Tropical Storm HAIKUI Advisory Sat Aug 04

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (HAIKUI) WARNING
NR 08//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 12W (HAIKUI), LOCATED APPROXIMATELY 175 NM EAST
OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED WEST-NORTHWESTWARD AT 16
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY SHOWS RE-BUILDING CENTRAL CONVECTION OVER THE LOW-LEVEL
CIRCULATION CENTER (LLCC) WITH PERSISTENT DEEP CONVECTION OVER THE
WESTERN PERIPHERY. THE CURRENT POSITION IS BASED ON THE ABOVE
MENTIONED IMAGERY WITH GOOD CONFIDENCE. THE CURRENT INTENSITY IS
BASED ON 45 KNOT DVORAK ESTIMATES FROM PGTW AND KNES. UPPER-LEVEL
ANALYSIS INDICATES TS 12W IS POSITIONED WELL SOUTH OF THE DEEP-
LAYERED SUBTROPICAL RIDGE (STR) AND CONTINUES TO BE STEERED BY ITS
SOUTHERN PERIPHERY. ANIMATED WATER VAPOR AND TOTAL PRECIPITABLE
WATER IMAGERY SHOW TS 12W COCOONING ITSELF WITHIN THE MARITIME
TROPICAL AIR MASS WITH THE PREVIOUSLY NOTED DRY SLOT BEGINNING TO
THIN. VERTICAL WIND SHEAR (VWS) SEEMS TO HAVE SLACKENED A BIT TO 05-
10 KNOTS, PERHAPS ALLOWING FOR THE RECENT CENTRAL FLARE.
EQUATORWARD OUTFLOW IS MINIMAL AND POLEWARD OUTFLOW REMAINS
MARGINAL.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 12W IS FORECAST TO CONTINUE TRACKING WEST-NORTHWESTWARD
THROUGH TAU 72 SOUTH OF THE STR. THE SYSTEM SHOULD CONTINUE TO
INTENSIFY UNDER WEAK VWS AND WARM (28-30C) SEA SURFACE TEMPERATURES
TO A PEAK OF 85 KNOTS AT TAU 72. MODEL GUIDANCE CONTINUES TO REMAIN
WELL GROUPED OUT TO TAU 36 WITH THE EXCEPTION OF GFDN AND WBAR,
WHICH TRACK THE LLCC MORE POLEWARD. THIS SEEMS HIGHLY UNLIKELY DUE
TO STRONG EASTERLY FLOW THROUGHOUT THE ENTIRE TROPOSPHERE IN THE
040000Z NAZE (28.39N 129.55E) SOUNDING AND THE 041200Z KAGOSHIMA
(31.55N 130.55E) SOUNDING. THERE IS HIGH CONFIDENCE IN THE TRACK
FORECAST UP TO TAU 36.
   C. BY TAU 96, TS 12W SHOULD BE JUST OFF THE COAST OF EASTERN
CHINA AND MAKE LANDFALL AS A SIGNIFICANT TYPHOON. DISSIPATION
OVERLAND WILL COMMENCE BY TAU 120 DUE TO FRICTIONAL DRAG. MODEL
GUIDANCE IS GREATLY VARIED BOTH IN TRACK SPEED AND LOCATION DURING
THIS TIME DUE TO THE POLEWARD TRACKS OF NOGAPS AND WBAR. ECMWF AND
EGRR REMAIN STABLE WITH A WESTWARD TRACK BUT TRACK SPEEDS ARE MUCH
FASTER THAN ALL OTHER OBJECTIVE AIDS. THE JTWC TRACK FORECAST
CONTINUES TO BUILD UPON PREVIOUS FORECASTS AND IS FASTER THAN THE
MODEL CONSENSUS TO OFFSET THE POLEWARD OUTLIERS BUT NOT AS FAST AS
ECMWF AND EGRR DUE TO MUCH UNCERTAINTY ABOUT THE SYNOPTIC
ENVIRONMENT AT THIS TIME. A RELATIVELY SHALLOW MID-LATITUDE TROUGH
WILL INTERACT WITH THE STEERING STR OVER THE NEXT TWO TO THREE DAYS
BUT AT THIS TIME THE MAGNITUDE OF INTERACTION IS UNCLEAR.
ADDITIONALLY, ANOTHER SHALLOW MID-LATITUDE TROUGH WILL AGAIN
INTERACT WITH THE STR BY THE FOUR TO FIVE MARK, BUT DEPICTION OF
THIS INTERACTION VARIES AMONGST THE MODELS. DUE TO THE HIGH LEVEL
OF UNCERTAINTY DURING THIS TIME TRACK FORECAST CONFIDENCE REMAINS
LOW.//
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