Advisories

WDPN33 PGTW 062100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 27W (KOGUMA) WARNING NR 
008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.7N 164.5E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 301 NM SOUTH-SOUTHWEST OF WAKE ISLAND
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
PERSISTENT CENTRAL DENSE OVERCAST (CDO) FEATURE, CHARACTERIZED BY
ASYMMETRIC DEEP CONVECTIVE BURSTING AND PERSISTENT OVERSHOOTING TOPS
CONCENTRATED NEAR THE GEOMETRIC CENTER. THE CONVECTIVE MORPHOLOGY
EXHIBITS CHARACTERISTICS OF CENTRAL COLD COVER (CCC), TYPICALLY
CORRELATED WITH A TEMPORARY ARREST IN TROPICAL CYCLONE CONSOLIDATION.
THE ABSENCE OF RECENT HIGH-RESOLUTION, MULTI-FREQUENCY MICROWAVE
IMAGERY AND SCATTEROMETRY PRECLUDES A HIGH-CONFIDENCE POSITION FIX;
ACCORDINGLY, THE CENTER IS POSITIONED PROXIMATE TO PERSISTENT
OVERSHOOTING TOPS WITH LOW CONFIDENCE. INITIAL INTENSITY IS ASSESSED
WITH LOW CONFIDENCE AS WELL, ATTRIBUTABLE TO DIVERGENT AGENCY DVORAK
ESTIMATES AND COMPETING AUTOMATED SCENE CLASSIFICATIONS WITHIN THE 
ADT AND AIDT ALGORITHMS. CIMSS D-MINT ESTIMATES (49 KTS) DERIVED FROM 
RECENT MICROWAVE DATA PROVIDE THE PRIMARY OBJECTIVE BASELINE FOR THE 
50-KNOT ASSESSMENT. ENVIRONMENTAL ANALYSIS REVEALS HIGHLY CONDUCIVE 
THERMODYNAMIC CONDITIONS, HIGHLIGHTED BY WARM SEA SURFACE 
TEMPERATURES (30-31C) AND ANOMALOUSLY HIGH OCEAN HEAT CONTENT (OHC 
~140 KJ/CM2), COUNTERBALANCED BY MARGINAL LOW DEEP-LAYER 
NORTHEASTERLY VWS, BUT PERSISTENT MODERATE MID-LEVEL SHEAR 
MAINTAINING A VERTICAL VORTEX TILT. ANIMATED WATER VAPOR IMAGERY AND 
ATMOSPHERIC MOTION VECTORS (AMVS) DEMONSTRATE UPPER-TROPOSPHERIC 
DIVERGENCE SPLITTING UPSTREAM TO THE EAST, DIVERTING EASTERLY 
ENVIRONMENTAL FLOW AROUND THE CORE AND CREATING A LOCALIZED LOW-SHEAR 
MICRO-ENVIRONMENT FAVORABLE FOR FUTURE RAPID INTENSIFICATION (RI).

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: COMPLEX STEERING PATTERN GOVERNED BY A
DISTANT SUBTROPICAL RIDGE (STR) TO THE NORTH, DYNAMICAL INTERACTION 
WITH TY 15E TO THE NORTH-NORTHWEST, AND A SECONDARY NEAR-EQUATORIAL 
RIDGE (NER) CENTERED NEAR 10N 175E. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T3.0 - 45 KTS
   PHFO: T2.5 - 35 KTS
   CIMSS ADT: 57 KTS AT 061740Z
   CIMSS AIDT: 46 KTS AT 061740Z
   CIMSS D-PRINT: 45 KTS AT 061820Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE WESTWARD
   OTHER FACTORS: HIGHLY TILTED VORTEX. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   INITIAL INTENSITY: LOW
   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) 27W IS FORECAST TO TRACK
SLOWLY WEST-NORTHWESTWARD FOR THE NEXT 24 HOURS. WHILE SHORT-TERM 
TRACK MOTION SUGGESTS PRECIPITOUS DECELERATION, THIS PRIMARILY 
REFLECTS POSITIONAL RE-ANALYSIS AND PERSISTENT FIX UNCERTAINTY OVER 
THE PAST 12 HOURS. MEAN TRANSLATION SPEEDS WILL REMAIN BELOW 10 KNOTS 
IN THE NEAR TERM OWING TO A WEAK STEERING ENVIRONMENT, AS TY 15E TO 
THE NORTH-NORTHWEST MAINTAINS A COL REGION WITHIN THE SUBTROPICAL 
RIDGE AXIS. BY TAU 24, 15E WILL HAVE PROGRESSED SUFFICIENTLY FAR 
WESTWARD TO ALLOW THE STR TO BUILD DOWNSTREAM. CONSEQUENTLY, 27W WILL 
ACCELERATE TO APPROXIMATELY 13 KNOTS ALONG A NORTHWESTWARD HEADING BY 
TAU 36. BY TAU 72, THE SYSTEM REACHES A CRITICAL SYNOPTIC INFLECTION 
POINT WHERE GUIDANCE DIVERGES BETWEEN CONTINUED NORTHWESTWARD 
PROGRESSION VERSUS EARLY POLEWARD RECURVATURE. THE CONTROLLING 
MECHANISM WILL BE THE FORWARD SPEED AND RECURVATURE DYNAMICS OF TY 
15E. RAPID POLEWARD RECURVATURE OF 15E (FAVORED BY ECMWF AND GFS) 
FAVORS A FASTER RIDGE BREAKDOWN, ENCOURAGING 27W TO TURN POLEWARD. 
CONVERSELY, AI SUITES PROJECT THAT THE STR WILL RE-ESTABLISH RAPIDLY 
BEHIND A RECURVING 15E, THAT ENFORCES A FLATTER NORTHWESTWARD TRACK. 
THE JTWC FORECAST MAINTAINS A NORTHWESTWARD TRACK BEYOND TAU 72, 
CLOSELY ALIGNED WITH AI SOLUTIONS AND RECENT CONTINUITY. THE SYSTEM 
REMAINS IN A CCC REGIME, EFFECTIVELY ARRESTING CONVECTIVE DEVELOPMENT 
AND CORE CONSOLIDATION IN THE SHORT TERM. GRADUAL INNER-CORE 
AXISYMMETRIZATION AND VERTICAL ALIGNMENT ARE PROJECTED TO COMPLETE 
NEAR TAU 24. COINCIDENT WITH VORTEX ALIGNMENT, 27W WILL TRAVERSE A 
REGION OF ANOMALOUSLY HIGH OCEAN THERMAL ENERGY (OHC REACHING 170 
KJ/CM2, REPRESENTING THE REGIONAL BASIN MAXIMUM NORTH OF 10N). 
REINFORCED BY PERSISTENT UPPER-LEVEL DIVERGENCE, 27W IS PROJECTED TO 
INITIATE A RAPID INTENSIFICATION (RI) CYCLE COMMENCING NEAR TAU 24 
AND EXTENDING THROUGH TAU 60, LIKELY ATTAINING PEAK INTENSITY BETWEEN 
TAUS 72 AND 96. BEYOND TAU 96, THE CYCLONE WILL INTERSECT THE COLD 
SEA SURFACE WAKE GENERATED BY TY 26W, INITIATING A GRADUAL WEAKENING 
TREND THROUGH THE END OF THE FORECAST PERIOD. 

MODEL DISCUSSION: TRACK GUIDANCE EXHIBITS GOOD CONSENSUS THROUGH TAU
72. CROSS-TRACK SPREAD WIDENS TO APPROXIMATELY 120 NM BY TAU 72,
BOUNDED BY THE ECMWF ENSEMBLE MEAN ON THE NORTHERN PERIPHERY AND
EC-AIFS ON THE SOUTHERN BOUNDARY. THROUGH TAU 72, THE JTWC FORECAST
HEAVILY FAVORS THE AI CONSENSUS (AICN) AND OPERATIONAL GOOGLE 
DEEPMIND TRACKERS WITH HIGH CONFIDENCE. BEYOND TAU 72, GUIDANCE 
BIFURCATES: PHYSICS-BASED DYNAMICAL SUITES DEPICT SHARP RECURVATURE, 
WHEREAS AI MODELS MAINTAIN A PERSISTENT NORTHWESTWARD HEADING. GALWEM 
AND DETERMINISTIC ECMWF ARE THE MOST AGGRESSIVE IN RECURVATURE, 
REACHING 30N 148E BY TAU 120. EC-AIFS REMAINS THE SOUTHERN OUTLIER, 
DIRECTING THE TRACK TOWARD IWO TO BY TAU 120 AND EXPANDING CROSS-
TRACK DISPERSION TO 515 NM. AICN TRACKS NEAR AIFS, WHILE GOOGLE 
DEEPMIND OCCUPIES THE MEDIAN CORRIDOR BETWEEN THE EC-AIFS AND 
DETERMINISTIC ECMWF OUTLIERS. THE JTWC FORECAST BEYOND TAU 72 IS 
POSITIONED NEAR THE GOOGLE DEEPMIND TRACKER WITH MEDIUM CONFIDENCE. 
INTENSITY GUIDANCE REMAINS BIFURCATED. STATISTICAL SHIPS, GFS, AND 
COTC PROJECT MODEST INTENSIFICATION CAPPING AT 85 KNOTS NEAR TAU 60. 
IN CONTRAST, REGIONAL DYNAMICAL AND ML GUIDANCE (HAFS-A, CTCX, 
DEEPMIND) AND MULTIPLE RI AIDS (DTOP, RIDE, RICN, CTR1) PREDICT A 
HIGH-END PEAK OF 110-135 KNOTS NEAR TAU 84. COAMPS-TC RI 
PROBABILITIES EXCEED 80 PERCENT, WHILE STATISTICAL/AI-RI PRODUCTS 
REFLECT 30-40 PERCENT ODDS. THE JTWC FORECAST CLOSELY FOLLOWS GOOGLE 
DEEPMIND GUIDANCE THROUGH THE PERIOD, REFLECTING SHORT-TERM CCC 
SUPPRESSION FOLLOWED BY HIGH-END RI, MAINTAINING MEDIUM CONFIDENCE. 

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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