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Hurricane IRMA


Hurricane Irma Discussion Number  17
NWS National Hurricane Center Miami FL       AL112017
1100 AM AST Sun Sep 03 2017

The eye of Irma is a little less distinct in geostationary satellite
images this morning, which suggests that the intensity of the
hurricane may be fluctuating yet again.  However, the initial
wind speed is maintained at 100 kt for this advisory, which is close
to a consensus of the various objective and subjective satellite
intensity estimates.  The first reconnaissance mission, a NOAA P-3
Hurricane Hurricane aircraft, is scheduled to depart Barbados for
tail Doppler radar mission into Irma late this afternoon and should
provide additional information on Irma's intensity by this evening.

A strong high pressure ridge over the central Atlantic is steering
Irma west-southwestward or 255/12 kt.  This general motion with
some reduction in forward speed is expected during the next day or
so.  After that time, Irma is forecast to turn westward, then
west-northwestward in about 72 hours as it approaches the western
portion of the ridge.  The various consensus aids are generally a
little slower than the previous advisory, but there cross-track
differences are small.  As a result, the updated NHC track is very
similar to the previous advisory, and is close to a consensus of the
ECMWF, GFS, UKMET, and HWRF, but is not as far south as the
latest runs of the UKMET or ECMWF.

Irma is forecast to move over slightly warmer SSTs and into a
moistening mid-level environment.  These conditions, along with a
favorable upper-level wind pattern, should allow for gradual
strengthening during the next 2 to 3 days. However, eyewall
replacement cycles could result in fluctuations in intensity
during the next several days.

While Irma is currently a small hurricane, the guidance suggests it
should grow in size during the next 72 h.  This will affect how soon
watches may be issued for portions of the Leeward and Virgin
Islands, and interests on those islands should continue to monitor
Irma's progress.

1. Irma is expected to be a major hurricane when it moves near or
over the northeastern Leeward Islands by the middle of this week,
and could cause dangerous wind, storm surge, and rainfall impacts,
along with rough surf and rip currents on some islands. Hurricane
and tropical storm watches will likely be issued for some of these
islands later today or tonight. Residents in these areas should
monitor the progress of Irma and listen to advice given by

2. Direct impacts from Irma are also possible in the Virgin Islands
and Puerto Rico later this week, and tropical storm or hurricane
watches could be issued for these islands by tomorrow.  Residents in
these areas should monitor the progress of Irma and listen to advice
given by officials.

3. The possibility of direct impacts from Irma in Hispaniola, the
Turks and Caicos, and the Bahamas later this week is increasing.
Residents in these areas should monitor the progress of Irma and
listen to advice given by officials.

4. It is too early to determine what direct impacts Irma might have
on the continental United States.  Regardless, everyone in
hurricane-prone areas should ensure that they have their hurricane
plan in place, as we are now near the peak of the season.


INIT  03/1500Z 17.7N  48.4W  100 KT 115 MPH
 12H  04/0000Z 17.1N  50.1W  105 KT 120 MPH
 24H  04/1200Z 16.6N  52.2W  110 KT 125 MPH
 36H  05/0000Z 16.4N  54.3W  115 KT 130 MPH
 48H  05/1200Z 16.7N  56.6W  120 KT 140 MPH
 72H  06/1200Z 18.2N  61.8W  120 KT 140 MPH
 96H  07/1200Z 20.4N  67.1W  115 KT 130 MPH
120H  08/1200Z 22.5N  72.0W  115 KT 130 MPH

Forecaster Brown