WDPS31 PGTW 091500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05P (FIVE) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.6S 177.0E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 120 NM SOUTHWEST OF SUVA, FIJI
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS CYCLING
CONVECTION NEAR AND OBSCURING THE ASSESSED LOW LEVEL CIRCULATION
CENTER (LLCC). THE CONVECTIVE MASS WAS VERY COMPACT, BUT WELL
DEFINED AT THE 1200Z HOUR, SUBSEQUENTLY WEAKENED AND BECAME
DISORGANIZED, BUT IS ONCE AGAIN FLARING BY THE 1330Z HOUR.
UNFORTUNATELY THERE HAS BEEN NO RECENT MICROWAVE IMAGERY, BUT
090924Z ASCAT-B AND 091019 ASCAT-C PASSES SHOWED THE COMPACT
CIRCULATION CENTER TO GOOD EFFECT, AND AN EXTRAPOLATION OF THESE
CENTERS PROVIDED MEDIUM CONFIDENCE TO THE INITIAL POSITION. THE
SCATTEROMETER PASSES SHOWED 35 KNOT WINDS WITHIN 60NM OF THE CENTER
TO BOTH THE NORTHWEST AND SOUTH OF THE CENTER, AND PROVIDED GOOD
SUPPORT TO INCREASE THE INITIAL INTENSITY TO 35 KNOTS. AGENCY
CURRENT INTENSITY ESTIMATES ROUGHLY ALIGNED WITH THE SCATTEROMETER
MEASUREMENTS AND GAVE HIGH CONFIDENCE TO THE INITIAL INTENSITY.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: COMPETING STEERING ENVIRONMENT BETWEEN
NEAR EQUATORIAL RIDGE (NER) TO THE NORTHEAST AND SUBTROPICAL RIDGE
(STR) TO THE SOUTH-SOUTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   PHFO: T3.0 - 45 KTS
   NFFN: T2.5 - 35 KTS
   CIMSS ADT: 39 KTS AT 091140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 20-25 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: WHILE THE SYSTEM HAS BEEN MOVING SOUTHEAST AT
A FAIRLY QUICK 11 KNOTS OVER THE PAST SIX HOURS, OVER THE LAST
COUPLE OF HOURS IT HAS SHOWN SIGNS OF STARTING TO SLOW DOWN. THIS
TREND IS EXPECTED TO CONTINUE OVER THE NEXT 12 HOURS AS THE NER TO
THE NORTHEAST WEAKENS AND MOVES AWAY TO THE NORTH. OVER THE NEXT 18
HOURS, THE STR TO THE SOUTH WILL BUILD IN AND BECOME THE PRIMARY
STEERING MECHANISM AND TC 05P WILL TURN TO THE WEST BY TAU 24. BY
TAU 36, THE STEERING PATTERN SHIFTS AGAIN, WITH THE A MAJOR
SHORTWAVE TROUGH MOVING IN FROM THE WEST AND ERODING THE STR,
ALLOWING TC 05P TO TURN SHARPLY SOUTH-SOUTHEASTWARD FROM TAU 48
THROUGH THE END OF THE FORECAST PERIOD. THE SYSTEM CURRENTLY SITS
AT THE BASE OF AN UPPER-LEVEL TROUGH, AND THE STRONG DIVERGENT
POLEWARD OUTFLOW ON THE EASTERN SIDE OF THE SYSTEM HAS ALLOWED FOR
THE RECENT INTENSIFICATION. MID-LEVEL DRY AIR IN THE WESTERN
SEMICIRCLE REMAINS PROBLEMATIC HOWEVER AND IS LIMITING THE
INTENSIFICATION FOR NOW. THE ATMOSPHERE IS EXPECTED TO MOISTEN OVER
THE NEXT 12 HOURS, ALLOWING FOR A SHORT SPURT OF INTENSIFICATION TO
45 KNOTS. THE BASE OF THE UPPER TROUGH PINCHES OFF TO AN
UPPER-LEVEL LOW OVER THE NEXT 12 HOURS, AND TC 05P WILL MOVE UNDER
THIS FEATURE BY TAU 24, AND THE CONVERGENCE FLOW ALOFT WILL LEAD TO
A BRIEF WEAKENING TREND THROUGH TAU 48. THE SYSTEM IS EXPECTED TO
ONCE AGAIN INTENSIFY AS IT MOVES AWAY FROM THE UPPER LOW, DEVELOPS
A WEAK ANTICYCLONE ALOFT AND TAPS INTO STRONG POLEWARD OUTFLOW,
PEAKING AT 50 KNOTS AT TAU 72. THE SYSTEM IS FORECAST TO CROSS THE
26C ISOTHERM SHORTLY AFTER TAU 72, AND FACE INCREASING SHEAR AND
DRY AIR ENTRAINMENT. SUBTROPICAL TRANSITION WILL BEGIN BY TAU 96,
AND BE COMPLETE NO LATER THAN TAU 120.   

MODEL DISCUSSION: THE BULK OF THE TRACK GUIDANCE IS IN GOOD
AGREEMENT, WITH THE EXCEPTION OF THE NAVGEM AND HWRF SOLUTIONS,
WHICH TAKE THE SYSTEM MUCH FURTHER SOUTHEAST THROUGH TAU 72, WHERE
THEY REJOIN THE REMAINDER OF THE GUIDANCE. ALONG TRACK SPREAD
INCREASES DRAMATICALLY AFTER TAU 72, AS THE SYSTEM UNDERGOES
SUBTROPICAL TRANSITION, WITH THE NAVGEM FAR OUTPACING ALL OTHER
CONSENSUS MEMBERS IN FORWARD SPEED. THE JTWC TRACK REMAINS
CONSISTENT WITH THE PREVIOUS FORECAST, AND IS ON THE SOUTHERN SIDE
OF THE GUIDANCE THROUGH TAU 36, THEN ON THE INSIDE EDGE OF THE
ENVELOPE THROUGH THE REMAINDER OF THE FORECAST. OVERALL CONFIDENCE
IS MEDIUM IN THE NEAR TERM, AND LOW IN THE EXTENDED FORECAST.
INTENSITY GUIDANCE MEMBERS ALL AGREE ON NEAR-TERM INTENSIFICATION,
PEAKING BETWEEN 45 AND 50 KNOTS, FOLLOWED BY A WEAKENING THROUGH
TAU 36, THEN REINTENSIFICATION TO A PEAK BETWEEN 50 AND 60 KNOTS.
THE JTWC FORECAST FOLLOWS THE OVERALL TREND, BUT REMAINS 5-10 KNOTS
LOWER THAN THE CONSENSUS MEAN. CONFIDENCE IS MEDIUM TRENDING TO
LOW. 

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