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Hurricane Irma Discussion Number 38
NWS National Hurricane Center Miami FL AL112017
1100 AM EDT Fri Sep 08 2017
Recent data from both NOAA and Air Force reconnaissance planes
indicate that Irma's intensity remains at 130 kt, although this
value could be 5 kt higher or lower. The central pressure has been
oscillating around 927 mb.
The environment continues to be favorable for Irma to maintain its
category 4 status, and only unpredictable eyewall replacement cycles
could result in intensity fluctuations during the next 48 hours.
Nevertheless, the NHC forecast brings Irma near south Florida as a
category 4 hurricane. Thereafter, interaction with land and an
increase in shear should induce gradual weakening.
Plane, satellite and radar fixes from Cuba indicate that the eye of
Irma is moving toward the west-northwest or 285 degrees at about 12
kt. The hurricane should continue on this track for the next 24
hours. After that time, Irma will reach the southwestern edge of
the subtropical high and begin to turn north-northwestward and
northward. This turn will occur, but the precise moment is still
uncertain, and that is why NHC emphasizes that nobody should focus
on the exact track of the center. The new NHC forecast was adjusted
just a little bit westward and is on top the latest ECMWF model and
the HFIP corrected consensus. In fact, these two aids are also very
close to each other.
1. Irma is an extremely dangerous Category 4 hurricane and will
continue to bring life-threatening wind, storm surge, and rainfall
hazards to the Bahamas through Saturday. Hurricane conditions will
spread over portions of the north coast of Cuba, especially over the
adjacent Cuban Keys, through Saturday.
2. Irma is likely to make landfall in Florida as a dangerous major
hurricane, and will bring life-threatening wind impacts to much of
the state regardless of the exact track of the center.
3. There is the danger of life-threatening storm surge inundation in
southern Florida and the Florida Keys during the next 36 hours,
where a Storm Surge Warning is in effect. In particular, the threat
of significant storm surge flooding along the southwest coast of
Florida has increased, and 6 to 12 feet of inundation above ground
level is possible in this area. This is a life-threatening
situation. Everyone in these areas should take all actions to
protect life and property from rising water and follow evacuation
instructions from local officials.
4. Irma is expected to produce very heavy rain and inland flooding.
Total rain accumulations of 4 to 12 inches, with isolated amounts of
20 inches are expected over the Florida peninsula Saturday through
Monday. The highest amounts are expected over the eastern Florida
peninsula and upper Florida Keys. Irma will likely bring periods of
heavy rain to much of Georgia, South Carolina, and western North
Carolina early next week, including some mountainous areas which are
more prone to flash flooding. All areas seeing heavy rainfall from
Irma will experience a risk of flooding and flash flooding.
FORECAST POSITIONS AND MAX WINDS
INIT 08/1500Z 22.0N 75.3W 130 KT 150 MPH
12H 09/0000Z 22.4N 77.1W 130 KT 150 MPH
24H 09/1200Z 22.8N 79.0W 130 KT 150 MPH
36H 10/0000Z 23.7N 80.3W 130 KT 150 MPH
48H 10/1200Z 25.0N 81.0W 125 KT 145 MPH...NEAR THE COAST
72H 11/1200Z 29.3N 82.3W 65 KT 75 MPH...INLAND
96H 12/1200Z 34.0N 85.0W 30 KT 35 MPH...INLAND
120H 13/1200Z 36.0N 87.0W 25 KT 30 MPH...INLAND