WDXS31 PGTW 020900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 01S (ANCHA) WARNING NR 
003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.4S 75.2E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 255 NM SOUTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS DEEP
CONVECTIVE BANDING FROM THE NORTHEAST WRAPPING INTO AN OBSCURED
LOW-LEVEL CIRCULATION CENTER. A WEDGE OF SUBSIDENT DRY AIR IN THE
NORTHWEST QUADRANT WRAPS INTO THE CIRCULATION CENTER. WATER VAPOR
IMAGERY REVEALS STRONG RADIAL OUTFLOW ALOFT. A 020403Z METOP-C
ASCAT IMAGE SUPPORTS THE CENTER POSITION AND THE 35KT WIND RADII.
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
AFOREMENTIONED ANIMATED MSI AND SCATTEROMETRY. THE INITIAL
INTENSITY OF 45 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE
AFOREMENTIONED SCATTEROMETRY ACCOMPANIED BY THE AGENCY AND
OBJECTIVE FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: ON THE WESTERN PERIPHERY OF A
SUBTROPICAL RIDGE TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T3.0 - 45 KTS
   FMEE: T3.5 - 55 KTS
   CIMSS SATCON: 61 KTS AT 020403Z
   CIMSS ADT: 49 KTS AT 020600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 (TC) 01S IS FORECAST TO TRACK
SOUTHWESTWARD APPROACHING THE AXIS OF A SUBTROPICAL RIDGE TO THE
EAST. THE SYSTEM WILL TRACK INTO A REGION OF HIGH VERTICAL WIND
SHEAR, WHICH WILL GRADUALLY ERODE THE SYSTEM INTENSITY TO 30KTS BY
TAU 72. IN THE MEANTIME, DRY AIR WILL ALSO ENTRAIN INTO THE SYSTEM
FROM THE WEST, WHICH WILL FURTHER DEGRADE THE ENVIRONMENT FOR
INTENSIFICATION. THE UPPER-LEVEL ENVIRONMENT AFTER TAU 48 WILL
BECOME STREAMLINED AND UNFAVORABLE. IT IS POSSIBLE THAT EARLIER
WEAKENING MAY OCCUR DUE TO THE COMPOUNDING AFFECTS OF THE NEGATIVE
ENVIRONMENTAL FEATURES.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN GOOD AGREEMENT
REGARDING THE SOUTHWESTWARD TRACK DIRECTION AND TRACK SPEED, AS
REPRESENTED BY A 200NM TRACK SPREAD BY TAU 72. THIS CONTRIBUTES TO
THE HIGH CONFIDENCE IN THE JTWC TRACK FORECAST. THE INTENSITY
FORECAST IS ALSO IN GOOD AGREEMENT, REFLECTING SLIGHT WEAKENING IN
THE NEAR-TERM MOSTLY DUE TO INCREASING SHEAR AND DRY AIR BEFORE
WEAKENING MORE RAPIDLY IN THE LATE-TERM. THE JTWC INTENSITY
FORECAST REFLECTS THE MULTI-MODEL CONSENSUS MEAN.

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