WTPA41 PHFO 181436
TCDCP1

TROPICAL STORM FERNANDA DISCUSSION NUMBER  12
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP062011
500 AM HST THU AUG 18 2011

DEEP CONVECTION PERSISTS OVER AND WITHIN 60 NM OF THE CENTER OF
FERNANDA...WITH A SMALL COLD CONVECTIVE AREA JUST SOUTHWEST OF THE
LLCC REGISTERING NEAR MINUS 80 DEGREES CELSIUS.  CPHC DERIVED A
FINAL T NUMBER OF 3.5 WHILE SAB DERIVED A 4.0 AT 1200 UTC...WITH A
FINAL TAFB T NUMBER SLIGHTLY HIGHER STILL.  UPON SATELLITE
INSPECTION...THE UNCHANGED SHORT-TERM ORGANIZATION OF THIS SYSTEM
AND THE LACK OF AN EYE INDICATES THAT FERNANDA IS A STRONG TROPICAL
STORM JUST BELOW HURRICANE STRENGTH.  THEREFORE WE WILL MAINTAIN 55
KNOTS AS THE INITIAL INTENSITY.  SINCE FERNANDA WILL BE MOVING OVER
MARGINAL SEA SURFACE TEMPERATURES AND NEUTRAL VERTICAL SHEAR...NO
SIGNIFICANT CHANGE IN STRENGTH IS ANTICIPATED FOR THE NEXT 12
HOURS. VERTICAL SHEAR IS EXPECTED TO INCREASE BEYOND 12 HOURS AND A
WEAKENING TREND SHOULD BEGIN AT THAT TIME.  BY THE TIME FERNANDA
PASSES SOUTH OF THE MAIN HAWAIIAN ISLANDS IT IS EXPECTED TO HAVE
WEAKENED TO A REMNANT LOW. 
 
LITTLE HAS CHANGED SYNOPTICALLY SINCE THE HANDOFF FROM THE NATIONAL
HURRICANE CENTER LAST NIGHT. HOWEVER...FERNANDA HAS SPED UP SLIGHTLY
OVER THE PAST 6 HOURS...MOVING TOWARD THE WEST-NORTHWEST OR 300
DEGREES AT 11 KNOTS.  THE LATITUDE GAIN CONTINUES DUE TO A WEAKNESS
IN THE SUBTROPICAL RIDGE NORTH OF FERNANDA AND JUST WEST OF 140W.
HOWEVER AS THE RIDGE REBUILDS BEYOND 12 HOURS...AS GFS AND NOGAPS
FORECASTS...SYSTEM MOVEMENT SHOULD BECOME MORE WESTERLY. LATER
IN THE FORECAST PERIOD...AS DEEP CONVECTION ASSOCIATED WITH FERNANDA
OR ITS REMNANT DECREASES...THIS SYSTEM WILL RESPOND TO LOWER LEVEL
STEERING AND MOTION WILL CLOSELY MIRROR TRADE WIND FLOW.  THE
OFFICIAL TRACK IS QUITE CLOSE TO THE PREVIOUS ONE AT ALL TAU.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  18/1500Z 13.7N 141.0W   55 KT  65 MPH
 12H  19/0000Z 14.4N 142.4W   55 KT  65 MPH
 24H  19/1200Z 15.1N 144.3W   50 KT  60 MPH
 36H  20/0000Z 15.8N 146.3W   45 KT  50 MPH
 48H  20/1200Z 16.3N 148.4W   40 KT  45 MPH
 72H  21/1200Z 17.0N 152.3W   30 KT  35 MPH
 96H  22/1200Z 16.8N 156.4W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  23/1200Z...DISSIPATED
 
$$
FORECASTER POWELL