WDPS31 PGTW 212100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 01P (ONE)        
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 9.4S 167.6E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 500 NM NORTH OF PORT VILA, VANUATU
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
CONSOLIDATING SYSTEM WITH IMPROVED DEEP CONVECTIVE BANDING OVER THE
SOUTHERN SEMICIRCLE WRAPPING INTO THE NORTHERN QUADRANT. AS
DEPICTED IN THE 211844Z SSMIS 91 GHZ COLOR COMPOSITE MICROWAVE
IMAGE, THERE IS EXCELLENT CONVECTIVE BANDING OVER THE SOUTHERN
SEMICIRCLE, WITH WEAKER, MORE DISORGANIZED BANDING OVER THE
NORTHERN SEMICIRCLE. CONSEQUENTLY, THERE IS MEDIUM CONFIDENCE IN
THE INITIAL POSITION. THERE IS HIGH CONFIDENCE IN THE INITIAL
INTENSITY BASED ON AGENCY DVORAK ESTIMATES OF T2.5 (35 KNOTS).

INITIAL WIND RADII BASIS: OTHER 

CURRENT STEERING MECHANISM: NORTH-SOUTH ORIENTED NEAR-EQUATORIAL
RIDGE (NER) POSITIONED TO THE EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   PHFO: T2.5 - 35 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 01P IS FORECAST TO TRACK
SLOWLY SOUTHWARD TO SOUTH-SOUTHWESTWARD ALONG THE WESTERN PERIPHERY
OF THE NER THROUGH TAU 48. DUE TO HIGHLY FAVORABLE ENVIRONMENTAL
CONDITIONS INCLUDING ENHANCED POLEWARD OUTFLOW, LOW VERTICAL WIND
SHEAR (VWS) AND WARM SST, TC 01P IS FORECAST TO RAPIDLY INTENSIFY
THROUGH TAU 48 TO A PEAK INTENSITY OF 100 KNOTS. AFTER TAU 48, TC
01P WILL TURN SOUTHWESTWARD AS AN EXTENSION OF THE SUBTROPICAL
RIDGE (STR) BUILDS TO THE SOUTH IN RESPONSE TO AN APPROACHING
SUBTROPICAL SHORTWAVE TROUGH. AFTER TAU 72, THE SYSTEM WILL BEGIN
TO ACCELERATE SOUTHWARD AS IT ENCOUNTERS WEAK SUBTROPICAL WESTERLY
FLOW. STEADY WEAKENING SHOULD OCCUR AFTER 60 AS ENVIRONMENTAL
CONDITIONS DEGRADE WITH INCREASING VWS AND COOLER SST (26-25 C).   
    
MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT
THROUGH TAU 36 WITH INCREASING UNCERTAINTY (LOW CONFIDENCE) AFTER
TAU 36. CROSS-TRACK SPREAD JUMPS FROM 205 NM AT TAU 72 TO 715 NM AT
TAU 120. THIS LARGE SPREAD IS ALSO REFLECTED IN THE 211200Z GEFS
AND EPS ENSEMBLE GUIDANCE ALTHOUGH THE BULK OF THE SOLUTIONS
INDICATE A TRACK TOWARD NEW CALEDONIA. OVERALL, TRACK CONFIDENCE IS
LOW THROUGH TAU 120. RELIABLE INTENSITY GUIDANCE IS IN FAIR
AGREEMENT WITH THE MESOSCALE MODELS (HAFS-A, COAMPS-TC (GFS AND
NAVGEM)) SHOWING PEAK INTENSITIES IN THE 98-107 KNOT RANGE FROM TAU
48 TO TAU 60. THE 211200Z COAMPS-TC ENSEMBLE (GFS VERSION)
INDICATES HIGH PROBABILITY VALUES OF 60 TO 90 PERCENT FROM TAU 12 TO
TAU 48. ADDITIONALLY, RAPID INTENSIFICATION (RI) GUIDANCE HAS
TRIGGERED SUPPORTING THE RI PHASE THROUGH TAU 48.   

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: LOW
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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