WDXS31 PGTW 271500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 03S (THREE) WARNING NR 
001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.7S 91.2E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 1155 NM EAST-SOUTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE 03S WITH A WELL-DEFINED, PARTIALLY EXPOSED LOW-LEVEL
CIRCULATION CENTER (LLCC). STRONG CONVECTIVE BURSTS ARE OFFSET TO
THE SOUTHWEST OF THE LLCC DUE TO THE HIGH NORTHERLY SHEAR ACTING ON
THE SYSTEM. ENVIRONMENTAL ANALYSIS INDICATES THAT 03S IS IN A
MARGINALLY FAVORABLE ENVIRONMENT FOR INTENSIFICATION CHARACTERIZED
BY STRONG POLEWARD OUTFLOW ALOFT, HIGH (25-30 KTS) VERTICAL WIND
SHEAR, AND WARM (27-28 C) SEA SURFACE TEMPERATURES. THE INITIAL
POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE PARTIALLY
EXPOSED LLCC IN THE ANIMATED MSI. THE INITIAL INTENSITY OF 35 KTS
IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE 2.0 TO 2.5 AGENCY
DVORAK FIXES AND A CIMSS DPRINT ESTIMATE AT 270900Z OF 39 KTS.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A NEAR EQUITORIAL
RIDGE (NER) TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   DEMS: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 25-30 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: 03S IS FORECAST TO TRACK GENERALLY SOUTHWARD
THROUGH TAU 36, ALONG THE WESTERN PERIPHERY OF THE NER TO THE EAST.
AFTER TAU 36, THE SYSTEM IS FORECAST TO ENTER A WEAK STEERING
ENVIRONMENT. A SUBTROPICAL RIDGE TO THE SOUTHWEST WILL COMPETE FOR
STEERING, CAUSING 03S TO BECOME QUASI-STATIONARY THROUGH TAU 48.
AFTER TAU 48, THE SYSTEM IS FORECAST TO TRACK WESTWARD, ALONG THE
NORTHERN PERIPHERY OF AN EXTENSION OF THE SUBTROPICAL RIDGE AS THE
NER REORIENTS AND NO LONGER HAS A STEERING INFLUENCE. REGARDING
INTENSITY, 03S IS FORECAST TO MARGINALLY INTENSIFY TO A PEAK OF 45
KTS AT TAU 24 AS THE VORTEX BECOMES MORE VERTICALLY ALIGNED.
VERTICAL WIND SHEAR AND COOLING SEA SURFACE TEMPERATURES ARE
EXPECTED TO HINDER ANY FURTHER INTENSIFICATION THOUGH. AFTER TAU
24, DRY AIR IS ANTICIPATED TO BEGIN ENTRAINING INTO THE CORE OF THE
VORTEX, CAUSING THE SYSTEM TO BEGIN WEAKENING AS IT DECOUPLES. THIS
WEAKENING TREND WILL THEN PERSIST THROUGH THE REMAINDER OF THE
FORECAST PERIOD AS 03S TRACKS WESTWARD WITH A DROP TO BELOW
TROPICAL STORM STRENGTH AROUND TAU 72. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
REGARDING THE TRACK OF 03S WITH A 110 NM CROSS-TRACK SPREAD AT TAU
72 AND NO SIGNIFICANT OUTLIERS. THE JTWC TRACK FORECAST IS PLACED
CLOSE TO CONSENSUS THROUGHOUT THE FORECAST PERIOD WITH HIGH
CONFIDENCE. INTENSITY GUIDANCE IS IN MODERATE AGREEMENT, WITH HWRF
AS THE MAIN OUTLIER, SUGGESTING A STEADY INTENSITY NEAR 30 KTS
THROUGH TAU 72. HAFS-A, GFS, AND COAMPS-TC ALL SUGGEST AN
INTENSIFICATION OVER THE NEXT 24 HOURS WITH WEAKENING THEREAFTER.
HAFS-A IS THE MOST AGGRESSIVE WITH A PEAK OF 55 KTS WHILE COAMPS-TC
HAS A PEAK OF AROUND 45 KTS. THE JTWC INTENSITY FORECAST IS PLACED
CLOSER TO COAMPS-TC, WITH MEDIUM CONFIDENCE. 

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