Tropical Storm FERNANDA

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TROPICAL STORM FERNANDA DISCUSSION NUMBER   6
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP062011
800 PM PDT TUE AUG 16 2011
 
SATELLITE IMAGES SHOW THAT THE CLOUD PATTERN OF THE STORM REMAINS
WELL ORGANIZED...WITH WELL-DEFINED CURVED BANDS.  HOWEVER THE CLOUD
TOPS HAVE WARMED SIGNIFICANTLY OVER THE PAST FEW HOURS...INDICATING
A DECREASE IN THE INTENSITY OF THE DEEP CONVECTION.  THIS DECREASE
IS PROBABLY ASSOCIATED WITH A DIURNAL FLUCTUATION AND IS LIKELY
ONLY TEMPORARY.  SATELLITE INTENSITY ESTIMATES REMAIN 45 KT SO THE
CURRENT WIND SPEED IS HELD AT THAT VALUE.  FERNANDA CONTINUES TO
EXHIBIT STRONG AND FAIRLY SYMMETRIC UPPER-LEVEL OUTFLOW... AND IS
FORECAST TO REMAIN OVER WATERS WARMER THAN 26 DEG C FOR THE NEXT
COUPLE OF DAYS.  HENCE THE CYCLONE IS LIKELY TO STRENGTHEN AND THE
OFFICIAL FORECAST SHOWS THE SYSTEM BECOMING A HURRICANE.  THIS IS
IN GOOD AGREEMENT WITH THE CONSENSUS OF THE NUMERICAL INTENSITY
GUIDANCE.  IN THE LATTER PART OF THE FORECAST PERIOD...
SOUTH-SOUTHWESTERLY SHEAR ASSOCIATED WITH AN UPPER-TROPOSPHERIC
TROUGH NEAR THE HAWAIIAN ISLANDS IS PREDICTED TO INCREASE TO NEAR
30 KT OVER FERNANDA.  THEREFORE THE SYSTEM SHOULD WEAKEN RAPIDLY BY
DAY 5 AND IS FORECAST TO BECOME A REMNANT LOW AROUND THAT TIME.

BASED ON THE LATEST FIXES AN ADDITIONAL...SLIGHT...SOUTHWARD
ADJUSTMENT TO THE TRACK HAS BEEN MADE.  THE INITIAL MOTION IS
WESTWARD NEAR 7 KT.  NOT MUCH CHANGE HAS BEEN MADE TO THE PREVIOUS
TRACK FORECAST OR REASONING.  A WEAKNESS IN THE SUBTROPICAL RIDGE
NEAR 140W LONGITUDE IS EXPECTED TO CAUSE THE CYCLONE TO TURN TOWARD
THE WEST-NORTHWEST TOMORROW.  THERE IS A FAIR AMOUNT OF SPREAD IN
THE TRACK GUIDANCE...WITH THE HWRF AND GFDL MODELS LYING ON THE
NORTHERN EDGE OF THE DYNAMICAL MODEL SUITE AND THE ECMWF AND UKMET
NEAR THE SOUTHERN EDGE.  THE OFFICIAL FORECAST IS ONLY A TAD SLOWER
THAN THE PREVIOUS ONE AND JUST SOUTH OF THE MODEL CONSENSUS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  17/0300Z 11.5N 136.2W   45 KT  50 MPH
 12H  17/1200Z 11.7N 137.3W   50 KT  60 MPH
 24H  18/0000Z 12.2N 138.6W   55 KT  65 MPH
 36H  18/1200Z 12.9N 140.1W   60 KT  70 MPH
 48H  19/0000Z 13.7N 141.8W   65 KT  75 MPH
 72H  20/0000Z 15.5N 145.5W   55 KT  65 MPH
 96H  21/0000Z 16.0N 149.5W   40 KT  45 MPH
120H  22/0000Z 16.0N 153.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER PASCH
 
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