WDPS31 PGTW 052100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 10P (NAT) 
WARNING NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.9S 163.5W
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 816 NM WEST OF PAPEETE, TAHITI
   MOVEMENT PAST 6 HOURS: EASTWARD AT 17 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY
EXPOSED LOW-LEVEL CIRCULATION (LLC) WITH DEEP CONVECTIVE BANDING
OVER THE NORTHERN SEMICIRCLE WRAPPING INTO THE EASTERN QUADRANT. A
051729Z 37 GHZ SSMIS MICROWAVE IMAGE REVEALS THAT THE LLC IS BROAD
WITH SHALLOW FRAGMENTED BANDING OVER THE WESTERN SEMICIRCLE.
CONSEQUENTLY, THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE
BASED ON THE SSMIS AND MSI IMAGERY, WITH THE INITIAL POSITION
OBSCURED UNDER THE WESTERN EDGE OF THE DEEP CONVECTION. UPPER-LEVEL
CONDITIONS REMAIN MARGINALLY FAVORABLE WITH LOW TO MODERATE 
NORTHWESTERLY VERTICAL WIND SHEAR OFFSET BY STRONG POLEWARD
OUTFLOW. AS A RESULT OF THE ENVIRONMENTAL CONDITIONS, THE INITIAL
INTENSITY REMAINS ASSESSED AT 35 KTS WITH HIGH CONFIDENCE BASED ON THE 
SUBJECTIVE AGENCY DVORAK ESTIMATES.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: NEAR-EQUATORIAL RIDGE (NER) POSITIONED
TO THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   PHFO: T2.5 - 35 KTS
   CIMSS ADT: 39 KTS AT 051740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 10P IS FORECASTED TO
TRACK EAST-SOUTHEASTWARD ALONG THE SOUTHERN PERIPHERY OF THE NER
THROUGH TAU 48. AFTER TAU 48, TC 10P WILL MAKE A MORE EASTWARD TO 
EAST-NORTHEASTWARD TRACK TOWARDS TAHITI AS THE NER REORIENTS. THE
SYSTEM IS EXPECTED TO GRADUALLY INTENSIFY TO A PEAK INTENSITY OF 45
KTS BY TAU 24 DUE TO THE STRONG POLEWARD OUTFLOW AND VERY WARM SST
VALUES (30-31 C). AFTER TAU 36, THE SYSTEM WILL WEAKEN QUICKLY DUE
TO THE INCREASE IN VERTICAL WIND SHEAR (30-35 KTS) AND DRY AIR
ENTRAINMENT. AFTER THE FORECAST PERIOD, TC 10P MAY REINTENSIFY AS A
SUBTROPICAL CYCLONE.

MODEL DISCUSSION: WITH THE EXCEPTION OF NAVGEM, NUMERICAL MODEL
GUIDANCE IS IN GOOD AGREEMENT WITH A 65 NM CROSS-TRACK SPREAD AT
TAU 72. THE 051200Z ECMWF AND GFS ENSEMBLES INDICATE A SIMILAR
SPREAD IN SOLUTIONS AND SUPPORT THE JTWC FORECAST TRACK WITH HIGH
CONFIDENCE. INTENSITY GUIDANCE IS IN FAIR AGREEMENT WITH A 15-20 KT
SPREAD IN PEAK INTENSITY VALUES, WITH COAMPS-TC (NAVGEM VERSION) 
INDICATING A PEAK INTENSITY OF 55 KTS AT TAU 24. AFTER THE FORECAST 
PERIOD, THE INTENSITY GUIDANCE INDICATES A POSSIBILITY FOR A
REINTENSIFICATION PHASE, HOWEVER THE SYSTEM WILL TRANSITION TO A
SUBTROPICAL CYCLONE.

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