WDPS31 PGTW 080300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 12P (TWELVE) WARNING NR 
001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.4S 153.4E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 200 NM EAST-NORTHEAST OF WILLIS ISLAND,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A BROAD
CONSOLIDATING SYSTEM WITH FRAGMENTED FORMATIVE BANDS TRAILING FROM
THE NORTHWEST THROUGH EAST AND A PARTLY EXPOSED LOW LEVEL
CIRCULATION (LLC). THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE LLC FEATURE IN THE MSI LOOP. THE INITIAL
INTENSITY IS ALSO PLACED WITH HIGH CONFIDENCE BASED ON
CLOSELY-CLUSTERED DVORAK FIXES FROM PGTW, ABRF AND KNES. ANALYSIS
INDICATES A FAVORABLE ENVIRONMENT WITH WARM SSTS, LOW VWS AND
STRONG EQUATORWARD OUTFLOW ALOFT.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA.

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE EAST. 

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

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

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: TC 12P WILL SHORTLY TRACK POLEWARD THEN
SOUTHEASTWARD TOWARD NEW ZEALAND AS IT ROUNDS THE STR AXIS. THE
FAVORABLE ENVIRONMENT, ENHANCED BY INCREASING POLEWARD OUTFLOW AS
THE TC TAPS INTO THE PREVAILING WESTERLIES ON THE POLEWARD SIDE OF
THE STR AXIS, WILL FUEL A SIGNIFICANT INTENSIFICATION TO A PEAK OF
75KTS, POSSIBLY HIGHER, BY TAU 48. AFTERWARD, INCREASING VWS AND
COOLING SST WILL GRADUALLY THEN RAPIDLY ERODE THE SYSTEM DOWN TO
50KTS BY TAU 120. CONCURRENTLY BY TAU 96, TC 12P WILL BEGIN
SUBTROPICAL TRANSITION AND BY TAU 120, WILL CONVERT INTO A
SUBTROPICAL SYSTEM WITH AN EXPANSIVE WIND FIELD.   

MODEL DISCUSSION: NUMERICAL TRACK MODELS ARE IN TIGHT AGREEMENT,
CONSIDERING THIS IS THE INITIAL WARNING, WITH A GRADUAL SPREADING
TO 350NM BY TAU 120 WITH NAVGEM THE SOLE RIGHT-OF-TRACK OUTLIER. UP
TO TAU 72, THERE IS HIGH CONFIDENCE IN THE JTWC TRACK FORECAST THAT
IS LAID JUST TO THE LEFT OF CONSENSUS TO OFFSET NAVGEM. AFTER TAU 72, 
THE TRACK CONFIDENCE IS MEDIUM AS THE SPREAD WIDENS. THE INTENSITY 
FORECAST IS MEDIUM UP TO TAU 72 THEN LOW AFTERWARD DUE TO THE 
UNCERTAINTY IN THE FORECAST INTENSITY DYNAMICS IN THE EXTENDED PERIOD.

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