000 WTNT45 KNHC 250851 TCDAT5 Hurricane Maria Discussion Number 37 NWS National Hurricane Center Miami FL AL152017 500 AM EDT Mon Sep 25 2017 A combination of conventional satellite imagery, scatterometer data, and reports from a NOAA Hurricane Hunter aircraft indicate that Maria is weakening and undergoing major changes in structure as it encounters the cool water left by Hurricane Jose. Satellite imagery shows that the low-level center has become exposed to the northwest of the remaining central convection, with some outer convective banding remaining mainly in the eastern semicircle. The scatterometer and aircraft data suggests that the inner wind core has collapsed, with no hurricane force winds occurring in the western semicircle. Based on the combination of these data, the initial intensity is lowered to a possibly generous 70 kt, and the initial and forecast wind radii have been significantly changed. The initial motion is 355/6. Maria is being steered by the flow between a mid- to upper-level cyclone over the southeastern U.S. and the subtropical ridge over the southwestern Atlantic. A mid-level ridge moving eastward across the northeastern U.S. will likely cause Maria's forward motion to slow some more over the next couple of days. After that time, the mid-latitude westerlies are expected to encroach on Maria, causing it to turn sharply to the east- northeast and accelerate. The guidance is in good agreement on this track scenario, and the new forecast track, which lies between the ECMWF and the various consensus models, is an update of the previous forecast. The environment of cool sea surface temperatures and moderate shear should keep Maria weakening. However, it unclear just how fast it will weaken, as the guidance has been generally forecasting a slower weakening than has actually occurred. The new intensity forecast will follow the trend of the guidance and the previous forecast of a gradual weakening, with Maria now forecast to weaken below hurricane status after 36 h. However, an alternate scenario is that the cyclone continues weakening at a faster rate and thus winds up weaker than the new intensity forecast. Maria is a large cyclone, so even if it weakens to a tropical storm and remains well offshore it is expected to bring tropical storm conditions to portions of the North Carolina coast during the next couple of days. 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 coast beginning Tuesday. A Tropical Storm Warning has been issued for a portion of the coast of North Carolina. 2. Storm surge flooding especially along the sound side of the North Carolina Outer Banks is possible beginning Tuesday, and a Storm Surge Watch has been issued for a portion of the North Carolina Outer Banks. 3. Swells from Maria are increasing along the coast of the southeastern United States and are expected to reach the Mid- Atlantic coast 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 25/0900Z 30.6N 73.0W 70 KT 80 MPH 12H 25/1800Z 31.4N 73.2W 70 KT 80 MPH 24H 26/0600Z 32.5N 73.3W 65 KT 75 MPH 36H 26/1800Z 33.5N 73.3W 65 KT 75 MPH 48H 27/0600Z 34.3N 73.2W 60 KT 70 MPH 72H 28/0600Z 35.5N 72.0W 60 KT 70 MPH 96H 29/0600Z 37.0N 66.5W 60 KT 70 MPH 120H 30/0600Z 40.0N 56.5W 60 KT 70 MPH $$ Forecaster Beven