WDPS31 PGTW 080900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 12P (GABRIELLE)  
WARNING NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.0S 152.8E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 406 NM EAST OF CAIRNS, AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
CONSOLIDATING SYSTEM WITH EXTENSIVE DEEP CONVECTIVE BANDING OVER
THE NORTHERN AND EASTERN SEMICIRCLES. THIS STRUCTURE IS EVIDENT IN
THE 080346Z AMSR2 WINDSPEED IMAGE, WHICH SHOWS AN EXPANSIVE REGION
OF GALE-FORCE WINDS OVER THE EASTERN SEMICIRCLE WITH SMALL PATCHES
OF 50 KNOT WINDS. A 080555Z SSMIS 91GHZ IMAGE REVEALS IMPROVED
ORGANIZATION WITH CONVECTIVE BANDING WRAPPING INTO A BROAD
LOW-LEVEL CIRCULATION CENTER, HOWEVER, BANDING IS FRAGMENTED OVER
THE WESTERN SEMICIRCLE. THE INITIAL POSITION IS PLACED WITH MEDIUM
CONFIDENCE BASED ON THE EIR AND SSMIS IMAGERY. THE INITIAL
INTENSITY OF 45 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE
SUBJECTIVE DVORAK ESTIMATES FROM PGTW, KNES AND ABRF.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
POSITIONED TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   APRF: T3.0 - 45 KTS
   CIMSS ADT: 39 KTS AT 080530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: HIGH
   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 12P WILL TRACK SOUTHWARD ALONG THE WESTERN
PERIPHERY OF THE STR THROUGH TAU 24. AFTER TAU 24, THE STR WILL
SHIFT TO THE NORTHEAST AS A DEEP TROUGH PROPAGATES OVER THE CORAL
SEA, WHICH WILL GENERALLY ACCELERATE THE SYSTEM SOUTHEASTWARD
WITHIN THE ENHANCED FLOW BETWEEN THE TROUGH AND THE STR. THERE IS A
SHORT 36-HOUR WINDOW FOR DEVELOPMENT WITH FAVORABLE CONDITIONS,
BEFORE THE SYSTEM INTERACTS WITH THE SHORTWAVE TROUGH AND
INCREASING VERTICAL WIND SHEAR (VWS). THEREFORE, THE PEAK INTENSITY
OF 75 KNOTS IS ANTICIPATED BY TAU 36 THEN STEADY WEAKENING THROUGH
THE REMAINDER OF THE FORECAST. TC 12P WILL SLOW AND UNDERGO
SUBTROPICAL TRANSITION AS IT NEARS NEW ZEALAND. VWS ASSOCIATED WITH
THE SUBTROPICAL JET WILL INCREASE TO 40 TO 60 KNOTS WHILE SST
VALUES COOL TO 24 TO 22C.     

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE REMAINS IN GOOD
AGREEMENT WITH A 100 TO 110NM SPREAD IN SOLUTIONS THROUGH THE
FORECAST PERIOD LENDING HIGH CONFIDENCE TO THE JTWC FORECAST TRACK.
AS INDICATED IN THE 071800Z COAMPS-TC ENSEMBLE, RAPID
INTENSIFICATION (RI) IS POSSIBLE WITHIN THE NEXT 36 HOURS WITH PEAK
PROBABILITIES OF 40 TO 50 PERCENT THROUGH TAU 24. ADDITIONALLY,
RAPID INTENSIFICATION AIDS HAVE TRIGGERED REFLECTING A CONDUCIVE RI
ENVIRONMENT CHARACTERIZED BY ROBUST POLEWARD OUTFLOW, LOW VERTICAL
WIND SHEAR AND WARM SST VALUES. 

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