Tropical Storm FERNANDA

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TROPICAL STORM FERNANDA DISCUSSION NUMBER  10
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP062011
800 PM PDT WED AUG 17 2011
 
DEEP CONVECTION NEAR THE STORM CENTER HAS INCREASED IN COVERAGE AND
INTENSITY...AND THE CURRENT WIND SPEED IS NOW ESTIMATED TO BE 50 KT
USING A BLEND OF DVORAK ESTIMATES FROM TAFB AND SAB.  GIVEN THAT
FERNANDA WILL BE MOVING INTO A RELATIVELY STABLE AIR MASS AND
TRAVERSING MARGINAL SEA SURFACE TEMPERATURES...NOT MUCH ADDITIONAL
STRENGTHENING IS ANTICIPATED FOR THE NEXT 24 HOURS OR SO.  BY 48
HOURS...THE VERTICAL SHEAR IS FORECAST TO INCREASE TO NEAR 20 KT
AND THE STORM SHOULD BE ON A WEAKENING TREND.  AROUND DAY 4...AN
UPPER-TROPOSPHERIC TROUGH IN THE VICINITY OF THE HAWAIIAN ISLANDS
IS FORECAST TO PRODUCE 25-30 KT OF SOUTH-SOUTHWESTERLY SHEAR ON THE
CYCLONE WHICH WILL LIKELY REDUCE FERNANDA TO A REMNANT LOW.  THE
OFFICIAL INTENSITY FORECAST IS CLOSE TO THE CONSENSUS OF THE
NUMERICAL GUIDANCE.

A WEAKNESS IN THE SUBTROPICAL RIDGE IN THE VICINITY OF 140W
LONGITUDE HAS CAUSED THE HEADING OF FERNANDA TO TURN TOWARD THE
WEST-NORTHWEST.  THE RIDGE IS FORECAST TO BUILD ONLY SLIGHTLY TO
THE NORTH OF THE TROPICAL CYCLONE AND THE TRACK GUIDANCE MODELS ARE
IN GENERALLY GOOD AGREEMENT ON A CONTINUED WEST-NORTHWESTWARD
MOTION WITH JUST A BIT OF AN INCREASE IN FORWARD SPEED OVER THE
NEXT 3 DAYS.  BY DAY 4...THE WEAK CYCLONE IS LIKELY TO TURN
WESTWARD AS IT MOVES MORE WITH THE LOW-LEVEL TRADE WINDS.  THE
OFFICIAL TRACK FORECAST IS VERY SIMILAR TO THE PREVIOUS ONE AND
CLOSE TO THE DYNAMICAL MODEL CONSENSUS.

BASED ON THE CURRENT FORECAST...FERNANDA WILL ENTER THE CENTRAL
PACIFIC HURRICANE CENTER AREA OF RESPONSIBILITY AROUND 1200 UTC.

FORECAST POSITIONS AND MAX WINDS
 
INIT  18/0300Z 12.6N 139.2W   50 KT  60 MPH
 12H  18/1200Z 13.2N 140.3W   50 KT  60 MPH
 24H  19/0000Z 14.1N 142.0W   50 KT  60 MPH
 36H  19/1200Z 14.7N 143.8W   45 KT  50 MPH
 48H  20/0000Z 15.4N 145.8W   40 KT  45 MPH
 72H  21/0000Z 16.5N 150.0W   35 KT  40 MPH
 96H  22/0000Z 17.0N 154.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  23/0000Z...DISSIPATED
 
$$
FORECASTER PASCH
 
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