Advisories

WDPN31 PGTW 260900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (SURIGAE) WARNING NR 013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.9N 126.8E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 223 NM SOUTH-SOUTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A RAPIDLY
ORGANIZING SYSTEM POSITIONED FAVORABLY FOR NEAR-TERM RAPID
INTENSIFICATION (RI). DEEP CONVECTION, FEATURING CONVECTIVE BURSTING
AND VORTICAL HOT TOWERS (VHTS), INITIATED IN THE NORTHWEST QUADRANT
APPROXIMATELY SIX HOURS AGO AND HAS CONTINUED TO SLOWLY WRAP AROUND
INTO THE SOUTHERN SEMICIRCLE OF THE ASSESSED LOW-LEVEL CIRCULATION
CENTER. A 260522Z ATMS 89GHZ MICROWAVE PASS REVEALS STRONG
CONVECTION REMAINS FOCUSED ON THE WESTERN FLANK OF THE EYE FEATURE,
WITH SECONDARY CURVED BANDING DEVELOPING IN THE SOUTHEASTERN
QUADRANT. EARLIER MICROWAVE IMAGERY FROM 260000Z INDICATED THAT
THE VORTEX HAD ALREADY ACHIEVED VERTICAL ALIGNMENT, THOUGH MSI
SUGGESTS RESIDUAL MODERATE MID-LEVEL SOUTHEASTERLY SHEAR CONTINUES TO
EXERT MINOR PRESSURE ON THE CORE. THE SYSTEM IS SITUATED WITHIN
A COL REGION AT THE SUBTROPICAL RIDGE (STR) AXIS, FACILITATING
ROBUST DUAL-CHANNEL OUTFLOW ALOFT AS EVIDENCED BY ANIMATED WATER 
VAPOR IMAGERY. THE CENTER OF 25W IS LOCATED ALONG THE SOUTHERN RANGE 
LIMIT OF THE JMA OKINAWA RADAR FEED; NONETHELESS, BASE REFLECTIVITY 
SUFFICIENTLY RESOLVES THE WESTERN EYEWALL ARC AND THE SOUTHWESTERN 
EYE BOUNDARY. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE 
BASED ON THE CONCURRENT ATMS AND RADAR FIXES. THE INITIAL INTENSITY 
IS ASSESSED WITH MEDIUM CONFIDENCE, BIASED HIGHER THAN THE BULK OF 
SUBJECTIVE AND OBJECTIVE ESTIMATES NOTED BELOW IN DEFERENCE TO RECENT 
SYNTHETIC APERTURE RADAR (SAR) DATA AND OBSERVED RAPID CONVECTIVE 
CONSOLIDATION. ENVIRONMENTAL CONDITIONS ARE HIGHLY FAVORABLE, 
CHARACTERIZED BY VERY WARM SSTS (29-30C), STRONG DUAL-CHANNEL OUTFLOW 
ALOFT, AND LOW DEEP-LAYER VERTICAL WIND SHEAR (VWS).

INITIAL WIND RADII BASIS: SCATTEROMETER AND SAR DATA. 

CURRENT STEERING MECHANISM: SYSTEM IS APPROACHING THE AXIS OF THE
SUBTROPICAL RIDGE (STR) CENTERED TO THE EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T3.0 - 45 KTS
   CIMSS SATCON: 53 KTS AT 260521Z
   CIMSS ADT: 51 KTS AT 260540Z
   CIMSS AIDT: 45 KTS AT 260540Z
   CIMSS D-MINT: 67 KTS AT 260522Z
   CIMSS D-PRINT: 57 KTS AT 260540Z

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 HAS REACHED THE RIDGE AXIS,
DECELERATED SIGNIFICANTLY, AND IS COMMENCING A GRADUAL POLEWARD TURN.
OVER THE NEXT 12 HOURS, 25W IS EXPECTED TO CONTINUE ITS SLOW 
NORTHWARD PROGRESSION, TURNING NORTHEASTWARD BY TAU 24. AFTER TAU 36, 
THE STR TO THE EAST RAPIDLY WEAKENS AND ELONGATES ALONG A SOUTHWEST-
TO-NORTHEAST AXIS, WHILE SIMULTANEOUSLY A MODERATELY STRONG MID-
LATITUDE SHORTWAVE TROUGH TRANSITS OVER SOUTHERN JAPAN. THIS LARGE-
SCALE EVOLUTION WILL FACILITATE FULL RECURVATURE AND DOWNSTREAM 
ACCELERATION NORTHEASTWARD THROUGH THE REMAINDER OF THE FORECAST 
PERIOD. THE SYSTEM WILL PASS SOUTHEAST OF TOKYO BY TAU 120 AS IT 
INITIATES EXTRATROPICAL TRANSITION (ETT). REGARDING INTENSITY: 25W 
RESIDES IN A NEAR-OPTIMAL ENVIRONMENT SUPPORTED BY A VERTICALLY 
ALIGNED VORTEX, HIGH OCEAN HEAT CONTENT, MINIMAL SHEAR, AND VIGOROUS 
DUAL-CHANNEL DIVERGENCE ALOFT. THE SYSTEM IS ANTICIPATED TO COMMENCE 
RAPID INTENSIFICATION (RI) SHORTLY, ATTAINING A PEAK OF AT LEAST 95 
KNOTS NEAR TAU 24. THESE OPTIMAL CONDITIONS WILL BE TRANSIENT; BY TAU 
36, THE SYSTEM WILL INITIATE A SLOW WEAKENING TREND AS UPPER-LEVEL 
OUTFLOW CHANNELS DIMINISH. MORE PRONOUNCED WEAKENING IS PROJECTED 
AFTER TAU 48 AS PROGRESSIVELY INCREASING VWS AND ENTRAINMENT OF DRY 
MID-LEVEL AIR DISRUPT CORE SYMMETRY. WEAKENING WILL CONTINUE THROUGH 
TAU 120. AN  ALTERNATIVE SCENARIO CANNOT BE ENTIRELY DISCOUNTED, AS 
THE GFS CONTINUES AS A PERSISTENT DYNAMICAL OUTLIER DEPICTING A 
RETROGRADE EVOLUTION. THE PRIMARY GOVERNING MECHANISMS GENERATING 
THIS DIVERGENCE ARE (1) THE FORECAST INTENSITY AND CORE STRUCTURE OF 
25W, (2) THE GENESIS AND INTENSIFICATION RATE OF A SECONDARY CYCLONE 
NEAR THE MARIANAS AND THEIR COMBINED IMPACT ON THE STR, AND (3) THE 
AMPLITUDE OF THE MID-LATITUDE TROUGH. THE GFS MAINTAINS 25W AS A 
DEEPER, MORE INTENSE CYCLONE FOR AN EXTENDED DURATION AND RAPIDLY 
DEVELOPS THE DOWNSTREAM MARIANAS CYCLONE. IN THE GFS SOLUTION, THESE 
TWO EXPANSIVE CIRCULATIONS AMPLIFY THE STR DOWNSTREAM, EFFECTIVELY 
PRECLUDING 25W FROM REACHING THE TROUGH INTERACTION ZONE (WHICH THE 
GFS SIMULTANEOUSLY RESOLVES AS WEAKER AND LESS DYNAMICALLY 
SUPPORTIVE). CONSEQUENTLY, THE GFS ARRESTS 25W NEAR THE LATITUDE OF 
OKINAWA BEFORE STEERING IT SOUTHWESTWARD ALONG THE EASTERN PERIPHERY 
OF STR OVER CHINA THROUGH TAU 120.  

MODEL DISCUSSION: TRACK GUIDANCE REMAINS BIFURCATED BETWEEN THE
AI/ML SUITES (ALONGSIDE DETERMINISTIC ECMWF) SUPPORTING THE JTWC
FORECAST AND THE GFS (WITH SECONDARY TENDENCIES IN GEFS AND NAVGEM)
REFLECTING THE ALTERNATE SCENARIO. THROUGH TAU 36, GUIDANCE REMAINS 
IN TIGHT CONSENSUS, EXHIBITING MINIMAL CROSS-TRACK AND MODEST ALONG-
TRACK DISPERSION. POST-RECURVATURE, HOWEVER, NUMERICAL SOLUTIONS 
DIVERGE RAPIDLY IN ALONG-TRACK TRANSLATION. NAVGEM TRANSLATES SLOWLY
NORTHEASTWARD AFTER TAU 36, ULTIMATELY REACHING THE VICINITY OF
YAKUSHIMA BY TAU 120. GFS REACHES THE LATITUDE OF OKINAWA AT TAU 72
PRIOR TO EXECUTING A 180-DEGREE RETROGRADE MOTION BACK TO THE 
SOUTHWEST, RETURNING TO NEAR ITS CURRENT COORDINATES BY TAU 120. 
CONVERSELY, THE AI MODELS CLUSTER POLEWARD OF 34N BY TAU 120, WITH 
OUTLIERS AS FAR NORTH AS 36N ADVECTED WELL TO THE EAST. THE 
DETERMINISTIC ECMWF IS POSITIONED POLEWARD OF THE AI CONSENSUS AT TAU 
120, CLOSELY ALIGNED WITH THE UKMET ENSEMBLE MEAN. THE RESULTANT 
CROSS-REGIME SPREAD EXCEEDS 1000 NM. THE JTWC FORECAST HEAVILY FAVORS 
THE AI CONSENSUS MEAN THROUGH THE PERIOD; CONFIDENCE REMAINS MEDIUM 
THROUGH TAU 72, BUT IS ASSESSED AS LOW BEYOND TAU 72 DUE TO EXTREME 
MULTI-MODEL DISPERSION. INTENSITY GUIDANCE EXHIBITS GENERAL AGREEMENT 
THROUGH TAU 72, WITH NEARLY ALL GUIDANCE DEPICTING A SHARP PEAK AT 
TAU 24 WITHIN A 75-110 KNOT ENVELOPE. MULTIPLE STATISTICAL RI AIDS 
ARE TRIGGERED THIS CYCLE, AND HAFS-A DYNAMICALLY RESOLVES AN RI 
CYCLE. WHILE THE JTWC INTENSITY FORECAST REMAINS JUST BELOW CRITERIA 
FOR EXPLICIT RI, A PEAK EXCEEDING 100 KNOTS REMAINS A DISTINCT 
DYNAMICAL POSSIBILITY GIVEN OPTIMAL CORE ORGANIZATION. GRADUAL DECAY 
WILL FOLLOW PEAK INTENSITY THROUGH THE REMAINDER OF THE FORECAST 
PERIOD. 

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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