WDXS31 PGTW 170900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 07S (DIKELEDI) WARNING 
NR 016//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 33.7S 54.8E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 792 NM SOUTH OF ST DENIS
   MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 28 KTS
   SIGNIFICANT WAVE HEIGHT: 24 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE (TC) 07S (DIKELEDI) AS A WEAKENING CYCLONE THROUGH
EXTRATROPICAL TRANSITION WHILE CONVECTION HAS BECOME INCREASINGLY
SHEARED EASTWARD AND POLEWARD OF THE LOW-LEVEL CIRCULATION CENTER
(LLCC). THE LLCC HAS BECOME FULLY-EXPOSED OVER THE LAST FEW HOURS
AS CONVECTION REMAINS RESTRICTED TO THE EASTERN PERIPHERY OF THE
SYSTEMS CIRCULATION, INDICATING AN INCREASING EASTWARD VERTICAL
TILT. ALOFT, MODERATE UPPER-LEVEL FLOW HAS CONTINUED WITH SUPPORT
FROM THE MID-LATITUDE WESTERLIES DIRECTLY TO THE SOUTH OF TC 07S.
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON
EXTRAPOLATION FROM A 170443Z ASCAT-B PASS AND THE AFOREMENTIONED
FULLY-EXPOSED LLCC. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE RAPIDLY DEGRADING NATURE OF TC 07S THROUGH
EXTRATROPICAL TRANSITION AND THE PGTW DVORAK ESTIMATE OF 45 KTS.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE
EAST-NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   CIMSS ADT: 72 KTS AT 170430Z
   CIMSS AIDT: 63 KTS AT 170430Z
   CIMSS D-PRINT: 41 KTS AT 0430Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 20-30 KTS
   SST: 21-22 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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 07S IS FORECASTED TO CONTINUE
EAST-SOUTHEASTWARD ALONG THE SOUTHERN PERIPHERY OF THE STR LOCATED
DIRECTLY TO THE EAST-NORTHEAST THROUGH DISSIPATION BY TAU 24 AS THE
SYSTEM BECOMES COMPLETELY EMBEDDED WITHIN HE MIDLATITUDE
BAROCLINIC ZONE. THROUGHOUT THE NEXT 24 HOURS, THE CYCLONE IS
EXPECTED TO CONTINUE EXTRATROPICAL TRANSITION, REACHING COMPLETION
BETWEEN TAU 18 AND TAU 24 BECAUSE OF THE HIGHLY UNFAVORABLE
ENVIRONMENT, WITH SEA SURFACE TEMPERATURES BELOW 24 C AND VERTICAL
WIND SHEAR (VWS) INCREASING ABOVE 30 KTS. WITH REGARD TO INTENSITY,
THE SYSTEM IS EXPECTED TO CONTINUE WEAKENING TO 35 KTS UNTIL
EXTRATROPICAL TRANSITION IS COMPLETE WHILE TC 07S BECOMES HIGHLY
ASYMMETRIC, TILTED, AND VOID OF SUPPORTIVE CONVECTION. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN VERY STRONG
AGREEMENT THAT TC 07S WILL CONTINUE GENERALLY EASTWARD THROUGH THE
FORECAST PERIOD ALONG THE SOUTHERN PERIPHERY OF THE STR TO THE
NORTH, WITH A CROSS-TRACK SPREAD OF JUST 96 NM BY TAU 24, LENDING
HIGH CONFIDENCE TO THE JTWC TRACK FORECAST. THE JTWC INTENSITY
FORECAST REMAINS CLOSE TO THE MULTI-MODEL INTENSITY CONSENSUS
THROUGHOUT EXTRATROPICAL TRANSITION INTO TAU 24, WITH EXPECTED
DECAY UNTIL THE COMPLETION OF EXTRATROPICAL TRANSITION. THE ONLY
OUTLIER IS THE DETERMINISTIC GFS SOLUTION, INDICATING A POTENTIAL
INCREASE IN INTENSITY OVER THE NEXT 12 HOURS WITH BAROCLINIC
SUPPORT DUE TO UPPER-LEVEL OUTFLOW INTO THE MIDLATITUDE WESTERLY
JET. THE INTENSITY FORECAST IS ASSESSED WITH MEDIUM CONFIDENCE DUE
THE ONGOING EXTRATROPICAL PHASE INTO COMPLETION BY TAU 24.

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