WDPS31 PGTW 281500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 18P (EIGHTEEN) WARNING 
NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.9S 173.7E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 272 NM WEST OF SUVA, FIJI
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 20 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE (TC) 18P WITH A COMPLETELY OBSCURED LOW-LEVEL CIRCULATION
CENTER (LLCC) AS DEEP CONVECTION CONTINUES TO BUILD OVER THE
CENTER. MODERATE AND INCREASING VERTICAL WIND SHEAR (VWS) OF 20-25
KTS HAS PERSISTED IN CLOSE PROXIMITY TO THE PRIMARY CONVECTIVE
STRUCTURE, ADDING ADDITIONAL PRESSURE TO THE NORTHWEST QUADRANT.
THE ENVIRONMENT REMAINS MARGINALLY FAVORABLE, WITH VERY WARM SEA
SURFACE TEMPERATURES BETWEEN 29-30 C, ROBUST POLEWARD OUTFLOW
ALOFT, AND THE AFOREMENTIONED MODERATE VWS. ANIMATED EIR SATELLITE 
IMAGERY HAS ALSO REVEALED A GROWING DRY SLOT AROUND THE SYSTEMS 
NORTHERN PERIPHERY, SLOWLY WRAPPING INTO THE CYCLONES EASTERN 
QUADRANT. THE INITIAL POSITION HAS BEEN PLACED WITH MEDIUM CONFIDENCE 
BASED ON EXTRAPOLATION FROM A 280922Z METOP-B ASCAT IMAGE AND 
ANIMATED EIR SATELLITE IMAGERY. THE INITIAL INTENSITY HAS BEEN 
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE SAME METOP-B DATA, 
SUBJECTIVE AGENCY DVORAK INTENSITY ESTIMATES, AND CIMSS OBJECTIVE 
INTENSITY ESTIMATES.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR)
CENTERED DIRECTLY TO THE SOUTHWEST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   PHFO: T3.5 - 55 KTS
   CIMSS ADT: 41 KTS AT 281130Z
   CIMSS AIDT: 34 KTS AT 281130Z
   CIMSS D-MINT: 34 KTS AT 280702Z
   CIMSS D-PRINT: 47 KTS AT 281230Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE FORECAST TRACK HAS SHIFTED
EASTWARD, BETWEEN 70-80NM NEAR THE STR AXIS.

FORECAST DISCUSSION: TC 18P IS FORECASTED TO CONTINUE ROUNDING THE
EASTERN EXTENT OF THE STR AXIS LOCATED DIRECTLY TO THE SOUTHWEST
THROUGHOUT THE REMAINDER OF THE FORECAST. OVER THE NEXT 12 HOURS,
THE CYCLONE IS EXPECTED TO MAINTAIN A SOUTHWARD TRACK PAST THE STR
AXIS, BECOMING SOUTHWESTWARD THEREAFTER UNTIL COMPLETE DISSIPATION
OVER WATER BY TAU 36. REGARDING INTENSITY, TC 18P IS EXPECTED TO
CONTINUE INTENSIFYING TOWARD 50 KTS OVER THE NEXT 12 HOURS WITHIN A
MARGINALLY FAVORABLE ENVIRONMENT. DURING THIS SAME PERIOD, VWS IS
FORECASTED TO INCREASE TO ABOVE 30 KTS, CREATING AN INCREASINGLY
HOSTILE ENVIRONMENT FOR FURTHER TC SUPPORT. FOLLOWING TAU 12,
SURFACE INTENSITIES ARE EXPECTED TO BEGIN WEAKENING DUE TO
UNFAVORABLE VWS BETWEEN 30-40 KTS AND INCREASING DRY-AIR
ENTRAINMENT. BETWEEN TAU 12-36, VWS AND A DRY ATMOSPHERE THROUGH
THE MID-LEVELS WILL ERODE THE SURFACE VORTEX WHILE TILTING THE
SYSTEMS VERTICAL PROFILE, DISSIPATING THE CYCLONE OVER WATER BY TAU
36. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE AND ARTIFICIAL
INTELLIGENCE (AI) SOLUTIONS ARE IN GOOD AGREEMENT THROUGHOUT THE
ENTIRETY OF THE 36 HOUR FORECAST. NEAR TAU 12, THE CROSS-TRACK
SPREAD HAS GROWN SLIGHTLY SINCE THE PREVIOUS WARNING, TO 61 NM.
AFTER TAU 12, THE CROSS-TRACK DISTANCE BETWEEN THE JTWC CONSENSUS
MEMBERS CONTINUES TO GRADUALLY WIDEN TO 125 NM BY TAU 36. DUE TO
THE GROWING CROSS-TRACK SPREAD OVER THE PREVIOUS SIX HOURS, THE
JTWC TRACK CONSENSUS HAS STARTED SHIFTING SLIGHTLY EASTWARD, BUT
CONTINUING TO ILLUSTRATE AN AGREED UPON TRACK AROUND THE STR AXIS 
UNTIL DISSIPATION. THE JTWC TRACK FORECAST HAS BEEN ALIGNED CLOSELY 
TO THE JTWC MULTI-MODEL CONSENSUS, LENDING MEDIUM CONFIDENCE TO THE
FORECAST. REGARDING INTENSITY, ALL JTWC INTENSITY CONSENSUS
SOLUTIONS CONTINUE TO CHARACTERIZE STEADY INTENSIFICATION OVER THE
NEXT 12 HOURS, WITH A QUICK WEAKENING TREND THEREAFTER. THE JTWC
INTENSITY FORECAST HAS BEEN PLACED SLIGHTLY HIGHER THAN THE GFS
DETERMINISTIC SOLUTION UNTIL TAU 12 NEAR 50 KTS, ALIGNING CLOSELY
TO THE JTWC INTENSITY CONSENSUS THEREAFTER UNTIL TAU 36, LENDING
MEDIUM CONFIDENCE TO INTENSITY FORECAST.

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