Tropical Storm SURIGAE Advisory Sat Apr 24

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 02W (SURIGAE) WARNING NR 040//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 02W (SURIGAE), LOCATED APPROXIMATELY 220 NM SOUTH-
SOUTHEAST OF KADENA AB, HAS TRACKED NORTHEASTWARD AT 12 KNOTS OVER
THE PAST SIX HOURS. THE CURRENT POSITION IS SITUATED WITHIN AN
EXPOSED LOW-LEVEL CENTER FEATURE EVIDENT IN 230600Z VISIBLE SATELLITE
IMAGERY. THE INTENSITY OF 65 KNOTS IS CONSISTENT WITH SUBJECTIVE
DVORAK CURRENT INTENSITY ESTIMATES OF 55-65 KNOTS FROM PGTW, KNES AND
RJTD AND RECENT ADVANCED DVORAK TECHNIQUE ESTIMATES. TY 02W CONTINUES
TO ROUND THE PERIPHERY OF DEEP-LAYER SUBTROPICAL RIDGING TO THE
SOUTHEAST. TY 02W HAS BECOME FULLY ENVELOPED BY A SHORTWAVE TROUGH
THAT DEVELOPED AND APPROACHED THE SYSTEM FROM THE NORTHWEST. VERY
STRONG WESTERLY VERTICAL WIND SHEAR (GREATER THAN 30 KNOTS) INDUCED
BY FLOW AROUND THE ENVELOPING TROUGH HAS SIGNIFICANTLY IMPACTED STORM
STRUCTURE OVER THE PAST SIX HOURS, LEAVING THE LOW-LEVEL CENTER OF TY
02W EXPOSED, AND CONVECTIVE ACTIVITY CONFINED TO THE EASTERN PORTION
OF THE CIRCULATION.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY
SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 02W WILL CONTINUE TO WEAKEN IN THE NEAR-TERM AS VERTICAL
WIND SHEAR PERSISTS AND THE SYSTEM PASSES OVER SLIGHTLY COOLER OCEAN
WATER. HOWEVER, THE SYSTEM IS TRANSITIONING TO A SUBTROPICAL
STRUCTURE, WITH THE AFOREMENTIONED SHORTWAVE TROUGH PROVIDING
BAROCLINIC SUPPORT THAT WILL LIMIT THE DEGREE OF NEAR-TERM WEAKENING.
THE SYSTEM IS EXPECTED TO TURN EASTWARD AND SLIGHTLY EQUATORWARD OVER
THE NEXT 36 HOURS FOLLOWING THE FLOW ASSOCIATED WITH REORIENTING
SUBTROPICAL RIDGING TO THE SOUTH, AND AHEAD OF AN AMPLIFYING, DEEP-
LAYER MID-LATITUDE TROUGH DEVELOPING TO THE NORTH. AROUND OR JUST
AFTER TAU 36, THIS AMPLIFYING TROUGH IS EXPECTED TO DIG FAR ENOUGH
EQUATORWARD TO DIRECTLY INTERACT WITH TY 02W. TRANSITION FROM A
SUBTROPICAL TO EXTRATROPICAL STRUCTURE WILL OCCUR AS 02W MERGES WITH
THIS TROUGH, WITH FULL TRANSITION ANTICIPATED BY TAU 72. FAVORABLE
BAROCLINIC INTERACTION BETWEEN THE MID-LATITUDE TROUGH AND 02W WILL
AID STRENGTHENING OF THE WIND FIELD AFTER TAU 36, RESULTING IN A
REINTENSIFICATION TO STORM FORCE (50 KNOTS) OR ABOVE. THE MAJORITY OF
AVAILABLE NUMERICAL MODEL TRACK FORECAST GUIDANCE FAVORS ACCELERATION
INTO THE MID-LATITUDE FLOW PATTERN FOLLOWING EXTRATROPICAL
TRANSITION. THIS GUIDANCE IS IN VERY GOOD AGREEMENT THROUGH TAU 48,
AND DIVERGES A BIT THEREAFTER DUE TO DIFFERING RATES OF ACCELERATION.
THE JTWC TRACK FORECAST REMAINS NEAR THE MULTI-MODEL CONSENSUS, WITH
HIGH CONFIDENCE OVERALL.//
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