000 WTNT45 KNHC 251440 TCDAT5 Hurricane Maria Discussion Number 38 NWS National Hurricane Center Miami FL AL152017 1100 AM EDT Mon Sep 25 2017 Satellite and aircraft data indicate that Maria's structure has changed considerably since yesterday. Deep convection is primarily confined to the eastern semicircle of the circulation and the radius of maximum winds has significantly increased. After not finding many SFMR winds over 60 kt during the overnight flights, the latest Air Force Reserve Aircraft measured SFMR winds of 65-70 kt about 90 n mi from the center over the eastern portion of the circulation. As a result, the initial wind speed is set at 70 kt, a slight readjustment from the 1200 UTC estimate indicated in the intermediate advisory. The 50-kt and 64-kt wind radii have also been adjusted outward primarily over the eastern semicircle based on the aircraft data. The intensity forecast reasoning remains the same as that in the previous advisory. Cool sea surface temperatures, moderate westerly shear, and dry air are expected to cause gradual weakening over the next couple of days. The global model guidance suggests Maria will remain a strong tropical cyclone as it accelerates northeastward later in the forecast period. Therefore, the NHC forecast is a little higher than the statistical guidance at those times. Maria continues to move northward or 360/6 kt. Although Maria is being steered northward between a mid- to upper-level low over the southeastern United States and a subtropical ridge over the southwestern Atlantic, the hurricane's forward motion should remain quite slow as it is currently being impeded by a mid-level ridge over the northeastern United States. A large mid-latitude trough is forecast to move across the Great Lakes region and into the northeast United States by the end of the week. This feature should cause Maria to accelerate east-northeastward to northeastward after 72 hours. The track guidance is in excellent agreement through 48 hours, but there are some differences in Maria's forward speed after that time. The NHC forecast track is near the middle of the guidance envelope through 48 h and is in between the ECMWF and various consensus models later in the period. KEY MESSAGES: 1. Maria is forecast to continue moving northward, paralleling the U.S. east coast, and it is likely that some direct impacts will occur along portions of the North Carolina coast beginning Tuesday, where a Tropical Storm Warning is in effect. 2. Storm surge flooding, especially along the sound side of the North Carolina Outer Banks, is possible beginning on Tuesday, and a Storm Surge Watch has been issued for portions of eastern North Carolina. 3. Swells from Maria are occurring along the coast of the southeastern United States and will be increasing along the Mid-Atlantic and southern New England coasts today. These swells will likely cause dangerous surf and rip currents at beaches in these areas through much of the week. For more information, please monitor information from your local National Weather Service office at www.weather.gov. FORECAST POSITIONS AND MAX WINDS INIT 25/1500Z 31.2N 72.9W 70 KT 80 MPH 12H 26/0000Z 31.8N 73.0W 70 KT 80 MPH 24H 26/1200Z 32.9N 73.1W 65 KT 75 MPH 36H 27/0000Z 33.8N 73.1W 65 KT 75 MPH 48H 27/1200Z 34.7N 73.0W 60 KT 70 MPH 72H 28/1200Z 35.7N 71.4W 60 KT 70 MPH 96H 29/1200Z 37.5N 64.5W 60 KT 70 MPH 120H 30/1200Z 42.0N 52.0W 60 KT 70 MPH $$ Forecaster Brown