WDPN33 PGTW 240300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (CO-MAY) WARNING NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.2N 118.6E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 169 NM NORTHWEST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM (TS) 11W IS EMBEDDED WITHIN THE SOUTHWESTERN EDGE
OF A LARGE CYCLONIC GYRE ROTATION, WHICH EXTENDS ACROSS A DIAMETER
OVER 1200NM, FROM TS 11W ALL THE WAY NORTHEASTWARD TO AND BEYOND TS
10W. THE CENTROID OR AXIS OF ROTATION OF THIS GYRE PATTERN IS
CURRENTLY POSITIONED IN THE PHILIPPINE SEA TO THE EAST OF THE LUZON
STRAIT, AND ANIMATED TOTAL PERCEPTIBLE WATER (TPW) IMAGERY SHOWS
MULTIPLE TROPICAL SYSTEMS ROTATING ABOUT THIS CENTROID. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI) CONTINUES TO DEPICT A
STRENGTHENING SYSTEM, WITH A SMALL BUT DENSE CDO OBSCURING THE LOW
LEVEL CIRCULATION CENTER (LLCC). A 232204Z WSF-M MWI COLOR-ENHANCED
37GHZ IMAGE REVEALED A MODEST AMOUNT OF WESTWARD VORTEX TILT,
INDUCED BY A MODERATE AMOUNT OF MID-LEVEL EASTERLY SHEAR. HOWEVER,
THE LATEST MSI FRAMES SUGGEST STRONG VERTICAL HOT TOWERS (VHTS)
CYCLING ON THE DOWNSHEAR LEFT SIDE OF THE STORM AND BEGINNING TO
ROTATE UPSHEAR. THIS COULD MARK THE BEGINNING OF ANOTHER ROUND OF
RI, THOUGH IT REMAINS TO BE SEEN IF THIS CYCLE WILL BE THE ONE OR
NOT. THE INITIAL POSITION IS ASSESSED WITH MEDIUM CONFIDENCE BASED
ON AN EXTRAPOLATION OF THE LLCC AS DEPICTED IN THE MICROWAVE IMAGE
NOTED ABOVE. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM
CONFIDENCE, HEDGED SLIGHTLY HIGHER THAN THE HIGHEST AGENCY DVORAK
ESTIMATES BASED ON THE MORE AGGRESSIVE ADT AND AIDT, WHICH ARE
TAKING THE MIC EYE INTO ACCOUNT. ENVIRONMENTAL CONDITIONS REMAIN
FAVORABLE, CHARACTERIZED BY LOW VWS, ROBUST DUAL-CHANNEL OUTFLOW
AND VERY WARM SSTS. MODERATE MID-LEVEL SHEAR AND VORTEX TILT REMAIN
THE ONLY HINDRANCE TO EXPLOSIVE DEVELOPMENT.

INITIAL WIND RADII BASIS: MODERATE EASTERLY MID-LEVEL SHEAR. 

CURRENT STEERING MECHANISM: THE SYSTEM IS TRACKING ALONG THE
GRADIENT FLOW BETWEEN A LARGE CYCLONIC MONSOON GYRE WITH A CENTROID
EAST OF LUZON STRAIT AND A NEAR EQUATORIAL RIDGE (NER) OVER THE
MALAY PENINSULA. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T3.5 - 55 KTS
   DEMS: T3.5 - 55 KTS
   CIMSS ADT: 77 KTS AT 240010Z
   CIMSS AIDT: 72 KTS AT 240010Z
   CIMSS D-MINT: 42 KTS AT 232252Z
   CIMSS D-PRINT: 56 KTS AT 240000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG DUAL-CHANNEL

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE FORECAST IS EXTENDED TO TAU 72. 

FORECAST DISCUSSION: OVER THE PAST SIX HOURS, TS 11W HAS SHIFTED
FROM A SOUTHWESTWARD TRACK TO A SOUTHEASTWARD OR EVEN EASTWARD
TRACK, HAVING REACHED AND PASSED THE INFLECTION POINT AT THE
SOUTHWESTERN END OF THE MONSOON GYRE. THE SYSTEM WILL NOW DRIFT
EASTWARD FOR ANOTHER FEW HOURS BEFORE IT IS CAUGHT UP IN THE TIGHT
GRADIENT FLOW BETWEEN THE STR TO THE EAST AND THE EASTERN SIDE OF
THE LARGE MONSOON GYRE AND ACCELERATES OFF TO THE NORTHEAST AFTER
TAU 12. THE SYSTEM IS CURRENTLY FORECAST TO PASS JUST WEST OF CAPE
BOLINAO BY TAU 12, THEN RAPIDLY TRANSIT NORTHEASTWARD, MAKING
LANDFALL NEAR VIGAN, PHILIPPINES AROUND TAU 18. THE SYSTEM THEN
CONTINUES ACCELERATING NORTHEASTWARD THROUGH TAU 48. AFTER TAU 48,
THE SYSTEM SLOWS SIGNIFICANTLY AND TURNS EASTWARD AS IT BECOMES
ABSORBED INTO THE MONSOON GYRE AND IS STEERED BY THE BELT OF
MONSOONAL WESTERLIES THAT DEVELOPS AS THE GYRE REALIGNS TO A MORE
EAST-WEST ORIENTATION. AS THE SYSTEM HAS TRACKED FURTHER SOUTHWARD,
IT HAS MOVED INTO A SLIGHTLY HIGHER SHEAR ENVIRONMENT, WHICH HAS
INHIBITED INTENSIFICATION. HOWEVER, NOW THAT IT IS, OR SHORTLY WILL
BE, MOVING BACK NORTHWARD, SHEAR CONDITIONS WILL IMPROVE, ALLOWING
FOR VORTEX ALIGNMENT. ONCE THAT OCCURS, THE SYSTEM WILL EMBARK ON
ANOTHER ROUND OF RI. THE CURRENT FORECAST CALLS FOR A PEAK
INTENSITY OF 85 KNOTS BY TAU 12. HOWEVER, AS THE NEXT FORECAST
POINT IS OVER LAND, THE ACTUAL PEAK INTENSITY IS NOT CAPTURED IN
THE FORECAST DIRECTLY AND IS LIKELY TO OCCUR BETWEEN TAU 12 AND 24
AND LIKELY WILL BE 10 TO 15 KNOTS HIGHER. ONCE THE SYSTEM MOVES
OVER LAND, IT WILL RAPIDLY WEAKEN DUE TO TERRAIN INTERACTIONS,
COMPOUNDED BY RAPIDLY INCREASING EASTERLY SHEAR. AFTER MOVING BACK
OVER WATER, THE SYSTEM IS SHEARED APART BY STRONG SHEAR AS IT
TRACKS NORTHWARD, OPENING UP INTO A TROUGH OR WAVE AXIS BY TAU 48
OR SO. BY THE END OF THE FORECAST PERIOD, THE SYSTEM WILL BE A WAVE
FEATURE EMBEDDED WITHIN THE MONSOON GYRE, AND NOT A DISCRETE
TROPICAL CYCLONE, ALTHOUGH ELEVATED WINDS WILL BE PRESENT ALONG THE
SOUTH AND EASTERN PERIPHERY OF THE WAVE FEATURE. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN MODEST
AGREEMENT THOUGH TAU 36. GFS SHOWS THE SYSTEM TURNING NORTHEASTWARD
A MUCH FASTER PACE, AND KEEPS THE VORTEX OVER WATER THROUGH THE
ENTIRE FORECAST PERIOD, WHILE THE REMAINDER OF THE GUIDANCE PACKAGE
TRACKS THE VORTEX OVER NORTHWESTERN LUZON. CROSS-TRACK UNCERTAINTY
INCREASES TO 140NM BY TAU 36, WITH SOME MODELS, INCLUDING THE
ECMWF, TRACKING THE VORTEX OVER THE BOLINAO PENINSULA AND BACK OVER
WATER SOUTH OF CAPE ENGANO. THE ENSEMBLE PACKAGE HAS ALSO SHIFTED
GENERALLY EASTWARD, BRINGING THE ENSEMBLE MEANS FURTHER OVER LUZON.
THE JTWC TRACK HAS SHIFTED EAST A BIT AND IS POSITIONED ON THE
WESTERN EDGE OF THE GUIDANCE PACKAGE THROUGH TAU 36. AFTER TAU 36,
BOTH CROSS- AND ALONG-TRACK UNCERTAINTY CONTINUE TO INCREASE, AS
MODELS BEGIN TO LOSE THE VORTEX AS IT OPENS UP INTO A WAVE AND
MERGES INTO THE LARGE CYLONIC GYRE PATTERN. BY THE END OF THE
FORECAST, THE POSITION IS PLACED NEAR THE GFS AND GEFS MEAN
TRACKERS, THOUGH UNCERTAINTY IS HIGH. INTENSITY GUIDANCE IS IN
OVERALL AGREEMENT THAT THE SYSTEM WILL INTENSIFY PRIOR TO LANDFALL,
THEN RAPIDLY AND STEADILY WEAKEN THROUGHOUT THE REMAINDER OF THE
FORECAST. THE HAFS-A AND HWRF PEAK THE SYSTEM AT 85 KNOTS WHILE THE
RICN, RIDE, AND RIPA PREDICT A PEAK INTENSITY OF 115 KNOTS. THE
ACTUAL PEAK IS MOST LIKELY TO FALL BETWEEN THE TWO EXTREMES, AT
AROUND TAU 18. STRONG SHEAR AND ABSORPTION INTO THE OVERALL GYRE
PATTERN WILL LEAD TO DISSIPATION AS A DISCRETE TROPICAL CYCLONE BY
TAU 72, THOUGH ELEVATED WINDS WILL REMAIN ALONG THE PERIPHERY OF
THE SYSTEM AS PART OF THE GYRE PATTERN. 

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