000 WTNT45 KNHC 190853 TCDAT5 Hurricane Maria Discussion Number 13 NWS National Hurricane Center Miami FL AL152017 500 AM AST Tue Sep 19 2017 Interaction of the small core of Maria with the mountainous terrain of Dominica caused only a slight diminution of the intensity of the hurricane. Data from the Air Force Hurricane Hunter aircraft after the center passed the island indicate an intensity of about 135 kt, at the high end of category 4 strength. Another Air Force aircraft has begun investigating Maria, and preliminary data from the plane suggest that the hurricane may have regained category 5 intensity. Maria will be moving through a low-shear atmospheric environment and mainly over warm waters for the next couple of days. Some fluctuations in intensity are possible in the early part of the forecast period due to eyewall replacement events. Land influences could cause some weakening within the next 36 hours. Later in the forecast period, a modest increase in vertical shear could cause some weakening. The official intensity forecast is near or above the latest model consensus. After smoothing out the trochoidal wobbles of Maria's eye, the initial motion estimate remains west-northwestward, or 300/8 kt. There is little change to the track forecast reasoning from the previous advisory package. A weak ridge situated over the western Atlantic is expected to steer Maria west-northwestward through 48 hours, and on this track the center of the hurricane 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, partially due to the influence of the large circulation of Hurricane Jose. This should cause Maria to turn northwestward, then north-northwestward by day 4-5. There is fairly good agreement amongst the reliable guidance, and the new official track forecast is very similar to the previous one. This is generally near the left side of the envelope of model tracks, and favors the ECMWF and the corrected consensus predictions. KEY MESSAGES: 1. Maria will affect portions of the northern Leeward Islands as an extremely dangerous major hurricane during the next day or so. 2. Maria is likely to affect Puerto Rico and the U.S. and British Virgin Islands as an extremely dangerous major hurricane tonight and Wednesday. Preparations to protect life and property should be rushed to completion. 3. A life-threatening storm surge, accompanied by large and destructive waves, is expected for the Leeward Islands, the U.S. and British 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 19/0900Z 16.0N 62.3W 135 KT 155 MPH 12H 19/1800Z 16.7N 63.4W 140 KT 160 MPH 24H 20/0600Z 17.6N 64.8W 135 KT 155 MPH 36H 20/1800Z 18.5N 66.3W 125 KT 145 MPH...NEAR PUERTO RICO 48H 21/0600Z 19.3N 67.8W 125 KT 145 MPH 72H 22/0600Z 21.2N 70.4W 120 KT 140 MPH 96H 23/0600Z 23.7N 71.7W 110 KT 125 MPH 120H 24/0600Z 26.5N 72.5W 100 KT 115 MPH $$ Forecaster Pasch