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Hurricane Irma Discussion Number 42
NWS National Hurricane Center Miami FL AL112017
1100 AM EDT Sat Sep 09 2017
The interaction of Irma's circulation with Cuba has resulted in
some weakening of the hurricane. Data from an Air Force plane
indicate that the maximum winds are now 110 kt. However, once the
circulation moves away from Cuba, restrengthening is forecast and
Irma is expected to remain a very dangerous hurricane for the next 2
days while moving very near the Florida peninsula.
The eye has been moving toward the west or 280 degrees at about 8
kt. The hurricane is about the reach the southwestern portion of
the subtropical high, and the expected turn to the northwest and
north-northwest should begin soon. The track guidance is tightly
packed and takes the hurricane over the Florida Keys and near or
over the Florida Peninsula. The NHC forecast is in the middle of
the guidance envelope and given the good agreement among models, the
confidence in the track forecast is high.
Irma is now under the scope of Key West radar, so hourly updates
will begin at 1600 UTC.
1. Irma will continue to bring life-threatening wind, storm surge,
and rainfall hazards to portions of the Bahamas and the north coast
of Cuba, especially over the adjacent Cuban Keys, through tonight.
2. Irma is expected to make landfall in Florida as an extremely
dangerous major hurricane, bringing life-threatening wind
impacts to much of the state regardless of the exact track of the
center. Wind hazards from Irma are also expected to spread northward
along the coast of Georgia and South Carolina where a Hurricane
Watch has been issued.
3. There is an imminent danger of life-threatening storm surge
flooding in portions of central and southern Florida, including the
Florida Keys, where a Storm Surge Warning is in effect. The threat
of catastrophic storm surge flooding is highest along the southwest
coast of Florida, where 10 to 15 feet of inundation above ground
level is expected. This is a life-threatening situation and everyone
in these areas should immediately follow any evacuation instructions
from local officials.
4. Irma is expected to produce very heavy rain and inland flooding.
Total rain accumulations of 10 to 20 inches, with isolated amounts
of between 20 and 25 inches, are expected over the Florida Keys, the
Florida peninsula, and southeast Georgia from Saturday through
Monday. Significant river flooding is possible in these areas. Early
next week Irma will also bring periods of heavy rain to much of the
southeast United States where an average of 2 to 6 inches is
forecast, with isolated higher amounts, from North and South
Carolina to Tennessee and eastern Alabama. This includes some
mountainous areas which are more prone to flash flooding. Residents
throughout the southeast states should remain aware of the flood
threat and stay tuned to forecasts and warnings.
FORECAST POSITIONS AND MAX WINDS
INIT 09/1500Z 22.8N 79.8W 110 KT 125 MPH
12H 10/0000Z 23.4N 80.7W 115 KT 130 MPH
24H 10/1200Z 24.5N 81.6W 120 KT 140 MPH
36H 11/0000Z 26.4N 82.1W 120 KT 140 MPH
48H 11/1200Z 29.0N 82.8W 100 KT 115 MPH
72H 12/1200Z 34.5N 86.0W 25 KT 30 MPH...POST-TROP/INLAND
96H 13/1200Z 36.0N 89.0W 25 KT 30 MPH...POST-TROP/INLAND
120H 14/1200Z 37.0N 88.5W 20 KT 25 MPH...POST-TROP/INLAND