ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM TROPICAL STORM FERNANDA DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL EP062011 200 PM PDT TUE AUG 16 2011 FERNANDA HAS GONE THROUGH AN INTERESTING EVOLUTION ON SATELLITE DURING THE PAST SEVERAL HOURS. WHILE OVERNIGHT IMAGES SUGGESTED A SHEARED SYSTEM...THE LATEST VISIBLE IMAGERY SHOWS A STORM CHARACTERIZED BY CURVED BANDING FEATURES AND NO SIGNS OF THE EARLIER SHEAR. SUBJECTIVE DVORAK INTENSITY ESTIMATES FROM BOTH TAFB AND SAB ARE 45 KT...SO THAT WILL BE THE INITIAL WIND SPEED. THE OUTFLOW PATTERN OF FERNANDA HAS A FAVORABLE SHAPE FOR FURTHER INTENSIFICATION WITH CIRRUS FANNING OUT NICELY IN ALL QUADRANTS. VISIBLE IMAGERY INDICATES THAT THE CENTER IS LOCATED A BIT TO THE SOUTH OF PREVIOUS ESTIMATES...SO THE STORM SHOULD HAVE A LONGER TIME IN ENVIRONMENTAL CONDITIONS CONDUCIVE FOR STRENGTHENING. ALMOST ALL OF THE GUIDANCE MODELS NOW MAKE FERNANDA A HURRICANE AT SOME POINT...AND CONSIDERING THE STORM SHOULD HAVE LIGHT SHEAR AND MARGINALLY WARM WATERS FOR ABOUT 48 HOURS...THERE IS NOT MUCH REASON TO DISCOUNT THE STRONGER SOLUTION. THUS...THE NEW NHC FORECAST CALLS FOR FERNANDA TO BRIEFLY REACH HURRICANE STRENGTH. IN THE LONGER RANGE...A COMBINATION OF INCREASING SOUTHERLY SHEAR AND COOLER WATER SHOULD INDUCE WEAKENING...AND THE NHC FORECAST REMAINS ON THE LOWER SIDE OF THE GUIDANCE AT THAT TIME. IT IS UNCLEAR WHETHER THIS SYSTEM HAS BEEN MOVING OR HAS REFORMED A BIT TO THE SOUTH DURING THE PAST SEVERAL HOURS...BUT THE BEST ESTIMATE OF INITIAL MOTION IS 265/9 KT. GLOBAL MODELS ARE SHOWING A DEEP TROUGH ALONG ABOUT 140W...WHICH LEAVES A WEAKNESS IN THE SUBTROPICAL RIDGE. AS FERNANDA APPROACHES THAT LONGITUDE...THE STORM SHOULD TURN A BIT MORE TO THE WEST-NORTHWEST OR NORTHWEST IN RESPONSE TO THE WEAKNESS. IN A FEW DAYS...A MID-LEVEL RIDGE NORTHEAST OF THE HAWAIIAN ISLANDS SHOULD CAUSE THE CYCLONE TO TURN BACK TOWARD THE WEST-NORTHWEST OR WEST. THE NHC FORECAST HAS BEEN SHIFTED A LITTLE TO THE SOUTH IN THE SHORT-TERM...MOSTLY DUE TO THE CENTER REFORMATION...BUT ENDS UP NORTH OF THE PREVIOUS FORECAST BY THE END. WHILE THE GUIDANCE HAS SHIFTED A BIT TO THE NORTH IN THE LONG RANGE...STRONG SHEAR AND COLDER-THAN-AVERAGE WATERS SHOULD REDUCE FERNANDA TO A REMNANT LOW BY DAY 5. FORECAST POSITIONS AND MAX WINDS INIT 16/2100Z 11.7N 135.7W 45 KT 50 MPH 12H 17/0600Z 11.6N 136.8W 50 KT 60 MPH 24H 17/1800Z 11.9N 138.2W 55 KT 65 MPH 36H 18/0600Z 12.6N 139.6W 60 KT 70 MPH 48H 18/1800Z 13.4N 141.2W 65 KT 75 MPH 72H 19/1800Z 15.0N 145.0W 50 KT 60 MPH 96H 20/1800Z 15.5N 149.0W 40 KT 45 MPH 120H 21/1800Z 15.5N 153.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ FORECASTER BLAKE NNNN
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