WDPN33 PGTW 242100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (CO-MAY) WARNING NR 
008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.7N 120.2E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 134 NM NORTH-NORTHWEST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM (TS) 11W IS FIRMLY ENTRENCHED IN THE FAR
SOUTHWESTERN REACHES OF A LARGE, ELONGATED, NORTH-SOUTH ORIENTED,
MONSOON GYRE WHICH EXTENDS FROM TS 11W ALL THE WAY TO TS 10W IN THE
EAST CHINA SEA. DURING THE OVERNIGHT HOURS, TS 11W TURNED EAST AND
APPROACHED THE WEST COAST OF LUZON. ANIMATED ENHANCED INFRARED
(EIR) SATELLITE IMAGERY AND PHILIPPINE RADAR DATA INDICATED TS 11W
MAKING A BRIEF LANDFALL OVER THE BOLINAO PENINSULA AROUND 241500Z.
BY 1800Z, PHILIPPINE RADAR DATA AND A 241808Z GMI 37GHZ MICROWAVE
IMAGE REVEALED A WEAK MICROWAVE EYE FEATURE POSITIONED IN THE
NORTHERN ENTRANCE TO THE LINGAYEN GULF. A LACK OF SUBSEQUENT
MICROWAVE IMAGERY AND RADAR DATA HAS MADE ANALYSIS OF THE TRACK
INCREASINGLY DIFFICULT TO DETERMINE. THE EIR HINTS THAT THE VORTEX
MAY BE TRACKING DUE NORTH, REMAINING OVER WATER TO THE WEST OF
VIGAN, PHILIPPINES. THERE MAY BE SOME VORTEX DECOUPLING OCCURRING
AND THE FIRST FRAMES OF VISIBLE IMAGERY WILL HELP CLARIFY THE
SITUATION. IN THE MEANTIME, THE INITIAL POSITION IS ASSESSED WITH
HIGH CONFIDENCE BASED ON THE NOTED MICROWAVE IMAGE. THE INITIAL
INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE
SUBJECTIVE AND OBJECTIVE ESTIMATES NOTED ABOVE. ENVIRONMENTAL
CONDITIONS ARE MARGINAL, WITH LOW SHEAR, WARM SSTS AND MODERATE
OUTFLOW ALOFT OFFSET BY PROXIMITY TO LAND AND THE RUGGED TERRAIN
FEATURES OF WESTERN LUZON.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SYSTEM IS ENTRENCHED WITHIN THE FAR
SOUTHWESTERN END OF A LARGE MONSOON GYRE THAT EXTENDS NORTHEASTWARD
TO TS 10W WEST OF OKINAWA AND IS BEING STEERED ALONG THE GRADIENT
FLOW ALONG THE EASTERN SIDE OF THE GYRE AND A SUBTROPICAL RIDGE
(STR) IN THE PHILIPPINE SEA. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T4.0 - 65 KTS
   RCTP: T4.0 - 65 KTS
   KNES: T5.0 - 90 KTS
   DEMS: T4.5 - 77 KTS
   CIMSS SATCON: 58 KTS AT 241730Z
   CIMSS ADT: 45 KTS AT 241730Z
   CIMSS AIDT: 57 KTS AT 241730Z
   CIMSS D-MINT: 33 KTS AT 241812Z
   CIMSS D-PRINT: 40 KTS AT 241830Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD
   OTHER FACTORS: PROXIMITY TO LAND. 

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS FORECAST INTRODUCES FULL
DISSIPATION, BELOW WARNING THRESHOLD, BY THE END OF THE FORECAST
PERIOD. 

FORECAST DISCUSSION: TS 11W IS MOST LIKELY IN THE PROCESS OF MAKING
A SECOND LANDFALL ALONG THE WESTERN COAST OF LUZON, IN THE VICINITY
OF SANTA CRUZ. HOWEVER, IT CANNOT BE RULED OUT THAT THE LLCC
REMAINS OFFSHORE, TRACKING NORTHWARD PARALLEL TO THE ELEVATED
TERRAIN FEATURES OF WESTERN LUZON. OVERALL STEERING FLOW IS
SOUTHWESTWARD, ALONG THE GRADIENT BETWEEN THE EASTERN SIDE OF THE
GYRE AND THE STR TO THE EAST. SO EVEN IF THE VORTEX IS MOVING NORTH
AT THE MOMENT, IT WILL EVENTUALLY RESPOND TO THE DEEP-LAYER FLOW
AND TURN NORTHEASTWARD. THE 12 HOUR FORECAST POINT IS POSITIONED IN
THE LUZON STRAIT, WITH THE LLCC EXPECTED TO BE TRACKING RAPIDLY
NORTHEASTWARD BY THAT POINT. A POSITION A BIT FURTHER SOUTHWEST IS
POSSIBLE IN LIGHT OF THE ABOVE DESCRIBED SCENARIO. ONCE OVER WATER
THOUGH, THE SYSTEM WILL RAPIDLY TRAVERSE NORTHEASTWARD ALONG THE
TIGHT STEERING GRADIENT ON THE EAST SIDE OF THE GYRE THROUGH TAU
24. THE SYSTEM BEGINS TO SLOW DOWN AND TURN SLIGHTLY MORE
NORTHWARD, AS IT UNDERGOES WEAK BINARY INTERACTION WITH THE
REMNANTS OF TS 10W NORTH OF TAIWAN. NEITHER SYSTEM IS STRONG ENOUGH
TO FULLY CAPTURE THE OTHER AND THE INTERACTION WILL BE WEAK AND
SHORT-LIVED. THE TRACK EVOLUTION AFTER TAU 24 IS HIGHLY COMPLEX,
WITH THE VORTEX EXPECTED TO OPEN UP INTO A WAVE FEATURE, WHILE
SIMULTANEOUSLY MERGING INTO THE MONSOON GYRE, WHICH WILL ITSELF BE
EVOLVING FROM A NORTH-SOUTH ORIENTATION TO A MORE EAST-WEST
ORIENTATION. THUS, AFTER TAU 36, THE REMNANTS OF TS 11W ARE
EXPECTED TO MOVE EASTWARD, STILL WITHIN THE GYRE, AS THE OVERALL
GYRE PATTERN REORIENTS. THE SYSTEM IS NOT EXPECTED TO INTENSIFY ANY
LONGER, DUE TO TERRAIN INTERACTIONS. THIS IS ESPECIALLY TRUE IF IT
MOVES OVER LUZON PROPER, WHERE IT WILL BE TORN APART BY THE HIGH
TERRAIN ON THE WEST SIDE OF THE ISLAND. THE VORTEX THAT EMERGES
OVER WATER INTO THE LUZON STRAIT WILL BE SIGNIFICANTLY DEGRADED AND
IN THE PROCESS OF RAPIDLY WEAKENING ALREADY, WHEN IT WILL BE
FURTHER TORN ASUNDER BY STRONG SOUTHEASTERLY SHEAR. CONTINUED RAPID
WEAKENING IS EXPECTED THROUGH THE REMAINDER OF THE FORECAST, WITH
THE SYSTEM DISSIPATING BY TAU 48 AS IT NEARS OKINAWA. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN FAIRLY GOOD
AGREEMENT THROUGH TAU 24. ALL CONSENSUS MEMBERS SHOW THE VORTEX
EMERGING OFF NORTHERN LUZON WEST OF APARRI THEN MOVING INTO THE FAR
EASTERN SIDE OF THE LUZON STRAIT. BOTH ALONG- AND CROSS-TRACK
UNCERTAINTY INCREASES AFTER TAU 12, EXACERBATED BY THE FACT THAT
SEVERAL MODELS LOSE THE VORTEX ENTIRELY AS EARLY AS TAU 24. BY THE
END OF THE FORECAST, CROSS-TRACK UNCERTAINTY IS SIGNIFICANT, WITH
POTENTIAL MODEL SOLUTIONS RANGING FROM WELL-WEST OF OKINAWA TO
WELL-EAST OF OKINAWA. THE JTWC FORECAST IS PLACED ON THE FAR
WESTERN EDGE OF THE GUIDANCE ENVELOPE AT TAU 12 IN LIGHT OF THE
NEAR-TERM UNCERTAINTY IN THE TRACK MOTION, THEN SLIGHTLY WEST OF
THE CONSENSUS MEAN THROUGH THE REMAINDER OF THE FORECAST PERIOD.
INTENSITY GUIDANCE IS IN GOOD AGREEMENT THAT THE SYSTEM WILL
STEADILY WEAKEN THROUGH THE FORECAST PERIOD, THOUGH THE BULK OF THE
GUIDANCE ARRESTS THE WEAKENING AT ABOUT 30 KNOTS AFTER TAU 36. THIS
IS LIKELY DUE TO THE VORTEX TRACKERS JUMPING CIRCULATIONS TO
ANOTHER POTENTIAL CIRCULATION THAT DEVELOPS TO THE EAST OF TS 11W.
THE JTWC FORECAST DEVIATES FROM THE MODEL ENVELOPE AFTER TAU 24,
SHOWING DISSIPATION BY TAU 48. 

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