WDPS31 PGTW 090300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05P (FIVE) WARNING NR 
002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.3S 174.7E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 211 NM WEST OF SUVA, FIJI
   MOVEMENT PAST 6 HOURS: EASTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 10 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A PARTIALLY-EXPOSED 
LOW-LEVEL CIRCULATION (LLC) WITH LIMITED DEEP CONVECTIVE BANDING 
OVER THE EASTERN QUADRANT, WHICH SUPPORTS THE INITIAL POSITION WITH 
MEDIUM CONFIDENCE. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH 
HIGH CONFIDENCE BASED ON THE PGTW, KNES AND PHFO DVORAK ESTIMATES. 
TC 05P IS LOCATED UNDER THE NORTHERN PERIPHERY OF AN UPPER-LEVEL 
TROUGH WITH LOW TO MODERATE VERTICAL WIND SHEAR (15 TO 20 KNOTS) AND 
POSSIBLE DRY AIR ENTRAINMENT, WHICH ARE HINDERING THE DEVELOPMENT OF 
CORE CONVECTION. 

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: COMPETING STEERING INFLUENCE BETWEEN
THE NEAR-EQUATORIAL RIDGE (NER) TO THE NORTHEAST AND THE SUBTROPICAL 
RIDGE (STR) TO THE SOUTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   PHFO: T2.0 - 30 KTS
   CIMSS ADT: 30 KTS AT 082340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 28-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: POSSIBLE DRY AIR ENTRAINMENT, ESPECIALLY OVER THE
WESTERN SEMICIRCLE.

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 05P IS FORECAST TO TRACK SLOWLY 
SOUTHEASTWARD THROUGH TAU 12 WITHIN THE COMPETING STEERING PATTERN 
BETWEEN THE NER AND STR. AFTER TAU 12, THE STR SHOULD BUILD TO THE 
SOUTH AND BECOME THE DOMINANT STEERING INFLUENCE THROUGH TAU 60 WITH 
A GENERALLY WESTWARD TO WEST-SOUTHWESTWARD TRACK. AFTER TAU 60, AN 
APPROACHING MAJOR SHORTWAVE TROUGH IS EXPECTED TO WEAKEN THE STR, 
WHICH WILL LEAD TO A FASTER SOUTHEASTWARD TRACK TOWARD THE BREAK IN 
THE STR ALONG THE WESTERN AND SOUTHWESTERN PERIPHERY OF THE WEAK 
STEERING RIDGE POSITIONED TO THE EAST. THE SYSTEM IS EXPECTED TO 
REMAIN WITHIN A COMPLEX UPPER-LEVEL ENVIRONMENT UNDER A BROAD UPPER-
LEVEL TROUGH, HOWEVER, SLIGHT INTENSIFICATION IS ANTICIPATED DUE TO 
ROBUST POLEWARD OUTFLOW WITH A PEAK INTENSITY OF 50 KNOTS EXPECTED 
AT TAU 36. AFTER TAU 36, TC 05P WILL GRADUALLY WEAKEN AS IT BECOMES 
FURTHER EMBEDDED WITHIN THE UPPER-LEVEL TROUGH. AFTER TAU 96, TC 05P 
IS FORECASTED TO GRADUALLY TRANSITION INTO A SUBTROPICAL CYCLONE. 

MODEL DISCUSSION: THE NUMERICAL MODELS AND ENSEMBLE GUIDANCE (EPS
AND GEFS) SUPPORT THE JTWC FORECAST TRACK WITH FAIR CONFIDENCE
WITH SOME UNCERTAINTY IN THE EXACT TRACK DUE TO THE COMPLEX,
RAPIDLY-EVOLVING SYNOPTIC PATTERN. THUS, OVERALL CONFIDENCE IN THE
JTWC TRACK IS MEDIUM. THERE IS ALSO UNCERTAINTY IN THE JTWC
INTENSITY FORECAST DUE TO THE PRESENCE OF THE UPPER-LEVEL TROUGH
OVER THE SYSTEM AND THE POTENTIAL FOR DRY AIR ENTRAINMENT, WHICH
IS EXPECTED TO LIMIT DEVELOPMENT. THE BULK OF THE RELIABLE INTENSITY
GUIDANCE SUPPORTS THE JTWC FORECAST WITH HWRF PEAKING SLIGHTLY
HIGHER TO 55 KNOTS AT TAU 24. AFTER TAU 72, THE JTWC INTENSITY 
FORECAST IS SIGNIFICANTLY LOWER THAN THE INTENSITY GUIDANCE DUE TO 
INCREASING VERTICAL WIND SHEAR AND COOLER SST VALUES (26-27C).  

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