WDPN31 PGTW 261500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (TRAMI) WARNING NR 
025//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.2N 110.8E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 161 NM EAST-NORTHEAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: WESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 32 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM (TS) 22W CONTINUES TO STRUGGLE UNDER HIGH EASTERLY 
VERTICAL WIND SHEAR (VWS), WITH CORE CONVECTION BECOMING MORE LINEAR 
AND DISPLACED OVER THE WESTERN QUADRANT. A 261104Z SSMIS 91GHZ COLOR 
COMPOSITE MICROWAVE IMAGE REVEALS A DEFINED, BROAD LOW-LEVEL 
CIRCULATION CENTER, WITH CURVED CONVECTIVE BANDING OVER THE WESTERN 
QUADRANT. DESPITE THE HIGH VWS, DEEP CONVECTION IS PERSISTING DUE TO 
MODERATE WESTERLY OUTFLOW. THE INITIAL POSITION IS ASSESSED WITH 
MEDIUM CONFIDENCE BASED ON THE SSMIS IMAGE. THE INITIAL INTENSITY IS 
ASSESSED AT 55 KNOTS, CONSISTENT WITH THE DEGRADED CONVECTIVE 
STRUCTURE, IS BASED ON THE LOWER END OF THE AGENCY DVORAK ESTIMATES 
AND RECENT CIMSS ADT, AIDT OBJECTIVE ESTIMATES.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T3.5 - 55 KTS
   KNES: T3.5 - 55 KTS
   DEMS: T4.0 - 65 KTS
   CIMSS ADT: 53 KTS AT 261200Z
   CIMSS AIDT: 57 KTS AT 261200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 25-30 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE WESTWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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 WILL CONTINUE TRACKING 
WESTWARD THROUGH TAU 12 ALONG THE SOUTHERN PERIPHERY OF THE STR TO THE 
NORTH. THE SYSTEM WILL WEAKEN STEADILY DUE TO PERSISTENT HIGH (25-30 
KNOTS) VERTICAL WIND SHEAR. AFTER TAU 12, THE STR WILL WEAKEN AS 
UPPER-LEVEL WESTERLIES SHIFT INTO SOUTHERN CHINA WEAKENING THE STR TO 
THE NORTH WHILE ANOTHER STR OVER THE BAY OF BENGAL EFFECTIVELY BLOCKS 
ANY FURTHER WESTWARD PROGRESSION. CONSEQUENTLY, THE SYSTEM WILL SLOW 
SIGNIFICANTLY AND STALL NEAR THE COAST OF CENTRAL VIETNAM, WHICH WILL 
RESULT IN FURTHER WEAKENING DUE TO FRICTIONAL EFFECTS. AFTER TAU 36, 
TS 22W WILL TRACK EASTWARD ALONG THE NORTHERN PERIPHERY OF A BELT OF 
LOW-LEVEL WESTERLIES THAT FEED INTO THE APPROACHING TROPICAL CYCLONE 
(23W), WITH STEADY DEVELOPMENT AND POSSIBLE DISSIPATION BY TAU 120.      

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE REMAINS IN GOOD 
AGREEMENT ONLY THROUGH TAU 12, WITH INCREASING HIGH UNCERTAINTY AFTER 
TAU 12 AS THE SYSTEM WEAKENS AND THE PRIMARY STEERING INFLUENCE TO THE 
NORTH WEAKENS. PROBABILISTIC GUIDANCE REVEALS A SIMILAR DEGREE OF 
UNCERTAINTY BUT ALSO CONFIRMS THE RAPID WEAKENING OF THE SYSTEM 
THROUGH THE FORECAST PERIOD.   

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