WDXS31 PGTW 070300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 02S (TWO) WARNING NR 
001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 7.3S 61.9E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 631 NM WEST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE 02S WITH A WELL-DEFINED, PARTIALLY EXPOSED LOW-LEVEL
CIRCULATION CENTER (LLCC) AND A PROMINENT CURVED BAND OF CONVECTION
ALONG THE EASTERN PERIPHERY. ENVIRONMENTAL ANALYSIS INDICATES THAT
02S IS IN A MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY
STRONG POLEWARD OUTFLOW, MODERATE (15-20 KTS) EASTERLY VERTICAL
WIND SHEAR, DRY AIR TO THE NORTH, AND WARM (26-27 C) SEA SURFACE
TEMPERATURES. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE PERTIALLY EXPOSED LLCC IN ANIMATED EIR IMAGERY. THE
INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE PGTW DVORAK FIX OF T2.5 (35 KTS).

INITIAL WIND RADII BASIS: PERSISTENCE FROM THE 061709Z ASCAT
SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A SUBTROPICAL
RIDGE CENTERED TO THE SOUTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT TO THE NORTH

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: 02S IS FORECAST TO CONTINUE TRACKING WESTWARD,
ALONG THE NORTHERN PERIPHERY OF THE SUBTROPICAL RIDGE THROUGHOUT
THE FORECAST PERIOD. REGARDING INTENSITY, 02S IS FORECAST TO
MAINTAIN INTENSITY THROUGH TAU 24 AS THE CORE OF THE VORTEX FIGHTS
OFF DRY AIR BEING PULLED IN FROM THE NORTH. AFTER TAU 24, DRY AIR
ENTRAINMENT WILL INCREASE SIGNIFICANTLY, LEADING TO THE DISSIPATION
OF THE SYSTEM NEAR TAU 36. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN MODERATE
AGREEMENT WITH A 160 NM CROSS-TRACK SPREAD AT TAU 36. INTENSITY
GUIDANCE OVERALL AGREES ON A STEADY INTENSITY THROUGH TAU 24 BEFORE
WEAKENING. THE JTWC TRACK AND INTENSITY FORECAST ARE BOTH PLACED
WITH MEDIUM CONFIDENCE, CLOSE TO THE MULTI-MODEL CONSENSUS.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM//
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