Tropical Storm HAISHEN Advisory Do, 01.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (ELEVEN) WARNING
NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 11W (ELEVEN), LOCATED APPROXIMATELY 256 NM
SOUTHEAST OF IWO TO, JAPAN, HAS TRACKED SOUTHWESTWARD AT 12 KNOTS
(KTS) OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY SHOWS FLARING DEEP CENTRAL CONVECTION SHEARED
SOUTHWESTWARD OF A PARTIALLY EXPOSED LOW LEVEL CIRCULATION. THE
INITIAL POSITION IS EXTRAPOLATED FROM THE EIR LOOP AND FROM A NOTCH
FEATURE IN THE 311625Z AMSR2 MICROWAVE IMAGE WITH LOW CONFIDENCE. THE
INITIAL INTENSITY OF 35KTS IS BASED ON THE DVORAK ESTIMATE OF
T2.5/35KTS FROM PGTW AND REFLECTS THE IMPROVED EIR SIGNATURE.
ANALYSIS INDICATES TS 11W IS UNDER A MARGINAL ENVIRONMENT WITH STRONG
EQUATORWARD UPPER LEVEL OUTFLOW AND WARM (30-31 CELSIUS) SEA SURFACE
TEMPERATURES (SST) THAT ARE BEING OFFSET BY MODERATE (20-25KT)
NORTHEASTERLY VERTICAL WIND SHEAR (VWS). THE CYCLONE IS TRACKING
UNDER THE COMBINED STEERING INFLUENCE OF A SUBTROPICAL RIDGE (STR) TO
THE WEST AND AN EXTENSION OF THE STR TO THE NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE LAST PROGNOSTIC REASONING MESSAGE.
   B. TS 11W WILL CONTINUE ON ITS CURRENT TRACK UP TO TAU 24 WITH
MINIMAL INTENSIFICATION TO 55KTS DUE TO THE MARGINAL ENVIRONMENT.
AFTERWARD, A MIDLATITUDE SHORTWAVE TROUGH APPROACHING FROM THE
NORTHWEST WILL BEGIN TO ERODE THE STR TO THE WEST. THE STR TO THE
NORTHEAST, ON THE OTHER HAND, WILL BUILD AND BECOME THE PRIMARY
STEERING MECHANISM AND DRIVE THE SYSTEM SLOWLY WESTWARD THEN
NORTHWESTWARD. VWS VALUES WILL DECREASE AFTER TAU 24 ALLOWING TS 11W
TO STEADILY INTENSIFY ALONG THE FORECAST TRACK TO 95KTS BY TAU 72.
NUMERICAL MODELS ARE IN FAIR AGREEMENT BUT GIVEN THE COMPLEX STEERING
AND THE FORMATIVE NATURE OF THE CYCLONE, THERE IS LOW CONFIDENCE IN
THIS PORTION OF THE JTWC TRACK FORECAST.
   C. BEYOND TAU 72, TS 11W WILL CONTINUE TO TRACK NORTHWESTWARD
ALONG THE PERIPHERY OF THE DOMINANT STR TO THE EAST. THE SYSTEM WILL
STEADILY INTENSIFY TO 115 KTS BY TAU 120 DUE TO CONTINUED FAVORABLE
ENVIRONMENTAL CONDITIONS OF LOW VWS, WARM SST, AND CONDUCIVE OCEAN
HEAT CONTENT VALUES. NUMERICAL MODELS ARE IN FAIR AGREEMENT IN THE
LATER TAUS, HOWEVER, GIVEN THE INITIAL TRACK UNCERTAINTY, THERE IS
ALSO A LOW CONFIDENCE IN THE EXTENDED PORTION OF THE JTWC TRACK
FORECAST.
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