000 WTNT44 KNHC 222052 TCDAT4 HURRICANE IRENE DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092011 500 PM AST MON AUG 22 2011 DATA FROM THE LAST AIR FORCE HURRICANE HUNTER AIRCRAFT AROUND 1700 UTC INDICATE THAT THE CENTRAL PRESSURE WAS STEADY AND THE WINDS HAVE NOT CHANGED DURING THE DAY. SINCE THEN...HIGH RESOLUTION SATELLITE IMAGES REVEAL SOME CONVECTIVE BANDS WRAPPING AROUND A CLUSTER OF DEEP CONVECTION NEAR THE CENTER...SUGGESTING THAT IRENE COULD BE SLOWLY INTENSIFYING. HOWEVER...DVORAK T-NUMBERS ARE 4.0 AND 4.5 WHICH SUPPORTS KEEPING THE INITIAL INTENSITY AT 70 KNOTS. ANOTHER PLANE WILL CHECK THE HURRICANE AROUND 0000 UTC TONIGHT. WITH THE EXCEPTION OF THE DISRUPTION OF THE OUTER CIRCULATION BY THE HIGH TERRAIN OF HISPANIOLA...WHICH PROBABLY WILL SLOW DOWN THE INTENSIFICATION PROCESS DURING THE NEXT 12 TO 24 HOURS...ALL OF THE INGREDIENTS ARE CONDUCIVE FOR IRENE TO INTENSIFY OVER THE NEXT FEW DAYS. THE OFFICIAL FORECAST CALLS FOR IRENE TO BECOME A STRONG CATEGORY 2 OR CATEGORY 3 HURRICANE ON THE SAFFIR-SIMPSON HURRICANE WIND SCALE AS IRENE MOVES ACROSS THE CENTRAL AND NORTHWESTERN BAHAMAS. IN FACT...BOTH THE GFS AND THE ECMWF GLOBAL MODELS INSIST ON MAKING IRENE A LARGE AND STRONG HURRICANE WITH MINIMUM PRESSURES AROUND 945 MB AND 952 MB...RESPECTIVELY. IRENE IS MOVING TOWARD THE WEST-NORTHWEST OR 295 DEGREES AT 11 KNOTS. CURRENTLY...THE MOTION OF THE HURRICANE IS BEING CONTROLLED BY A NARROW SUBTROPICAL RIDGE TO ITS NORTH. HOWEVER...THE FUTURE TRACK WILL DEPEND ON THE DEVELOPMENT OF A LARGE MID- TO UPPER-LEVEL TROUGH ALONG THE EAST COAST OF THE UNITED STATES. THIS PATTERN WILL INDUCE A GRADUAL NORTHWESTWARD AND THEN NORTHWARD TRACK THROUGH THE FORECAST PERIOD WITH A SLIGHT DECREASE IN FORWARD SPEED. THERE IS MORE CONFIDENCE IN THE FORECAST SINCE MOST OF THE TRACK MODELS... WITH THE EXCEPTION OF THE GFDL...HAVE NOW FOLLOWED THE LEAD OF THE ECMWF MODEL. THE GUIDANCE IS NOW IN BETTER AGREEMENT IN TURNING IRENE NORTHWARD ALONG 78 OR 79 DEGREES LONGITUDE. ALTHOUGH IT IS STILL TOO EARLY TO BE CERTAIN...THE GUIDANCE TREND CONTINUES TO LESSENS THE THREAT TO SOUTH FLORIDA BUT INCREASES THE THREAT TO THE CAROLINAS. 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 22/2100Z 19.5N 68.6W 70 KT 80 MPH 12H 23/0600Z 20.1N 70.2W 80 KT 90 MPH 24H 23/1800Z 20.8N 72.5W 85 KT 100 MPH 36H 24/0600Z 21.5N 74.0W 90 KT 105 MPH 48H 24/1800Z 23.0N 75.5W 95 KT 110 MPH 72H 25/1800Z 26.0N 78.0W 100 KT 115 MPH 96H 26/1800Z 29.5N 79.0W 100 KT 115 MPH 120H 27/1800Z 34.0N 79.0W 80 KT 90 MPH...INLAND $$ FORECASTER AVILA