WDXS31 PGTW 222100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 21S (CHARLOTTE) 
WARNING 
NR 010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.8S 109.1E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 390 NM NORTHWEST OF LEARMONTH, AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTHWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
MEDIUM-SIZED SYSTEM WITH DEEP CENTRAL CONVECTION REMAINING TO THE
SOUTHERN EDGE OF THE LOW-LEVEL CIRCULATION (LLC). THE EIR LOOP ALSO
INDICATES SUBSIDENCE CONTINUING TO REDUCE ALONG THE NORTHERN EDGES 
AND TRANSVERSE BANDING ENGULFING THE SOUTHWESTERN PERIPHERIES 
EXTENDING FROM THE CENTER OF THE SYSTEM TOWARDS DIRK HARTOG ISLAND, 
AUSTRALIA. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE 
BASED ON THE EIR LOOP AND EXTRAPOLATION OF A PARTIAL 221441Z METOP-B 
ASCAT 25KM IMAGE. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM 
CONFIDENCE OF 80KTS. THE MEDIUM CONFIDENCE IS BASED ON MULTIPLE 
AGENCY DVORAK FIXES INDICATING ARE ON THE DECLINE IN THE FINAL T 
ESTIMATES, BUT REMAIN HELD AT T5.0-90KTS BASED UPON CONSTRAINTS. 
OVER THE LAST 6 HOURS THE TREND FROM THE MULTIPLE AGENCIES HAS 
DECREASED TO INCLUDE THE ADVANCED DVORAK TECHNIQUE (ADT). ANALYSIS 
INDICATES A MARGINALLY UNFAVORABLE ENVIRONMENT WITH THE ROBUST 
POLEWARD OUTFLOW AND WARM SST OFFSET BY MODERATE TO STRONG VERTICAL 
WIND SHEAR. THE CYCLONE IS TRACKING ALONG THE NORTHWEST PERIPHERY OF 
THE STR TO THE SOUTHEAST.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: DEEP LAYER SUBTROPICAL RIDGE (STR) TO
THE SOUTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   APRF: T5.0 - 90 KTS
   CIMSS ADT: 85 KTS AT 221840Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 20-25 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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 21S CHARLOTTE WILL CONTINUE SOUTHWESTWARD
UNDER THE STEERING INFLUENCE OF THE STR. THE SYSTEM IS CURRENTLY IN
THE PROCESS OF ROUNDING THE STR AXIS AND WILL TRACK SOUTHWARD THEN
SOUTHEASTWARD TOWARD PERTH, AUSTRALIA THROUGH THE REMAINDER OF THE
FORECAST. THE ENVIRONMENT WILL REMAIN MARGINALLY UNFAVORABLE, AND BY 
TAU 60, TC CHARLOTTE WILL MOVE INTO A MORE UNFAVORABLE ENVIRONMENT 
WITH INCREASING VWS AND COOLING ALONG-TRACK SST. SHORTLY AFTER TAU 
60 AND BEFORE TAU 72, TC 21S WILL BEGIN TRANSITIONING INTO A 
SUBTROPICAL SYSTEM AND COMPLETE THE TRANSITION AS A GALE FORCED 
SUBTROPICAL SYSTEM WITH AN EXPANDING WIND FIELD BY TAU 96.  

MODEL DISCUSSION: NUMERICAL MODELS ARE IN OVERALL FAIR AGREEMENT
UNTIL TAU 72. ONCE THE SUBTROPICAL TRANSITION BEGINS, THE
MODELING GUIDANCE BEGINS TO DIVERGE SIGNIFICANTLY WITH SEVERAL
MODELS, INCLUDING AFUM, UKMET, EEMN, ECMF AND DEPICTS ERRATIC
REVERSALS IN THE STORM MOTION. THE OVERALL JTWC TRACK AND INTENSITY
GUIDANCE IS BASED ON MEDIUM CONFIDENCE NEAR TAU UP TO 72 AND LOW
THEREAFTER.

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