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11pm AST Sunday NHC Discussion

Posted by Chris in Tampa on 9/17/2017, 11:05 pm

Hurricane Maria Discussion Number   7
NWS National Hurricane Center Miami FL       AL152017
1100 PM AST Sun Sep 17 2017

Reports from an Air Force Reserve Hurricane Hunter aircraft received
just after the previous advisory indicated that Maria's maximum
sustained winds had increased to 70 kt.  Since that time, a large
central dense overcast with cloud tops colder than -80C has formed,
and data from the radar on Martinique shows 60-70 percent of an
eyewall is present under the overcast.  Satellite intensity
estimates have increased to 75 kt, and that is the initial
intensity.

The initial motion is 290/11.  The subtropical ridge to the north
is expected to steer Maria generally west-northwestward for the
next 72 h, with some decrease in the forward speed.  After that
time, the guidance suggests that the hurricane should turn more
toward the northwest as it approaches the western end of the ridge.
The track guidance remains tightly clustered, and the new forecast
track, which is similar to the previous track, is in best overall
agreement with the HFIP corrected consensus and ECMWF models.

Analyses from CIMSS at the University of Wisconsin suggest that
Maria is currently experiencing light to moderate southwesterly
shear.  However, all indications are that the shear should diminish
during the next 24-48 h, which should allow steady to rapid
strengthening.  The Rapid Intensification Index of the SHIPS model
forecast better than a 50 percent chance of 25-30 kt of
strengthening during the next 24 h, and about a 35 percent chance
of 55 kt of strengthening during the next 48 h.  Based on this, the
intensity forecast has been increased to show Maria becoming a
major hurricane in 24 h and a category 4 hurricane in 48 h.
 Late in
the forecast period, a combination of land interaction and
increasing shear should cause some weakening.  The new intensity
forecast is near the upper edge of the guidance in best overall
agreement with the HWRF.


KEY MESSAGES:

1. Maria continues to strengthen and is expected to be at major
hurricane intensity when it affects portions of the Leeward Islands
over the next few days, bringing dangerous wind, storm surge and
rainfall hazards.  Hurricane and tropical storm warnings have been
issued for portions of the Leeward Islands, and these warnings will
likely be extended northward and westward on Monday.

2. Maria is likely to affect the British and U.S. Virgin Islands and
Puerto Rico by mid week as a dangerous major hurricane.  Hurricane
watches have been issued for the U.S. and British Virgin Islands and
could be extended to Puerto Rico early Monday.  Interests in these
areas should monitor the progress of Maria and follow any advice
given by local officials.



FORECAST POSITIONS AND MAX WINDS

INIT  18/0300Z 14.2N  58.4W   75 KT  85 MPH
12H  18/1200Z 14.7N  59.8W   85 KT 100 MPH
24H  19/0000Z 15.4N  61.2W  100 KT 115 MPH
36H  19/1200Z 16.2N  62.6W  110 KT 125 MPH
48H  20/0000Z 16.9N  63.9W  115 KT 130 MPH
72H  21/0000Z 18.5N  67.0W  120 KT 140 MPH...OVER PUERTO RICO
96H  22/0000Z 20.0N  69.5W  115 KT 130 MPH...OVER WATER
120H  23/0000Z 22.0N  71.5W  105 KT 120 MPH

$$
Forecaster Beven

115



In this thread:

11pm AST Sun: Maria strengthening. Forecast to be major hurricane as it moves near Leewards - Chris in Tampa, 9/17/2017, 11:03 pm

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