WDXS31 PGTW 021500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 01S (ANCHA) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.5S 74.6E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 292 NM SOUTH-SOUTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 19 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS
CONVECTIVE BANDING WRAPPING AROUND THE EASTERN PERIPHERY OF
TROPICAL CYCLONE (TC) 01S WITH A WEDGE OF SUBSIDENT DRY AIR
INTRUDING INTO THE NORTHWESTERN QUADRANT. MODERATE 10-15KT WIND
SHEAR FROM THE WEST ACCOMPANIES THE DRY AIR ERODING THE STRUCTURE
OF TC 01S. WATER VAPOR IMAGERY REVEALS RADIAL UPPER-LEVEL OUTFLOW.
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
AFOREMENTIONED ANIMATED EIR. THE INITIAL INTENSITY OF 50 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY AND OBJECTIVE
FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: A NEAR EQUATORIAL RIDGE TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   FMEE: T3.5 - 55 KTS
   CIMSS ADT: 47 KTS AT 021200Z

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

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 01S WILL CONTINUE TO TRACK SOUTHWESTWARD
WHILE ROUNDING THE NEAR EQUATORIAL RIDGE TO THE EAST. WHILE
TRACKING SOUTHWEST, THE SYSTEM WILL GRADUALLY WEAKEN AS IT ENTERS A
REGION OF HIGH SHEAR AS A DEEP-LAYER TROUGH APPROACHES FROM THE
WEST. THE TROUGH WILL INTRODUCE UNFAVORABLE HIGH VERTICAL WIND
SHEAR AND AN UNFAVORABLE UPPER-LEVEL ENVIRONMENT AS THE SYSTEM
APPROACHES THE UPPER-LEVEL JET. IT IS POSSIBLE THAT WEAKENING MAY
OCCUR EARLIER, CLOSER TO TAU 72, DUE TO THE COMPOUNDING EFFECTS OF
THE NEGATIVE ENVIRONMENTAL FEATURES.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE AGREES STRONGLY THAT
TC 01S WILL TRACK SOUTHWESTWARD THROUGHOUT THE FORECAST PERIOD, AS
SUPPORTED BY A 200NM CROSS-TRACK SPREAD BY TAU 72. THE INTENSITY
GUIDANCE HAS CHANGED SLIGHTLY SINCE THE LAST MODEL RUN. GFS AND THE
GFS-BASED COAMPS-TC SOLUTIONS FORECAST CONSISTENT WEAKENING, WHILE
HAFS-A PREDICTS INTENSIFICATION FOR THE FIRST 24 HOURS BEFORE
WEAKENING, DESPITE TAKING A SIMILAR TRACK TO OTHER MULTI-MODEL
CONSENSUS MEMBERS. THE JTWC INTENSITY FORECAST REMAINS CONSISTENT
WITH THE PREVIOUS FORECAST AND THE MULTI-MODEL CONSENSUS.

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