Tropical Storm KAI-TAK Advisory Pzt, 13.08.

MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 14W (FOURTEEN)
WARNING NR 02 RELOCATED//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TROPICAL DEPRESSION (TD) 14W (FOURTEEN), LOCATED APPROXIMATELY
465 NM EAST-NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD
AT 12 KNOTS OVER THE PAST SIX HOURS. THE CURRENT POSITION IS BASED
ON RECENT POSITION FIXES FROM PGTW, KNES, AND RJTD AND RECENT
MICROWAVE SATELLITE IMAGERY. THE CURRENT INTENSITY ESTIMATE OF 25
KNOTS IS SLIGHTLY LOWER THAN THE DVORAK SATELLITE INTENSITY
CONSENSUS OF 30 KNOTS BASED ON A 121216Z ASCAT PASS SHOWING HIGHER
WIND SPEEDS CONFINED TO THE WESTERN PERIPHERY OF THE CYCLONE IN AN
AREA OF LOW-LEVEL CONVERGENT FLOW. RECENT ANIMATED INFRARED
SATELLITE IMAGERY SHOWS DEEP CONVECTION PERSISTING TO THE WEST OF
THE CYCLONE CIRCULATION CENTER. TD 14W LIES EQUATORWARD OF AN UPPER-
LEVEL RIDGE AXIS IN AN AREA OF LOW TO MODERATE VERTICAL WIND SHEAR
AND FAVORABLE EQUATORWARD OUTFLOW ALOFT.  A WEAK UPPER LEVEL LOW TO
THE NORTHEAST HAS ALSO SPURRED THE DEVELOPMENT OF A POLEWARD OUTFLOW
CHANNEL OVER THE PAST SIX HOURS. TD 14W CONTINUES TO TRACK WESTWARD
ALONG THE SOUTHER PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE.
3. FORECAST REASONING.
   A. THE CURRENT TRACK FORECAST LIES FARTHER POLEWARD IN THE EARLY
TAUS AND DEPICTS A SHARPER WESTWARD TURN IN THE LATER TAUS THAN THE
PREVIOUS FORECAST. THIS CHANGE REFLECTS EXPECTATIONS OF A MORE
CONTINUOUS ZONAL STEERING INFLUENCE FROM THE SUBTROPICAL RIDGE.
   B. TD 14W IS EXPECTED TO TRACK WESTWARD TO NORTHWESTWARD THROUGH
TAU 72 AS IT MOVES ALONG THE PERIPHERY OF THE CURRENT SUBTROPICAL
STEERING RIDGE. MODERATE VERTICAL WIND SHEAR WILL VIE WITH IMPROVED
UPPER-LEVEL OUTFLOW TO HOLD INTENSIFICATION TO A SLOW RATE EARLY IN
THE FORECAST PERIOD. HOWEVER, SHEAR IS EXPECTED TO RELAX AFTER TAU
36 AS THE SYSTEM APPROACHES THE UPPER-LEVEL RIDGE AXIS AND THE
INTENSIFYING CYCLONE BEGINS TO DEVELOP A MESOSCALE ANTICYCLONE
ALOFT.
   C. AFTER TAU 72, TD 14W IS EXPECTED TO TURN MORE TO THE WEST AS
SUBTROPICAL RIDGING STRENGTHENS IN THE WAKE OF A TRANSIENT SHORTWAVE
TROUGH THAT WILL PASS ACROSS NORTHEASTERN CHINA, FAR TO THE NORTH OF
THE CYCLONE. DECREASING OCEAN HEAT CONTENT AND INCREASINGLY
RESTRICTED POLEWARD OUTFLOW SHOULD CAUSE THE SYSTEM TO WEAKEN
SLIGHTLY PRIOR TO LANDFALL. TD 14W WILL DISSIPATE RAPIDLY AFTER
LANDFALL. THE NUMERICAL MODELS REMAIN IN POOR AGREEMENT REGARDING
THE TRACK OF TD 14W, ALTHOUGH MOST DEPICT A GENERALLY NORTHWESTWARD
TRACK TOWARD THE ISLAND OF TAIWAN WITH THE WBAR REMAINING THE
EXTREME WESTWARD OUTLIER. THE CURRENT FORECAST FAVORS THE ECMWF
MODEL, WHICH DEPICTS A MORE CONTINUOUS STEERING RIDGE CONSISTENT
WITH THE CURRENT ANALYSIS AND SYNOPTIC FORECAST REASONING. GIVEN
GENERALLY POOR AGREEMENT OF THE OBJECTIVE AID PACKAGE, PARTICULARLY
WITH REGARD TO TRANSLATIONAL SPEED, TRACK FORECAST CONFIDENCE
REMAINS LOW.
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