WDPN31 PGTW 220900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (TRAMI)        
WARNING NR 008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.0N 126.6E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 328 NM EAST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS DEEP CONVECTIVE 
BANDING OVER THE WESTERN SEMICIRCLE WRAPPING INTO THE SOUTHERN 
QUADRANT OF AN EXPOSED, BROAD LOW-LEVEL CIRCULATION CENTER. AS 
REVEALED IN A 220148Z MHS 89GHZ MICROWAVE IMAGE, THE BULK OF THE DEEP 
CONVECTIVE BANDING IS DISPLACED OVER THE SOUTHWESTERN QUADRANT DUE TO 
NORTHEASTERLY VERTICAL WIND SHEAR. A RECENT SCATTEROMETER IMAGE 
DEPICTS AN ELONGATED CENTER, WHICH SUPPORTS THE INITIAL POSITION, WITH 
A SWATH OF 35-40 KNOT WINDS OVER THE SOUTHERN SEMICIRCLE AND WEAKER 
WINDS ELSEWHERE. UPPER-LEVEL ANALYSIS INDICATES A MARGINALLY FAVORABLE 
ENVIRONMENT WITH LOW TO MODERATE NORTHEASTERLY VERTICAL WIND SHEAR 
OFFSET BY MODERATE WESTWARD VENTING, WHICH IS SUSTAINING DEEP 
CONVECTION AND CURVED BANDING OVER THE WESTERN SEMICIRCLE. THE INITIAL 
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON MSI AND THE 
AFOREMENTIONED SCATTEROMETER IMAGE. THE INITIAL INTENSITY OF 35 KTS IS 
ASSESSED WITH MEDIUM CONFIDENCE BASED ON AGENCY SUBJECTIVE DVORAK 
ESTIMATES RANGING FROM 2.0 TO 2.5 (30-35 KNOTS).

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: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 40 KTS AT 220233Z
   CIMSS ADT: 34 KTS AT 220530Z

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

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM (TS) 22W IS FORECAST TO TRACK
WEST-NORTHWESTWARD THROUGH TAU 24 ALONG THE SOUTHWESTERN PERIPHERY
OF THE STR, TOWARD A BREAK IN THE STR PRODUCED BY A MIDLATITUDE
SHORTWAVE TROUGH DIGGING INTO THE EAST CHINA SEA. AFTER TAU 24, THE
STR WILL REBUILD TO THE NORTH TURNING THE SYSTEM ONTO A MORE WESTWARD 
TRAJECTORY. THE SYSTEM WILL INTENSIFY SLIGHTLY BEFORE LANDFALL UNDER 
THE MARGINALLY FAVORABLE CONDITIONS. LANDFALL OVER EASTERN LUZON WILL 
OCCUR NEAR TAU 30, WITH SIGNIFICANT WEAKENING COMMENCING. AFTER TAU 
36, TS 22W WILL WEAKEN AND DECOUPLE WHILE CROSSING THE RUGGED TERRAIN 
OF LUZON, WITH A LIKELY LEESIDE JUMP. THIS WILL RESULT IN AN APPARENT 
DIP IN THE FORECAST TRACK AS A NEW PRESSURE CENTER FORMS AND 
STRENGTHENS OFF THE WEST COAST OF LUZON NEAR TAU 48. AFTER TAU 48, THE 
SYSTEM WILL RESUME A WESTWARD TRACK UNDER THE STR TO THE NORTH WITH 
STEADY INTENSIFICATION TO ABOUT 60 KNOTS BY TAU 96.     

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE REMAINS IN GOOD 
AGREEMENT THROUGH THE FORECAST PERIOD, WITH AN 80NM TO 90NM CROSS-
TRACK SPREAD FROM TAU 72 TO TAU 120. PROBABILISTIC GUIDANCE INDICATES 
A WIDER SPREAD OF SOLUTIONS FROM NORTHERN HAINAN ISLAND TO ABOUT 17N 
LATITUDE SUGGESTING A LIKELY LANDFALL OVER CENTRAL VIETNAM JUST AFTER 
TAU 120. RELIABLE INTENSITY GUIDANCE SHOWS A PEAK INTENSITY AT TAU 84 
RANGING FROM 55 KNOTS (HAFS-A) TO AS HIGH AS 71 KNOTS (HWRF).      

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