Update: Hurricane IRENE Forecast

Hurricane IRENE Forecast Discussion
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Hurricane IRENE Forecast Discussion
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WTNT44 KNHC 270857
TCDAT4

HURRICANE IRENE DISCUSSION NUMBER 28
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092011
500 AM EDT SAT AUG 27 2011

SATELLITE IMAGERY AND COASTAL RADAR DATA SHOW THAT IRENE HAS LOST
SOME ORGANIZATION THIS MORNING. THE CLOUD TOPS HAVE WARMED
SIGNIFICANTLY IN THE WESTERN SEMICIRCLE...AND THERE IS A LACK OF
CONVECTIVE BANDING IN THE SOUTHWESTERN QUADRANT IN THE RADAR DATA.
THIS SUGGESTS THAT DRY AIR SEEN IN WATER VAPOR IMAGERY TO THE WEST
OF IRENE IS STARTING TO ENTRAIN INTO THE HURRICANE. AN AIR FORCE
RESERVE HURRICANE HUNTER AIRCRAFT CONTINUES TO OBSERVE 90-100 KT
WINDS AT 700 MB OVER THE EASTERN SEMICIRCLE. HOWEVER...THE HIGHEST
SURFACE WIND ESTIMATES FROM THE SFMR HAVE ONLY BEEN 70-75 KT. THE
INITIAL INTENSITY IS REDUCED TO 80 KT...AND THIS COULD BE A LITTLE
GENEROUS. DESPITE THE DECREASE IN CONVECTIVE ORGANIZATION...THE
AIRCRAFT REPORTS THAT THE CENTRAL PRESSURE REMAINS NEAR 952 MB.

THE INITIAL MOTION IS 020/12. IRENE IS WEST OF THE SUBTROPICAL
RIDGE...WITH WATER VAPOR IMAGERY SHOWING A MID/UPPER-LEVEL
SHORTWAVE TROUGH IN THE WESTERLIES MOVING ACROSS THE GREAT LAKES.
IRENE SHOULD CONTINUE TO MOVE NORTH-NORTHEASTWARD INTO THE
WESTERLIES DURING THE NEXT 36-48 HOURS...WITH THE CENTER MOVING
OVER EASTERN NORTH CAROLINA...OVER OR NEAR THE COAST OF THE
MID-ATLANTIC STATES...AND THEN OVER NEW ENGLAND. AFTER 48 HOURS...
THE CYCLONE SHOULD TURN NORTHEASTWARD AND THEN EAST-NORTHEASTWARD
WITH AN INCREASE IN FORWARD SPEED AS IT REACHES THE CORE OF THE
WESTERLIES. THE NEW FORECAST TRACK IS AN UPDATE OF THE PREVIOUS
TRACK AND LIES IN THE CENTER OF THE GUIDANCE ENVELOPE.

LAND INTERACTION...DRY AIR ENTRAINMENT...AND INCREASING VERTICAL
WIND SHEAR SHOULD CAUSE IRENE TO WEAKEN AS IT MOVES ALONG THE U.S.
EAST COAST. HOWEVER...THE CYCLONE IS EXPECTED TO REMAIN A
HURRICANE WITH A VERY LARGE WIND FIELD UNTIL AFTER LANDFALL IN NEW
ENGLAND. EXTRATROPICAL TRANSITION SHOULD OCCUR AFTER THE NEW
ENGLAND LANDFALL...WITH IRENE GRADUALLY WEAKENING FROM 48-120 HR.

THE RADAR PRESENTATION OF THE CENTER OF IRENE HAS DECREASED TO THE
POINT THAT WE WILL BE REVERTING TO THREE-HOURLY INTERMEDIATE
ADVISORIES.

FORECAST POSITIONS AND MAX WINDS

INIT 27/0900Z 34.1N 76.5W 80 KT 90 MPH
12H 27/1800Z 35.7N 75.8W 75 KT 85 MPH...INLAND
24H 28/0600Z 38.4N 74.6W 70 KT 80 MPH...OVER WATER
36H 28/1800Z 41.9N 72.7W 65 KT 75 MPH...INLAND
48H 29/0600Z 46.3N 69.6W 50 KT 60 MPH...POST-TROP/EXTRATROP
72H 30/0600Z 54.0N 59.0W 40 KT 45 MPH...POST-TROP/EXTRATROP
96H 31/0600Z 57.0N 41.0W 40 KT 45 MPH...POST-TROP/EXTRATROP
120H 01/0600Z 58.0N 23.0W 35 KT 40 MPH...POST-TROP/EXTRATROP

$$
FORECASTER BEVEN

http://www.nhc.noaa.gov/text/refresh/MIATCDAT4+shtml/270857.shtml