WDXS31 PGTW 030900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 01S (ANCHA) 
WARNING NR 006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.7S 72.4E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 336 NM SOUTH OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE 01S (ANCHA) WITH DISSIPATING CONVECTION OVER THE CENTER
THAT HAS STARTED TO EXPOSE THE LOW-LEVEL CIRCULATION CENTER (LLCC).
ENVIRONMENTAL ANALYSIS INDICATES THAT 01S IS IN AN UNFAVORABLE 
ENVIRONMENT CHARACTERIZED BY STRONG EQUATORWARD OUTFLOW ALOFT AND 
MODERATE VERTICAL WIND SHEAR GREATLY OFFSET BY EXTENSIVE DRY AIR TO 
THE WEST AND COOLING SEA SURFACE TEMPERATURES. THE INITIAL POSITION 
IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE PARTIALLY EXPOSED LLCC 
SEEN IN THE ANIMATED MSI. THE INITIAL INTENSITY OF 45 KTS IS ASSESSED 
WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK AND OBJECTIVE 
INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: SMOS DATA

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) POSITIONED TO
THE EAST-SOUTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   DEMS: T3.0 - 45 KTS
   FMEE: T3.5 - 55 KTS
   CIMSS ADT: 49 KTS AT 030600Z
   CIMSS AIDT: 38 KTS AT 030600Z
   CIMSS DPRINT: 38 KTS AT 030600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 15-20 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR TO THE WEST

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: 01S IS FORECAST TO CONTINUE TRACKING
SOUTHWESTWARD ALONG THE WESTERN PERIPHERY OF THE STR TO THE
EAST-SOUTHEAST THROUGH THE REMAINDER OF THE FORECAST PERIOD.
CONTINUED DRY AIR ENTRAINMENT, COOLING SEA SURFACE TEMPERATURES,
AND INCREASING VERTICAL WIND SHEAR WILL ALL CAUSE THE SYSTEM TO
WEAKEN OVER THE NEXT 36 HOURS. DISSIPATION IS FORECAST TO OCCUR
AROUND TAU 36, HOWEVER AN EARLIER DISSIPATION COULD OCCUR DEPENDING
ON HOW LONG THE VORTEX IS ABLE TO HOLD TOGETHER WHILE WITHIN THE
DRY ENVIRONMENT AND COOLING SEA SURFACE TEMPERATURES.  

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT ON
THE SOUTHWESTWARD TRACK OF 01S WITH A 130 NM CROSS-TRACK SPREAD AT
TAU 36. THE JTWC TRACK FORECAST IS PLACED CLOSE TO CONSENSUS WITH
HIGH CONFIDENCE. INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT
CONCERNING THE INTENSITY OF 01S WITH A STEADY WEAKENING TREND. DUE
TO THE POSSIBILITY OF A MORE RAPID RATE OF WEAKENING, THE JTWC
INTENSITY FORECAST IS PLACED WITH MEDIUM CONFIDENCE.

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