WDXS31 PGTW 151500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 11S (FREDDY) WARNING 
NR 026//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.0S 84.9E
   INITIAL INTENSITY: 135 KTS
   GEOGRAPHIC REFERENCE: 870 NM SOUTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 39 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) AND A 151256Z SSMIS
91GHZ IMAGE DEPICT A VERY WELL ORGANIZED SYSTEM WITH A 13 NM
DIAMETER EYE. THERE IS EVIDENCE OF PRESSURE ON THE EASTERN
PERIPHERY AS THE SYSTEM IS TRACKING UNDER AN AREA OF WESTWARD
UPPER-LEVEL WIND FLOW ESTIMATED AT 35-40 KNOTS. ENVIRONMENTAL
ANALYSIS INDICATES TC 11S TO BE IN MARGINALLY FAVORABLE CONDITIONS
FOR CONTINUAL TROPICAL DEVELOPMENT. THESE CONDITIONS ARE
CHARACTERIZED BY THE AFOREMENTIONED OUTFLOW ALOFT, MODERATE (15-20
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 MICROWAVE IMAGERY. THE INITIAL INTENSITY OF 135
KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A BLEND OF
MULTI-AGENCY AND AUTOMATED DVORAK ESTIMATES.

INITIAL WIND RADII BASIS: PERSISTENCE 

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 
   FMEE: T6.5 - 127 KTS
   CIMSS SATCON: 124 KTS AT 150742Z
   CIMSS ADT: 127 KTS AT 150915Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE WESTWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: TC FREDDY CONTINUES ITS WESTWARD TRACK AS IT
TRANSITS THE NORTHERN PERIPHERY OF THE STR TO THE SOUTH. THE SYSTEM
WILL CONTINUE THIS TRAJECTORY UNTIL APPROXIMATELY TAU 36 WHEN IT
WILL EXPERIENCE A SLIGHT DIP WEST-SOUTHWESTWARD DUE TO THE
SUPPORTING STR MIGRATING TO THE EAST. THERE IS COPIOUS AMOUNTS OF
DRY AIR SURROUNDING THE SYSTEM, HOWEVER, TC FREDDY WILL STAY
COCOONED IN ITS OWN MOISTURE POCKET DURING ITS FORECAST TRACK. TC
11S IS FORECAST TO SLOWLY BUT SURELY DECREASE IN INTENSITY
THROUGHOUT THE FORECAST PERIOD, CONVERSELY, THE SYSTEM HAS
UNDERGONE THREE PEAK INTENSITY EVENTS AND THE POSSIBILITY OF A
FOURTH EVENT SHOULD NOT BE RULED OUT.

MODEL DISCUSSION: THE JTWC MODEL TRACK CONSENSUS REMAINS IN TIGHT
AGREEMENT WITH A GRADUAL SPREAD TO 50 NM AT TAU 48. AFTERWARDS, THE
SPREAD INCREASES TO 200 NM BY TAU 120. BECAUSE OF THIS, THE JTWC
FORECAST TRACK IS PLACED WITH HIGH CONFIDENCE UP TO TAU 72, THEN
MEDIUM CONFIDENCE OUT TO TAU 120. ALL CONSENSUS MEMBERS AGREE ON
THE WEST-SOUTHWESTWARD SHIFT IN TRACK AFTER TAU 36. 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 UP TO TAU
72, THEN LOW CONFIDENCE THEREAFTER. THIS IS DUE TO THE INCREASE OF
INTENSITY OBSERVED OVER THE PAST 12 HOURS.

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