WDIO31 PGTW 051500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 02A (SHAKHTI) WARNING 
NR 011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.0N 60.6E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 104 NM EAST-SOUTHEAST OF MASIRAH ISLAND
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A COMPACT
AND FULLY OBSCURED LOW LEVEL CIRCULATION CENTER (LLCC) WITH
LOW-LEVEL CLOUD BANDS WRAPPING TIGHTLY INTO THE CENTER.
ANIMATED MSI ALSO REVEALS THAT TROPICAL CYCLONE (TC) 02A HAS
MAINTAINED ITS VISUAL APPEARANCE OVER THE PAST 6 HOURS. HOWEVER, A
051327Z WSFM MICROWAVE IMAGE REVEALS THAT THE INTERNAL STRUCTURE
HAS DEGRADED SHOWING A BREAK IN THE MICROWAVE EYE IN THE NORTHERN 
SEMICIRCLE. 02A REMAINS IN AN UNFAVORABLE ENVIRONMENT CHARACTERIZED 
BY HIGH (25-30 KTS) VERTICAL WIND SHEAR AND SIGNIFICANT DRY AIR 
ENTRAINMENT. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE 
BASED ON EXTRAPOLATION TO THE PREVIOUSLY MENTIONED 051327Z WSFM 
MICROWAVE IMAGE. THE INITIAL INTENSITY OF 60 KTS IS ASSESSED WITH 
MEDIUM CONFIDENCE BASED ON OBJECTIVE INTENSITY ESTIMATES AND AGENCY 
DVORAK FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: COMPETING STEERING ENVIRONMENT BETWEEN
A SUBTROPICAL RIDGE (STR) POSITIONED OVER SAUDI ARABIA AND AN STR
POSITIONED OVER THE EASTERN ARABIAN SEA

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   KNES: T4.5 - 77 KTS
   DEMS: T3.5 - 55 KTS
   CIMSS SATCON: 59 KTS AT 051200Z
   CIMSS ADT: 51 KTS AT 051200Z
   CIMSS AIDT: 61 KTS AT 051200Z
   CIMSS D-MINT: 43 KTS AT 051130Z
   CIMSS D-PRINT: 57 KTS AT 051200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 25-30 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   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 WILL CONTINUE ITS SLOW SOUTHWESTWARD
TRACK FOR THE NEXT 12 HOURS AS IT REMAINS UNDER THE INFLUENCE OF
THE SOUTHEASTERN PERIPHERY OF THE PRIMARY STEERING RIDGE OVER SAUDI
ARABIA. BETWEEN TAUS 12-24, 02A WILL BECOME QUASI-STATIONARY AS THE
UPPER-LEVEL TROUGH WEAKENS THE STR POSITIONED OVER THE EASTERN
ARABIAN SEA, CREATING A MORE CONFUSING STEERING ENVIRONMENT. AFTER
TAU 24, 02A WILL TRACK SOUTHEAST ALONG THE NORTHWESTERN PERIPHERY
OF THE STR. 02A IS FORECAST TO RAPIDLY WEAKEN THROUGH THE END OF THE
FORECAST PERIOD DUE TO THE SIGNIFICANT DRY AIR ENTRAINMENT AND HIGH
VERTICAL WIND SHEAR. UPWELLING DUE TO THE STORM'S QUASI-STATIONARY
MOVEMENT IS ALSO EXPECTED TO EXPEDITE DISSIPATION. DISSIPATION IS
FORECAST TO OCCUR NO LATER THAN TAU 36.

MODEL DISCUSSION: DETERMINISTIC TRACK MODELS ARE IN DECENT
AGREEMENT ON A SOUTHWESTWARD TRACK THROUGH TAU 12 WITH THE
SOUTHEASTWARD TURN COMMENCING AT AROUND TAU 24. THE VARYING MODEL
TRACK SPEEDS IMPACT THE LOCATION AT WHICH 02A WILL TURN SOUTHEAST,
INTRODUCING UNCERTAINTY TO THE JTWC TRACK FORECAST. MAJOR OUTLIERS
ARE NAVGEM -- WHICH TRACKS 02A SOUTH-SOUTHWEST UNTIL TAU 24, AND
GFS -- THE ONLY MODEL FAILING TO PREDICT A RECURVE PRIOR TO
DISSIPATION. THE JTWC TRACK FORECAST IS PLACED IN AGREEMENT WITH
THE MULTI-MODEL CONSENSUS WITH MEDIUM CONFIDENCE. INTENSITY
GUIDANCE IS IN STRONG AGREEMENT THROUGH TAU 36, WITH ALL MODELS
PREDICTING A CONSISTENT WEAKENING TREND WITH DISSIPATION IN 36 HOURS. 
AS A RESULT, THE JTWC INTENSITY FORECAST IS PLACED WITH HIGH 
CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   INTENSITY 00-72 HR: HIGH//
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