Typhoon In-Fa

WDPN31 PGTW 262100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 30W (IN-FA) WARNING NR 014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.1N 162.6E
   INITIAL INTENSITY: 110 KTS
   GEOGRAPHIC REFERENCE: 387 NM SOUTHWEST OF WAKE ISLAND
   MOVEMENT PAST 6 HOURS: WESTWARD AT 01 KTS
   SIGNIFICANT WAVE HEIGHT: 36 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TYPHOON
(TY) 30W WITH AN INCREASINGLY CLOUD FILLED EYE AND COOLING CLOUD
TOPS OVER THE PAST FEW HOURS. THE SYSTEM HAS REMAINED NEARLY
STATIONARY OVER THE PAST 6 HOURS WITH ONLY A SMALL WESTWARD DRIFT
IN A COMPETING STEERING ENVIRONMENT. DESPITE THE SLOW MOTION VECTOR
AND LIKELY COLD WATER UPWELLING, THE SYSTEM HAS MANAGED TO
ESTABLISH IMPROVED RADIAL OUTFLOW. THE INITIAL POSITION IS PLACED
WITH HIGH CONFIDENCE BASED ON THE STILL-PRESENT EYE FEATURE IN
ANIMATED EIR. THE INITIAL INTENSITY OF 110 KTS IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON A BLEND OF THE AGENCY DVORAK FIXES AND
CIMSS OBJECTIVE INTENSITY ESTIMATES, ALTHOUGH THERE WERE NO
MICROWAVE PASSES TO ASSESS THE OVERALL STRUCTURE. THE ENVIRONMENT
IS CHARACTERIZED AS FAVORABLE WITH WARM SEA SURFACE TEMPERATURES,
HIGH OCEAN HEAT CONTENT, AND IMPROVED RADIAL OUTFLOW BEING OFFSET
BY THE EFFECT OF COLD WATER UPWELLING.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: COMPETING STEERING ENVIRONMENT BETWEEN
THE SOUTHEASTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) CENTERED
SOUTH OF HONSHU AND A NEAR-EQUATORIAL RIDGE TO THE SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T5.5 - 102 KTS
   RCTP: T5.5 - 102 KTS
   PHFO: T5.5 - 102 KTS
   CIMSS SATCON: 84 KTS AT 261507Z
   CIMSS ADT: 109 KTS AT 261730Z
   CIMSS AIDT: 106 KTS AT 261730Z
   CIMSS D-MINT: 109 KTS AT 261508Z
   CIMSS D-PRINT: 106 KTS AT 261730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL
   OTHER FACTORS: UPWELLING OF COOLER WATER DUE TO THE SLOW TRACK
SPEED

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: THE TRACK MOTION OF TY 30W HAS STALLED OVER
THE PAST 6 HOURS TO JUST 1 KT OF FORWARD SPEED AS THE STR TO THE
NORTHWEST AND THE NER TO THE SOUTHEAST BATTLE FOR STEERING CONTROL.
AN EXTENSION OF THE STR IS EXPECTED TO BREAK OFF AND TRANSIT
EASTWARD TO THE NORTH OF THE SYSTEM WHILE THE NER WEAKENS AND MOVES
WESTWARD THROUGH THE NEXT 36 HOURS. THE FORECAST TRACK REFLECTS
THIS SETUP WITH A SLOW TRACK SPEED TAU 36 THAT SLOWLY ACCELERATES
THROUGH TAU 96. AFTER TAU 96, TY 30W IS EXPECTED TO APPROACH ANOTHER
WEAK STEERING PATTERN AND SLOW DOWN AGAIN THROUGH THE REMAINDER OF
THE FORECAST PERIOD. THE INTENSITY FORECAST EXPLICITLY CALLS FOR A
PERIOD OF WEAKENING OVER THE FIRST 12 HOURS RESULTING FROM THE
EFFECT OF SLOW MOTION AND COLD WATER UPWELLING. THE ENVIRONMENT
REMAINS GENERALLY FAVORABLE THROUGH TAU 72 AND THE INTENSITY IS
EXPECTED TO RESPOND ACCORDINGLY, REACHING A PEAK OF 135 KTS AROUND
TAU 72. A GRADUAL WEAKENING TREND FROM TAU 72 TO 120 IS FORECAST
PRIMARILY AS A RESULT OF INTERNAL DYNAMICS OF THE SYSTEM AND THE
POTENTIAL FOR EYEWALL REPLACEMENT CYCLES.

MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN GOOD AGREEMENT WITH A
CROSS-TRACK SPREAD OF 75 NM AT TAU 72 AND MINIMAL ALONG-TRACK
DEVIATIONS, EXCEPTING AIFS AS A SOUTHERN OUTLIER. AFTER TAU 72,
CROSS-TRACK SPREAD INCREASES, ESPECIALLY AT TAU 120 WHEN THE SYSTEM
IS EXPECTED TO BE IN A WEAK STEERING ENVIRONMENT. THE JTWC TRACK
FORECAST IS PLACED CLOSE TO THE MODIFIED CONSENSUS THAT INCLUDES
PHYSICS-BASED AND AI MODELS. THE INTENSITY GUIDANCE IS LESS
CERTAIN, WITH GFS AS THE ANOMALOUSLY WEAKER MODEL WHILE HAFS-A
PARADOXICALLY PREDICTS SHORT-TERM INTENSIFICATION DESPITE THE SLOW
FORWARD PROGRESS EXPECTED. BOTH THE EXPERIMENTAL AND OPERATIONAL
GOOGLE DEEPMIND SOLUTIONS DEPICT A MORE REALISTIC SHORT-TERM
WEAKENING TREND FOLLOWED BY STEADY INTENSIFICATION. THE JTWC
INTENSITY FORECAST FAVORS THE DEEPMIND SOLUTIONS, WHICH RESULTS IN
AN INTENSITY LOWER THAN THE CONSENSUS OVER THE FIRST 36 HOURS, THEN
UP TO 30 KTS HIGHER THAN THE CONSENSUS, WHICH IS PULLED LOWER BY
HAFS-A AND GFS.

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