WDPN31 PGTW 250300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 08W (DAMREY) WARNING NR 
009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.8N 154.5E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 325 NM SOUTH OF MINAMI TORI SHIMA
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 19 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) OVER THE PAST SIX TO
EIGHT HOURS SHOWS THAT THE DISCRETE LOW LEVEL CIRCULATION CENTER
(LLCC) ASSOCIATED WITH TS 08W HAS MERGED WITH THE AREA OF VORTICITY
PREVIOUSLY KNOWN AS INVEST 92W. AS A RESULT OF THIS MERGER, THE
LLCC HAS TIGHTENED UP AND BECOME INCREASINGLY WELL-ORGANIZED AND
OBVIOUS IN AVAILABLE SATELLITE IMAGERY. THE LLCC IS FOCUSED NOW IN
THE NORTHEASTERN END OF A BROAD CIRCULATION THAT EXTENDS FAR TO THE
SOUTHWEST. A 242217Z ASCAT-B BULLSEYE PASS CAME IN RIGHT WHEN WE
NEEDED IT MOST AND CONFIRMED THE PRESENCE OF A DISTINCT LLCC WITH A
40NM RADIUS OF MAXIMUM WINDS (RMW) AND 35-40 KNOT SURFACE WINDS IN
THE SOUTHEASTERN QUADRANT. SURFACE WINDS REMAIN LIGHT ON THE INSIDE
OR WESTERN PORTION OF THE CIRCULATION, WHILE THE 25-30 KNOT WIND
FIELD EXTENDS AT LEAST 200NM OUT TO THE EAST, HIGHLIGHTING THE
EXTREME ASYMMETRY OF THE CIRCULATION. THE INITIAL POSITION IS
ASSESSED WITH HIGH CONFIDENCE BASED ON THE WELL-DEFINED LLCC IN
ANIMATED HIGH-RESOLUTION VISIBLE IMAGERY AND THE LLCC IN THE ASCAT
DATA. THE INITIAL INTENSITY OF 40 KNOTS IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE ASCAT DATA, HEDGED ABOVE THE AGENCY DVORAK
INTENSITY ESTIMATES AND ABOUT FIVE KNOTS HIGHER THAN THE CIMSS
AUTOMATED INTENSITY ESTIMATES. THE ENVIRONMENT IS MARGINALLY
FAVORABLE, WITH WARM SSTS AND ROBUST POLEWARD OUTFLOW OFFSET BY
MODERATE (20-25 KNOTS) SOUTHERLY SHEAR AND DRY MID-LEVEL AIR
PUNCHING INTO THE SOUTHERN PERIPHERY OF THE STORM FROM THE WEST.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A NEAR EQUATORIAL
RIDGE (NER) CENTERED TO THE SOUTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   CIMSS ADT: 35 KTS AT 242330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: NOW THAT TS 08W HAS BECOME MORE DEFINED AND
CONFIDENCE IN THE INITIAL POSITION HAS IMPROVED, THE FORECAST IS
STARTING TO FIRM UP. OVER THE NEXT 12 HOURS, TS 08W WILL RACE OFF
TO THE NORTHEAST ALONG THE STRONG GRADIENT ON THE NORTHWEST SIDE OF
THE STEERING RIDGE TO THE SOUTHEAST. THIS RIDGE WILL SLIDE
SOUTHWEST AFTER TAU 12, WEAKENING THE GRADIENT A BIT AND ALLOWING
TS 08W TO SLOW DOWN A BIT AS IT MAKES A SHARP TURN TOWARDS THE
NORTH. BY TAU 24, THE STEERING INFLUENCE SHIFTS TO THE VERY STRONG
SUBTROPICAL RIDGE (STR) ANOMALOUSLY PARKED NEAR 40N. AT THE SAME TIME
A DEEP-LAYER GYRE BEGINS TO SET UP ACROSS THE NORTHWEST PACIFIC. THE
GRADIENT BETWEEN THE GYRE AND THE STR WILL BE EXCEPTIONALLY STRONG,
AND TS 08W WILL RIDE THIS GRADIENT TOWARDS THE NORTHWEST AT SPEEDS
APPROACHING 25 KNOTS THROUGH TAU 72. THE SYSTEM SLOWS DOWN AGAIN BY
TAU 72 AS IT BEGINS TO ROUND THE RIDGE AXIS AND BEGINS
EXTRATROPICAL TRANSITION (ETT), THEN ACCELERATES NORTHEASTWARD
AFTER ROUNDING THE AXIS AND COMPLETES ETT BY THE END OF THE
FORECAST PERIOD. AS THE LLCC BECOMES INCREASINGLY ORGANIZED AND
VERTICALLY ALIGNED, IT SHOULD BE ABLE TO FIGHT OFF THE MODERATE
SHEAR CURRENTLY INHIBITING CONSOLIDATION. AS THE TUTT-CELL
CURRENTLY DUE NORTH OF THE SYSTEM PASSES TO WEST OF 150E, THE
SYSTEM WILL TAP AN INCREDIBLE AMOUNT OF UPPER-LEVEL OUTFLOW WHICH
WILL SUPPORT INTENSIFICATION TO AT LEAST 60 KNOTS BY TAU 48. THE
GFS GLOBAL MODEL FIELDS IN PARTICULAR INDICATE THE SYSTEM WILL
SIT AT THE TAIL END OF AN AREA OF SOUTHEASTERLY 200MB FLOW ON THE
EASTERN SIDE OF THE VERY STRONG TUTT, AND TO THE WEST OF A 200MB
ANTICYCLONE, EXCEEDING 95 KNOTS. THIS ANOMALOUS SET UP COULD
POTENTIALLY FUEL A MUCH HIGHER DEGREE OF INTENSIFICATION (AS
INDICATED IN SOME OF THE MODEL GUIDANCE) BUT THE EXACT PLACEMENT OF
THE LLCC IN RELATION TO THE JET MAX AND THUS SHEAR, WILL DRIVE THE
ULTIMATE INTENSITY. THE SYSTEM WILL BEGIN A SLOW WEAKENING PHASE BY
TAU 72 AS IT BEGINS ETT, BUT IS STILL ANTICIPATED TO BECOME A STORM
FORCE EXTRATROPICAL LOW BY THE END OF THE FORECAST PERIOD. 

MODEL DISCUSSION: TRACK GUIDANCE HAS SIGNIFICANTLY IMPROVED SINCE
THE PREVIOUS RUN, WITH THE CROSS-TRACK SPREAD DECREASING
DRASTICALLY, TO 95NM AT TAU 48, INCREASING TO 250NM AT TAU 96.
ALONG-TRACK SPREAD HAS DECREASED TO MINIMAL LEVELS, PROVIDING
INCREASED CONFIDENCE TO THE JTWC FORECAST TRACK. INTENSITY GUIDANCE
DEPICTS A DIFFERENT TALE. THE GUIDANCE PACKAGE HAS SHIFTED UP
SIGNIFICANTLY WITH THIS RUN, WITH THE ICNW MEAN PEAKING AT 65 KNOTS
AND THE OTHER GUIDANCE MUCH HIGHER THAN THAT. THE RIPA, RICN AND
FRIA RAPID INTENSIFICATION (RI) AIDS ARE TRIGGERED AND PEAK THE
SYSTEM AROUND 90 KNOTS. ON THE OPPOSITE END OF THE SPECTRUM THE
SHIPS GUIDANCE PEAKS AT JUST 50 KNOTS. THE JTWC FORECAST LIES ON
THE LOWER END OF THE GUIDANCE ENVELOPE WITH LOW CONFIDENCE. 

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