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Hurricane Maria Discussion Number 12
NWS National Hurricane Center Miami FL AL152017
1100 PM AST Mon Sep 18 2017
The Air Force Hurricane Hunters were able to fly a single pass
from northwest to southeast through the eye of Maria just prior to
0000 UTC. The aircraft found a peak SFMR wind of 139 kt in the
northwest eyewall, i.e. category 5 intensity. Raw objective
T-numbers from UW/CIMSS reached as high as T7.3 just before the
center moved over land. Based on these data, the initial wind speed
was increased to 140 kt on the earlier special advisory, and that
intensity is maintained for this advisory, although some slight
weakening may have occurred as the small core of the hurricane
passed over Dominica. Since the center has moved over land, the
aircraft has not been able to make a second pass through the eye.
The aircraft will be in the storm a few more hours and should be
able to provide additional center fixes once the eye moves west of
Dominica.
Maria is forecast to remain within an environment of low wind shear
and over warm water during the next couple of days. Given these
favorable atmospheric and oceanic conditions, Maria is expected to
remain a Category 4 or 5 hurricane when it approaches the Virgin
Islands and Puerto Rico, however some fluctuations in intensity are
possible due during the next 24 to 36 h due to eyewall cycles. Land
interaction and a slight increase in shear are likely to cause some
gradual weakening after Maria moves over the southwestern Atlantic
in 3 to 4 days.
Maria is moving west-northwestward or 300/8 kt. A weak ridge
located over the western Atlantic is expected to steer the
hurricane west-northwestward through 48 hours, and on this track the
center of Maria 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, which should allow Maria to turn
northwestward, then north-northwestward by day 5. The track
guidance is in good agreement and little change was required to the
NHC track forecast through 72 hours. At days 4 and 5, the global
model envelope has shifted slightly eastward and the NHC forecast
was adjusted accordingly to be in better agreement with the HFIP
correct consensus and ECMWF model.