WDPN33 PGTW 240900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (NEOGURI) WARNING NR 
024//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 30.5N 155.4E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 385 NM NORTH OF MINAMI TORI SHIMA
   MOVEMENT PAST 6 HOURS: EASTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A HIGHLY
SHEARED SYSTEM WITH AN OBSCURED LOW-LEVEL CIRCULATION CENTER
(LLCC). AN UPSTREAM TROUGH IS THE CAUSE OF THE UNFAVORABLE 20-25KT
VERTICAL WIND SHEAR, TILTING THE DEEP CONVECTION POLEWARD AND
EQUATORWARD OF THE CIRCULATION CENTER. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED EIR AND A
LATER 240703Z WSFM MWI 37GHZ MICROWAVE IMAGE REVEALING A BROAD
LOW-LEVEL BANDING EYE FEATURE. THE INITIAL INTENSITY OF 50 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY AND OBJECTIVE
FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: COMPLEX STEERING ENVIRONMENT BETWEEN
TWO SUBTROPICAL RIDGES, WITH THE PRIMARY TO THE SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RCTP: T3.0 - 45 KTS
   CIMSS ADT: 41 KTS AT 240540Z
   CIMSS AIDT: 56 KTS AT 240540Z
   CIMSS D-MINT: 49 KTS AT 240317Z
   CIMSS D-PRINT: 49 KTS AT 240540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 20-25 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TROPICAL STORM (TS) 25W WILL CONTINUE TO TRACK
NORTHEASTWARD SLOWLY OVER THE NEXT 12 HOURS WHILE UNDER THE
STEERING INFLUENCE OF THE SUBTROPICAL RIDGE TO THE EAST, WHICH IS
SLANTED ON A SOUTH-SOUTHWEST TO NORTH-NORTHEAST AXIS. THE COMPETING
RIDGE TO THE WEST WILL CONTINUE TO SLOW TRACK MOTION THROUGH TAU
48. HOWEVER BETWEEN TAU 12-48 A DEEP-LAYER TROUGH WILL WEAKEN THE
RIDGE TO THE WEST, RESULTING IN A SHARP TURN WEST-SOUTHWESTWARD.
THE DEEP-LAYER TROUGH WILL THEN ENHANCE THE TRACK SPEED AS TS 25W
IS STEERED NORTH OF THE RIDGE AXIS FOR THE REMAINDER OF THE
FORECAST PERIOD. DUE TO THE COMPLEXITY OF THE STEERING ENVIRONMENT,
IT IS POSSIBLE THAT ERRATIC JAGGED OR LOOPING TRACK MOTION MAY
OCCUR BETWEEN TAUS AND IS NOT CAPTURED WITHIN THE WARNING GRAPHIC.
HIGH VERTICAL WIND SHEAR ASSOCIATED WITH THE TROUGH WILL HINDER
DEVELOPMENT IN THE NEAR-TERM. THE HIGH SHEAR MAY BE COUNTERBALANCED
BY FAVORABLE WARMER WATERS THAT TS 25W PASSES INTO OVER WITHIN THE
NEXT 12 HOURS, ALLOWING TS 25W TO MAINTAIN AN INTENSITY OF 50KTS.
AFTER TAU 12, A TRACK RECURVE SOUTHWESTWARD WILL BRING THE SYSTEM
BACK OVER THE COOL WAKE FROM PREVIOUS UPWELLING, REMOVING THE HEAT
SOURCE AND INITIATING WEAKENING BY TAU 24. GRADUAL WEAKENING IS
EXPECTED TO CONTINUE THROUGH TAU 48. BAROCLINIC FORCING AS THE
SYSTEM BEGINS EXTRATROPICAL TRANSITION AT TAU 72 WILL SLIGHTLY
INCREASE THE INTENSITY, LEADING TS 25W TO BE A 55KT EXTRATROPICAL
CYCLONE BY THE END OF THE FORECAST PERIOD. 

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN MODERATE
AGREEMENT THAT TS 25W WILL TRACK SLOWLY IN A ZIG-ZAG MOTION DUE TO
THE COMPLICATED STEERING ENVIRONMENT. THERE ARE SLIGHT DEVIATIONS
IN THE ANGLE WHICH TS 25W RECURVES TO THE SOUTHWEST DUE TO
UNCERTAINTY IN HOW STRONGLY THE WESTERN SUBTROPICAL RIDGE WILL
WEAKEN. IN THE LATE-TERM FORECAST, THERE IS A SIGNIFICANT
ALONG-TRACK SPREAD OF 380NM, EXCLUDING THE OUTLIER OF NAVGEM, DUE
TO VARIATIONS IN THE STRENGTH OF THE DEEP-LAYER TROUGH. THE
INTENSITY GUIDANCE IS IN BETTER AGREEMENT AND SIGNALS WEAKENING IN
THE NEAR-TERM FOLLOWED BY STRENGTHENING DUE TO BAROCLINIC FORCING.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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