000
WTNT44 KNHC 221504
TCDAT4
HURRICANE IRENE DISCUSSION NUMBER 8
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092011
1100 AM AST MON AUG 22 2011
DATA FROM A RECONNAISSANCE PLANE...RADAR AND SATELLITE IMAGERY INDICATE THAT IRENE HAS CONTINUED TO GRADUALLY BECOME BETTER ORGANIZED. HOWEVER THE WINDS WINDS HAVE NOT INCREASED SIGNIFICANTLY AND THE MINIMUM CENTRAL PRESSURE WAS AROUND 988 MB IN THE LAST CENTER DROPSONDE. THE INITIAL INTENSITY HAS BEEN INCREASED TO 70 KNOTS IN THIS ADVISORY. SINCE THE CORE OF THE HURRICANE IS NOT FORECAST TO MOVE DIRECTLY OVER THE HIGH TERRAIN OF HISPANIOLA...AND THE OCEANIC AND ATMOSPHERIC CONDITIONS ARE QUITE FAVORABLE... THE OFFICIAL FORECAST CALLS FOR INTENSIFICATION...AND MAKES IRENE A CATEGORY 3 HURRICANE AS IT MOVES ACROSS THE CENTRAL BAHAMAS. THIS IS CONSISTENT WITH MOST OF THE DYNAMICAL GUIDANCE AND IN FACT...EVEN GLOBAL MODELS FORECAST A SIGNIFICANT DROP IN THE CENTRAL PRESSURE OVER THE NEXT TWO OR THREE DAYS. IRENE IS BECOMING A LARGE CYCLONE...AND BASED ON BUOY OBSERVATIONS THE TROPICAL STORM FORCE WINDS EXTEND 160 N MI TO THE NORTHEAST OF THE CENTER.
RADAR AND RECONNAISSANCE FIXES INDICATE THAT THE HURRICANE IS MOVING TOWARD THE WEST-NORTHWEST OR 295 DEGREES AT ABOUT 12 KNOTS. IRENE IS CURRENTLY LOCATED SOUTH OF A NARROW SUBTROPICAL RIDGE WHICH IS FORCING THE CYCLONE ON A WEST-NORTHWEST TRACK. HOWEVER...MOST OF THE GLOBAL MODELS SHOW THE GRADUAL DEVELOPMENT A LARGE UPPER TROUGH ALONG THE UNITED STATES EAST COAST. THIS PATTERN WILL INDUCE A MORE NORTHWESTWARD AND THEN NORTHWARD TRACK THROUGH THE FORECAST PERIOD WITH A DECREASE IN FORWARD SPEED. BASED ON THE LATEST GUIDANCE... THE OFFICIAL TRACK FORECAST HAS BEEN SHIFTED TO THE EAST...BUT STILL REMAINS SLIGHTLY WEST OF THE MODEL CONSENSUS. ALTHOUGH IT IS TOO EARLY TO BE CERTAIN...THE CURRENT GUIDANCE LESSENS THE THREAT TO SOUTH FLORIDA.
DO NOT TO FOCUS ON THE EXACT FORECAST TRACK...ESPECIALLY AT DAYS 4 TO 5...SINCE THE MOST RECENT 5-YEAR AVERAGE ERRORS AT THOSE FORECAST TIMES ARE 200 AND 250 MILES...RESPECTIVELY.
FORECAST POSITIONS AND MAX WINDS
INIT 22/1500Z 19.2N 67.5W 70 KT 80 MPH
12H 23/0000Z 19.9N 69.2W 75 KT 85 MPH
24H 23/1200Z 20.5N 71.4W 80 KT 90 MPH
36H 24/0000Z 21.2N 73.2W 85 KT 100 MPH
48H 24/1200Z 22.0N 75.0W 90 KT 105 MPH
72H 25/1200Z 25.0N 77.5W 100 KT 115 MPH
96H 26/1200Z 28.5N 79.0W 100 KT 115 MPH
120H 27/1200Z 32.5N 80.0W 100 KT 115 MPH
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FORECASTER AVILA