WDIO31 PGTW 032100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 02A (SHAKHTI) WARNING 
NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.1N 65.8E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 404 NM EAST-NORTHEAST OF MASIRAH ISLAND
   MOVEMENT PAST 6 HOURS: WESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN
ASYMMETRIC REGION OF FLARING DEEP CONVECTION OVER THE WESTERN
SEMICIRCLE. A 031624Z MHS 89GHZ MICROWAVE IMAGE INDICATES LIMITED
DEEP CONVECTIVE BANDING OVER THE WESTERN SEMICIRCLE WITH SHALLOW
BANDING WRAPPING INTO A WEAKLY DEFINED LOW-LEVEL CIRCULATION
CENTER. A 031716Z ASCAT-C IMAGE REVEALS A WELL-DEFINED CENTER, WITH
45-50 KNOT WINDS OVER THE WESTERN QUADRANT. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE ASCAT-C BULLSEYE IMAGE.
THE INITIAL INTENSITY OF 50 KTS IS ASSESSED WITH HIGH CONFIDENCE
BASED ON THE ASCAT-C DATA. THIS IS SUPPORTED BY SUBJECTIVE DVORAK
ESTIMATES RANGING FROM 45-55 KNOTS. CIMSS OBJECTIVE ESTIMATES RANGE
FROM 45-50 KNOTS FURTHER BOLSTERING THE JTWC INITIAL INTENSITY
ESTIMATE.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: COMPETING STEERING PATTERN WITH A STRONG 
SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTH AND NORTHWEST, AND A 
WEAKER STR TO THE SOUTH AND SOUTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   DEMS: T3.0 - 45 KTS
   CIMSS SATCON: 45 KTS AT 031714Z
   CIMSS ADT: 49 KTS AT 031800Z
   CIMSS AIDT: 40 KTS AT 031700Z
   CIMSS D-PRINT: 49 KTS AT 031830Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: MID-LEVEL DRY AIR ENTRAINMENT

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) 02A IS FORECAST TO TRACK
SLOWLY WEST-SOUTHWESTWARD THROUGH TAU 36 ALONG THE SOUTHEASTERN
PERIPHERY OF THE PRIMARY STEERING RIDGE POSITIONED OVER THE SAUDI
PENINSULA. THE STR TO THE SOUTHEAST WILL REMAIN WEAK THROUGH THIS
PERIOD. AFTER TAU 36, THE SYSTEM WILL BE EFFECTIVELY BOXED IN WITH
RIDGING TO THE NORTHWEST (SAUDI PENINSULA), TO THE SOUTHEAST
(EXTENDING WESTWARD FROM CENTRAL INDIA) AND TO THE SOUTH (BUILDING
RIDGE). CONSEQUENTLY, TRACK MOTION WILL BE ERRATIC, WITH A SLOW
TURN SOUTHWARD TO SOUTHEASTWARD. DETERMINISTIC MODELS VARY
SIGNIFICANTLY ON THE LOCATION OF THIS STALL AND TURN, WITH A 150NM
SPREAD BETWEEN THE MODELS. TC 02A IS EXPECTED TO WEAKEN RAPIDLY
AFTER TAU 36 DUE TO THE ENTRAINMENT OF SIGNIFICANT DRY AIR THROUGH
ALL LEVELS. AFTER TAU 48, THE SYSTEM WILL BE EMBEDDED WITHIN A VERY
DRY ENVIRONMENT, WHICH WILL LEAD TO DISSIPATION NO LATER THAN TAU
96. AS THE SYSTEM WEAKENS, IT WILL TRACK EASTWARD TO EAST-
NORTHEASTWARD ALONG THE NORTHERN PERIPHERY OF THE LOW-LEVEL
RIDGE TO THE SOUTH.  

MODEL DISCUSSION: DETERMINISTIC GUIDANCE IS IN GOOD AGREEMENT THROUGH 
TAU 24. AFTER TAU 24, GUIDANCE DIVERGES QUICKLY WITH INCREASING 
UNCERTAINTY IN THE JTWC TRACK FORECAST AND MAJOR DIFFERENCES IN THE 
TIMING OF THE SHARP EASTWARD RECURVE. DESPITE THE RAPIDLY EVOLVING 
STEERING PATTERN, PROBABILISTIC GUIDANCE IS IN FAIR AGREEMENT 
SUPPORTING THE JTWC TRACK FORECAST. OVERALL, THERE IS LOW CONFIDENCE 
IN THE JTWC INTENSITY FORECAST DUE TO THE PRESENCE OF DRY AIR THROUGH 
THE FORECAST PERIOD, WHICH IS HAMPERING CONVECTIVE DEVELOPMENT.  

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