WDXS31 PGTW 080300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 11S (FREDDY) WARNING 
NR 008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.1S 114.5E
   INITIAL INTENSITY: 90 KTS
   GEOGRAPHIC REFERENCE: 433 NM NORTH OF LEARMONTH, AUSTRALIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 36 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED SATELLITE IMAGERY SHOWS A DEEP COMPACT
SYSTEM THAT HAS SLIGHTLY WEAKENED AS EVIDENCED BY WARMING CLOUD
TOPS IN THE CENTRAL DENSE OVERCAST. THE INITIAL POSITION IS PLACED
WITH HIGH CONFIDENCE BASED ON A DIMPLED EYE IN THE 072330Z VISIBLE
SATELLITE IMAGERY, ADJUSTED FOR TILT AND LINED UP WITH A MICROWAVE
EYE IN THE 072232Z SSMIS 91GHZ IMAGE. THE INITIAL INTENSITY IS ALSO
ASSESSED WITH HIGH CONFIDENCE BASED ON CLOSELY CLUSTERED AGENCY AND
AUTOMATED DVORAK ESTIMATES AND REFLECTS THE SLIGHT 6-HR WEAKENING.
THE ENVIRONMENT HAS BECOME MARGINAL WITH WARM SSTS AND MODERATE
RADIAL OUTFLOW ALOFT OFFSET BY INCREASING VWS.

INITIAL WIND RADII BASIS: PERSISTENCE FROM RECENT SCATTEROMETER
DATA.

CURRENT STEERING MECHANISM: NORTHWEST PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE SOUTH.


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   KNES: T5.0 - 90 KTS
   APRF: T5.0 - 90 KTS
   CIMSS SATCON: 87 KTS AT 072232Z
   CIMSS ADT: 87 KTS AT 072330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   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 FREDDY WILL CONTINUE ON ITS CURRENT
WEST-SOUTHWESTWARD TRACK OVER THE NEXT 24 HOURS; AFTERWARD, IT WILL
LEVEL OFF ON A MORE WESTWARD TRAJECTORY AS THE STEERING STR BUILDS
AND EXTENDS WESTWARD. THE MARGINAL ENVIRONMENT, COMPOUNDED BY THE
INFLUX OF DRY AIR IN THE MID-LEVELS WILL GRADUALLY WEAKEN THE
SYSTEM DOWN TO 75KTS BY TAU 36. AFTERWARD, VWS WILL ONCE AGAIN
RELAX AND PROMOTE A SECONDARY, ALBEIT SHORT-LIVED INTENSIFICATION
TO 90KTS BY TAU 72 BEFORE REVERTING TO THE WEAKENING TREND AS VWS
ONCE AGAIN PICKS UP, REDUCING TC 11S TO 85KTS BY TAU 120. 

MODEL DISCUSSION: NUMERICAL TRACK MODELS ARE IN TIGHT AGREEMENT
WITH A GRADUAL SPREADING TO 195NM BY TAU 120 WITH NAVGEM THE SOLE
LEFT-OF-TRACK OUTLIER. UP TO TAU 72, THERE IS HIGH CONFIDENCE IN
THE JTWC TRACK FORECAST THAT IS LAID JUST TO THE RIGHT OF
CONSENSUS TO OFFSET NAVGEM. AFTER TAU 72, THE TRACK CONFIDENCE IS 
MEDIUM AS THE SPREAD WIDENS. THE INTENSITY FORECAST IS MEDIUM UP TO 
TAU 72 THEN LOW AFTERWARD DUE TO THE UNCERTAINTY IN THE FORECAST
INTENSITY DYNAMICS IN THE EXTENDED PERIOD.

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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