WDPN31 PGTW 282100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (JANGMI) WARNING NR 
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.7N 134.4E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 799 NM SOUTH-SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DEEP
CONVECTION WRAPPING HALFWAY AROUND AN EXPANSIVE, BROAD CIRCULATION.
TS 06W IS A LARGE SYSTEM WITH A CENTRAL REGION OF CALM TO LIGHT WINDS 
MEASURING 100 NM IN DIAMETER. WEAK TO MODERATE DEEP LAYER SHEAR IS 
PRESENTLY INHIBITING THE UPPER LEVEL OUTFLOW IN THE WESTERN 
SEMICIRCLE. RELATIVELY DRIER AIR IN THE MID-UPPER TROPOSPHERE IS 
SUPPRESSING CONVECTION POLEWARD OF THE CENTER, RESULTING IN A 
FRAGMENTED LOWER LEVEL CORE AS DEPICTED IN THE 281628Z 36 GHZ AMSR2 
IMAGE. THESE LIMITING FACTORS ARE MORE THAN OFFSET BY THE
HIGH OCEAN HEAT CONTENT (OHC) OF 150 KJ PER CM2, ALLOWING FOR
GRADUAL CONSOLIDATION OF THE LOW LEVEL CIRCULATION CENTER (LLCC). A
281206Z ASCAT-C PASS MEASURED 25-30 KT WINDS, BUT IT MISSED THE
STRONGEST WINDS ALONG THE EASTERN FLANK. OSCAT-3 AT 281417Z
ESTIMATED HIGHER WINDS IN A RAIN-FREE REGION. BASED ON THE OSCAT-3
PASS, SUBJECTIVE DVORAK FIXES OF T2.5 FROM PGTW, KNES, AND RCTP,
AND RISING OBJECTIVE ESTIMATES FROM CIMSS, THE INITIAL INTENSITY IS
RAISED TO 40 KTS WITH HIGH CONFIDENCE. THE INITIAL POSITION IS
ASSESSED WITH MEDIUM CONFIDENCE DUE TO THE BROAD NATURE OF THE
CIRCULATION CENTER.

INITIAL WIND RADII BASIS: SCATTEROMETER AND AMSR2 WIND SPEED DATA 

CURRENT STEERING MECHANISM: LOW TO MID LEVEL SUBTROPICAL RIDGE
CENTERED OVER THE MARIANA ISLANDS

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 40 KTS AT 281800Z
   CIMSS ADT: 30 KTS AT 281800Z
   CIMSS AIDT: 35 KTS AT 281800Z
   CIMSS D-MINT: 39 KTS AT 281628Z
   CIMSS D-PRINT: 44 KTS AT 281800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE WESTWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE PORTION OF THE FORECAST TRACK IN
THE VICINITY OF OKINAWA HAS SHIFTED 30 NM TO THE WEST.

FORECAST DISCUSSION: TS 06W IS BEING STEERED TO THE NW BY A
SUBTROPICAL RIDGE (STR) CENTERED OVER THE MARIANA ISLANDS. AS THE
STR BUILDS, THE SYSTEM MOTION WILL REMAIN UNCHANGED THROUGH TAU 36.
TS 06W WILL THEN APPROACH THE STR RIDGE AXIS AND TURN POLEWARD,
TRACKING VERY CLOSE TO OKINAWA AT TAU 96. THE FORECAST TRACK AT
THIS POINT HAS IMPORTANTLY SHIFTED 30 NM TO THE WEST, PLACING
OKINAWA INSIDE THE PORTION OF THE STORM WITH THE HIGHEST WINDS.
ONCE POLEWARD OF THE AXIS, THE SYSTEM WILL ACCELERATE TOWARDS THE
NE AND PASS NEAR OR SOUTH OF KYUSHU, WHERE MID-LATITUDE WESTERLIES
WILL BEGIN TO EXERT SOME INFLUENCE. THE ENVIRONMENTAL CONDITIONS
WILL BE FAVORABLE FOR INTENSIFICATION FOR THE NEXT 60 HOURS. THE
OHC WILL BE HIGH, AND THE VERTICAL WIND SHEAR WILL ABATE. THE INNER
CORE WILL NEED AN ADDITIONAL 12-18 HOURS TO CONSOLIDATE, AFTER
WHICH TIME MORE RAPID INTENSIFICATION WILL COMMENCE. THE STORM WILL
PEAK WITH AN INTENSITY OF AT LEAST 95 KTS AT TAU 60, WHICH THE
FORECAST DOES NOT EXPLICITLY SHOW, BEFORE ENCOUNTERING COOLER SST.
TS 06W WILL STEADILY WEAKEN DURING FINAL APPROACH TO OKINAWA AND DUE 
TO COOLER, MARGINAL SST OF 25-26 DEGREES CELSIUS AND LOW OHC. HOWEVER, 
THE SIZE OF TS 06W WILL EXPAND AS IT GAINS LATITUDE, MEANING THAT 
IMPACTS WILL BE FELT FAR FROM THE CENTER.

MODEL DISCUSSION: MODELS ARE IN GOOD AGREEMENT THROUGH TAU 48 WITH
A CROSS-TRACK SPREAD OF 90 NM. THE SPREAD AMONG THE RELIABLE
GUIDANCE INCREASES TO 130 NM AT TAU 96. THE TRACK FOLLOWS THE
MULTI-MODEL CONSENSUS, WHICH IS AT THE CENTER OF THE SPREAD,
THROUGH TAU 48 AND THEN HEDGES CLOSER TO THE AI MODELS ON THE
EASTERN SIDE OF THE GUIDANCE ENVELOPE THROUGH TAU 120. THE ENTIRE
SUITE OF MODELS HAS SHIFTED WESTWARD, AND THE GFS, ECMWF, AND
HAFS-A MODELS ARE WEST OF THE FORECAST TRACK. ADDITIONAL SHIFTS TO
THE WEST IN FUTURE FORECASTS CANNOT BE RULED OUT. IF THIS OCCURS,
THEN THE WARMER WATERS OF 27-28 DEGREES CELSIUS ASSOCIATED WITH THE
KUROSHIO CURRENT WEST OF OKINAWA WILL OFFSET THE RATE OF WEAKENING 
WHEN THE SYSTEM APPROACHES MAINLAND JAPAN. ANOTHER AREA OF UNCERTAINTY 
IS IN THE ALONG-TRACK SPREAD, WHICH INCREASES AT TAU 120. THE AI 
MODELS ARE FASTER WITH MOVING THE SYSTEM EASTWARD, WHILE HAFS-A, GFS, 
AND ECMWF ARE QUITE A BIT SLOWER AND CLOSER TO KYUSHU. IN FACT, HAFS-A 
BRINGS THE SYSTEM DIRECTLY INTO KYUSHU. THE INTENSITY FORECAST IS SET 
CLOSE TO THE CONSENSUS FOR THE FIRST 24 HOURS AND ALIGNS WELL WITH GFS 
AND THE EXPERIMENTAL GOOGLE DEEPMIND MODELS. HAFS-A REMAINS ON THE LOW
END OF THE SPREAD, PEAKING AT 80 KTS.

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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