WDXS31 PGTW 090300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 11S (FREDDY) WARNING 
NR 012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.0S 111.0E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 417 NM NORTH-NORTHWEST OF LEARMONTH,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 31 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) AND ENHANCED
INFRARED (EIR) SATELLITE IMAGERY SHOW THE LOW-LEVEL CIRCULATION
CENTER (LLCC) REMAINS IN AN EMBEDDED CENTER. THE INITIAL POSITION
IS PLACED WITH HIGH CONFIDENCE USING EXTRAPOLATION BASED UPON THE
FORMATION OF A MICROWAVE EYE 082219Z SSMIS 37GHZ MICROWAVE IMAGE
AND A 082212Z RCM SAR IMAGE. THE INITIAL INTENSITY OF 75 KTS
REMAINS HIGHER THAN THE OBJECTIVE INTENSITY AIDS, LOWER THAN
MULTIPLE AGENCY FIXES LISTED BELOW, AND IS CLOSER TO THE 70 KNOTS
FROM THE RCM SAR IMAGE. ENVIRONMENTAL CONDITIONS REMAIN HIGH WITH
(20-25 KNOTS) EASTERLY VERTICAL WIND SHEAR (VWS), SLIGHTLY OFFSET
BY MODERATE WESTWARD OUTFLOW AND WARM SSTS (29-30C).

INITIAL WIND RADII BASIS: SAR DATA AT 082212Z 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
POSITIONED TO THE SOUTH OVER WESTERN AUSTRALIA

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   KNES: T5.0 - 90 KTS
   DEMS: T5.0 - 90 KTS
   APRF: T4.5 - 77 KTS
   CIMSS ADT: 61 KTS AT 082330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE WESTWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   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 11S IS FORECAST TO CONTINUE ON A WESTWARD
TRACK ALONG THE NORTHERN PERIPHERY OF THE STR THROUGH THE FORECAST
PERIOD. THE HIGH VWS, WHICH HAS PERSISTED TO PRESS EASTERLY ON THE
SYSTEM AND WEAKEN IT SLIGHTLY THROUGH THE NEXT 24 TO 36 HOURS.
BEYOND TAU 36, THE SYSTEM WILL BEGIN TO RE-INTENSIFY TO THE PEAK OF
80 KNOTS AS IT MOVES INTO A REGION OF SLACKENED VWS. THE SYSTEM
WILL CONTINUE TO MOVE ON A WESTERLY TRACK UNIMPEDED FOR THE
DURATION OF THE FORECAST PERIOD AS IT SLOWLY DECREASES IN INTENSITY
BY TAU 120.

MODEL DISCUSSION: NAVGEM REMAINS THE SOLE OUTLIER LEFT OF TRACK
UNTIL TAU 36, WHILE THE BULK OF THE DETERMINISTIC GUIDANCE REMAINS
IN TIGHT AGREEMENT WITH ONLY A 45 TO 75NM SPREAD IN SOLUTIONS FROM
TAU 12 TO TAU 72. AFTER TAU 72 AND FOR THE REMAINING TRACK, THE
MODEL GUIDANCE ONLY SPREADS TO 180NM, INCLUDING NAVGEM, UNTIL THE
END OF THE FORECAST PERIOD. THEREFORE, THERE IS HIGH CONFIDENCE
THROUGH TAU 72 AND MEDIUM THEREAFTER AS THE SPREAD INCREASES. THERE
IS SIGNIFICANT UNCERTAINTY IN THE JTWC INTENSITY FORECAST, WITH
MODEL GUIDANCE INDICATING A DISPARITY BETWEEN HWRF EXTREME HIGH OF
110 KNOTS AND THE LOW FROM COAMPS OF 45 KNOTS AT TAU 48. DUE TO
THIS DISPARITY, THE OVERALL JTWC INTENSITY FORECAST LENDS MEDIUM
CONFIDENCE OUT TO TAU 72 AND THEN LOW FOR THE REMAINDER OF THE
FORECAST. 

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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