Tropical Storm KAI-TAK Advisory 14.08.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 14W (KAI-TAK) WARNING
NR 07//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 14W (KAI-TAK), LOCATED APPROXIMATELY 305 NM
NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 11 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
DEPICTS AN OVERALL LARGE LOW-LEVEL CIRCULATION CENTER (LLCC) WHICH
SEEMS TO BE PARTIALLY-EXPOSED OVER THE NORTHEASTERN QUADRANT. THE
DEEP FLARE OF CONVECTION NOTICED SEVERAL HOURS AGO DURING THE
DIURNAL MAXIMUM HAS SINCE WEAKENED, AS OBSERVED IN THE WARMING
CLOUD TOPS IN THE ENHANCED INFRARED IMAGERY. VERTICAL WIND SHEAR
(VWS) REMAINS MODERATE (15-20 KNOTS) FROM THE NORTHEAST BUT SPEED
DIVERGENCE, PRODUCED FROM AMPLE EQUATORWARD OUTFLOW, CONTINUES TO
PROVIDE AN EXHAUST MECHANISM FOR THE DEEP CONVECTION OVER THE
SOUTHWESTERN QUADRANT OF THE LLCC. TS 14W'S SURFACE CIRCULATION
CONTINUES TO STRUGGLE IN ACHIEVING SYMMETRY UNDER THESE COMPETING
INFLUENCES AND MID-LEVEL CIRCULATIONS CAN BE SEEN EXITING
CYCLONICALLY FROM UNDERNEATH THE STRONG CONVECTION. THE CURRENT
POSITION WAS BASED ON A 142217Z TRMM 37 GHZ IMAGE. HOWEVER, A MORE
RECENT 140016Z SSMIS 37 GHZ IMAGE SUGGESTS THE LLCC IS LOCATED NEAR
18.1N 125.7E, APPROXIMATELY 35 NM NORTH OF THE CURRENT BEST TRACK
POSITION. SOME SLIGHT ADJUSTMENT WILL BE MADE TO THE CURRENT
POSITION BUT OVERALL POSITION CONFIDENCE IS STILL GOOD. THE CURRENT
INTENSITY IS BASED ON THE PGTW DVORAK ESTIMATE OF 45 KNOTS IN
COMBINATION WITH THE 131800Z SATCON ESTIMATE OF 47 KNOTS. UPPER-
LEVEL ANALYSIS INDICATES THAT TS 14W IS LOCATED APPROXIMATELY 14
DEGREES EQUATORWARD OF THE SUBTROPICAL RIDGE AXIS AND HAS A POINT
SOURCE OF DIVERGENCE LESS THEN TWO DEGREES TO THE EAST.
ADDITIONALLY, UPPER-LEVEL TROUGHING AND CONVERGENCE IS BEING
INDUCED BETWEEN THIS POINT SOURCE AND A NEAR EQUATORIAL
ANTICYCLONIC CENTER LOCATED ABOUT 15 DEGREES FURTHER EAST OF THE
LLCC. ALL OF THIS IS PRODUCING EXCELLENT EQUATORWARD OUTFLOW BUT
THERE SEEMS TO BE PRESSURE OVER THE EASTERN PORTION. ANIMATED WATER
VAPOR IMAGERY STILL HINTS TO A SLIGHT CONNECTION TO POLEWARD
OUTFLOW INTO A TROPICAL UPPER-TROPOSPHERIC TROUGH NORTH OF THE
SYSTEM. TS 14W IS BEING STEERED IN A GENERAL WEST-NORTHWESTWARD
DIRECTION UNDER THE INFLUENCE OF THE DEEP-LAYERED SUBTROPICAL RIDGE
(STR) CENTERED FAR TO THE NORTHEAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 14W IS EXPECTED TO CONTINUE TRACKING WEST-NORTHWESTWARD
ALONG THE SOUTHERN PERIPHERY OF THE DEEP-LAYERED STR FOR THE
REMAINDER OF THE FORECAST PERIOD. A MID-LATITUDE TROUGH PROPAGATING
OVER EASTERN CHINA BY TAU 36 MAY SLIGHTLY ERODE THE STEERING STR
THUS ALLOWING FOR A MORE NORTHWESTWARD TRACK DURING THIS TIME.
HOWEVER, THE TROUGH SEEMS TO BE SHALLOW IN NATURE AND THE WESTERN
EXTENT OF THE PREVIOUSLY BROKEN DOWN STR SHOULD BUILD BACK IN OVER
SOUTHEASTERN CHINA, AND THE SYSTEM, AFTER TAU 72. GRADUAL
INTENSIFICATION IS EXPECTED DUE TO COMPETING INFLUENCES OF VERY
WARM ALONG TRACK SEA SURFACE TEMPERATURES (SST) (28-30 DEGREES
CELSIUS), MODERATE VWS, AND DIURNAL MAXIMUM CYCLES. THE SYSTEM
SHOULD REACH TYPHOON INTENSITY BY TAU 36 AND BE ABLE TO MAINTAIN
SUCH INTENSITIES THROUGH TAU 48 AND INTO LANDFALL NEAR TAU 60.
OVERALL PEAK INTENSITY MAY NEED TO BE ADJUSTED BEFORE LANDFALL DUE
TO EXTREMELY WARM SST'S (> 30 DEGREES CELSIUS) BUT VWS DURING THIS
TIME WILL ALSO PLAY A CRITICAL FACTOR.
   C. AFTER TAU 72 TS 14W WILL BEGIN A SLOW DISSIPATION OVERLAND
DUE TO FRICTIONAL DRAG AND LOSS OF OCEAN HEAT. NUMERICAL MODEL
GUIDANCE CONTINUES TO CONVERGE INTO BETTER AGREEMENT UP TO TAU 36,
AFTER WHICH THE SPREAD INCREASES WITH NOGAPS, JGSM, AND WBAR
PROVIDING FOR A BIFURCATION BETWEEN THE MORE WESTWARD TRACKERS OF
THE REMAINING OBJECTIVE AIDS. THE OFFICIAL TRACK FORECAST REMAINS
SLIGHTLY EQUATORWARD OF CONSENSUS TO OFFSET THE MORE POLEWARD
TRACKERS BASED ON THE SYNOPTIC ANALYSIS AND FUTURE EVOLUTION OF
THESE FEATURES. HIGH CONFIDENCE REMAINS IN THE JTWC TRACK
FORECAST.//
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