WDXS31 PGTW 080300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 11S (FREDDY)     
WARNING NR 052//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.3S 41.0E
   INITIAL INTENSITY: 100 KTS
   GEOGRAPHIC REFERENCE: 45 NM EAST OF EUROPA ISLAND
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
OVER THE PAST 12 HOURS, THE CORE CONVECTIVE STRUCTURE OF TROPICAL
CYCLONE (TC) 11S HAS FLUCTUATED RAPIDLY WITH A WELL-FORMED,
SYMMETRIC EYE FORMING NEAR 071800Z BUT BECOMING MORE OBLONG AFTER
072100Z. SINCE 072350Z, THE EYE HAS FILLED AND THE CENTRAL DENSE
OVERCAST FEATURE HAS BECOME MORE ASYMMETRIC AS INDICATED IN
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY. A 080047Z SSMIS
91GHZ MICROWAVE IMAGE ALSO REVEALS ERODING CORE CONVECTION OVER THE
WESTERN SEMICIRCLE WITH A PARTIALLY EXPOSED LOW-LEVEL CIRCULATION
AND A RAGGED MICROWAVE EYE FEATURE. SURFACE OBSERVATIONS FROM
EUROPA ISLAND, APPROXIMATELY 35NM WEST OF THE CURRENT POSITION,
INDICATE SOUTHERLY WINDS AT 39 KNOTS WITH SLP NEAR 991.4MB. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON EIR AND
THE SSMIS IMAGE. THE INITIAL INTENSITY OF 100 KTS IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON THE PGTW, KNES AND DEMS DVORAK
ESTIMATES. INITIAL WIND RADII WERE ADJUSTED BASED ON A DETAILED
ANALYSIS OF A 071543Z RCM SAR IMAGE, WHICH SHOWED MAXIMUM WINDS OF
95 KNOTS WITH RELATIVELY LOW INCIDENCE ANGLES NEAR 20 DEGREES.

INITIAL WIND RADII BASIS: SAR DATA 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
POSITIONED TO THE WEST AND SOUTHWEST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   KNES: T5.5 - 102 KTS
   DEMS: T5.5 - 102 KTS
   FMEE: T5.0 - 90 KTS
   CIMSS SATCON: 89 KTS AT 072241Z
   CIMSS ADT: 97 KTS AT 080000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 11S IS EXPECTED TO TRACK NORTHWESTWARD
ALONG THE NORTHEASTERN PERIPHERY OF THE STR THROUGH TAU 72. THE
SYSTEM WILL MAKE LANDFALL OVER MOZAMBIQUE NEAR TAU 72 AND IS THEN
FORECAST TO SLOW AND TURN WEST-NORTHWESTWARD WITH POSSIBLE
QUASI-STATIONARY MOTION DUE TO COMPETING STEERING INFLUENCES. TC
11S IS FORECAST TO GRADUALLY WEAKEN THROUGH THE FORECAST PERIOD AS
SST VALUES COOL SLIGHTLY. ADDITIONALLY, POLEWARD OUTFLOW SHOULD
WEAKEN GRADUALLY AS THE SYSTEM TRACKS EQUATORWARD AWAY FROM THE
SUBTROPICAL WESTERLIES WITH WEAK DIVERGENCE ALOFT ANTICIPATED AS
THE SYSTEM APPROACHES THE COAST OF MOZAMBIQUE.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN GOOD AGREEMENT
WITH A 75NM SPREAD IN SOLUTIONS AT TAU 72 THUS HIGH CONFIDENCE IN
THE JTWC FORECAST TRACK THROUGH TAU 72. ALTHOUGH THE ECMWF ENSEMBLE
(EPS) INDICATES A WIDER SPREAD OF SOLUTIONS, IT GENERALLY SUPPORTS
THE JTWC FORECAST TRACK SCENARIO. RELIABLE INTENSITY GUIDANCE
INDICATES A STEADY WEAKENING TREND THROUGH THE FORECAST PERIOD WITH
RAPID WEAKENING AFTER TAU 72 AS TC 11S TRACKS INLAND. THE UNCOUPLED
HWRF IS THE SOLE OUTLIER SHOWING A SHARP INTENSIFICATION TREND
AFTER TAU 36 TO A PEAK OF 105 KNOTS BY TAU 60, HOWEVER, THIS IS
ASSESSED AS UNLIKELY DUE TO THE DEGRADING ENVIRONMENTAL CONDITIONS.

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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