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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

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