Tropical Cyclone DARIAN (05S)

WTXS32 PGTW 200900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 25S (TWENTYFIVE) WARNING NR 002//
RMKS/
1. TROPICAL CYCLONE 25S (TWENTYFIVE) WARNING NR 002    
   02 ACTIVE TROPICAL CYCLONES IN SOUTHIO
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
   WIND RADII VALID OVER OPEN WATER ONLY
    ---
   WARNING POSITION:
   200600Z --- NEAR 2.6S 76.6E
     MOVEMENT PAST SIX HOURS - 115 DEGREES AT 08 KTS
     POSITION ACCURATE TO WITHIN 040 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
   REPEAT POSIT: 2.6S 76.6E
    ---
   FORECASTS:
   12 HRS, VALID AT:
   201800Z --- 2.9S 78.1E
   MAX SUSTAINED WINDS - 025 KT, GUSTS 035 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
    ---
REMARKS:
200900Z POSITION NEAR 2.7S 77.0E.
20MAY24. TROPICAL CYCLONE 25S (TWENTYFIVE), LOCATED APPROXIMATELY
365 NM NORTHEAST OF DIEGO GARCIA, HAS TRACKED EAST-SOUTHEASTWARD
AT 08 KNOTS OVER THE PAST SIX HOURS. THE CURRENT POSITION AND 
INTENSITY ARE SUPPORTED BY RECENT METOP-B AND METOP-C ASCAT PASSES, 
WHICH SHOW A RAPIDLY WEAKENING LOW-LEVEL CIRCULATION WITH LIMITED 25-
30 KT WINDS DISPLACED WELL TO THE SOUTHWEST OF THE CENTER. THE 
CIRCULATION WILL CONTINUE TO WEAKEN UNDER THE INFLUENCE OF 30 KTS AND 
GREATER NORTHEASTERLY VERTICAL WIND SHEAR IN THE NEAR-TERM. 
THEREFORE, THIS IS THE FINAL WARNING ON THIS SYSTEM BY THE JOINT 
TYPHOON WRNCEN PEARL HARBOR HI. THE SYSTEM WILL BE CLOSELY MONITORED 
FOR SIGNS OF REGENERATION. MINIMUM CENTRAL PRESSURE AT 200600Z IS 
1005 MB. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 200600Z IS 11 FEET. REFER 
TO TROPICAL CYCLONE 24S (IALY) WARNINGS (WTXS31 PGTW) FOR TWELVE-
HOURLY UPDATES.//
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WDXS32 PGTW 192100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 25S (TWENTY-FIVE) 
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 2.3S 75.2E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 330 NM NORTH-NORTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
DESPITE VERY STRONG (40-50 KNOTS), PERSISTENT NORTHEASTERLY VERTICAL 
WIND SHEAR (VWS) AND A LOW-LATITUDE POSITION, TROPICAL CYCLONE (TC) 
25S HAS BEEN ABLE TO MAINTAIN A LIMITED AND UNIFORM AREA OF INTENSE 
DEEP CONVECTION WITH CLOUD TOP TEMPERATURES COLDER THAN -88 C. 
ANIMATED SHORTWAVE INFRARED (SWIR) SATELLITE IMAGERY DEPICTS A 
PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION (LLC) POSITIONED ALONG THE 
EASTERN EDGE OF THE DEEP CONVECTION. RECENT MICROWAVE IMAGERY 
INDICATES FAIRLY WEAK LOW-LEVEL BANDING STRUCTURE. HOWEVER,
A 191653Z ASCAT-C BULLSEYE IMAGE REVEALS A DEFINED CIRCULATION WITH
A SWATH OF 30-35 KNOT WINDS OVER THE WESTERN SEMICIRCLE (VERY
ISOLATED 40 KNOT WINDS) WRAPPING INTO THE NORTHERN QUADRANT, WITH
SIGNIFICANTLY WEAKER 15-25 KNOT WINDS OVER THE EASTERN SEMICIRCLE.
BASED ON THE OVERALL LOW-LEVEL WIND FIELD, THERE IS SUFFICIENT
JUSTIFICATION FOR ASSESSING THE SYSTEM AT 35 KNOTS AND ISSUING THE
FIRST TC WARNING. SUBJECTIVE DVORAK CURRENT INTENSITY ESTIMATES OF
35 KNOTS ALSO SUPPORT THE INITIAL INTENSITY.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: LOW-LEVEL NEAR-EQUATORIAL RIDGE (NER),
WITH ENHANCED WESTERLY FLOW.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 30+ KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG WESTWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TC 25S FORMED PRIMARILY DUE TO THE ENHANCED
WESTERLIES ALONG THE EQUATOR AND WILL TRACK EASTWARD THROUGH THE
FORECAST PERIOD UNDER THE ENHANCED LOW-LEVEL WESTERLY FLOW. VWS
WILL REMAIN STRONG (30-40 KNOTS) THROUGH THE FORECAST PERIOD,
LEADING TO DISSIPATION BY TAU 36 OR PERHAPS EARLIER.   

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN FAIR AGREEMENT
SHOWING AN EASTWARD TO SOUTHEASTWARD TRACK TRAJECTORY THROUGH TAU
36. RELIABLE INTENSITY GUIDANCE IS SPARSE LENDING MEDIUM OVERALL
CONFIDENCE TO THE JTWC INTENSITY FORECAST.  

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