WDPS31 PGTW 160300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 08P (EIGHT) WARNING NR 
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.4S 172.0E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 254 NM EAST-NORTHEAST OF PORT VILA,
VANUATU
   MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A TIGHT,
MOSTLY EXPOSED LLCC THAT HAS BECOME DECOUPLED FROM THE REMNANT
MID-LEVEL CIRCULATION TO THE EAST. A NEW CONVECTIVE BURST HAS
ENVELOPED THE EASTERN SIDE OF THE LLCC, BUT THE OVERALL CONVECTIVE
PATTERN IS RAGGED AND CONFINED TO THE EASTERN AND NORTHEASTERN
SECTOR OF THE CIRCULATION. THIS IS DUE TO 20-25 KT OF WESTERLY
VERTICAL SHEAR THAT PERSISTS IN THE ENVIRONMENT, COUPLED WITH A
MID-LEVEL DRY AIR MASS TO THE WEST OF THE STORM. THE INITIAL
INTENSITY IS MAINTAINED AT 35 KT BASED ON A BLEND OF OBJECTIVE AND
SUBJECTIVE SATELLITE-BASED INTENSITY ESTIMATES.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: NEAR-EQUATORIAL RIDGE TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   PHFO: T3.0 - 45 KTS
   CIMSS SATCON: 43 KTS AT 151839Z
   CIMSS ADT: 51 KTS AT 152030Z
   CIMSS D-MINT: 33 KTS AT 151839Z
   CIMSS D-PRINT: 27 KTS AT 152300Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 20-25 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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: TROPICAL CYCLONE 08P CONTINUES TO DECOUPLE DUE
TO PERSISTENT MODERATE SHEAR, WITH THE REMNANTS OF THE ORIGINAL
MID-LEVEL CIRCULATION NOW RACING OFF TO THE EAST OF THE LLCC. THIS
DEGRADATION IN THE VORTEX STRUCTURE AND CONTINUING SHEAR SHOULD
SEND 08P INTO A TERMINAL DECAY PHASE, PERHAPS PUNCTUATED BY
CONVECTIVE BURSTS THAT TEMPORARILY SPIN UP THE LLCC FOR SEVERAL
HOURS AT A TIME. DYNAMICAL MODELS CONTINUE TO EXHIBIT ABNORMALLY
HIGH TRACK SPREAD DUE TO A RANGE OF INITIALIZATION BIASES. MODELS
INITIALIZING 08P STRONGER AND MORE VERTICALLY ERECT THAN IT
ACTUALLY IS, SUCH AS THE GFS AND GFS-BASED GUIDANCE, KEEP THE STORM
STRONGER FOR LONGER AND WHISK IT BRISKLY EASTWARD WITHIN THE
DEEP-LAYER STEERING FLOW. OTHER MODELS SUCH AS THE ECMWF, AIFS, AND
UKMET ARE MORE REALISTIC IN MOVING THE SHALLOW CYCLONE MORE SLOWLY
EAST-NORTHEASTWARD WITHIN THE WEAKER NEAR-SURFACE STEERING FLOW.
THE JTWC FORECAST CONTINUES TO FOLLOW THIS PHILOSOPHY, LEANING
TOWARD THE SLOWER GROUPING. THE INTENSITY FORECAST SHOWS
NEAR-STEADY INTENSITY THROUGH TAU 36, THEN WEAKENING BELOW WARNING
THRESHOLD BY TAU 48. THERE REMAINS UNCERTAINTY IN HOW LONG 08P WILL
REMAIN AT WARNING THRESHOLD INTENSITY, GIVEN THAT PERIODIC BURSTS
OF CONVECTION COULD INTERMITTENTLY SUSTAIN GALES DURING THE NEXT
DAY OR TWO. QUICKER WEAKENING BELOW 35 KT THAN FORECAST IS ALSO A
POSSIBILITY.

MODEL DISCUSSION: THE JTWC TRACK FORECAST IS CLOSE TO THE
MULTI-MODEL CONSENSUS, LEANING TOWARDS THE ECMWF, AIFS, ECMWF
ENSEMBLE MEAN, AND UKMET. THE JTWC INTENSITY FORECAST IS CLOSE TO
THE MULTI-MODEL CONSENSUS, THE MEMBERS OF WHICH HAVE COME INTO
BETTER AGREEMENT THIS CYCLE.

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