WDPS31 PGTW 082100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 03P (JASPER) WARNING 
NR 016//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.3S 156.4E
   INITIAL INTENSITY: 95 KTS
   GEOGRAPHIC REFERENCE: 618 NM EAST OF CAIRNS, AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 33 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
SIGNIFICANTLY WEAKENED AND ERODED SYSTEM, WITH THE RAGGED EYE
PREVIOUSLY OBSERVED, HAVING FILLED-IN AND DISSIPATED. DEEP
CONVECTION CONTINUES TO DEVELOP IN VICINITY OF THE LOW LEVEL
CIRCULATION CENTER (LLCC) BUT REMAINS DISORGANIZED. DUE TO A LACK
OF RECENT MICROWAVE IMAGERY AND THE IRREGULAR NATURE OF THE
CIRCULATION, THERE IS LOW CONFIDENCE IN THE INITIAL POSITION, WHICH
IS ASSESSED PRIMARILY USING AGENCY FIX POSITIONS. THE INITIAL
INTENSITY IS ASSESSED WITH LOW CONFIDENCE, HEDGED LOWER THAN THE
AGENCY CURRENT INTENSITY (CI) ESTIMATES DUE TO THE MUCH LOWER
OBJECTIVE INTENSITY ESTIMATES FROM THE AIDT (97 KTS), DPRINT (90
KTS) AND THE SATCON (95 KTS). THE SYSTEM IS CURRENTLY DRIFTING
SLOWLY SOUTHWARD, PASSING THROUGH AN INFLECTION POINT BETWEEN A
NEAR EQUATORIAL RIDGE (NER) TO THE NORTHEAST AND A SUBTROPICAL
RIDGE (STR) TO THE SOUTHWEST. ANALYSIS REVEALS A MARGINAL
ENVIRONMENT, CHARACTERIZED BY WARM SSTS, AND STRONG POLEWARD
OUTFLOW BEING OFFSET BY HIGH (20-25 KTS) WESTERLY WIND SHEAR. THE
STRONG SHEAR IS ALSO USHERING IN AN INFLUX OF VERY DRY MID-LEVEL
AIR FROM THE WEST, WHICH IS WRAPPING INTO THE CORE OF THE SYSTEM
FROM THE NORTHWEST.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: TRANSITION POINT BETWEEN NEAR
EQUATORIAL RIDGE (NER) TO THE NORTHEAST AND SUBTROPICAL RIDGE (STR)
TO THE SOUTHWEST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   KNES: T6.0 - 115 KTS
   ABRF: T5.5 - 102 KTS
   CIMSS SATCON: 95 KTS AT 081730Z
   CIMSS ADT: 107 KTS AT 081730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 20-25 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR MOVING IN FROM THE WEST. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   INITIAL INTENSITY: LOW
   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 03P (JASPER) IS FORECAST TO CONTINUE
DRIFTING SLOWLY TO THE SOUTH-SOUTHWEST OVER THE NEXT 6-12 HOURS, AS
IT CONTINUES TO MOVE THROUGH A RELATIVELY WEAK STEERING
ENVIRONMENT, WITH A LARGE COL-REGION TO THE SOUTHEAST. BY TAU 12,
THE STR TO THE SOUTH WILL ASSUME THE DOMINANT STEERING ROLE, AND
THE TRACK WILL SHIFT QUICKLY TO A WEST-SOUTHWEST THEN DUE WEST
COURSE THROUGH TAU 72. AS THE SYSTEM BEGINS MOVING WEST, IT WILL
ALSO ACCELERATE ALONG THE NORTH SIDE OF THE STR, PASSING THE
OUTERMOST CORAL SEA REEFS BY AROUND TAU 60. THE STEERING RIDGE TO
THE SOUTH IS EXPECTED TO PUSH A BIT NORTHWARD AROUND TAU 72, AND IN
RESPONSE, THE TRACK OF TC 03P SHIFTS TO WEST-NORTHWEST FROM TAU 48
TO TAU 96. THE SYSTEM IS EXPECTED TO MAKE LANDFALL NORTH OF CAIRNS
AROUND TAU 108, BEFORE CONTINUING INLAND OVER THE SOUTHERN PORTION
OF THE CAPE YORK PENINSULA. IN TERMS OF INTENSITY, THE COMBINATION
OF THE STRONG WESTERLY SHEAR AND THE SMOTHERING EFFECT OF THE
MID-LEVEL DRY AIR, WILL COMBINE TO STEADILY WEAKEN THE SYSTEM
THROUGH THE NEXT 72 HOURS. THE CURRENT FORECAST CALLS FOR THE
SYSTEM TO BOTTOM OUT AT 60 KNOTS AT TAU 72, BUT IT IS POSSIBLE IT
COULD WEAKEN A BIT FURTHER PRIOR TO THAT POINT. BY TAU 72, SHEAR IS
FORECAST TO SLACKEN WHILE THE ENVIRONMENT MOISTENS SIGNIFICANTLY.
COMBINED WITH THE FACT THAT THE SYSTEM WILL AT THIS POINT BE MOVING
OVER THE SHALLOW, VERY WARM WATERS OF THE GREAT BARRIER REEF, A
FAIR AMOUNT OF INTENSIFICATION IS EXPECTED UP THROUGH LANDFALL. THE
FORECAST CALLS FOR A PEAK OF 70 KNOTS BY TAU 96, HOWEVER THE ACTUAL
PEAK INTENSITY COULD BE HIGHER AND OCCUR VERY CLOSE TO LANDFALL.
AFTER LANDFALL, THE SYSTEM WILL RAPIDLY WEAKEN WHILE MOVING INLAND
DUE TO FRICTIONAL EFFECTS. 

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN GOOD OVERALL
AGREEMENT ON THE OVERALL FORECAST PHILOSOPHY. THE MODEL PACKAGE
SHOWS MINIMAL SPREAD, WHICH REACHES JUST 85NM AT TAU 72, SUPPORTING
A HIGH CONFIDENCE FORECAST TRACK, WHICH LIES ON THE NORTHERN SIDE OF
THE GUIDANCE ENVELOPE. TRACK GUIDANCE BEGINS TO DIVERGE
SIGNIFICANTLY AFTER TAU 72, WITH THE UKMET, EGRR AND GALWEM
TRACKING THE SYSTEM OVER THE NORTHERN CAPE YORK PENINSULA, WHILE
THE NAVGEM SHOWING THE SYSTEM MAKING LANDFALL WELL TO THE SOUTH OF
CAIRNS. THE BULK OF THE GUIDANCE, INCLUDING THE GFS, GEFS, ECMWF
AND ECENS, LIES CLOSELY PACKED NEAR THE CONSENSUS MEAN AND THE JTWC
FORECAST TRACK. HOWEVER, FORECAST CONFIDENCE IS TEMPERED BY THE
250NM SPREAD IN THE DETERMINISTIC GUIDANCE AT TAU 120 AND THE LARGE
SPREAD IN THE ENSEMBLE SOLUTIONS OF APPROXIMATELY 400NM BY THE END
OF THE FORECAST PERIOD. INTENSITY GUIDANCE AGREES ON THE OVERALL
SCENARIO OF WEAKENING FOLLOWED BY A SECOND ROUND OF INTENSIFICATION
LATE IN THE FORECAST PERIOD. THE PACKAGE SHOWS A BOTTOM BETWEEN
40-60 KNOTS WITH A SECOND PEAK 50-70 KNOTS. THE COAMPS-TC ENSEMBLE
AND GEFS INTENSITY TREND GUIDANCE BOTH INDICATE A LOW-PROBABILITY
(10-20 PERCENT) OF RAPID INTENSIFICATION (RI) AT THE END OF THE
FORECAST PRIOR TO LANDFALL, THUS THE MENTION OF A POSSIBLE PEAK
INTENSITY OCCURRING BETWEEN THE TAU 96 AND TAU 120 FORECAST POINTS.
 

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