WDXS31 PGTW 212100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05S (DARIAN) WARNING 
NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.2S 89.0E
   INITIAL INTENSITY: 130 KTS
   GEOGRAPHIC REFERENCE: 1040 NM EAST-SOUTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 50 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THE SYSTEM
HAS MAINTAINED A MEDIUM-SIZED, HIGHLY-SYMMETRICAL STRUCTURE WITH A
DEFINED PINHOLE EYE. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON A MICROWAVE EYE FEATURE IN THE 211822Z GPM
IMAGE AND LINED UP WITH A DEFINED LOW LEVEL CIRCULATION CENTER IN
THE 211603Z ASCAT BULLSEYE PASS. THE INITIAL INTENSITY IS BASED ON
OVERALL ASSESSMENT OF AGENCY AND AUTOMATED DVORAK ESTIMATES AND
REFLECTS THE SUSTAINED CONVECTIVE SIGNATURE. TC DARIAN HAS TRACKED
MORE POLEWARD OVER THE LAST SIX HOURS. LIKELY DUE TO STRONGER
STEERING STR THAN ANTICIPATED. ALSO, ANALYSIS OF RECENT MICROWAVE
SATELLITE IMAGES, INCLUDING THE 211822Z GPM PASS, SHOWS THE SYSTEM
MAY BE UNDERGOING A SLOW EYEWALL REPLACEMENT CYCLE.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA.

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO
THE SOUTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T7.0 - 140 KTS 
   KNES: T7.0 - 140 KTS 
   CIMSS ADT: 137 KTS AT 211515Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG RADIAL

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: TC DARIAN WILL TRACK MORE WESTWARD UNDER THE
STEERING INFLUENCE OF THE STR TO THE SOUTH THAT IS RECEDING
EASTWARD. BY TAU 72, THE CYCLONE WILL BEGIN TO ROUND THE STR AXIS
AND TRACK MORE SOUTHWARD. THE UPPER LEVEL ENVIRONMENT WILL REMAIN
FAVORABLE WITH LOW VWS AND STRONG RADIAL OUTFLOW; HOWEVER, THE
ALONG-TRACK SST IS PROJECTED TO SLOWLY COOL LEADING TO A GRADUAL
WEAKENING UP TO TAU 72. AFTERWARD, AS THE SYSTEM TRACKS MORE
POLEWARD, SST IS EXPECTED TO COOL MORE RAPIDLY, RESULTING IN A MORE
ACCELERATED WEAKENING. BY TAU 120, TC 05S WILL BE REDUCED TO 60
KTS. 

MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT WITH A
GRADUAL AND EVEN SPREADING TO 84NM AT TAU 72. AFTERWARD, THE
MEMBERS SPREAD OUT SIGNIFICANTLY ALONG-TRACK AND UP TO 286NM
ACROSS-TRACK BY TAU 120 WITH NVGM ON THE RIGHT AND EEMN ON THE LEFT
MARGIN OF THE MODEL ENVELOPE. IN VIEW OF THIS, THERE IS HIGH
CONFIDENCE IN THE JTWC TRACK FORECAST UP TO TAU 72, THEN LOW
CONFIDENCE AFTERWARD. 

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