WDPS31 PGTW 090900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 11P (ELEVEN) WARNING 
NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.0S 169.0E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 144 NM SOUTH-SOUTHEAST OF PORT VILA,
VANUATU
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THE SYSTEM HAS
MAINTAINED ITS RAGGED FORMATIVE BANDS AND CENTRAL CONVECTION AS IT
SLOWED DOWN AND BEGAN TO TURN POLEWARD. THE INITIAL POSITION IS
PLACED WITH MEDIUM CONFIDENCE BASED ON A NOTCH FEATURE IN THE
080611Z SSMIS 91GHZ MICROWAVE IMAGE. THE INITIAL INTENSITY OF 35KTS
IS BASED ON AGENCY DVORAK ESTIMATES (SEE BELOW). ANALYSIS INDICATES
A MARGINALLY FAVORABLE ENVIRONMENT WITH LOW VWS AND WARM (28-29C)
SST OFFSET BY WEAK EQUATORWARD OUTFLOW. THE CYCLONE IS TRACKING
ALONG THE NORTHWEST PERIPHERY OF THE STR TO THE SOUTHEAST.

INITIAL WIND RADII BASIS: PERSISTENCE.

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE
SOUTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   PHFO: T2.5 - 35 KTS
   CIMSS ADT: 39 KTS AT 090540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: WEAK EQUATORWARD

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: TC 11P WILL TRACK SOUTH-SOUTHWESTWARD THEN
AFTER TAU 48, SOUTHWARD UNDER THE STEERING INFLUENCE OF THE STR.
THE MARGINALLY FAVORABLE ENVIRONMENT WILL FUEL STEADY
INTENSIFICATION TO A PEAK OF 65KTS BY TAU 48. AFTERWARD, COOLING SST
AND INCREASING VWS WILL WEAKEN THE SYSTEM DOWN TO 60KTS BY TAU 72.
CONCURRENTLY AT TAU 48, THE CYCLONE WILL BEGIN SUBTROPICAL
TRANSITION AND BY TAU 72, WILL BECOME SUBTROPICAL WITH AN EXPANDING
WIND FIELD.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT WITH
GRADUAL AND EVEN SPREADING TO A MERE 138NM AT TAU 72. HOWEVER GIVEN
THE UNCERTAINTY IN THE INITIAL STORM MOTION, THERE IS ONLY MEDIUM
CONFIDENCE IN THE JTWC TRACK FORECAST THAT IS LAID CLOSE TO THE
MODEL CONSENSUS. 

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