WDXS32 PGTW 250900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 06S (ANGGREK) WARNING 
NR 021//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.1S 90.0E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 1130 NM SOUTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE (TC) 06S TRACKING SOUTHWEST AT 09KTS. THE SYSTEM APPEARS TO
BE INTENSIFYING IN A REGION OF LOW SHEAR (5-10KTS) AND FAVORABLE
SEA SURFACE TEMPERATURES (SST) OF 27-28 C. CLOUD TOPS AT THE UPPER
LEVELS ARE AS COLD AS -80C. THE STEERING ENVIRONMENT IS DRIVING THE 
STORM TO THE SOUTHWEST ALONG THE NORTHWESTERN SIDE OF A SUBTROPICAL 
RIDGE (STR) SOUTH THAT APPEARS TO BE BUILDING TO THE SOUTHEAST. THE 
INITIAL POSITION WAS DETERMINED VIA MSI AND AN EXTRAPOLATED 0310Z 
AMSU-B 89GHZ MICROWAVE IMAGE DEPICTING MODEST CONVECTIVE BANDING 
FEATURES WRAPPING INTO A LOW LEVEL CIRCULATION CENTER (LLCC). THE 
INITIAL INTENSITY IS DETERMINED BASED ON AGENCY AND OBJECTIVE FIXES 
AND WAS CONFIRMED BY A 2331Z SAR RCM-3 PASS DEPICTING UP TO 80KT 
WINDS, PREDOMINANTLY IN THE EASTERN HEMISPHERE OF THE CIRCULATION.

INITIAL WIND RADII BASIS: SAR DATA 

CURRENT STEERING MECHANISM: NORTHWESTERN PERIPHERY OF A STR TO THE
SOUTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   KNES: T4.5 - 77 KTS
   DEMS: T4.0 - 65 KTS
   APRF: T4.5 - 77 KTS
   CIMSS ADT: 84 KTS AT 0645Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL CYCLONE 06S (ANGGREK) IS FORECAST TO
CONTINUE ON A SOUTHWESTWARD TRACK THROUGH TAU 36, BEFORE TURNING
ONTO A MORE WEST-SOUTHWESTWARD TRACK THROUGH TAU 72. FROM TAU 72
THROUGH THE END OF THE FORECAST PERIOD, THE SYSTEM IS EXPECTED TO
CURVE TO THE SOUTH-SOUTHWEST AS IT ROUNDS THE STR AXIS. THE
INTENSITY OF TC 06S IS EXPECTED TO INCREASE STEADILY TO 105KTS
THROUGH TAU 72 AS WIND SHEAR IS EXPECTED TO REMAIN LOW (5-10KTS),
AND SST WILL BE FAVORABLE (27-28C), AND UPPER-LEVEL OUTFLOW
CONDITIONS IMPROVE SLIGHTLY. AFTER TAU 96, THE SYSTEM WILL BEGIN TO
WEAKEN AS SHEAR PICKS UP SLIGHTLY (10-15KTS) AND DRY MID-LEVEL AIR
INTRUDES FROM THE NORTH AND WEST. BY TAU 120, TC 06S IS ANTICIPATED
TO HAVE A MORE RAPID DROP IN INTENSITY AS SHEAR IS EXPECTED TO
INCREASE SIGNIFICANTLY TO APPROXIMATELY 20KTS AND DECAPITATE THE
STORM'S VORTEX AT THE MID-LEVELS. COUPLED WITH DRY AIR ENTRAINMENT,
THE STORM IS FORECAST TO DECREASE TO 80KTS BY THE END OF THE
FORECAST PERIOD. 

MODEL DISCUSSION: DETERMINISTIC MODELS ARE IN GENERAL AGREEMENT
THAT TROPICAL CYCLONE 06S WILL TRANSIT SOUTHWEST THROUGH TAU 36
WITH A CROSS-TRACK DEVIATION OF ONLY 70NM. BEYOND TAU 36, THE
SYSTEM OPENS APPROXIMATELY 300NM, SHOWING JTWC CONSENSUS
DISAGREEMENT ON HOW STARKLY THE STORM WILL CUT TO THE WEST AS
INFLUENCED BY THE SUBTROPICAL RIDGE TO THE SOUTH. THE CROSS-TRACK
DEVIATION WILL OPEN TO 470NM BY THE END OF THE FORECAST PERIOD, AS
ECMWF ANTICIPATES THE RIDGE INFLUENCING A MORE SOUTHERLY TRACK
WHILE GFS EXPECTS A MORE SOUTHWESTERLY TRACK. THE INTENSITY
GUIDANCE IS IN GENERAL AGREEMENT THAT THE SYSTEM WILL PEAK AT TAU
72 AND GRADUALLY DECLINE TOWARDS THE END OF THE FORECAST PERIOD,
HOWEVER THE INTENSITY OF THAT PEAK VARIES GREATLY DUE TO THE SMALL
SIZE OF THE SYSTEM. THE COAMPS-TC (NAVGEM VERSION) FORECASTS AN
UNREASONABLE 135KTS AT ITS MAXIMUM, WHILE JTWC SHIPS GUIDANCE
EXPECTS A PEAK OF 95KTS. 

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