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Hurricane Maria Forecast Discussion Number 9
2017-09-18 16:59:39| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Mon Sep 18 2017 000 WTNT45 KNHC 181459 TCDAT5 Hurricane Maria Discussion Number 9 NWS National Hurricane Center Miami FL AL152017 1100 AM AST Mon Sep 18 2017 Reports from an Air Force Reserve Hurricane Hunter aircraft indicate that Maria is undergoing rapid intensification. The aircraft reported 700-mb flight-level winds of 115 kt in the northeastern eyewall, along with reliable-looking surface wind estimates from the Stepped Frequency Microwave radiometer as high as 104 kt. In addition, the estimated central pressure inside the 10 n mi wide eye has fallen to 959 mb. The initial intensity is increased to 100 kt, making Maria a major category 3 hurricane on the Saffir-Simpson Hurricane Wind Scale. The small eye is also apparent in radar data from Martinique. The initial motion is 285/9, a little to the left of the previous motion. Other than that, there is little change in either the forecast philosophy or the forecast track. A high pressure area to the north of Maria should maintain a general west-northwestward motion for the next three days or so. After that, the high weakens, which should allow the hurricane to turn gradually northwestward and north-northwestward. The new forecast track is changed little from the previous one, and it calls for Maria to move through the Leeward Islands in 12-24 h, approach the Virgin Islands in about 36 h, then cross Puerto Rico between 48-72 h. The new track lies to the left of the center of the guidance envelope in best agreement with the ECMWF. Atmospheric and oceanic conditions appear favorable for additional rapid strengthening for the next 24 h and possibly longer. This is reflected in the intensity forecast, which now calls for Maria to become a category 4 hurricane in 12 h and reach a possibly conservative peak intensity of 130 kt in about 36 h. From 72-120 h, land interaction and less favorable upper-level winds are expected to cause some weakening. On top of these general trends, there is also the possibility that eyewall replacement cycles could occur that would affect the intensity. However, Maria is likely to maintain category 3 to 4 intensity through the forecast period. 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 watch is in effect for that island. A hurricane warning will likely be issued later today. 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 18/1500Z 14.7N 60.1W 105 KT 120 MPH 12H 19/0000Z 15.1N 61.2W 115 KT 130 MPH 24H 19/1200Z 15.9N 62.6W 125 KT 145 MPH 36H 20/0000Z 16.8N 64.1W 130 KT 150 MPH 48H 20/1200Z 17.6N 65.5W 130 KT 150 MPH 72H 21/1200Z 19.5N 68.5W 125 KT 145 MPH 96H 22/1200Z 21.5N 71.0W 120 KT 140 MPH 120H 23/1200Z 24.0N 72.5W 110 KT 125 MPH $$ Forecaster Beven
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