Tropical Storm FERNANDA

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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
 
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