Advisories

WDPN31 PGTW 282100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (SURIGAE) WARNING NR 023//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 28.1N 133.2E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 303 NM EAST-NORTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TYPHOON 25W HAS SHED 60 KTS OF INTENSITY IN THE PAST 24 HOURS ON AN
EXTREMELY RAPID WEAKENING TREND. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY DEPICTS A COMPACT, FULLY EXPOSED LOW-LEVEL
CIRCULATION CENTER (LLCC) THAT IS QUICKLY DECOUPLING FROM THE
MID-LEVEL CIRCULATION AND THE ASSOCIATED CONVECTION. POWERFUL
NORTHWESTERLY VERTICAL WIND SHEAR (VWS) OF 30-40 KTS IS DEGRADING
THE STORM STRUCTURE, SIGNIFICANTLY TILTING THE VORTEX SOUTHEASTWARD
WITH HEIGHT, RESTRICTING POLEWARD OUTFLOW ALOFT, AND ENTRAINING DRY
AIR INTO THE CIRCULATION. THESE FACTORS OUTWEIGH THE FAVORABLE
INFLUENCE OF WARM SEA SURFACE TEMPERATURES (SST) OF 27-29 DEGREES
CELSIUS AND CONSTITUTE A HIGHLY UNFAVORABLE ENVIRONMENT FOR
DEVELOPMENT. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE FULLY EXPOSED LLCC. THE CONTINUED RAPID DETERIORATION
OF THE CONVECTIVE STRUCTURE SUPPORTS MAINTAINING THE RAPID
WEAKENING TREND. THE INITIAL INTENSITY HAS BEEN LOWERED TO 70 KTS
WITH MEDIUM CONFIDENCE, WHICH IS BELOW THE DVORAK CLASSIFICATIONS
BUT NEAR THE HIGHER END OF THE OBJECTIVE ESTIMATES FROM CIMSS.

INITIAL WIND RADII BASIS: PERSISTENCE

CURRENT STEERING MECHANISM: NORTHWESTERN FLANK OF A SUBTROPICAL
RIDGE (STR) CENTERED EAST-SOUTHEAST OF HONSHU

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T5.5 - 102 KTS
   RCTP: T4.5 - 77 KTS
   CIMSS SATCON: 60 KTS AT 281710Z
   CIMSS ADT: 74 KTS AT 281740Z
   CIMSS AIDT: 68 KTS AT 281710Z
   CIMSS D-MINT: 50 KTS AT 281709Z
   CIMSS D-PRINT: 43 KTS AT 281810Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 30-40 KTS
   SST: 27-29 CELSIUS
   OUTFLOW: WEAK EQUATORWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE FORECAST TRACK HAS SHIFTED
SLIGHTLY POLEWARD AND CLOSER TO HONSHU, AND THE FORECAST INTENSITY
HAS BEEN LOWERED THROUGH TAU 72.

FORECAST DISCUSSION: TY 25W WILL MAINTAIN A NORTHEAST MOTION ALONG
THE NORTHWESTERN PERIPHERY OF A LARGE SUBTROPICAL RIDGE CENTERED
NEAR 33N 160E. THIS STEERING MECHANISM WILL REMAIN THE PRIMARY
STEERING MECHANISM THROUGH TAU 48. THEREAFTER, STRONGER DEEP-LAYER
WESTERLY FLOW AND INTERACTION WITH A MID-LATITUDE TROUGH WILL CAUSE
THE SYSTEM TO ACCELERATE NORTHEASTWARD. TY 25W WILL CONTINUE TO
RAPIDLY WEAKEN THROUGH TAU 12 UNDER STRONG VWS. AFTER TAU 12, A
140-KT JET STREAM CURRENTLY POSITIONED OVER THE SEA OF JAPAN WILL
LIFT NORTHWARD. CONSEQUENTLY, VWS WILL EASE TO 20-25 KTS, SLOWING
THE RATE OF WEAKENING. FROM TAU 48 TO TAU 60, THERMAL ADVECTION
WILL INCREASE AS THE SYSTEM ENTERS A MORE BAROCLINIC ENVIRONMENT
AND APPROACHES WATERS OF NEAR 26 DEGREES CELSIUS. EXTRATROPICAL
TRANSITION WILL COMPLETE BY TAU 72. DURING THIS PERIOD, THE
CIRCULATION WILL PHASE WITH A DEEP TROUGH PASSING OVER NORTHERN
HONSHU, SUPPORTING SLIGHT REINTENSIFICATION TO 45 KTS.

MODEL DISCUSSION: CROSS-TRACK GUIDANCE IS TIGHTLY PACKED, WITH
SPREAD INCREASING FROM 40 NM AT TAU 36 TO 80 NM AT TAU 60. THE
ALONG-TRACK SPREAD, HOWEVER, IS MUCH LARGER, INCREASING FROM 75 NM
AT TAU 36 TO 190 NM AT TAU 60. RELATIVE TO THE PREVIOUS FORECAST
CYCLE, THE OVERALL GUIDANCE SUITE HAS SHIFTED ROUGHLY 40 NM
POLEWARD. AS SUCH, THE JTWC FORECAST TRACK HAS BEEN SHIFTED
POLEWARD, THOUGH NOT AS FAR POLEWARD AS THE GUIDANCE ENVELOPE,
RETAINING A POSITION CLOSER TO THE PREVIOUS FORECAST. THE FORECAST
TRACK IS BASED ON A BLEND OF THE JTWC CONSENSUS (CONW), WHICH
CONSISTS OF STATISTICAL AND DYNAMICAL MODELS, AND THE MEAN OF THE
AI MODELS. THE INITIAL INTENSITY IS LOWER THAN PREVIOUSLY FORECAST
DUE TO EXTREMELY RAPID WEAKENING. THE INTENSITY AIDS REFLECT THIS
DOWNGRADE AND DEPICT FURTHER WEAKENING. THE JTWC FORECAST INTENSITY
FOR TY 25W HAS BEEN NUDGED DOWNWARD BUT REMAINS SLIGHTLY HIGHER
THAN THE CONSENSUS. THE GOOGLE DEEPMIND SOLUTION IS THE WEAKEST,
DEPICTING 35 KTS BY TAU 60. ADDITIONAL DOWNWARD ADJUSTMENTS TO THE
INTENSITY FORECAST MAY BE NEEDED IN SUBSEQUENT FORECASTS.

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