WDIO31 PGTW 031500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 02A (SHAKHTI) WARNING 
NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.0N 66.4E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 171 NM SOUTH OF KARACHI, PAKISTAN
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 19 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS A COMPACT,
ASYMMETRICAL, BUT SLOWLY INTENSIFYING AND CONSOLIDATING TROPICAL 
CYCLONE (TC) 02A (SHAKHTI).  ENVIRONMENTAL ANALYSIS SUGGESTS 
FAVORABLE CONDITIONS FOR FURTHER INTENSIFICATION, CHARACTERIZED BY 
ELEVATED SEA SURFACE TEMPERATURES (SST) IN THE RANGE OF 28-29 C, 
STRONG UPPER-LEVEL DIVERGENCE ENHANCING OUTFLOW, AND LOW VERTICAL 
WIND SHEAR (VWS) OF 5-10 KTS. THE SYSTEM IS SURROUNDED BY DRY AIR, 
BUT IT IS CURRENTLY MANAGING TO PROTECT ITSELF FROM INTRUSION INTO 
THE CORE OF THE VORTEX. THE INITIAL POSITION IS ESTIMATED WITH MEDIUM 
CONFIDENCE, GIVEN THE PERSISTENT CENTRAL CONVECTION WHICH OBSCURES 
THE LOW-LEVEL CIRCULATION CENTER (LLCC). THE INITIAL INTENSITY IS 
ASSESSED AT 45 KTS WITH MEDIUM CONFIDENCE, SUPPORTED BY AGENCY DVORAK 
FIXES AND ALIGNMENT WITH OBJECTIVE INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: EXTENSION OF A DEEP-LAYER SUBTROPICAL
RIDGE (STR) CENTERED TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   DEMS: T2.5 - 35 KTS
   CIMSS SATCON: 48 KTS AT 030849Z
   CIMSS ADT: 43 KTS AT 030900Z
   CIMSS AIDT: 41 KTS AT 031100Z
   CIMSS D-MINT: 41 KTS AT 030849Z
   CIMSS D-PRINT: 46 KTS AT 031130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 02A IS SLOWLY TRACKING NORTHWESTWARD AND IS
FORECAST TO BEGIN A WEST-SOUTHWESTWARD TURN UNDER THE INFLUENCE OF
A STRENGTHENING SUBTROPICAL RIDGE TO THE NORTH WITHIN THE NEXT 6 TO
12 HOURS. SUBSEQUENTLY, THE SYSTEM IS EXPECTED TO CONSOLIDATE AND
INTENSIFY, REACHING PEAK INTENSITY OF 65 KTS AROUND TAU 36. HOWEVER, 
A DEEP SHORTWAVE TROUGH DEVELOPING TO THE NORTH WILL WEAKEN THE 
STEERING PATTERN, CAUSING A SHIFT IN THE PRIMARY STEERING INFLUENCE 
TO ANOTHER RIDGE CENTERED TO THE SOUTHEAST. THIS CHANGE WILL REVERSE 
THE TRACK OF THE SYSTEM TO EAST-NORTHEASTWARD AND INITIATE A 
WEAKENING TREND, RESULTING FROM BOTH INCREASED VERTICAL WIND SHEAR 
AND SIGNIFICANT DRY AIR ENTRAINMENT INTO THE CORE OF THE VORTEX. AS 
THE SYSTEM APPROACHES THE COAST OF INDIA, IT IS EXPECTED TO BEGIN 
RAPIDLY WEAKENING, WITH COMPLETE DISSIPATION ANTICIPATED BY OR BEFORE 
TAU 120, FOLLOWING LANDFALL.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE SHOWS REASONABLE
AGREEMENT, PARTICULARLY CONSIDERING THE COMPLEXITY OF THE STEERING
PATTERN TRANSITION. THE JTWC OFFICIAL FORECAST IS PLACED WITH
MEDIUM CONFIDENCE IN THE SHORT TERM. THE TIMING OF THE TRACK U-TURN
INCREASES PREDICTION UNCERTAINTY, RESULTING IN A LOW CONFIDENCE
ASSESSMENT FOR THE LONG TERM. INTENSITY GUIDANCE HOWEVER, SHOWS
GOOD CONSENSUS WITH MINIMAL VARIABILITY AMONG DETERMINISTIC
MULTI-MODEL CONSENSUS MEMBERS. ALL AVAILABLE MODELS INDICATE A
WEAKENING TREND BEGINNING AROUND TAU 36, CONSISTENT WITH THE
EXPECTED SHIFT IN STEERING PATTERN.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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