WDXS31 PGTW 142100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 07S (DIKELEDI) WARNING 
NR 011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.9S 39.8E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 199 NM NORTH OF EUROPA ISLAND
   MOVEMENT PAST 6 HOURS: SOUTHWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 26 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE 07S (DIKELEDI) WITH RESTORED CENTRAL CONVECTION AS IT
TRACKS FURTHER POLEWARD WITHIN THE MOZAMBIQUE CHANNEL.
ENVIRONMENTAL ANALYSIS INDICATES THAT 07S IS IN A FAVORABLE
ENVIRONMENT CHARACTERIZED BY STRONG EQUATORWARD OUTFLOW ALOFT, LOW
TO MODERATE (15-20 KTS) VERTICAL WIND SHEAR, AND WARM (29-30 C) SEA
SURFACE TEMPERATURES. THE INITIAL POSITION IS PLACED WITH MEDIUM
CONFIDENCE BASED ON THE OBSCURED LOW-LEVEL CIRCULATION CENTER
(LLCC) IN ANIMATED EIR IMAGERY. ADDITIONALLY, EXTRAPOLATION FROM A
141600Z SSMIS 91 GHZ MICROWAVE IMAGE AIDED IN PLACING THE INITIAL
POSITION. THE INITIAL INTENSITY OF 60 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE AGENCY DVORAK AND OBJECTIVE INTENSITY
ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) POSITIONED TO THE SOUTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   KNES: T3.5 - 55 KTS
   DEMS: T3.5 - 55 KTS
   FMEE: T4.0 - 65 KTS
   CIMSS ADT: 47 KTS AT 141800Z
   CIMSS AIDT: 62 KTS AT 141800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: 07S IS FORECAST TO TRACK SOUTH-SOUTHEASTWARD
ALONG THE WESTERN PERIPHERY OF THE STR TO THE SOUTHEAST THROUGH TAU
36. AFTER TAU 36, 07S IS EXPECTED TO BEGIN TRACKING WITH A MORE
EASTWARD TRAJECTORY AS IT PASSES SOUTH OF MADAGASCAR AND ROUNDS THE
RIDGE AXIS. 07S IS THEN FORECAST TO BEGIN EXTRATROPICAL TRANSITION
AROUND TAU 72 WITH COMPLETION AROUND TAU 96 AS THE SYSTEM
TRANSITIONS INTO A GALE-FORCE COLD-CORE LOW. REGARDING INTENSITY,
07S IS FORECAST TO STEADILY INTENSIFY TO A PEAK OF 80 KTS NEAR TAU
36. THE MAIN FACTORS WILL BE THE COMBINATION OF AN IMPROVING
POLEWARD OUTFLOW CHANNEL INTO THE JET AND WARM SEA SURFACE
TEMPERATURES WITHIN THE MOZAMBIQUE CHANNEL. SHEAR IS EXPECTED TO
REMAIN AROUND 15 KTS THROUGH TAU 18, BUT THEN BRIEFLY LOWER DURING
THE TAU 24 TO 36 TIMEFRAME. AT TAU 48, SHEAR INCREASES TO 20 KTS
AND SEA SURFACE TEMPERATURES DROP TO BELOW 25 C, WHICH WILL
INITIATE THE WEAKENING TREND THAT WILL PERSIST THROUGHOUT THE
REMAINDER OF THE FORECAST PERIOD. SHEAR GREATLY INCREASES TO
UPWARDS OF 40 KTS AT TAU 72 AND SEA SURFACE TEMPERATURES DROP TO 23
C, CREATING A VERY HOSTILE ENVIRONMENT FOR 07S. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN VERY GOOD
AGREEMENT REGARDING THE TRACK OF 07S THROUGH TAU 48 WITH A 50 NM
CROSS-TRACK SPREAD AT THAT TIME. AFTER TAU 48, ALONG-TRACK SPREAD
INCREASES DUE TO DIFFERENCES IN HOW THE VORTEX INTERACTS WITH THE
JET. THE JTWC TRACK FORECAST IS PLACED CLOSE CONSENSUS WITH HIGH
CONFIDENCE THROUGH TAU 72 AND THEN MEDIUM CONFIDENCE THEREAFTER.
INTENSITY GUIDANCE IS IN SLIGHTLY WORSE AGREEMENT THIS CYCLE. THE
COAMPS-TC AND GFS BOTH SUGGEST WEAKENING AFTER TAU 12 WITH
INTENSITIES BELOW 55 KTS AT TAU 36. HAFS-A AND HWRF DIFFER IN THAT
THEY BOTH SUGGEST INTENSIFICATION THROUGH TAU 36 WITH PEAK
INTENSITIES RANGING FROM 75-80 KTS. THE JTWC INTENSITY FORECAST IS
PLACED IN LINE WITH THE HAFS-A AND HWRF MODELS DUE TO THE OVERALL
FAVORABLE ENVIRONMENT EXPECTED THROUGH TAU 36. 

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