WTPA45 PHFO 260302
TCDCP5

TROPICAL STORM HILDA DISCUSSION NUMBER  15
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP112009
500 PM HST TUE AUG 25 2009

AT THE MOMENT...HILDA APPEARS TO BE A FAILING TROPICAL CYCLONE.
DESPITE MODEST SHEAR...ABOUT 5 TO 10 KT FROM THE NORTHEAST...DEEP
CONVECTION NEAR THE CENTER OF HILDA HAS NOT BEEN ABLE TO PERSIST.
THE PRESUMED CAUSE MAY BE THE INGESTION OF DRIER AIR AS SUGGESTED
BY WATER VAPOR IMAGES AND SATELLITE SOUNDER PRECIPITABLE WATER
DATA. A LATE MORNING BURST DISSIPATED LEAVING A CIRRUS CANOPY TO
OBSCURE THE LOW LEVEL CLOUD CENTER. RECENT IMAGES SHOW NEW
CUMULONIMBUS DEVELOPMENT NEAR THE PRESUMED CENTER SO HILDA CANNOT
BE WRITTEN OFF JUST YET. SUBJECTIVE DVORAK ESTIMATES CONTINUE TO
RANGE FROM 45 TO 65 KT. CIMSS ADT CAME IN AT 47 KT. AN ASCAT PASS
FROM AROUND 2000 UTC SHOWED LOWER WINDS SINCE THE MORNING QUIKSCAT
PASS AND 35 KT ONLY IN THE NW QUADRANT. BASED ON A BLEND OF THE
OBJECTIVE AND SUBJECTIVE ESTIMATES...THE INITIAL INTENSITY HAS BEEN
LOWERED TO 40 KT.

HILDA HAS BEEN MOVING TOWARD THE WEST-SOUTHWEST THROUGH THE DAY.
THIS MOTION IS EXPECTED TO PERSIST OVER THE NEXT 36 HOURS...THEN
TURN WEST-NORTHWESTWARD AS HILDA MOVES TOWARD A WEAKNESS IN THE
SUBTROPICAL RIDGE. MOST OF THE DYNAMICAL OBJECTIVE AIDS...INCLUDING
GFDL...HWRF AND TVCN...ARE IN GENERAL AGREEMENT WITH THIS SCENARIO.
THE OFFICIAL FORECAST IS CLOSE TO HWRF AND TVCN AND HAS BEEN NUDGED
SOUTH SLIGHTLY FROM THE PREVIOUS FORECAST. NOGAPS CONTINUES TO BE
THE NORTHERN OUTLIER BUT KEEPS HILDA SOUTHWEST OF THE HAWAIIAN
ISLANDS. 
 
THE INTENSITY FORECAST REMAINS PROBLEMATIC.  ASIDE FROM PRESUMED DRY
AIR EFFECTS...HILDA CONTINUES TO MOVE WITHIN A MODEST SHEAR
ENVIRONMENT AND MORE THAN ADEQUATE SST/S. SINCE THE OBJECTIVE AIDS
SHOW CONTINUED STRENGTHENING...IT IS EXPECTED FOR NOW THAT HILDA
WILL BE ABLE TO OVERCOME THE DRY AIR EFFECTS. GLOBAL MODELS SHOW
NORTHWESTERLY TO NORTHERLY VERTICAL SHEAR IMPACTING HILDA BEYOND 72
HOURS. THUS...THE FORECAST CALLS FOR SLIGHT WEAKENING INITIALLY
FOLLOWED BY STRENGTHENING THROUGH 72 HOURS.  BEYOND 72 HOURS...THE
VERTICAL SHEAR IS EXPECTED TO WEAKEN THE CYCLONE AND PREVENT IT
FROM REACHING HURRICANE STRENGTH. THIS FORECAST IS ON THE LOW END
OF THE OBJECTIVE GUIDANCE ENVELOPE. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      26/0300Z 13.7N 149.8W    40 KT
 12HR VT     26/1200Z 13.3N 151.0W    35 KT
 24HR VT     27/0000Z 12.8N 152.6W    40 KT
 36HR VT     27/1200Z 12.6N 154.2W    45 KT
 48HR VT     28/0000Z 12.7N 155.8W    50 KT
 72HR VT     29/0000Z 13.1N 159.5W    55 KT
 96HR VT     30/0000Z 13.9N 163.9W    50 KT
120HR VT     31/0000Z 15.9N 168.0W    45 KT
 
$$
FORECASTER KODAMA