WDIO31 PGTW 042100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 02A (SHAKHTI) WARNING 
NR 008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.1N 62.5E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 212 NM EAST-NORTHEAST OF MASIRAH ISLAND
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DRY AIR
BOUNDING THE NORTHWESTERN QUADRANT OF THE CONVECTIVE ENVELOPE OF
TROPICAL CYCLONE (TC) 02A. ENHANCED VERTICAL WIND SHEAR FROM THE
NORTHWEST APPLIES AN APPARENT TILT TO THE VERTICAL STRUCTURE. WATER
VAPOR IMAGERY REVEALS STRONG POLEWARD OUTFLOW ENHANCED BY AN
UPPER-LEVEL TROUGH TO THE NORTH AND STRONG EQUATORWARD OUTFLOW. THE
INITIAL POSITION IS PLACED WITH LOW CONFIDENCE BASED ON THE
AFOREMENTIONED ANIMATED EIR, WHICH DEPICTED CENTRAL DENSE OVERCAST
CONVECTION OBSCURING THE LOW-LEVEL CIRCULATION CENTER. THE INITIAL
INTENSITY OF 75 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE
AGENCY AND OBJECTIVE FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: 041607Z METOP-B SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: A COMPETING STEERING ENVIRONMENT
BETWEEN A DEEP-LAYER RIDGE OVER THE ARABIAN PENINSULA AND A
NEAR-EQUATORIAL RIDGE OVER SOUTHERN INDIA.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   KNES: T3.5 - 55 KTS
   DEMS: T3.5 - 55 KTS
   CIMSS SATCON: 62 KTS AT 041653Z
   CIMSS ADT: 79 KTS AT 041800Z
   CIMSS AIDT: 75 KTS AT 041700Z
   CIMSS D-PRINT: 72 KTS AT 041800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 02A WILL TRACK SOUTHWESTWARD FOR THE NEXT
24 HOURS WHILE REMAINING IN A COMPLEX STEERING ENVIRONMENT BETWEEN
A DEEP-LAYER RIDGE OVER THE ARABIAN PENINSULA AND A NEAR-EQUATORIAL
RIDGE TO THE SOUTHEAST. THE NEAR-EQUATORIAL RIDGE WILL WEAKEN AFTER
TAU 36 AS A DEEP-LAYER TROUGH DEEPENS OVER INDIA, RESULTING IN A
GRADUAL TRACK RECURVE EASTWARD FROM TAU 36-72. HIGH VERTICAL WIND
SHEAR AND DRY AIR WILL ERODE THE VERTICAL STRUCTURE OF TC 02A.
AFTER TAU 24, THERE WILL BE MINIMAL AVAILABLE WARM SEA SURFACE
TEMPERATURES DUE TO SLOWING TRACK MOTION AND ENHANCED UPWELLING IN
THE SOMALI JET REGION. THE WEAKENING RATE WILL SIGNIFICANTLY
INCREASE, LEADING TO COMPLETE DISSIPATION BY THE END OF THE
FORECAST PERIOD. 

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN MODERATELY
GOOD AGREEMENT THAT TC 02A WILL TRACK SOUTHWESTWARD AND RECURVE
EASTWARD BETWEEN 36-60 HOURS. HOWEVER, THE DIFFERENCES BETWEEN
MODEL SOLUTIONS VARY BASED ON HOW STRONGLY THE NEAR EQUATORIAL
RIDGE WEAKENS. THERE IS MINIMAL SPREAD IN THE INTENSITY GUIDANCE,
WHICH INDICATES CONTINUED WEAKENING TROUGH THE FORECAST PERIOD.

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