WDXS31 PGTW 220300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 21S (CHARLOTTE) 
WARNING NR 007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.6S 109.3E
   INITIAL INTENSITY: 90 KTS
   GEOGRAPHIC REFERENCE: 437 NM NORTHWEST OF LEARMONTH, AUSTRALIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 27 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DEEP
CONVECTION IN A GRADUALLY WARMING CENTRAL DENSE OVERCAST WRAPPING
AROUND A RAGGED EYE THAT IS CURRENTLY IN THE PROCESS OF FILLING.
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE GIVEN THE SMALL
EYE EVIDENT IN THE 212237Z SSMIS 91GHZ MICROWAVE IMAGE. THE INITIAL
INTENSITY IS SET AT 90 KNOTS WITH MEDIUM CONFIDENCE USING A BLEND
OF AGENCY DVORAK ESTIMATES AND A 211821Z AMSR2 PASS INDICATING
WINDS JUST ABOVE 80 KNOTS. BASED ON THE BRIEF CLEARING OF THE EYE
IN ANIMATED EIR, FOLLOWED BY SUBSEQUENT FILLING AND THE WARMING OF
CLOUD TOPS, THE PEAK INTENSITY OF TC 21S WAS LIKELY REACHED IN THE
HOURS BETWEEN THAT AMSR2 PASS AND THE CURRENT WARNING. THE
UPPER-LEVEL OUTFLOW IS BEGINNING TO BE CONSTRICTED IN THE NORTHERN
SEMICIRCLE, BUT POLEWARD OUTFLOW REMAINS EXCELLENT.

INITIAL WIND RADII BASIS: OTHER 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   APRF: T5.5 - 102 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 WILL CONTINUE TRACKING TOWARD THE
SOUTHWEST UNDER THE STEERING INFLUENCE OF THE STR TO THE SOUTHEAST.
VERTICAL WIND SHEAR IS GRADUALLY INCREASING, WITH RESTRICTED
EQUATORWARD OUTFLOW. OVER THE LAST 6 HOURS, TC 21S APPEARS TO HAVE
REACHED ITS PEAK INTENSITY, AND THE RAGGED EYE IS BEGINNING TO FILL
WITH CONVECTIVE CLOUD TOPS WARMING. GRADUAL WEAKENING IS OCCURING
AND SHOULD BECOME MORE RAPID WITH TIME AS THE ENVIRONMENT BECOMES
MORE HOSTILE. BY TAU 48, TC 21S IS FORECAST TO MAKE A TURN TOWARD
THE SOUTH AND SOUTHEAST WITH AN INCREASE IN SPEED AS THE STR TO THE
EAST WEAKENS AND THE SYSTEM INTERACTS WITH AN APPROACHING
MID-LATITUDE TROUGH FROM THE WEST. INCREASING VERTICAL WIND SHEAR,
DRY AIR ENTRAINMENT, AND INTERACTION WITH THE BAROCLINIC ZONE WILL
INDUCE SUBTROPICAL TRANSITION AROUND TAU 72. TC 21S IS FORECAST TO
COMPLETE SUBTROPICAL TRANSITION BY TAU 96.

MODEL DISCUSSION: WITH THE EXCEPTION OF NAVGEM, WHICH CONTINUES TO
BE THE WESTERN OUTLIER, NUMERICAL MODEL GUIDANCE IS IN FAIR
AGREEMENT WITH A 165NM SPREAD AT TAU 72, SUPPORTING THE JTWC
FORECAST TRACK WITH MEDIUM CONFIDENCE. THE JTWC FORECAST TRACK IS
POSITIONED CLOSE TO THE MULTI-MODEL CONSENSUS (CONW), BUT
ACCOUNTING FOR THE NAVGEM OUTLIER. THE JTWC INTENSITY FORECAST
FOLLOWS THE WEAKENING TREND OF THE INTENSITY GUIDANCE BUT MORE
GRADUALLY, GIVEN THE INTENSIFICATION PERIOD THAT OCCURRED TODAY.
ONCE THE RAGGED EYE COLLAPSES AND DRY AIR ENTRAINS INTO THE SYSTEM,
MORE RAPID WEAKENING SHOULD COMMENCE. DSHA AND DSHN REMAINS WELL
ABOVE THE REST OF THE INTENSITY GUIDANCE, BUT THOSE
STATISTICAL-DYNAMICAL SOLUTIONS ARE BEING FORCED BY THE RAPID
INTENSIFICATION OF THE LAST 12 HOURS, SO THOSE SOLUTIONS ARE
DISREGARDED FOR THIS WARNING CYCLE.

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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