Advisories

WDPS31 PGTW 182100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 01P (WATI) WARNING NR 
006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.6S 160.2W
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 158 NM NORTH OF RAROTONGA
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 17 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE (TC) 01P (WATI) WITH A PERSISTENT CENTRAL DENSE OVERCAST
(CDO) CONTINUING TO BE SHEARED TO THE SOUTHEAST, REVEALING THE LOW-
LEVEL BANDING ON THE NORTHWESTERN FLANK. WHILE THE LOW LEVEL 
CIRCULATION CENTER (LLCC) REMAINS OBSCURED BY THE EDGE OF THE CIRRUS 
CANOPY, THE VORTEX IS ASSESSED TO BE DECOUPLING AS AN 181602Z F-17 
SSMIS PASS REVEALED THE DEEPEST CONVECTION IN THE 91 GHZ IMAGE 
DISPLACED SOUTHEAST OF THE LLCC, WHILE THE 37 GHZ IMAGE REFLECTED A 
PARTIAL MICROWAVE EYE FEATURE STRONGEST IN THE SOUTHEASTERN QUADRANT.
ENVIRONMENTAL CONDITIONS ARE ASSESSED AS UNFAVORABLE AS 01P HAS
CROSSED THE 26 C ISOTHERM AND EXPERIENCES MODERATE TO HIGH (20-25
KTS) OF VERTICAL WIND SHEAR, CAUSED BY ITS APPROACH TOWARDS THE UPPER-
LEVEL JET, ALSO CAUSING STRONG POLEWARD OUTFLOW ALOFT. THE INITIAL 
POSITION IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON EXTRAPOLATION 
FROM THE SSMIS IMAGERY. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM 
CONFIDENCE USING A BLEND OF THE AGENCY DVORAK FIXES AND OBJECTIVE 
ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE CENTERED TO THE
NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   PHFO: T2.5 - 35 KTS
   CIMSS SATCON: 52 KTS AT 181602Z
   CIMSS ADT: 57 KTS AT 181740Z
   CIMSS AIDT: 60 KTS AT 181740Z
   CIMSS D-MINT: 43 KTS AT 181531Z
   CIMSS D-PRINT: 43 KTS AT 181910Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 25-30 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: VORTEX DECOUPLING

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: WATI IS FORECAST TO ACCELERATE SOUTHEASTWARD
FOR THE REMAINDER OF THE FORECAST PERIOD ALONG THE SOUTHWESTERN
EDGE OF THE SUBTROPICAL RIDGE (STR) CENTERED TO THE SOUTHEAST. BY
TAU 12 THE SYSTEM WILL APPROACH THE BAROCLINIC ZONE, BEGINNING
EXTRATROPICAL TRANSITION (ETT), AND COMPLETING ETT NO LATER THAN
TAU 36 AS IT TRACKS NEAR THE UPPER-LEVEL JET. REGARDING INTENSITY,
TC 01P IS EXPECTED TO WEAKEN FOR THE REMAINDER OF THE FORECAST
PERIOD AS VWS BECOMES INCREASINGLY HOSTILE, FURTHERING THE
DECOUPLING OF THE VORTEX AND IT CONTINUES INTO COOLER SSTS. THE
INTENSITY IS EXPECTED TO REMAIN ABOVE TROPICAL STORM STRENGTH AS IT
TRANSITIONS.

MODEL DISCUSSION: TRACK MODEL GUIDANCE IS IN GOOD AGREEMENT FOR THE
ENTIRETY OF THE FORECAST PERIOD, WITH AI BASED MODELS DEPICTING A
SLIGHTLY FASTER TRACK SPEED THAN PHYSICS-BASED MODELS AS ETT
OCCURS. THE OFFICIAL JTWC FORECAST TRACK IS PLACED WITH HIGH
CONFIDENCE, CLOSELY BETWEEN THE MULTI-MODEL AND AI CONSENSUS. THE
INTENSITY MODEL GUIDANCE IS ALSO IN GOOD AGREEMENT ON A SHARP
WEAKENING FOR THE REMAINDER OF THE FORECAST PERIOD, WITH COAMPS-TC
BEING THE MOST GRADUAL WHILE DECAY SHIPS WEAKENS THE MOST QUICKLY.
THE OFFICIAL JTWC FORECAST IS ASSESSED WITH MEDIUM CONFIDENCE,
SLIGHTLY ABOVE THE MULTI-MODEL CONSENSUS AS THE SYSTEM TRANSITIONS.

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