ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM HURRICANE IRWIN DISCUSSION NUMBER 7 NWS NATIONAL HURRICANE CENTER MIAMI FL EP112011 200 PM PDT FRI OCT 07 2011 THE CLOUD PATTERN OF THE HURRICANE HAS BECOME A LITTLE BETTER ORGANIZED OVER THE PAST SEVERAL HOURS WITH MORE DEFINITIVE BANDING FEATURES AND THE EYE BECOMING APPARENT ON VISIBLE IMAGES. TAKING A BLEND OF DVORAK INTENSITY ESTIMATES FROM TAFB AND SAB YIELDS AN INITIAL INTENSITY ESTIMATE OF 80 KT. IRWIN IS CURRENTLY IN AN ENVIRONMENT OF MODEST EASTERLY SHEAR...BUT IN A COUPLE OF DAYS THIS SHEAR IS FORECAST TO INCREASE. THEREFORE...THE STRENGTHENING TREND IS PREDICTED TO END IN 36 TO 48 HOURS...AND THE OFFICIAL INTENSITY FORECAST IS VERY SIMILAR TO THE LATEST STATISTICAL-DYNAMICAL GUIDANCE. SOME OF THE DYNAMICAL GUIDANCE INDICATES RESTRENGTHENING NEAR THE END OF THE FORECAST PERIOD...BUT GIVEN THE UNCERTAINTIES IN PREDICTING INTENSITY CHANGE AT 5 DAYS...THE OFFICIAL FORECAST DOES NOT GO WITH THAT SCENARIO. THE MOTION CONTINUES TO SLOW AND IS NOW ABOUT 295/5. AS THE MID-LEVEL RIDGE TO THE NORTHEAST OF IRWIN RETREATS TO THE EAST AND SOUTH...THE TROPICAL CYCLONE IS FORECAST TO TURN TOWARD THE RIGHT OVER THE NEXT COUPLE OF DAYS. THEREAFTER IRWIN SHOULD BEGIN MOVING EASTWARD WITHIN A REGION OF BROAD WESTERLY LOW- TO MID-LEVEL FLOW. SOME OF THE TRACK GUIDANCE SUCH AS THE GFS IS NOT TAKING IRWIN AS FAR EAST AS PREVIOUSLY. THIS IS CONSISTENT WITH THAT MODEL SHOWING A MID-TROPOSPHERIC RIDGE BEGINNING TO BUILD TO THE NORTH OF IRWIN BY DAY 5. THE OFFICIAL TRACK FORECAST GENERALLY LIES BETWEEN THE GFS AND THE LATEST ECMWF TRACK. FORECAST POSITIONS AND MAX WINDS INIT 07/2100Z 14.0N 120.9W 80 KT 90 MPH 12H 08/0600Z 14.2N 121.2W 85 KT 100 MPH 24H 08/1800Z 14.7N 121.2W 90 KT 105 MPH 36H 09/0600Z 14.8N 120.6W 90 KT 105 MPH 48H 09/1800Z 15.0N 119.5W 85 KT 100 MPH 72H 10/1800Z 15.0N 117.0W 75 KT 85 MPH 96H 11/1800Z 15.5N 113.0W 70 KT 80 MPH 120H 12/1800Z 16.5N 109.0W 65 KT 75 MPH $$ FORECASTER PASCH NNNN
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Page last modified: Tuesday, 17-Jul-2012 13:44:19 UTC