Tropical Storm HAIKUI Advisory dom, 12-11

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 30W (HAIKUI)
WARNING NR 10//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 30W (HAIKUI), LOCATED APPROXIMATELY 398 NM
EAST-NORTHEAST OF DA NANG, VIETNAM, HAS TRACKED WEST-NORTHWESTWARD AT
08 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI) SHOWS THE ASSOCIATED CONVECTION HAS SIGNIFICANTLY
COLLAPSED, FRAGMENTED, AND DISPLACED, PARTLY EXPOSING THE LOW LEVEL
CIRCULATION (LLC). THE MSI LOOP ALSO SHOWS STRATOCUMULUS (SC) CLOUD
LINES STREAMING IN FROM THE NORTH, DIAMETRICAL TO THE HIGH CIRRUS
FLOW, BEFORE CURLING INTO THE LLC. THE INITIAL POSITION IS PLACED
WITH HIGH CONFIDENCE BASED ON THE MSI LOOP AND LINED UP WITH AN LLC
FEATURE IN THE 110140Z OSCAT BULLSEYE PASS. THE INITIAL INTENSITY OF
35 KNOTS IS BASED ON CONGRUENT DVORAK ESTIMATES FROM PGTW AND RJTD
AND SUPPORTED BY RECENT SCATTEROMETRY DATA. UPPER LEVEL ANALYSIS
INDICATES THE SYSTEM IS IN AN AREA OF LOW TO MODERATE (10-15 KNOT)
VERTICAL WIND SHEAR (VWS); HOWEVER, FACTORING IN THE STORM MOTION
RESULTS IN MODERATE TO STRONG (15-20 KNOT) RELATIVE VWS. THERE IS,
HOWEVER, A STEADY STREAM OF POLEWARD OUTFLOW THAT IS PROVIDING SOME
VENTILATION TO THE WAYWARD CONVECTION. THE CYCLONE IS TRACKING ALONG
THE SOUTHERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) TO THE NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS HAIKUI WILL PLATEAU TO A WESTWARD STORM MOTION THEN DESCEND
WEST-SOUTHWESTWARD AS A SECONDARY STR THE NORTHWEST ASSUMES
STEERING. DESPITE THE WARM WATERS OF THE SOUTH CHINA SEA, INCREASING
VWS AND INFLUX OF COOL DRY AIR IN THE LOW LEVELS, AS INDICATED BY THE
INFLOW OF SC CLOUDS, WILL PRIMARILY BE RESPONSIBLE FOR ITS DECAY AND
EVENTUAL DISSIPATION BY TAU 36, POSSIBLY SOONER. DYNAMIC MODEL
GUIDANCE HAVE BECOME WIDELY SPREAD AND ERRATIC BEYOND TAU 12, AN
INDICATION OF A WEAK VORTEX. IN VIEW OF THIS, THERE IS LOW CONFIDENCE
IN THE JTWC FORECAST TRACK.//
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