WDXS32 PGTW 220900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 06S (ANGGREK) WARNING 
NR 015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.3S 91.5E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 315 NM WEST OF COCOS ISLAND
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 17 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE (TC) 06S (ANGGREK) SOMEWHAT QUASI-STATIONARY (QS) IN A WEAK
STEERING ENVIRONMENT WITH A NEAR EQUATORIAL RIDGE (NER) TO THE
NORTH AND A SUBTROPICAL RIDGE (STR) TO THE SOUTHWEST. THE
LOWER-LEVEL CIRCULATION CENTER (LLCC) IS REVEALED ON MSI WITH A
BROAD, DEVELOPING EYE-LIKE FEATURE. OUTFLOW ALOFT IS DEGRADED DUE
TO DRY AIR ENTRAINMENT FROM THE SOUTHEAST AND MODERATE VERTICAL
WIND SHEAR (18KTS PER CIMSS SHEAR ANALYSIS). SKIM AMOUNTS OF
TENDRIL-LIKE OUTFLOW IS DRIVEN EQUATORWARD BY VERTICAL WIND SHEAR
FROM THE SOUTH. UNFAVORABLE SEA SURFACE TEMPERATURES ARE DEPICTED
ON THE 220300Z HAFS-A RUN BETWEEN 22-25C DUE TO UPWELLING AS THE
STORM HAS REMAINED IN THE AREA OVER THE PAST FEW DAYS. THE INITIAL
POSITION WAS ASSESSED WITH HIGH CONFIDENCE BASED ON A 220315Z
AMSU-B 89GHZ MICROWAVE IMAGE REVEALING LOWER-LEVEL BANDS CURVING
INTO A MICROWAVE EYE-LIKE STRUCTURE. THE INITIAL INTENSITY WAS
ASSESSED WITH LOW CONFIDENCE BASED ON PERSISTENCE, AGENCY FIXES,
AND OBJECTIVE FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WEAK STEERING ENVIRONMENT AS THE STORM
IS BETWEEN A WEAK NER TO THE NORTH AND WEAK STR TO THE SOUTHWEST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   APRF: T3.0 - 45 KTS
   CIMSS SATCON: 50 KTS AT 0630Z
   CIMSS ADT: 49 KTS AT 220530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: WEAK EQUATORWARD

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

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
WITH MEDIUM CONFIDENCE TO TRACK SOUTHWEST AT 2 KTS THROUGH TAU 36
BEFORE PICKING UP TRACK SPEED SIGNIFICANTLY, TRANSITING AT 10KTS BY
TAU 120. THE TRACK SPEED INCREASE IS ANTICIPATED TO BE DRIVEN BY A
STR BUILDING TO THE SOUTHEAST, INFLUENCING TRACK SPEED BY TAU 60.
INTENSITY IS FORECAST TO CONTINUE TO INCREASE THROUGH TAU 60 WITH A
PEAK OF APPROXIMATELY 80KTS. THE INTENSIFICATION IS EXPECTED DUE TO
A DECREASE OF WIND SHEAR AND FAVORABLE SEA SURFACE TEMPERATURES AS
THE SYSTEM TRANSITIONS OUT OF ITS PREVIOUSLY QUASI-STATIONARY
STATE. BEYOND TAU 60, THE APPROACH OF A SHARP MID-LATITUDE TROUGH
FROM THE WEST AND A DECREASE IN VERTICAL WIND SHEAR IS ANTICIPATED
TO SUPPORT IMPROVED POLEWARD OUTFLOW. HOWEVER, DRY AIR FROM THE
EAST IS EXPECTED TO SEPARATE THE CENTRAL VORTEX AT THE MID-LEVEL,
CAUSING AN EXPECTED DECLINE IN STORM INTENSITY TO 65KTS BY TAU 96.
BETWEEN TAU 96-120, THE ATMOSPHERE IS EXPECTED TO MOISTEN AND
OUTFLOW IS EXPECTED TO IMPROVE ONCE AGAIN, ALLOWING FOR THE SYSTEM
TO MAINTAIN INTENSITY THROUGH THE END OF THE FORECAST.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN GOOD AGREEMENT
IN TERMS OF TRACK DIRECTION BUT DIFFERS GREATLY IN TRACK SPEED. THE
MAXIMUM CROSS-TRACK SPREAD IS 200NM AT TAU 120. THE LEVEL AT WHICH
THE STR WILL IMPACT THE STORM'S SPEED VARIES LITTLE AT TAU 48 BUT
MODEL DISAGREEMENT INCREASES THE ALONG-TRACK DISTANCE TO 670NM BY
TAU 120, WITH UKMET SLOWEST AND GFS FASTEST. INTENSITY FOR TC 06S
GENERALLY AGREES ON INTENSIFICATION BETWEEN TAU 0-48 BUT BEGINS TO 
DISAGREE ON THE RATE AT WHICH THE STORM WILL WEAKEN AND
WHETHER OR NOT THE STORM WILL REINTENSIFY. HWRF ANTICIPATES A DRASTIC 
INTENSIFICATION TO 100KTS BY THE END OF THE FORECAST PERIOD, WHILE 
COAMPS-TC EXPECTS DISSIPATION TO 30KTS. 

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