WDXS31 PGTW 191500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 11S (FREDDY) WARNING 
NR 034//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.4S 64.1E
   INITIAL INTENSITY: 130 KTS
   GEOGRAPHIC REFERENCE: 419 NM EAST-NORTHEAST OF PORT LOUIS,
MAURITIU
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 46 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FAIRLY
SYMMETRICAL SYSTEM WITH RELATIVELY RAGGED BANDING IN THE NORTHERN
AND SOUTHERN PERIPHERIES. TC FREDDY IS SHOWING SIGNS OF A SLOWLY
EXPANDING EYE WHICH INDICATES A WEAKENING TREND. A 190523Z ASCAT-B 
IMAGE SHOWS THE 34, 50, AND 64 KNOT WIND RADII TO BE IN A SOMEWHAT 
BALANCED DISTRIBUTION AROUND THE LOW LEVEL CIRCULATION CENTER (LLCC). 
ENVIRONMENTAL ANALYSIS INDICATES TC 11S TO BE IN FAVORABLE CONDITIONS 
FOR CONTINUAL TROPICAL DEVELOPMENT. THESE CONDITIONS ARE 
CHARACTERIZED BY CONSISTENT WESTERLY OUTFLOW ALOFT, LOW (5-10 KTS) 
VERTICAL WIND SHEAR (VWS), A VERY STRONG 850 MB VORTICITY SIGNATURE, 
AND WARM (27-28 C) SEA SURFACE TEMPERATURES (SST). THE INITIAL 
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE ABOVE MENTIONED 
MSI AND SCATTEROMETRY IMAGES. THE INITIAL INTENSITY OF 130 KTS IS 
ASSESSED WITH MEDIUM CONFIDENCE SET SLIGHTLY HIGHER THAN MULTI-AGENCY 
AND AUTOMATED DVORAK ESTIMATES.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE
SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   KNES: T6.5 - 127 KTS
   DEMS: T6.5 - 127 KTS
   FMEE: T6.5 - 127 KTS
   CIMSS SATCON: 122 KTS AT 190859Z
   CIMSS ADT: 125 KTS AT 191230Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE WESTWARD

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 FREDDY CONTINUES ITS WEST-SOUTHWESTWARD
TRACK AS IT TRANSITS THE NORTHEASTERN PERIPHERY OF THE STR TO THE
SOUTHEAST. COPIOUS AMOUNTS OF DRY AIR WILL CONTINUE TO SURROUND THE
SYSTEM, HOWEVER, TC FREDDY WILL STAY COCOONED IN ITS OWN MOISTURE
POCKET THROUGHOUT ITS FORECAST TRACK. THE SYSTEM WILL CONTINUE ITS
WEST-SOUTHWESTWARD TRAJECTORY AND GRADUALLY DECREASE IN INTENSITY
TO 105 KNOTS AS IT MAKES ITS APPROACH TO THE EAST COAST OF
MADAGASCAR SHORTLY AFTER TAU 48. TC 11S IS FORECAST TO FURTHER
DECREASE IN INTENSITY TO 45 KNOTS BY TAU 72 AS IT TRANSITS ACROSS
THE MOUNTAINOUS TERRAIN OF SOUTHERN MADAGASCAR. BY TAU 96, THE SYSTEM 
WILL BE IN ANOTHER FAVORABLE ENVIRONMENT OVER THE MOZAMBIQUE CHANNEL 
AND RE-INTENSIFY TO 55 KNOTS AS A RESULT. BY TAU 120, TC FREDDY WILL 
APPROACH THE MOZAMBIQUE COAST SOUTH OF BEIRA AND DECREASE TO 45 KNOTS 
DUE TO LAND INTERACTION.

MODEL DISCUSSION: THE JTWC MODEL TRACK CONSENSUS REMAINS IN TIGHT
AGREEMENT WITH A GRADUAL SPREAD TO 70 NM BY TAU 48. AFTERWARDS, THE
SPREAD INCREASES TO 240 NM BY TAU 120 AS THE MEMBERS DISAGREE WITH
THE TRAJECTORY OVER THE MOZAMBIQUE CHANNEL. GFS DETERMINISTIC AND
ENSEMBLE GUIDANCE TAKES TC 11S ON A MORE WEST-NORTHWESTWARD TRACK
WHILE CROSSING OVER THE MOZAMBIQUE CHANNEL, WHEREAS THE OTHER
MEMBERS KEEP THE SYSTEM ON A WEST-SOUTHWESTWARD TRACK. THE FORECAST
TRACK IS SET SLIGHTLY TO THE RIGHT OF CONSENSUS AFTER TAU 72 TO
ACCOUNT FOR THE OFFSET OF THE GFS GUIDANCE. BECAUSE OF THIS, THE
JTWC FORECAST TRACK IS PLACED WITH HIGH CONFIDENCE UP TO TAU 72,
THEN MEDIUM CONFIDENCE THEREAFTER. THE INTENSITY GUIDANCE IS ALSO
IN GOOD AGREEMENT WITH THE EXCEPTION OF GFS WHICH DECREASES THE
INTENSITY WELL BEYOND THE OTHER CONSENSUS MEMBERS. THE JTWC
INTENSITY FORECAST IS SET WITH MEDIUM CONFIDENCE.

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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