WDPN31 PGTW 222100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (TRAMI) WARNING NR 
010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.1N 125.1E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 240 NM EAST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A COLD DENSE
OVERCAST REGION SLIGHTLY OFFSET FROM THE CENTER POSITION,
INDICATING THE SYSTEM IS SLIGHTLY SHEARED AND EXPERIENCING PRESSURE
FROM THE NORTHEAST SIDE. LITTLE CHANGE IN THE CONVECTIVE ACTIVITY OVER 
THE PAST SEVERAL HOURS INDICATES DEVELOPMENT HAS SLOWED OR STALLED. 
MODERATE AND DIFFUSE WESTWARD OUTFLOW IS PRESENT FROM THE EQUATORWARD 
SIDE, BUT OUTFLOW IS STRUGGLING TO VENT IN THE POLEWARD DIRECTION. A 
221530Z OSCAT IMAGE WAS USED TO AID IN THE INITIAL PLACEMENT. THE 
INITIAL INTENSITY WAS ASSESSED USING THE PGTW SUBJECTIVE DVORAK 
ESTIMATE.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
POSITIONED TO THE NORTH-NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   CIMSS ADT: 32 KTS AT 221730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE WESTWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: THE SYSTEM WILL TRACK NORTHWESTWARD INITIALLY
AND TURN WESTWARD PRIOR TO AN EXPECTED LANDFALL ALONG THE EAST
COAST OF LUZON WITHIN THE NEXT 24 HOURS, DRIVEN BY THE SOUTHWESTERN
EDGE OF THE SUBTROPICAL RIDGE (STR) TO THE NORTHEAST. A SHORT-LIVED
BREAK IN THE STR DUE TO A MAJOR SHORTWAVE TROUGH IN THE
MIDLATITUDES IS ALLOWING FOR THE INITIAL NORTHWESTWARD SHIFT. THE
STR IS EXPECTED TO REBUILD TO THE NORTH AND REMAIN IN PLACE THROUGH
THE MAJORITY OF THE CYCLONE'S LIFE CYCLE, RESULTING IN A
PREDOMINANTLY WESTWARD TRACK. DEVELOPMENT PRIOR TO LANDFALL IS
EXPECTED TO BE HAMPERED BY THE PRESSURE THE SYSTEM IS EXPERIENCING
ON THE NORTHEAST SIDE, ALONG WITH SOME VERTICAL WIND SHEAR AND
CONVERGENCE ALOFT. THE INTERACTION WITH LAND NEAR TAU 24 AND TAU 36
WILL WEAKEN THE STORM AS IT TRACKS WESTWARD ACROSS LUZON, AND A
LEESIDE JUMP CAN BE EXPECTED, THOUGH IT IS UNCERTAIN WHAT
THE RESULTANT LOCATION WILL BE WHEN THE SYSTEM EMERGES FROM THE
WEST COAST OF LUZON. DURING THE WESTWARD TRACK OVER THE SOUTH CHINA
SEA, MODEST STRENGTHENING CAN BE EXPECTED. A RIDGE IS EXPECTED TO
BUILD OVER SOUTHEAST ASIA, WHICH MAY ALTOGETHER PREVENT A LANDFALL
AND CAUSE TS 22W TO REMAIN OFFSHORE FROM VIETNAM. IF THIS RIDGE
DOES SET UP AND BLOCK FORWARD MOTION, THE TRACK COULD CURVE NORTH
OR SOUTH AFTER TAU 120.

MODEL DISCUSSION: THE MORE RELIABLE TRACK GUIDANCE SITS SOUTH OF
THE CONSENSUS MEAN, WHICH IS WHERE THE JTWC FORECAST IS ALSO
HEDGED. OVERALL, THE TRACK GUIDANCE IS TIGHT IN BRINGING TS 22W TO
A LANDFALLING LOCATION ALONG THE EAST COAST OF LUZON PRIOR TO TAU
24. THE UNCERTAINTY OF HOW A LEESIDE JUMP WILL PLAY OUT IS
RESULTING IN A WIDER TRACK SPREAD AS THE SURFACE LOW REFORMS WEST
OF LUZON NEAR TAU 36. TOWARD THE END OF THE FORECAST PERIOD, MODEL
GUIDANCE INDICATES A STALL AND LOOPING TRACK IS POSSIBLE, WHICH
COULD BIFURCATE THE TRACK GUIDANCE BEYOND TAU 120. THE INTENSITY
GUIDANCE SUGGESTS VERY LIMITED OR STALLED DEVELOPMENT WILL BE
LIKELY OVER THE NEXT 24 HOURS. A DIP IN THE INTENSITY IS REFLECTED
IN ALL THE GUIDANCE AS THE SYSTEM TRAVERSES LUZON, AND SLOW AND
STEADY DEVELOPMENT IS DEPICTED THEREAFTER. THE JTWC FORECAST
INTENSITY AND TRACK CONFIDENCE IS MEDIUM.

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