WTPA43 PHFO 110256
TCDCP3

TROPICAL DEPRESSION ONE-C DISCUSSION NUMBER   1
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   CP012009
500 PM HST MON AUG 10 2009

SATELLITE IMAGERY DURING THE LAST SEVERAL HOURS INDICATES THAT THE
CONVECTION ASSOCIATED WITH THE DISTURBANCE A COUPLE HUNDRED MILES
SOUTH-SOUTHWEST OF JOHNSTON ISLAND HAS AQUIRED ENOUGH ORGANIZATION
TO BE CLASSIFIED AS A TROPICAL DEPRESSION. DVORAK FINAL T NUMBERS 
FROM PHFO...JTWC...AND SAB WERE A CONSENSUS 2.0 AT 0000 UTC.  IN
ADDITION...MANUAL ANALYSIS OF THE DIRECTIONAL AMBIGUITIES FROM AN
EARLIER QUIKSCAT PASS AT 1730 UTC PROVIDES EVIDENCE OF A SURFACE
CIRCULATION THAT IS COLOCATED WITH THE CLOUD-TOP ROTATION SEEN IN
GOES IMAGERY.  BASED ON BOTH THE DVORAK CLASSIFCATIONS AND THE 25
TO 30 KT WIND SPEEDS IN THE QUIKSCAT DATA...THE ADVISORY INTENSITY
IS SET TO 30 KT.

THE INITIAL MOTION IS 285/12. ONE-C IS TO THE SOUTH OF A LARGE
SUBTROPICAL RIDGE...AND GLOBAL MODELS FORECAST THE RIDGE TO KEEP IT
ON A WEST-NORTHWEST TRACK THROUGH ABOUT 48 HOURS. AFTER THAT...THE
CYCLONE IS EXPECTED TO MAKE A TURN TOWARD THE NORTHWEST AS A
WEAKNESS IN THE RIDGE AT MID AND UPPER LEVELS DEVELOPS NORTH OF THE
SYSTEM. THE GLOBAL MODELS ARE IN GOOD AGREEMENT WITH THIS
SCENARIO...AND THE OFFICIAL FORECAST LIES BETWEEN THE NOGAPS AND
GFS SOLUTIONS.

THE DEPRESSION IS WELL-SEPARATED FROM OTHER ITCZ CONVECTION AND IS
EXPECTED TO REMAIN OVER SEA-SURFACE TEMPERATURES NEAR 28 CELSIUS
OVER THE NEXT FIVE DAYS. IN ADDITION...WEAK SHEAR IS EXPECTED TO
PERSIST THROUGH THE NEXT 72 HOURS WHICH SHOULD ALLOW THE DEPRESSION
TO INTENSIFY TO HURRICANE STRENGTH AS FORECAST BY THE SHIPS
GUIDANCE. IN FACT...THE SHIPS RAPID INTENSIFICATION INDEX INDICATES
A 75 PERCENT CHANCE OF A 25 KT INCREASE IN THE NEXT 24 HOURS...
WHICH IS REFLECTED IN THE OFFICIAL FORECAST. BEYOND DAY 3...THE
CYCLONE IS FORECAST TO ENCOUNTER INCREASING UPPER LEVEL
SOUTHWESTERLIES AHEAD OF AN UPPER LEVEL TROUGH TO THE NORTH OF THE
CYCLONE...AND THUS A WEAKENING TREND IS INDICATED BY THE END OF THE
FORECAST PERIOD.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      11/0300Z 13.7N 170.6W    30 KT
 12HR VT     11/1200Z 14.1N 172.3W    40 KT
 24HR VT     12/0000Z 14.7N 174.5W    55 KT
 36HR VT     12/1200Z 15.3N 176.4W    60 KT
 48HR VT     13/0000Z 15.9N 178.0W    65 KT
 72HR VT     14/0000Z 17.5N 179.5E    70 KT
 96HR VT     15/0000Z 19.5N 177.5E    65 KT
120HR VT     16/0000Z 21.5N 176.5E    60 KT
 
$$
FORECASTER R BALLARD/KNABB