WDPS31 PGTW 100900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05P (CODY) 
WARNING NR 007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.3S 175.8E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 198 NM SOUTHWEST OF SUVA, FIJI
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY
EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) DISPLACED TO THE
NORTHEAST OF A BROAD AREA OF WEAK, CYCLONICALLY CURVED CONVECTION
TO THE SOUTH AND WEST. A 100431Z SSMIS 37GHZ MICROWAVE IMAGE SHOWED
A BROAD SWATH OF CONVECTIVE BANDING EXTENDING ACROSS THE SOUTHERN
AND EASTERN PERIPHERY OF THE CIRCULATION. THE INITIAL POSITION IS
ASSESSED WITH HIGH CONFIDENCE BASED ON THE PARTIALLY EXPOSED LLCC
AND AN EXTRAPOLATION OF THE LLC EVIDENT IN THE MICROWAVE IMAGERY.
THE INITIAL INTENSITY OF 40 KNOTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON AN AVERAGING OF AGENCY CURRENT INTENSITY
ESTIMATES RANGING BETWEEN T2.5 (PGTW AND KNES) AND T3.0 (PHFO), AND
SLIGHTLY LOWER THAN THE OBJECTIVE ADT ESTIMATE OF 43 KNOTS. CIMSS
ATMOSPHERIC MOTION VECTORS AND MODEL ANALYSIS REVEALS A CLOSED LOW
AT 200MB CENTERED JUST TO THE NORTHWEST OF THE LLCC, GENERATING
CONVERGENCE ALOFT AND INHIBITING DEVELOPMENT AT THIS TIME.
MID-LEVEL DRY AIR IS BEING PULLED IN FROM THE WEST AND IS BEGINNING
TO PUNCH IN TOWARDS THE CORE, SERVING AS AN ADDITIONAL BRAKING
MECHANISM ON DEVELOPMENT.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF THE DEEP
SUBTROPICAL RIDGE (STR) TO THE SOUTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   PHFO: T3.0 - 45 KTS
   CIMSS ADT: 43 KTS AT 100540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: MID-LEVEL DRY AIR ENTRAINMENT ON WEST AND NORTH
OF THE LLCC. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: TC 05P HAS ONCE AGAIN PICKED UP SOME FORWARD
SPEED AFTER STEADYING UP ON ITS CURRENT WESTWARD COURSE ALONG THE
NORTHERN SIDE OF A DEEP STR CENTERED TO THE SOUTH. THE WESTWARD
COURSE WILL NOT BE LONG LIVED HOWEVER, AS A SERIES OF MAJOR
SHORTWAVE TROUGHS PASSING TO THE SOUTH WILL ERODE AND BREAK THE
STR, AND TC 05P WILL TURN SHARPLY POLEWARD AROUND TAU 24. ONCE
TURNED POLEWARD THE SYSTEM WILL STEADILY ACCELERATE IN THE GRADIENT
BETWEEN THE WESTERN PERIPHERY OF THE STR TO THE SOUTH AND LARGE,
DEEP TROUGH TO THE WEST. NOW THAT THE SYSTEM IS UNDER THE
UPPER-LEVEL LOW, LOW VWS WILL BE OFFSET BY CONVERGENCE ALOFT,
LEADING TO A NEAR-TERM WEAKENING TREND THROUGH TAU 24. THE SYSTEM
WILL MOVE OUT FROM UNDER THE UPPER LOW AROUND TAU 36, AND TAP INTO
STRONG POLEWARD OUTFLOW, WHICH WILL OFFSET QUICKLY INCREASING VWS,
AT LEAST FOR A PERIOD OF TIME. TC 05P WILL PEAK AT 45 KNOTS BY TAU
48, BEFORE THE COMBINATION OF INCREASING VWS AND DECREASING SSTS
WILL WEAKEN THE SYSTEM. AS TC 05P PASSES SOUTH OF THE 25S LATITUDE,
AROUND TAU 72, IT WILL PASS THE 26C ISOTHERM AND BEING THE GRADUAL
PROCESS OF SUBTROPICAL TRANSITION, WHICH WILL BE COMPLETE NO LATER
THAN TAU 120. 

MODEL DISCUSSION: TRACK GUIDANCE GENERALLY AGREE ON THE OVERALL
SCENARIO, WITH SOME UNCERTAINTY IN THE TIMING AND SHARPNESS OF THE
TURN POLEWARD, AND INCREASED ALONG-TRACK SPREAD AFTER TAU 72 AS THE
SYSTEM TRANSITIONS TO SUBTROPICAL. THE JTWC FORECAST LIES ALONG THE
NORTHERN EDGE OF THE ENVELOPE THROUGH TAU 24, THEN SLIGHTLY OUTSIDE
OF THE CONSENSUS MEAN AFTER THE TURN POLEWARD, WITH MEDIUM
CONFIDENCE. INTENSITY GUIDANCE IS GENERALLY HIGHER THAN THE JTWC
FORECAST BY ABOUT 5 KNOTS THROUGHOUT THE FORECAST PERIOD, BUT
SUPPORTS THE FORECAST INTENSITY TRENDS. 

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