangerous hurricane. Some weakening is likely while the system crosses Puerto Rico. Later in the forecast period, less favorable upper-level winds should cause further weakening, but Maria is likely to remain a large and powerful hurricane for the next 5 days. The official intensity forecast is near or a little above the model consensus. Maria continues to move between west-northwest and northwest at about 9 kt. The flow on the south side of a weak mid-level ridge over the western Atlantic is expected to steer the hurricane on this general heading over the next couple of days. This track will bring the center of Maria across Puerto Rico and just north of the eastern Dominican Republic over the next day or so. After that time a break in the ridge, partially associated with Tropical Storm Jose, should cause Maria to turn north-northwestward, then northward by the end of the forecast period. The track guidance remains tightly clustered through 72 hours, giving fairly high confidence in the track forecast through that time. There is some increase in the spread of the models at days 4 and 5, with the latest ECMWF prediction near the western edge of the guidance envelope but with all of the reliable models well offshore of the southeast U.S. at the end of the period. The official forecast is very close to the latest FSU Superensemble track. KEY MESSAGES: 1. Maria's core will make landfall over Puerto Rico within the next couple of hours, bringing life-threatening wind, storm surge, and rainfall impacts to the island. Everyone in Puerto Rico should follow advice from local officials to avoid life-threatening flooding from storm surge and rainfall. 2. Wind speeds atop and on the windward sides of hills and mountains and on high-rise buildings could be much stronger than the near-surface winds indicated in this advisory. 3. A Hurricane Warning is also in effect for the Virgin Islands, 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 20/0900Z 17.9N 65.6W 135 KT 155 MPH 12H 20/1800Z 18.6N 66.7W 125 KT 145 MPH...INLAND 24H 21/0600Z 19.5N 68.2W 120 KT 140 MPH 36H 21/1800Z 20.5N 69.4W 120 KT 140 MPH 48H 22/0600Z 21.5N 70.5W 115 KT 130 MPH 72H 23/0600Z 24.2N 72.0W 105 KT 120 MPH 96H 24/0600Z 27.3N 73.0W 100 KT 115 MPH 120H 25/0600Z 30.5N 73.0W 85 KT 100 MPH $$ Forecaster Pasch
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