WDPS31 PGTW 062100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 23P (FILI) WARNING NR 
011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.8S 164.1E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 113 NM WEST OF NOUMEA, NEW CALEDONIA
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 24 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
COMPACT SYSTEM WHICH HAS BECOME STEADILY MORE SYMMETRICAL IN NATURE
OVER THE PAST TWELVE HOURS, SLIDING DOWN THE WESTERN SIDE OF GRANDE
TERRE, NEW CALEDONIA. OVER THE PREVIOUS FEW HOURS, A WEAK CENTRAL
DENSE OVERCAST HAS REDEVELOPED, AND IS NOW OBSCURING THE LOW LEVEL
CIRCULATION CENTER (LLCC). WHILE THE CDO HAS REDEVELOPED, THE LOW
LEVEL BANDING FEATURES REMAIN FRAGMENTED AND WEAK, PARTICULARLY
ALONG THE WESTERN PORTION OF THE CIRCULATION, WHERE THE SHEAR
GRADIENT IS STRONGER AND THE AIR MASS IS MORE STABLE. HWRF MODEL
CROSS-SECTIONS SHOW A VERTICAL VORTEX UP TO ABOUT 700MB, WHICH THEN
TILTS SHARPLY DOWNSHEAR TOWARDS THE NORTHEAST. A 061705Z SSMIS
91GHZ MICROWAVE IMAGE INDICATED A STRONG EYEWALL TYPE FEATURE ON
THE NORTHEAST SIDE OF THE CENTER BUT THE EYEWALL IS OPEN ON THE
SOUTHWESTERN SIDE DUE TO THE IMPACT OF THE SOUTHWESTERLY SHEAR. THE
INITIAL POSITION WAS ASSESSED WITH HIGH CONFIDENCE BASED ON THE LOW
EMISSIVITY REGION IN THE 37GHZ BAND IN THE MICROWAVE IMAGE NOTED
ABOVE. THE INITIAL INTENSITY REMAINS AS 55 KNOTS, IN LINE WITH THE
MAJORITY OF THE AGENCY FIXES, THE SATCON AND THE AIDT OF 54 KNOTS.
ANALYSIS INDICATES A MARGINALLY UNFAVORABLE ENVIRONMENT,
CONSTRAINED BY MODERATE SOUTHWESTERLY SHEAR, WARM, BUT DECREASING
SSTS AND MODERATE POLEWARD OUTFLOW.

INITIAL WIND RADII BASIS: PERSISTENCE WITH PREVIOUS SCATTEROMETER
DATA. 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   KNES: T3.0 - 45 KTS
   PHFO: T3.5 - 55 KTS
   NFFN: T3.5 - 55 KTS
   CIMSS SATCON: 55 KTS AT 061444Z
   CIMSS ADT: 49 KTS AT 061740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 20-25 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: MODERATE EASTWARD
   OTHER FACTORS: MID-LEVEL DRY AIR ENCROACHING FROM THE WEST. 

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 FILI HAS CONTINUED TO HOLD ON TO ITS
CURRENT INTENSITY RATHER WELL, IN THE FACE OF PERSISTENCE
SOUTHWESTERLY SHEAR AND INCREASING DRY AIR ENCROACHMENT. BUT ITS
DAYS ARE NUMBERED AS THE ENVIRONMENT IS FORECAST TO STEADILY
DETERIORATE OVER THE NEXT DAY. THE SYSTEM WILL CONTINUE TO TRACK
SOUTHEASTWARD ALONG THE SOUTH-SOUTHWEST PERIPHERY OF A DEEP STR
CURRENTLY CENTERED NEAR FIJI. OVER THE DURATION OF THE FORECAST,
THE STR WILL SHIFT RAPIDLY TO THE WEST TO A POSITION NORTH OF TC
FILI, LEADING TO A SLOW DOWN IN THE FORWARD SPEED AND A GRADUAL TURN
TO THE EAST COMMENCING BY THE END OF THE CURRENT FORECAST. AS
MENTIONED, THE ENVIRONMENT WILL BEGIN TO DETERIORATE OVER THE NEXT
12 HOURS OR SO, WITH STEADILY INCREASING WESTERLY SHEAR USHERING IN
SIGNIFICANT DRY AIR DIRECTLY INTO AND OVER TOP OF THE CORE. THUS,
AS THE SYSTEM MOVES OVER STEADILY DECREASING SSTS, THE SHEAR AND
DRY AIR WILL CONSPIRE TO ELIMINATE ANY SIGNIFICANT CORE CONVECTION,
LEADING TO FAIRLY RAPID WEAKENING AFTER TAU 12. THE SYSTEM WILL
COMMENCE SUBTROPICAL TRANSITION WITHIN THE NEXT 12 HOURS AND IS
EXPECTED TO BE COMPLETE NO LATER THAN TAU 36, AS THE SYSTEM
TRANSITIONS TO A GALE-FORCE SUBTROPICAL LOW PRESSURE SYSTEM. 

MODEL DISCUSSION: AS COULD BE EXPECTED, DETERMINISTIC AND ENSEMBLE
TRACK GUIDANCE IS HIGHLY FOCUSED THROUGH THE SHORT DURATION OF THE
FORECAST PERIOD, WITH MINIMAL CROSS AND ALONG-TRACK SPREAD BETWEEN
THE CONSENSUS MEMBERS. THE SMALL ENVELOPE IS DEFINED WITH THE GFS
ON THE NORTHERN EDGE AND THE ECMWF ON THE SOUTHERN EDGE. THE JTWC
FORECAST TRACK LIES ON THE SOUTH-WEST SIDE OF THE ENVELOPE AS A NOD
TO THE RECENT TRACK MOTION, WITH HIGH CONFIDENCE. INTENSITY
GUIDANCE IS MIXED, WITH THE GLOBAL DECAY-SHIPS GUIDANCE SUGGESTING
RAPID WEAKENING AND DISSIPATION BELOW 35 KNOTS WITHIN 36-48 HOURS,
WHILE THE MESOSCALE MODELS INCLUDING HWRF AND COAMPS-TC HOLD ON TO
THE INTENSITY THROUGH THE FULL SEVEN DAY MODEL RUN, AS THE SYSTEM
LINGERS AS A SUBTROPICAL SYSTEM. THE JTWC FORECAST LIES ALONG THE
LOWER END OF THE MESOSCALE GROUPING, BUT ABOVE THE SHIPS GUIDANCE,
WITH MEDIUM CONFIDENCE. 

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