WDPS32 PGTW 071500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 11P (ELEVEN) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.5S 165.6W
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 323 NM EAST-SOUTHEAST OF PAGO PAGO
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS A
MIDGET-SIZED SYSTEM WITH SHALLOW RAIN BANDS FEEDING INTO THE LOW LEVEL
CIRCULATION (LLC) THAT IS OBSCURED BY A COLD DENSE OVERCAST THAT
HAS DEEPENED SLIGHTLY IN THE LAST SIX HOURS. THE INITIAL POSITION
IS PLACED WITH HIGH CONFIDENCE BASED ON A DEFINED LLC FEATURE IN
THE 071211Z ATMS MICROWAVE IMAGE. THE INITIAL INTENSITY IS PLACED
WITH MEDIUM CONFIDENCE BASED ON THE AVERAGE OF AGENCY AND AUTOMATED
DVORAK ESTIMATES AND REFLECTS THE SLIGHT CONVECTIVE IMPROVEMENT.
ANALYSIS INDICATES A MARGINALLY FAVORABLE ENVIRONMENT WITH WARM SST
AND STRONG POLEWARD OUTFLOW OFFSET BY MODERATE-HIGH VWS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: NEAR EQUATORIAL RIDGE (NER) TO THE
NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   PHFO: T2.5 - 35 KTS
   CIMSS ADT: 53 KTS AT 071140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 20-25 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 11P WILL CONTINUE SOUTHEASTWARD UNDER THE
STEERING NER UP TO TAU 24. AFTERWARD, A SUBTROPICAL RIDGE (STR) TO
THE SOUTH WILL BLOCK ITS FORWARD MOTION AND COMPETE FOR STEERING.
THE MARGINALLY FAVORABLE ENVIRONMENT WILL BECOME UNFAVORABLE WITH
INCREASING VWS AS THE SYSTEM DRIFTS INTO THE PREVAILING WESTERLIES,
LEADING TO GRADUAL DECAY AND EVENTUAL DISSIPATION BY TAU 36. 

MODEL DISCUSSION: NUMERICAL MODELS ARE IN GOOD AGREEMENT WITH AN
EVEN SPREAD TO 95NM BY TAU 24. AFTERWARD, A WESTWARD AND EASTWARD
TRACK BIFURCATION SCENARIO ENSUES WITH THE STR AND THE NER
COMPETING FOR STEERING. IN VIEW OF THIS, THERE IS ONLY MEDIUM
CONFIDENCE IN THE JTWC TRACK AND INTENSITY FORECASTS. 

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