WDXS31 PGTW 101500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 11S (FREDDY) WARNING 
NR 016//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.8S 106.5E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 624 NM NORTHWEST OF LEARMONTH, AUSTRALIA
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A VERY
COMPACT SYSTEM WITH A SUSTAINED CENTRAL DENSE OVERCAST (CDO)
FEATURING A FEW HOT TOWERS FIRING NEAR THE ASSESSED CENTER. WHILE
MODERATE EASTERLY SHEAR HAS BEEN PERSISTENT OVER THE PAST DAY OR
SO, THE MOST RECENT CIMSS ATMOSPHERIC MOTION VECTOR (AMV) ANALYSIS
REVEALS THAT THE PERSISTENT DEEP CONVECTION HAS BEEN SUCCESSFUL IN
PUSHING BACK AGAINST THE SHEAR, WITH THE UPPER-LEVEL WINDS NOW
DIVERGING AROUND THE CDO AND CREATING AN OUTFLOW FRONT FACING THE
SHEAR VECTOR. ADDITIONALLY, ANIMATED WATER VAPOR SHOWS A REGION OF
SUBSIDENCE AND DRYING TO THE EAST OF THE OUTFLOW FRONT. THESE
SIGNATURES ARE POTENTIALLY INDICATIVE OF THE POTENTIAL FOR ONSET OF
RAPID INTENSIFICATION IN THE NEAR FUTURE. THE INITIAL POSITION WAS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON AN EXTRAPOLATION OF A
MICROWAVE EYE FEATURE IN A 100853Z AND IS IN AGREEMENT WITH A TIGHT
CLUSTER OF AGENCY FIX POSITIONS. THE INITIAL INTENSITY REMAINS SET
AT 70 KNOTS, WITH HIGH CONFIDENCE BASED ON AN AVERAGE OF THE AGENCY
CURRENT INTENSITY ESTIMATES BETWEEN T4.0 AND T4.5 (65 TO 77 KTS)
AND THE CIMSS ADT AND AIDT ESTIMATES BETWEEN 71 KTS AND 77 KTS. THE
ENVIRONMENT IS FAVORABLE FOR INTENSIFICATION, WITH LOW (10-15 KTS)
VWS, STRONG WESTWARD AND LIGHT POLEWARD OUTFLOW AND WARM SSTS. THE
SYSTEM IS ALSO MOVING OVER A POOL OF MODERATE OCEAN HEAT CONTENT,
PROVIDING AN ADDITIONAL BOOST OF ENERGY IN THE NEAR-TERM.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   KNES: T4.0 - 65 KTS
   DEMS: T4.5 - 77 KTS
   APRF: T4.0 - 65 KTS
   CIMSS ADT: 74 KTS AT 101130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE WESTWARD
   OTHER FACTORS: WEAK POLEWARD OUTFLOW. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: HIGH
   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 11S (FREDDY) HAS TRACED A RATHER WOBBLY
TRACK OVER THE PAST 24 HOURS BUT HAS FINALLY SETTLED DOWN ONTO A
MORE WEST-NORTHWESTWARD COURSE OVER THE LAST 12 HOURS. OVER THE
NEXT 12 HOURS OR SO, THE STEERING RIDGE TO THE SOUTH IS EXPECTED TO
BUILD TOWARDS THE EAST, AND IN RESPONSE TC 11S IS EXPECTED TO BEGIN
TRACKING NEARLY DUE WEST. SLIGHT DEVIATIONS NORTH AND SOUTH OF DUE
WEST ARE EXPECTED THROUGH THE FORECAST PERIOD, BUT THE OVERALL
COURSE WILL BE WESTWARD ALL THE WAY TO THE END OF THE FORECAST. TC
11S HAS BEEN LIKE THE LITTLE ENGINE THAT COULD, PUSHING BACK
AGAINST THE PERSISTENT EASTERLY SHEAR AND INTENSIFYING FROM 50
KNOTS 24 HOURS AGO TO 70 KNOTS AT PRESENT. AS NOTED IN THE OPENING
PARAGRAPH, RECENT SATELLITE IMAGERY AND AMV ANALYSIS SUGGESTS THAT
THE ENVIRONMENT IS SETTING UP TO SUPPORT A RI EVENT, EVEN IN THE
FACE OF THE MODERATE EASTERLY SHEAR REGIME. AS LONG AS THE DEEP
CONVECTION CONTINUES TO FIRE AND ROTATE UPSHEAR AS IT HAS BEEN
DOING, THEN THE CORE OF THE SYSTEM WILL BE COCOONED IN A REGION OF
LOWER SHEAR THAN WHAT THE OVERALL ENVIRONMENTAL SHEAR WOULD
OTHERWISE SUGGEST. THIS WILL ALLOW FOR RAPID INTENSIFICATION, TO A
PEAK OF 100 KNOTS BY TAU 36. AFTER THIS POINT, THE GLOBAL MODELS
SUGGEST A PATTERN SHIFT IN THE UPPER-LEVELS, WHICH WILL INTRODUCE
CONVERGENT NORTHEASTERLY FLOW AND SIGNIFICANTLY HIGHER SHEAR
VALUES, WHICH WILL OVERWHELM THE SYSTEM AND LEAD TO A GOOD AMOUNT
OF WEAKENING THROUGH TAU 72. AFTER TAU 72, THE PATTERN SHIFTS AGAIN
AND THE SYSTEM DEVELOPS A POINT SOURCE ALOFT AND TAPS INTO SOME
GOOD POLEWARD OUTFLOW, ALLOWING FOR REINTENSIFICATION BY TAU 120. 

MODEL DISCUSSION: TRACK GUIDANCE IS IN GOOD AGREEMENT THROUGH THE
FIRST 72 HOURS OF THE FORECAST, WITH ALL CONSENSUS MEMBERS ENCASED
IN A 60NM ENVELOPE. THEREAFTER THE TRACKERS DIVERGE SIGNIFICANTLY,
WITH THE NAVGEM AND THE NAVGEM VERSION OF COAMPS-TC DEVIATING FAR
TO THE SOUTH, WHILE THE REMAINDER OF THE GUIDANCE MAINTAINS A
GENERALLY WESTWARD TRACK. THE JTWC FORECAST TRACES THE NORTHERN
EDGE OF THE ENVELOPE THROUGH TAU 72, THEN REMAINS CONSISTENT WITH
THE GFS AND CONSENSUS MEAN THROUGH TAU 120. CONFIDENCE IS HIGH IN
THE FIRST PORTION OF THE FORECAST, TRENDING TO MEDIUM IN THE LATER
TAUS. INTENSITY GUIDANCE IS MIXED, WITH A VERY LARGE SPREAD IN PEAK
INTENSITIES BETWEEN 75 KNOTS AND 135 KNOTS. BOTH VERSIONS OF THE
DECAY-SHIPS INDICATE A PEAK AT OR BELOW 85 KNOTS, AS DOES THE GFS
DETERMINISTIC GUIDANCE. MEANWHILE THE COAMPS-TC (GFS VERSION) PEAKS
AT 135 KNOTS. ADDITIONALLY, THE CTR1, RICN, AND DTOP RI AIDS ARE
ALL TRIGGERED WITH THIS RUN, AND COAMPS-TC RI PROBABILITIES
APPROACH 50 PERCENT. IN LIGHT OF THE POSSIBLE SATELLITE-BASED
INDICATORS DISCUSSED ABOVE, THE JTWC FORECAST BREAKS FROM THE BULK
OF THE GUIDANCE AND BITES ON THE RI AIDS, BUT NOT TO THE EXTENT OF
THE UNREALISTIC COAMPS-TC. 

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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