WDPS31 PGTW 230300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 28P (TWENTYEIGHT) 
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.2S 162.5E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 333 NM WEST OF PORT VILA, VANUATU
   MOVEMENT PAST 6 HOURS: SOUTHWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A HIGHLY
ASYMMETRIC CLOUD STRUCTURE, WITH A LINEAR BAND OF DEEP CONVECTION
EXTENDING EQUATORWARD FROM THE EASTERN SIDE OF THE LOW LEVEL
CIRCULATION CENTER (LLCC). EXPOSED LOW-LEVEL CLOUD LINES ARE
EVIDENT WRAPPING INTO THE LLCC IN THE NORTHWESTERN QUADRANT, WITH
DRY MID-LEVEL AIR DRYING INHIBITING CONVECTIVE DEVELOPMENT IN THAT
SECTOR. A 222251Z ASCAT-C PASS REVEALED A WELL-DEFINED LLCC, WITH
LIGHT WINDS IN THE WESTERN SEMI-CIRCLE AND 30-35 KNOT WINDS IN THE
EASTERN SEMI-CIRCLE. THE INITIAL POSITION IS ASSESSED WITH HIGH
CONFIDENCE BASED ON AN EXTRAPOLATION OF THE LLCC IN THE ASCAT DATA.
THE INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE AS WELL,
CONSISTENT WITH THE MAXIMUM WINDS OBSERVED IN THE ASCAT DATA.
ENVIRONMENTAL CONDITIONS ARE MARGINALLY FAVORABLE, CONSISTING OF
LOW TO MODERATE SHEAR, WARM SSTS AND ROBUST POLEWARD OUTFLOW.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A LARGE,
DEEP-LAYER SUBTROPICAL RIDGE (STR) POSITIONED SOUTH OF FIJI. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T3.0 - 45 KTS
   PHFO: T3.0 - 45 KTS
   CIMSS D-PRINT: 34 KTS AT 230100Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: ASYMMETRIC WIND FIELD AND DRY AIR ENTRAINMENT IN
THE WESTERN SEMI-CIRCLE. 

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 28P HAS BEEN SLOWLY
CONSOLIDATING OVER THE LAST 48 HOURS AND HAS NOW ACHIEVED A LEVEL OF 
SYMMETRY WARRANTING THE INITIATION OF TC WARNINGS. THE SYSTEM IS 
FORECAST TO TRACK GENERALLY SOUTHWARD THROUGH THE ENTIRETY OF THE 
FORECAST PERIOD, ALONG THE TIGHT GRADIENT BETWEEN THE STR TO THE EAST 
AND A DEEP UPPER-LEVEL TROUGH, WHICH IS EXPECTED TO DEVELOP INTO A 
VERTICALLY STACKED, COLD-CORE UPPER-LEVEL LOW WITHIN THE NEXT 12 TO 
18 HOURS, POSITIONED TO THE WEST. REGARDING INTENSITY, THE SYSTEM HAS 
A SHORT WINDOW OF OPPORTUNITY IN WHICH TO INTENSIFY, BEFORE IT BEGINS 
TO INTERACT WITH A FINGER OF THE SUBTROPICAL JET STREAM AND 
EXPERIENCES RAPIDLY INCREASING SHEAR. PEAK INTENSITY OF 45 KNOTS IS 
FORECAST TO BE REACHED BY TAU 24 AS THE SYSTEM PASSES NEW CALEDONIA. 
BY TAU 12, TC 28P WILL ALREADY BE IN THE EARLY PHASES OF SUBTROPICAL 
TRANSITION (STT). THE SYSTEM CROSSES THE 26C ISOTHERM BY TAU 24 AND 
COMPLETION OF STT IS ANTICIPATED BETWEEN TAU 24 AND TAU 36. 

MODEL DISCUSSION: CONSENSUS MODEL GUIDANCE IS IN GOOD AGREEMENT,
WITH ALL MEMBERS OF THE MODEL PACKAGE DEPICTING A SOUTHWARD TRACK,
WITH CROSS-TRACK SPREAD INCREASING TO 130NM BY TAU 36. THE JTWC
FORECAST IS PLACED NEAR THE MULTI-MODEL CONSENSUS MEAN WITH HIGH
CONFIDENCE. INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT,
INDICATING A MODEST AMOUNT OF INTENSIFICATION THROUGH TAU 36, WITH
A PEAK INTENSITY BAND BETWEEN 40-55 KNOTS, FOLLOWED BY SLOW
WEAKENING THEREAFTER, BEYOND THE STT POINT AND END OF THE FORECAST.


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