WDXS31 PGTW 210300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 21S (CHARLOTTE) 
WARNING NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.6S 111.8E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 480 NM NORTH-NORTHWEST OF LEARMONTH,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY OVER THE
PREVIOUS SIX HOURS SHOWED THAT WHILE THE OVERALL STRUCTURE WAS
IMPROVING, CLOUD TOPS WERE WARMING, SUGGESTING A SHORT PAUSE IN THE
INTENSIFICATION RATE. SHORTLY PRIOR TO THE 210000Z HOUR HOWEVER, A
NEW ROUND OF INTENSIFICATION SET IN WITH THE DEVELOPMENT OF A SMALL
CENTRAL DENSE OVERCAST WITH THE COLDEST CLOUD TOPS REACHING -85C
NEAR THE CORE. WHILE THE EIR AND MULTISPECTRAL IMAGERY DOES NOT YET
REFLECT AN EYE FEATURE, A 202250Z SSMIS 91GHZ MICROWAVE DEPICTED A
PINHOLE MICROWAVE EYE FEATURE SURROUNDED BY MODERATE TO STRONG
CONVECTIVE BANDS. THE ACCOMPANYING 37GHZ IMAGE DID NOT SHOW A
DISTINCT MICROWAVE EYE FEATURE SUGGESTING THE SYSTEM IS STILL
ORGANIZING IN THE LOWER LEVELS AND MAY BE SLIGHTLY TILTED WITH
HEIGHT. THE INITIAL POSITION WAS ASSESSED WITH MEDIUM CONFIDENCE
DUE TO THE DISPARITY BETWEEN THE UPPER-LEVEL MICROWAVE EYE AND THE
AGENCY FIX POSITIONS TO THE NORTHWEST. THE INITIAL INTENSITY IS
HEDGED HIGHER THAN THE AGENCY FIXES OF T3.0 (45 KNOTS) FROM PGTW,
KNES AND APRF, IN LIGHT OF A NOAA ADT RAW ESTIMATE OF T3.7. A
202214Z SMAP BULLSEYE INDICATING A MAXIMUM 10-MIN WIND OF 56 KNOTS,
WHICH WHEN CONVERTED TO 1-MIN EQUATES TO 60 KNOTS.

INITIAL WIND RADII BASIS: SMAP DATA 

CURRENT STEERING MECHANISM: NORTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE EAST, AND THE WESTERN SIDE OF A
MID-LEVEL NEAR-EQUATORIAL RIDGE (NER) IN THE TIMOR SEA. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   APRF: T3.0 - 45 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG RADIAL
   OTHER FACTORS: MODERATE AND INCREASING POLEWARD OUTFLOW INTO THE
SUBTROPICAL WESTERLIES 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: HIGH

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE OVERALL TRACK PHILOSOPHY HAS NOT
CHANGED, HOWEVER THE PEAK INTENSITY HAS BEEN INCREASED
SIGNIFICANTLY DUE TO THE ONGOING RAPID INTENSIFICATION TREND, AND
THE TRANSITION TYPE HAS BEEN CHANGED FROM DISSIPATION TO
SUBTROPICAL TRANSITION. 

FORECAST DISCUSSION: OVER THE PAST SIX HOURS, TC CHARLOTTE HAS
TAKEN A BIT OF A MORE SOUTHERLY JOG VERSUS THE FORECAST TRACK,
LIKELY DUE TO THE PRESENCE OF A STRONGER THAN ANTICIPATED MID-LEVEL
NER TO ITS EAST AND A WEAKER WESTWARD EXTENSION OF THE STR. A MORE
SOUTHWESTWARD TRACK IS THUS FORECAST THROUGH TAU 24. AFTER THIS
POINT THE STR IS STILL EXPECTED TO RIDGE WESTWARD TO THE SOUTH OF
THE SYSTEM, WHICH WILL PUSH IT ONTO A SLIGHTLY MORE WEST-SOUTHWEST
TRACK THROUGH TAU 72, STEADILY SLOWING AS IT MOVES WEST. AN STRONG
SUBTROPICAL LOW WILL MOVE IN FROM THE WEST  AROUND TAU 72 AND
RAPIDLY ERODE THE STEERING RIDGE AND TC 21S WILL TAKE A HARD LEFT
TURN INTO THE INDUCED WEAKNESS AFTER TAU 72. THE SYSTEM WILL THEN
ACCELERATE POLEWARD IN THE GRADIENT BETWEEN THE STR AND THE
APPROACHING UPPER-LEVEL LOW. IN TERMS OF INTENSITY, THE SYSTEM IS
RAPIDLY INTENSIFYING UNDER VERY FAVORABLE CONDITIONS. THE POINT
SOURCE OVER THE SYSTEM IS VERY STRONG, PROVIDING STRONG OUTFLOW
ALOFT. WITH THE ADDITION OF A DEVELOPING POLEWARD OUTFLOW CHANNEL,
THERE IS LITTLE IN THE WAY OF ADDITIONAL RAPID INTENSIFICATION FOR
THE NEXT 24 TO 36 HOURS. JUST AFTER TAU 24 HOWEVER, THE POINT
SOURCE IS EXPECTED TO BREAK DOWN, LEADING TO DECREASED OUTFLOW AND
INCREASING WESTERLY SHEAR WHICH WILL START TO WEAKEN THE SYSTEM,
SLOWLY AT FIRST BUT THEN STEADILY PICKING UP PACE. MID-LEVEL DRY
AIR WILL PUNCH IN FROM THE NORTHWEST AND BEGIN TO WRAP INTO THE
CORE BY TAU 48, WHICH COMBINED WITH CONVERGENT FLOW ALOFT AND
MODERATE SHEAR WILL QUICKEN THE PACE OF WEAKENING THROUGH TAU 96.
AROUND TAU 96, THE SYSTEM WILL COMMENCE SUBTROPICAL TRANSITION AS
IT MOVES SOUTH OF THE 26C SST ISOTHERM AND BEGINS TO INTERACT WITH
A THE UPPER-LEVEL WESTERLIES AND A 500MB LOW. TRANSITION TO A
GALE-FORCE SUBTROPICAL LOW IS ANTICIPATED NO LATER THAN TAU 120. 

MODEL DISCUSSION: TRACK GUIDANCE AGREES ON THE OVERALL SCENARIO BUT
DISPLAYS INCREASED UNCERTAINTY SINCE THE PREVIOUS RUN. THE NEWEST
ECMWF RUN HAS MOVED CLOSER TO THE OTHER CONSENSUS MEMBERS, BUT THE
GFS AND GFS ENSEMBLE HAVE MOVED AWAY ON THE OTHER SIDE OF THE MEAN
WITH A NET INCREASE IN SPREAD TO 150NM AT TAU 48, INCREASING TO
175NM AT TAU 72 AND 250NM AT TAU 120. THE JTWC FORECAST LIES ON THE
SOUTHERN SIDE OF THE ENVELOPE AND CLOSE TO THE GFS SOLUTION,
THROUGH TAU 48 DUE TO THE RECENT JOG TO THE SOUTH IN THE BEST
TRACK. THE JTWC FORECAST REMAINS ON THE SOUTHERN EDGE OF THE
ENVELOPE UNTIL THE SYSTEM TURNS POLEWARD, WHEREUPON THE FORECAST
LIES ON THE WESTERN SIDE OF THE GUIDANCE PACKAGE. CONFIDENCE IS
MEDIUM THROUGH THE FORECAST PERIOD. THE INTENSITY FORECAST HAS BEEN
INCREASED DRAMATICALLY AND CLOSELY TRACKS THE 24 HOUR RIPA GUIDANCE
TO A PEAK OF 90 KNOTS AT TAU 24. THE 36 HOUR RIPA AND HWRF ARE
OUTLIERS, AND SUGGEST A PEAK CLOSER TO 100 KNOTS AT TAU 36, BUT THE
OVERALL ENVIRONMENT WOULD SUGGEST THERE IS ONLY A 24 HOUR WINDOW OF
OPTIMUM CONDITIONS. THE JTWC FORECAST TRACKS CLOSE TO THE CONSENSUS
THROUGH THE MID-RANGE FORECAST, THEN IS BELOW THE BULK OF THE
GUIDANCE IN THE LONG-RANGE AS THE SYSTEM GOES SUBTROPICAL. 

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