WDPS31 PGTW 070300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 23P (FILI) WARNING NR 
012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.6S 164.4E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 99 NM WEST-SOUTHWEST OF NOUMEA, NEW
CALEDONIA
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
AS TC 23P CONTINUES TO SLIDE DOWN THE WESTERN COAST OF GRANDE
TERRE, ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) REVEALS THE
LOW LEVEL CIRCULATION CENTER (LLCC) IS BEGINNING TO POP OUT FROM
UNDER THE WESTERN EDGE OF THE CONVECTIVE ENVELOPE, THE INFLUX OF
DRY AIR AND THE PERSISTENT WESTERLY SHEAR FINALLY STARTING TO
OVERPOWER THE SYSTEM. THE INITIAL POSITION IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE PARTIALLY EXPOSED LLCC SEEN IN THE MSI. THE
INITIAL INTENSITY OF 50 KNOTS IS ASSESSED WITH MEDIUM CONFIDENCE
ROUGHLY AT THE AVERAGE OF THE AGENCY DVORAK CURRENT INTENSITY
ESTIMATES, AND IN LINE WITH THE ADT AND AIDT 0000Z ESTIMATES.
ANIMATED WATER VAPOR IMAGERY AND HIGH RESOLUTION HWRF MODEL
CROSS-SECTIONS CONFIRM THE RAPID INFLUX OF DRY AIR EXTENDING DOWN
INTO THE LOWER LEVELS OF THE VORTEX AS WELL AS THE STRONG DOWNSHEAR
VORTEX TILT TOWARDS THE EAST. THE COMBINATION OF FACTORS MEANS THAT
TC 23P IS RAPIDLY APPROACHING THE END STAGE.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED TO THE EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   PHFO: T3.5 - 55 KTS
   NFFN: T3.5 - 55 KTS
   CIMSS SATCON: 57 KTS AT 062215Z
   CIMSS ADT: 49 KTS AT 062340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 25-30 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: MODERATE EASTWARD
   OTHER FACTORS: SIGNIFICANT DRY AIR ENTRAINMENT IN THE MID TO
LOWER LEVELS. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 23P IS FORECAST TO CONTINUE TRACKING TO THE
SOUTHEAST ALONG THE WESTERN SIDE OF A DEEP STR CENTERED TO THE
EAST, THROUGH THE FORECAST PERIOD. AT THE TAIL END OF THE FORECAST,
THE FORECAST CALLS FOR THE START OF A SLOW TURN TOWARDS THE EAST
BUT THIS TURN WILL NOT COMPLETE PRIOR TO THE END OF THE FORECAST.
AS DISCUSSED ABOVE, THE INFLUX OF A WEDGE OF DRY AIR INTO THE LOWER
LEVEL CORE OF THE VORTEX, AND THE PERSISTENT SHEAR, HAVE BEGUN TO
OVERWHELM TC 23P. UNFORTUNATELY FOR TC 23P, THIS TREND IS NOT
EXPECTED TO DECREASE, AND THE REMAINING CONVECTION IS EXPECTED TO
FULLY DECOUPLE FROM THE LOW LEVEL CIRCULATION WITHIN THE NEXT 24
HOURS. THE SYSTEM WILL COMMENCE SUBTROPICAL TRANSITION (STT) DURING
THE SAME TIME FRAME, WITH ANTICIPATED COMPLETION OF THE STT NO
LATER THAN TAU 36 AND POTENTIALLY AS EARLY AS TAU 24. HOWEVER, EVEN
WHILE THE SYSTEM WILL BE DECOUPLED AND TRANSITION TO A SUBTROPICAL
LOW, IT WILL TAKE SOME TIME FOR THE WIND FIELD TO SPIN DOWN, AND
THUS THE FORECAST CALLS FOR SLOW WEAKENING THROUGH THE FORECAST
PERIOD, WITH TRANSITION TO A GALE-FORCE SUBTROPICAL LOW BY TAU 36. 


MODEL DISCUSSION: THROUGH THE DURATION OF THE FORECAST PERIOD,
TRACK GUIDANCE IS IN VERY GOOD AGREEMENT WITH MINIMAL CROSS AND
ALONG-TRACK SPREAD, LENDING HIGH CONFIDENCE TO THE JTWC TRACK
FORECAST. OUTSIDE OF THE FORECAST PERIOD, MODEL GUIDANCE DIVERGES
SIGNIFICANTLY AS THE SYSTEM GOES SUBTROPICAL, BUT THE BOTTOM LINE
IS THAT THE REMNANT SUBTROPICAL LOW IS LIKELY TO LINGER FOR SOME
TIME IN THE SOUTH PACIFIC. INTENSITY GUIDANCE IS SPLIT, WITH THE
GLOBAL DECAY SHIPS MODELS DEPICTING RAPID WEAKENING TO 15 KNOTS BY
TAU 48, WHILE THE MESOSCALE MODELS HOLD ONTO THE CIRCULATION ABOVE
40 KNOTS, WITH THE HWRF EVEN INTENSIFYING THE SYSTEM IN THE LONG
RANGE FORECAST. THE JTWC FORECAST LIES ROUGHLY ANALOGOUS TO THE
CONSENSUS MEAN THROUGH THE FORECAST PERIOD WITH HIGH CONFIDENCE. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   INTENSITY 0 - 72 HR: HIGH//
NNNN