WDXS31 PGTW 251500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05S (DARIAN) WARNING 
NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.9S 85.0E
   INITIAL INTENSITY: 90 KTS
   GEOGRAPHIC REFERENCE: 904 NM SOUTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 34 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE 05S (DARIAN) FLARED UP AGAIN DURING THE PAST 8
HOURS. 12 HOURS AGO THE EYE HAD COLLAPSED AND THE EYEWALL OVER THE
NORTHEAST QUADRANT WAS ALL BUT GONE DUE TO MID-LEVEL DRY AIR
ENTRAINMENT AND 15KTS OF NORTHWESTERLY VERTICAL WIND SHEAR. NOW THE
EYE HAS RE-DEVELOPED AND IS SURROUNDED BY A RING OF DEEP AND
VIGOROUS CONVECTION. THREE SSMIS MICROWAVE SERIES--251038Z 251103Z
AND 251248Z--VERIFY IMPROVED ORGANIZATION AND THE MOST RECENT JTWC
DVORAK ASSESSMENT HAS RISEN TO T5.0 USING THE EYE TECHNIQUE ON A
RAGGED 15NM EYE. KNES AND FMEE ARE ALSO WEIGHING IN AT T5.0. SEA
SURFACE TEMPERATURES INCREASED A DEGREE TO 27C AND STORM MOTION HAS
ACCELERATED ENOUGH TO REDUCE THE EFFECTS OF UPWELLING ON THE STORM.
DARIAN IS MOVING THROUGH A PATCH OF 26-27 DEGREE WATERS. VERTICAL
WIND SHEAR REMAINS STEADY NEAR 15KTS BUT DEEP MOISTURE SURROUNDING
THE CORE IS EXPANDING. ANIMATED WATER VAPOR IMAGERY ALSO INDICATES
THE MID AND HIGH LEVEL MOISTURE FIELDS ARE EXPANDING AND THAT THE
SYSTEM HAS EXCELLENT AND IMPROVING RADIAL OUTFLOW.

INITIAL WIND RADII BASIS: PERSISTENCE.

CURRENT STEERING MECHANISM: AN EXTENSION OF THE NEAR EQUATORIAL
RIDGE IS NUDGING THE SYSTEM TOWARDS THE SOUTH-SOUTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   KNES: T5.0 - 90 KTS
   FMEE: T5.0 - 90 KTS
   CIMSS SATCON: 91 KTS AT 250809Z
   CIMSS ADT: 67 KTS AT 250915Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG RADIAL
   OTHER FACTORS: HWRF 700-300 HPA RH SERIES INDICATES THAT A
TONGUE OF DRY AIR IS BEGINNING TO WRAP AROUND THE NORTHERN
PERIMETER OF THE SYSTEM. 

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: TROPICAL CYCLONE 05S WILL LEAVE THE STEERING
INFLUENCE OF THE NEAR EQUATORIAL RIDGE DURING THE NEXT 12 HOURS AND
BEGIN A LAZY ROLL OVER TO THE SOUTHWEST LEG OF ITS JOURNEY. 26-27
DEGREE CELSIUS SEA WATERS ALONG TRACK COUPLED WITH VERTICAL WIND SHEAR 
THAT
ONLY INCREASES BY A KNOT OR TWO OVER THE NEXT 24 HOURS WILL MAKE
FOR A SLOW DECLINE IN INTENSITY. DRY AIR ENTRAINMENT WILL ALSO
STEADILY WRAP AROUND THE SYSTEM AND EVENTUALLY STRANGLE THE CORE,
BUT THIS TOO WILL BE A SLOW PROCESS. THE SUBTROPICAL TRANSITION
PROCESS WILL ALSO BE A SLOW ONE, WITH THE SYSTEM NOT EXPECTED TO
COMPLETE SUBTROPICAL TRANSITION UNTIL IT IS SOUTH OF THE 25TH
LATITUDE. NO PRONOUNCED CHANGES IN THE ENVIRONMENT ARE EXPECTED,
JUST A GRADUAL INCREASE IN UNFAVORABLE FACTORS. SEA SURFACE
TEMPERATURES WILL FALL TO 25C DURING THE NEXT 24 HOURS BUT AFTER
THAT THEY WILL REMAIN IN THE 24-25 DEGREE RANGE THROUGH THE
DURATION OF THE FORECAST. VERTICAL WIND SHEAR WILL INCREASE BUT
REMAIN BELOW 20 KNOTS THROUGH TAU 36. HENCE, THE BASIS FOR A
SLOW AND STEADY DECLINE ALONG A SOUTHWESTWARD TRACK SCENARIO. 

MODEL DISCUSSION: TRACK GUIDANCE HAS BEEN RELIABLE AND REMAINS
TIGHT THROUGH THE DURATION OF THE FORECAST. THE JTWC TRACK FORECAST
STAYS VERY CLOSE TO THE MULTI-MODEL CONSENSUS. INADEQUACIES IN THE
INTENSITY GUIDANCE ARE NOW IN THE REARVIEW MIRROR AND THE STABLE
ENVIRONMENT IS GIVING MUCH HIGHER CONFIDENCE TO THE SCENARIO OF A
GRADUAL DECLINE THROUGH SUBTROPICAL TRANSITION. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: HIGH
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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