Advisories

WDPN31 PGTW 270300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 30W (IN-FA) WARNING NR 015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.3N 162.4E
   INITIAL INTENSITY: 110 KTS
   GEOGRAPHIC REFERENCE: 385 NM SOUTHWEST OF WAKE ISLAND
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 36 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON (TY)
30W WITH A DIMPLE EYE FEATURE THAT REMAINS CLOUD FILLED. THE
FORWARD PROGRESS OF THE SYSTEM HAS BEEN STAGNANT AGAIN OVER THE
PAST 6 HOURS BUT IT HAS MANAGED TO MAINTAIN ITS INTENSITY DESPITE
SITTING OVER ITS OWN COLD WAKE. THE OCEAN HEAT CONTENT (OHC) VALUES
OVER 100 KJ PER CM2 ARE LIKELY PREVENTING THE UPWELLING FROM HAVING
AN OVERLY DETRIMENTAL EFFECT ON THE INTENSITY. RADIAL OUTFLOW HAS
ALSO REMAINED FAIRLY GOOD, HELPING TO SUPPORT THE CONSTANT
INTENSITY. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE DIMPLE EYE FEATURE IN THE MSI IMAGERY. THE INITIAL
INTENSITY OF 110 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON A
BLEND OF THE AGENCY DVORAK FIXES ON THE HIGHER END AND CIMSS
OBJECTIVE INTENSITY ESTIMATES ON THE LOWER END. A 262231 METOP-C
ASCAT PASS REVEALED A COMPACT GALE FORCE WIND FIELD AND A VERY
COMPACT, HIGH INTENSITY CENTRAL CORE. THE ENVIRONMENT IS
CHARACTERIZED AS FAVORABLE, WITH WARM SEA SURFACE TEMPERATURES, LOW
VERTICAL WIND SHEAR (VWS), AND GOOD RADIAL OUTFLOW. THE ONLY
REMAINING NEGATIVE ENVIRONMENTAL FACTOR IS THE LIKELY EFFECT OF
COLD WATER UPWELLING.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T5.5 - 102 KTS
   RCTP: T6.0 - 115 KTS
   PHFO: T6.0 - 115 KTS
   CIMSS ADT: 107 KTS AT 270000Z
   CIMSS AIDT: 108 KTS AT 270000Z
   CIMSS D-MINT: 114 KTS AT 262304Z
   CIMSS D-PRINT: 104 KTS AT 270030Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 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: HIGH
   INITIAL WIND RADII: HIGH

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 CONTINUED AT A SLOW
2 KTS OVER THE PAST 6 HOURS IN A COMPETING STEERING ENVIRONMENT
CHARACTERIZED BY THE SOUTHEASTERN PERIPHERY OF AN STR CENTERED SOUTH 
OF HONSHU AND A NER TO THE SOUTHEAST. 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 24 TO 36 
HOURS. THE TRACK FORECAST DEPICTS A GENERALLY WESTWARD MOTION OVER 
THE NEXT 24-36 HOURS BECAUSE OF THE STEERING ENVIRONMENT, THEN 
MODESTLY ACCELERATES TO MORE TYPICAL SPEEDS THROUGH TAU 96. AFTER TAU 
96, TY 30W IS EXPECTED TO APPROACH A WEAK STEERING PATTERN AND SLOW 
DOWN AGAIN THROUGH THE REMAINDER OF THE FORECAST PERIOD. THE LATTER 
WEAK STEERING ENVIRONMENT BEGINS TO INTRODUCE SOME UNCERTAINTY IN THE 
TRACK FORECAST DURING THE LATE TAUS. THE INTENSITY FORECAST NO LONGER 
INCLUDES A SHORT-TERM WEAKENING TREND GIVEN HOW WELL THE SYSTEM HAS 
MAINTAINED ITS INTENSITY WHIL MOVING SO SLOWLY. THE ENVIRONMENT IS 
EXPECTED TO REMAIN GENERALLY FAVORABLE THROUGHOUT THE FORECAST PERIOD 
AND STEADY INTENSIFICATION IS FORECAST THROUGH TAU 48, THEN LEVEL OFF 
AROUND 130 KTS. A WEAKENING TREND BEGINS AFTER TAU 72, WHERE OHC 
VALUES AND INTERNAL DYNAMICS OF THE SYSTEM, WITH THE POTENTIAL FOR 
EYEWALL REPLACEMENT CYCLES, SHOULD PUT A CAP ON THE INTENSITY.

MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN GOOD AGREEMENT WITH A
CROSS-TRACK SPREAD OF 60 NM AT TAU 72 AND MINIMAL ALONG-TRACK
DEVIATIONS. CROSS-TRACK SPREAD INCREASES SIGNIFICANTLY TO 220 NM BY
TAU 120 IN THE WEAK STEERING ENVIRONMENT, WITH ECMWF AS THE MOST
NORTHERN SOLUTION AND JGSM MAKING UP THE SOUTHERN LIMIT OF THE
ENVELOPE. THE REMAINDER OF GUIDANCE FILLS IN THE ENVELOPE EVENLY.
THE JTWC TRACK FORECAST IS PLACED CLOSE TO THE MULTI-MODEL
CONSENSUS WITH A SLIGHT SOUTH BIAS ENCOURAGED BY THE AI CONSENSUS
MEAN. THE INTENSITY GUIDANCE HAS COME INTO SLIGHTLY BETTER
AGREEMENT THIS CYCLE, WITH HAFS-A TRENDING CLOSER TO THE GOOGLE
DEEPMIND SOLUTIONS, WHICH HAVE REMAIND VERY CONSISTENT. A VERY WEAK
GFS SOLUTION IS PULLING DOWN THE CONSENSUS AND THE JTWC INTENSITY
FORECAST IS ABOVE IT AFTER TAU 24, HEDGED JUST BELOW THE MORE
AGGRESSIVE GOOGLE DEEPMIND SOLUTIONS.

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