Tropical Storm FOUR Advisory Dom, 30-06

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (FOUR)
WARNING NR 06//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 04W (FOUR), LOCATED APPROXIMATELY 510 NM EAST OF
MANILA, PHILIPPINES, HAS TRACKED NORTHWESTWARD AT 11 KNOTS OVER
THE PAST SIX HOURS. THE CURRENT POSITION IS BASED ON RECENT MICROWAVE
SATELLITE IMAGERY INCLUDING A 292214Z SSMIS AND A 292127Z CORIOLIS
IMAGE. THE INTENSITY OF 35 KNOTS IS CONSISTENT WITH DVORAK CURRENT
INTENSITY ESTIMATES OF T2.5 FROM PGTW AND KNES. TD 04W IS TRACKING
NORTHWESTWARD ALONG THE PERIPHERY OF A SUBTROPICAL STEERING RIDGE
SITUATED TO THE NORTH AND EAST. THE LOW LEVEL CIRCULATION CENTER
(LLCC) HAS BECOME LESS DEFINED IN MICROWAVE AND VISIBLE SATELLITE
IMAGERY. ALTHOUGH A PATCH OF DEEP CONVECTION PERSISTS OVER THE
SOUTHWESTERN PORTION OF THE CIRCULATION, NEARLY ALL CONVECTION HAS
DIMINISHED NEAR THE CENTER. THIS STRUCTURAL CHANGE SUGGESTS THAT
VERTICAL WIND SHEARS (VWS) IS EFFECTING THE SYSTEM MORE THAN
PREVIOUSLY ANTICIPATED. DIFFLUENCE ALOFT REMAINS STRONG, AND SEA
SURFACE TEMPERATURES ARE VERY SUPPORTIVE AT ABOUT 30 DEGREES CELSIUS.
3. FORECAST REASONING.
  A. FORECAST INTENSITIES HAVE BEEN REDUCED FROM THE PREVIOUS WARNING
BASED ON ONGOING AND ANTICIPATED DISRUPTION TO THE STORM STRUCTURE BY
PERSISTENT VWS. OTHERWISE, THERE IS NO MAJOR CHANGE TO THE FORECAST
PHILOSOPHY FROM THE PREVIOUS WARNING.
  B. TS 04W IS EXPECTED TO TRACK GENERALLY NORTHWESTWARD FOLLOWING
THE STEERING FLOW ASSOCIATED WITH THE SUBTROPICAL STEERING TO THE
NORTH AND EAST FOR THE NEXT 72 HOURS. VWS WILL DECREASE SLIGHTLY
THROUGH TAU 48, WHICH MAY ALLOW THE SYSTEM TO INTENSIFY SLOWLY WITH
THE SUPPORT OF VERY WARM SEA SURFACE TEMPERATURES AND STRONG
DIFFLUENCE ALOFT. HOWEVER, RECENT DISORGANIZATION OF THE STORM
STRUCTURE MAY HAMPER FURTHER INTENSIFICATION AND LEAVE THE STORM
VULNERABLE TO DISSIPATING EARLIER THAN THE CURRENT FORECAST
INDICATES. THIS EARLY DISSIPATION IS CONSIDERED A PLAUSIBLE ALTERNATE
SCENARIO TO THE CURRENT FORECAST. NUMERICAL MODELS ARE IN FAIR
AGREEMENT REGARDING THE GENERAL NORTHWESTWARD TRACK OF TS 04W THROUGH
TAU 72, ALTHOUGH THE LATEST NAVGEM RUN PREDICTS RECURVATURE OF A
STRONGER THAN EXPECTED SYSTEM TO THE EAST OF TAIWAN AND SEVERAL
MODELS DISSIPATE THE SYSTEM PRIOR TO LANDFALL. THE CURRENT FORECAST
TRACK IS CONSERVATIVELY CONSISTENT WITH THE PREVIOUS FORECAST TRACK
AND IS SUPPORTED BY SEVERAL MODEL SOLUTIONS. GIVEN NOTED MODEL
DIVERGENCE, CONFIDENCE IN THE FORECAST TRACK IS LOW.
  C. IN THE EXTENDED RANGE, TS 04W IS EXPECTED TO TRACK INLAND AND
DISSIPATE OVER SOUTHEASTERN CHINA, IF IT SURVIVES TO THAT POINT.
NUMERICAL GUIDANCE DIVERGES SIGNIFICANTLY, ALTHOUGH ALL MODELS
SUPPORT DISSIPATION. CONFIDENCE IN THE EXTENDED FORECAST PORTION OF
THE JTWC TRACK FORECAST IS ALSO LOW.//
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