Advisories

WDPN31 PGTW 261500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (SURIGAE) WARNING NR 014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 23.3N 126.9E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 198 NM SOUTH-SOUTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
SLOW-MOVING SYSTEM, ATTEMPTING TO CLEAR OUT AN EYE FEATURE, THOUGH
AS OF YET, NOT SUCCEEDING IN THIS ENDEAVOR. THE MOST RECENT FRAMES
OF EIR HOWEVER, AT 1320Z SHOW A NASCENT PINHOLE EYE, BUT WHETHER
THIS WILL BE ANOTHER IN A STRING OF FAILED ATTEMPTS, OR THE REAL
DEAL, IS YET TO BE DETERMINED. THE SYSTEM HAS SLOWED TO 4 KNOTS; 
TROCHOIDAL WOBBLING OF THE INNER CORE HAS RESULTED IN ERRATIC SHORT-
TERM TRACK MOTION AS CONVECTIVE ORGANIZATION PROCEEDS. A 261141Z 
ASCAT-B PASS DEMONSTRATES THAT WHILE THE CENTRAL DENSE OVERCAST (CDO) 
AND CONVECTIVE CANOPY REMAIN ASYMMETRIC, THE UNDERLYING LOW-LEVEL 
CIRCULATION IS HIGHLY SYMMETRIC AND WELL DEFINED. MAXIMUM SAMPLED 
SCATTEROMETER WINDS WERE 55 KNOTS; HOWEVER, GIVEN THE EXTREMELY 
COMPACT INNER CORE AND TYPICAL ASCAT RAIN ATTENUATION/RESOLUTION 
LIMITATIONS AT HIGHER WIND SPEEDS, OPERATIONAL SURFACE WINDS ARE 
ASSESSED TO BE 10-15 KNOTS STRONGER. THE INNER CORE REMAINS BEYOND 
JMA RADAR COVERAGE, THOUGH THE NORTHERN ARC OF THE DEVELOPING EYEWALL 
REMAINS DETECTABLE. THE INITIAL POSITION IS ASSESSED WITH HIGH 
CONFIDENCE BASED ON THE ASCAT-B FIX. THE INITIAL INTENSITY IS 
ASSESSED WITH MEDIUM CONFIDENCE, BIASED HIGHER THAN THE BULK OF 
SUBJECTIVE AND AUTOMATED ESTIMATES IN DEFERENCE TO SCATTEROMETER 
DATA. PERSISTENCE AMONG SUBJECTIVE AND OBJECTIVE FIXES OVER THE PAST 
SIX HOURS SUGGESTS THE SYSTEM HAS ENTERED A TEMPORARY PLATEAU IN 
INTENSIFICATION PENDING STABLE EYEWALL DEVELOPMENT. ENVIRONMENTAL 
CONDITIONS REMAIN HIGHLY FAVORABLE, CHARACTERIZED BY MINIMAL DEEP-
LAYER SHEAR, HIGH SSTS (29-30C), HIGH OHC, STRONG DUAL-CHANNEL 
OUTFLOW, AND A VERY LOW VENTILATION INDEX OF 0.004.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: THE SYSTEM IS AT THE RIDGE AXIS, IN A
GENERALLY WEAK STEERING ENVIRONMENT. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T3.5 - 55 KTS
   CIMSS SATCON: 57 KTS AT 261020Z
   CIMSS ADT: 51 KTS AT 261140Z
   CIMSS AIDT: 52 KTS AT 261140Z
   CIMSS D-PRINT: 75 KTS AT 261240Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG DUAL-CHANNEL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TYPHOON (TY) 25W RESIDES ENTIRELY WITHIN
A LARGE COL REGION BETWEEN AN EXPANSIVE SUBTROPICAL RIDGE (STR) TO 
THE EAST AND A BROAD CONTINENTAL RIDGE CENTERED OVER SOUTHWESTERN 
CHINA. HAVING ENTERED THIS WEAK STEERING ENVIRONMENT APPROXIMATELY 
SIX HOURS AGO, THE SYSTEM HAS DECELERATED MARKEDLY, DRIFTING SLOWLY 
NORTHWARD AT 4 KNOTS. THE STR TO THE EAST IS FORECAST TO WEAKEN AND 
RECEDE SOUTHWESTWARD OVER THE NEXT 12 TO 24 HOURS, ALLOWING TY 25W TO 
ROUND THE RIDGE AXIS, EXIT THE COL, AND INITIATE RECURVATURE TO THE 
NORTHEAST UNDER THE INFLUENCE OF A PROGRESSIVE, RELATIVELY WEAK MID-
LATITUDE SHORTWAVE TROUGH. BEYOND TAU 36, THE STR TO THE SOUTHEAST 
REMAINS WEAKENED WHILE MID-LATITUDE FLOW TO THE NORTH BECOMES 
PREDOMINANTLY ZONAL; TY 25W WILL TRANSLATE NORTHEASTWARD ALONG
THIS RELAXED STEERING GRADIENT AT 9-10 KNOTS THROUGH TAU 120. 
REGARDING INTENSITY: THE SYSTEM APPEARS POISED TO COMPLETE EYE 
FORMATION; RETENTION OF AN EYE WILL BE THE PIVOTAL FACTOR GOVERNING 
NEAR-TERM INTENSIFICATION. THERMODYNAMIC CONDITIONS STRONGLY FAVOR 
INTENSIFICATION, INCLUDING A MODERATE PROBABILITY OF RAPID 
INTENSIFICATION (RI) OVER THE NEXT 24 HOURS. BEYOND TAU 24, 
INCREASING VWS WILL BE PARTIALLY COUNTERBALANCED BY VIGOROUS POLEWARD 
OUTFLOW, LEADING TO A GRADUAL WEAKENING TREND THROUGH TAU 72. IN THE 
EXTENDED FORECAST, 25W WILL WEAKEN MORE RAPIDLY DUE TO LOWER SSTS, 
ELEVATED SHEAR, DRY AIR ENTRAINMENT, AND THE ONSET OF EXTRATROPICAL 
TRANSITION (ETT). THE SYNOPTIC PHILOSOPHY REMAINS UNCHANGED, WITH THE 
BIFURCATED ALTERNATIVE SCENARIO STILL VIABLE. THE GFS AND HAFS-A 
PERSIST AS THE PRIMARY OUTLIERS ADVANCING THIS ALTERNATIVE, 
CONTRIBUTING TO ELEVATED FORECAST UNCERTAINTY. THE GFS SUSTAINS 25W 
AS A MORE INTENSE CYCLONE FOR AN EXTENDED PERIOD, WHILE 
SIMULTANEOUSLY ACCELERATING CYCLOGENESIS OF A SECONDARY DISTURBANCE 
NEAR THE MARIANAS. IN THE GFS SOLUTION, THESE COMBINED SYSTEMS 
REINFORCE DEVELOPMENT OF A STRONG RIDGE TO THE NORTH AND EAST OF 25W, 
EFFECTIVELY BLOCKING POLEWARD PROGRESSION. ADDITIONALLY, THE GFS 
DEPICTS A WEAKER, LESS DYNAMIC TROUGH THAT FAILS TO EXTEND 
SUFFICIENTLY EQUATORWARD TO INDUCE RECURVATURE.  

MODEL DISCUSSION: TRACK GUIDANCE WITHIN THE 120-HOUR FORECAST WINDOW
EXHIBITS PRONOUNCED DISPERSION EXCEEDING 1200 NM, RANGING FROM
SOUTHEAST OF OKINAWA TO NORTHEAST OF TOKYO, WITH SPREAD IN POST-TAU 
120 TIMEFRAME EXCEEDING 2000 NM. MULTI-MODEL ENSEMBLES DEPICT EXTREME
INTRA-MEMBER VARIANCE; THE ENSEMBLE SPREAD AT TAU 120 BOUNDS AN
ENVELOPE SPANNING FROM LUZON TO SHEMYA ISLAND, REPRESENTING 
HISTORICALLY ANOMALOUS TRACK DISPERSION FOR A WEST PACIFIC RECURVING 
TYPHOON. THE GUIDANCE ENVELOPE REMAINS TIGHT THROUGH TAU 24 BEFORE 
ALONG-TRACK DISPERSION ACCELERATES RAPIDLY. GFS ARRESTS FORWARD 
MOTION AT TAU 48 NEAR THE LATITUDE OF OKINAWA BEFORE COMMENCING A 
RETROGRADE SOUTHWESTWARD DRIFT THROUGH TAU 120. NAVGEM HAS SHIFTED 
NORTHEASTWARD BUT REMAINS AN ALONG-TRACK SLOW OUTLIER. NOTEWORTHILY, 
THE 1200Z ECMWF HAS ADJUSTED APPROXIMATELY 600 NM EQUATORWARD 
COMPARED TO ITS 0600Z RUN, ALIGNING CLOSER IN FORWARD SPEED TO NAVGEM 
AND THE MULTI-MODEL CONSENSUS (CONW). AMONG THE REMAINING GUIDANCE, 
UKMET ENSEMBLE, ECEPS, THE AI CONSENSUS (AICN), AND EC-AIFS ARE 
TIGHTLY CLUSTERED APPROXIMATELY 100 NM NORTHEAST OF THE JTWC FORECAST 
AT TAU 120. GOOGLE DEEPMIND, EXPERIMENTAL DEEPMIND, AND WINDBORNE AI 
RESIDE 200-400 NM FURTHER DOWNSTREAM (FASTER). THE JTWC TRACK CLOSELY 
MIRRORS AICN THROUGH TAU 48, THEN REFLECTS A MORE CONSERVATIVE 
FORWARD SPEED, PLACED NEAR THE MIDPOINT BETWEEN AICN AND CONW AT TAU 
120. INTENSITY GUIDANCE DEMONSTRATES SOLID CONSENSUS FOR AN INITIAL 
PEAK AT TAU 24, FOLLOWED BY GRADUAL WEAKENING. MULTIPLE RI AIDS 
REMAIN TRIGGERED, PROJECTING PEAKS UP TO 110 KNOTS (CTCX PEAKS AT 105 
KTS; HAFS-A AT 95 KTS). CIMSS AI-RI GUIDANCE INDICATES A 50 PERCENT 
PROBABILITY OF RI25 AND A 53 PERCENT PROBABILITY OF RI35. THE JTWC 
FORECAST PREDICTS A 25-KNOT INTENSIFICATION OVER 24 HOURS (MATCHING 
RI25 THRESHOLDS), JUST BELOW THE STANDARD 30-KNOT RI BENCHMARK; 
HOWEVER, HIGHER PEAK WINDS REMAIN A STRONG PROBABILITY GIVEN THE 
ENVIRONMENT. DOWNSTREAM INTENSITY GENERALLY FOLLOWS THE MULTI-MODEL 
CONSENSUS MEAN. 

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