WDPS31 PGTW 010300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 15P (JUDY) WARNING NR 
009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.2S 168.6E
   INITIAL INTENSITY: 95 KTS
   GEOGRAPHIC REFERENCE: 35 NM SOUTH-SOUTHEAST OF PORT VILA,
VANUATU
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 35 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE 15P (JUDY) MADE A DIRECT HIT ON THE ISLAND OF
EFATE, PASSING A FEW MILES EAST OF PORT VILA, VANUATU, AT AROUND
2200Z WITH AN ESTIMATED INTENSITY OF 90-95 KNOTS. A WEATHER STATION
AT PORT VILA REPORTED A MINIMUM PRESSURE OF 961MB AT 2230Z, AS THE
CORE WAS AT ITS CLOSEST POINT OF APPROACH, YIELDING A CENTRAL
PRESSURE ESTIMATE IN THE HIGH 950S, SUPPORTING THE INTENSITY
ESTIMATE OF 90 KNOTS AT LANDFALL. THE SYSTEM CONTINUES TO FLIRT
WITH AN EYE, AND THE CIMSS ADT IS FLUCTUATING BETWEEN UNIFORM CDO
AND PINHOLE EYE. BUT THE EYE REMAINS FAIRLY COLD AND HAS YET TO
FULLY OPEN UP, BUT IT STILL HAS TIME. DUE TO A LACK OF RECENT
MICROWAVE IMAGERY, THE INITIAL POSITION IS ASSESSED WITH MEDIUM
CONFIDENCE, WITHIN THE PINHOLE EYE FEATURE IN THE EIR. THE INITIAL
INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, AT A CONSERVATIVE 95
KNOTS, ROUGHLY AT THE AVERAGE OF THE AGENCY FIXES, AND CLOSE TO THE
SATCON ESTIMATE OF 94 KNOTS. THE ADT CI REMAINS LOW AT T4.0 BUT THE
RAW ADT IS UP TO T6.6 AT 010030Z. SIMILARLY, THE LAST DEEP MICRONET
ESTIMATE WAS APPROXIMATELY 90 KNOTS JUST PRIOR TO LANDFALL, WHILE
THE OPEN-AIIR ESTIMATES HAVE INCREASED SHARPLY, NOW OVER 110 KNOTS.
ENVIRONMENTAL CONDITIONS REMAIN FAVORABLE FOR DEVELOPMENT, WITH
WARM SSTS AND STRONG POLEWARD AND EQUATORWARD OUTFLOW. SHEAR HAS
PICKED UP A BIT, NOW APPROACHING 15 KNOTS, BUT THE INTENSE CORE IS
STILL ABLE TO FIGHT OFF THE SHEAR FOR NOW. THE SYSTEM CONTINUES
TRACKING SOUTH-SOUTHEASTWARD ALONG THE WEST SIDE OF THE SUBTROPICAL
RIDGE (STR) TO THE EAST.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   KNES: T6.0 - 115 KTS
   PHFO: T5.0 - 90 KTS
   CIMSS SATCON: 94 KTS AT 282140Z
   CIMSS ADT: 65 KTS AT 282330Z

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

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: HAVING PASSED DIRECTLY OVER THE ISLAND OF
EFATE NEAR THE 2200Z HOUR, TC 15P IS NOW TAKING AIM ON THE SOUTHERN
ISLAND OF ERROMANGO AND TANNA AND WILL BE CROSSING OVER THESE
ISLANDS OVER THE NEXT FEW HOURS. THE SYSTEM HAS CROSSED THE RIDGE
AXIS AND IS NOW TRACKING MORE SOUTHEASTWARD AND IS EXPECTED TO
BEGIN ACCELERATING ALONG THE WESTERN SIDE OF THE STEERING RIDGE.
THIS GENERAL MOTION IS FORECAST TO CONTINUE THROUGH THE DURATION OF
THE FORECAST WITH A SLIGHT TURN MORE EASTWARD BY THE END OF THE
FORECAST PERIOD. SHEAR HAS ALREADY STARTED TO PICK UP, WITH THE
LATEST CIMSS SHEAR ESTIMATE UP TO 14 KNOTS FROM THE WEST. BUT THE
STRONG CORE OF CONVECTION WILL BE ABLE TO FIGHT OFF THIS SHEAR FOR
A BIT LONGER, WHILE THE STRENGTHENING POLEWARD OUTFLOW CHANNEL WILL
PROVIDE A MECHANISM FOR CONTINUED INTENSIFICATION. THE FAVORABLE
CONDITIONS WILL BE SHORT-LIVED HOWEVER, WITH THE PEAK INTENSITY
EXPECTED TO BE REACHED WITHIN THE NEXT 12 HOURS. BY TAU 18, AN
APPROACHING MID-LATITUDE TROUGH WILL BEGIN TO EXERT ITS INFLUENCE
AND USHER IN SHARPLY HIGHER SHEAR. SHEAR WILL CONTINUE TO STEADILY
INCREASE AND IS FORECAST TO EXCEED 40 KNOTS BY TAU 48. AT THE SAME
TIME, THE SYSTEM WILL MOVE INTO COOLER WATERS AND A MID-LEVEL WEDGE
OF DRY AIR WILL MOVE OVER TOP OF THE SYSTEM, LEADING TO
DECAPITATION OF THE UPPER-LEVELS OF THE SYSTEM. THIS PROCESS ALSO
MARKS THE ONSET OF SUBTROPICAL TRANSITION (STT), WHICH IS EXPECTED
TO OCCUR QUITE RAPIDLY AS THE SYSTEM TRACKS FURTHER SOUTHEAST INTO
INCREASINGLY HOSTILE ENVIRONMENTAL CONDITIONS. FULL TRANSITION TO A
STORM FORCE SUBTROPICAL LOW IS ANTICIPATED AS EARLY AS TAU 48, BUT
NO LATER THAN TAU 72. 

MODEL DISCUSSION: TRACK GUIDANCE REMAINS IN VERY GOOD AGREEMENT
THROUGH THE FORECAST PERIOD, WITH NO SIGNIFICANT CROSS-TRACK SPREAD
THROUGH TAU 72. A MARGINAL AMOUNT OF ALONG-TRACK SPREAD SEEPS IN
AFTER TAU 48 BUT REMAINS FAIRLY SMALL. THE JTWC FORECAST TRACK
REMAINS CONSISTENT WITH THE PREVIOUS FORECAST AND LIES CLOSE TO THE
CONSENSUS MEAN WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS MIXED,
WITH THE GFS, HWRF AND COAMPS-TC INDICATING A WEAKENING TREND FROM
THE START OF THE FORECAST. THE DECAY-SHIPS (GFS AND NAVGEM)
MEANWHILE SHOW THE SYSTEM INTENSIFYING ANOTHER 5-10 KNOTS PRIOR TO
WEAKENING. THE RIPA RAPID INTENSIFICATION (RI) AID IS ALSO
TRIGGERED, WHICH PEAKS THE SYSTEM AT 120 KNOTS. THE JTWC FORECAST
FOLLOWS THE RIPA TREND TO TAU 12, THOUGH REMAINS ABOUT 10 KNOTS
LOWER THAN THE RIPA PEAK INTENSITY, THEN REJOINS THE CONSENSUS
THEREAFTER WITH MEDIUM CONFIDENCE. 

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