WDPN31 PGTW 270900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (TRAMI) WARNING NR 
028//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.1N 107.8E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 29 NM WEST-NORTHWEST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 07 KTS

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM (TS) 22W MADE LANDFALL OVER VIETNAM BETWEEN DA NANG
(VVDN) AND HUE (VVPB) AT APPROXIMATELY 270300Z AND HAS DRIFTED SLOWLY 
INLAND OVER THE PAST FEW HOURS. ANIMATED ENHANCED INFRARED SATELLITE 
IMAGERY (EIR) DEPICTS A RAPIDLY ERODING LOW-LEVEL CIRCULATION (LLC) 
WITH WARMING CLOUD TOP TEMPERATURES AND A WEAKENING CONVECTIVE 
STRUCTURE. A 270241Z ASCAT-B IMAGE PROVIDES CLEAR EVIDENCE THAT THE 
LLCC IS NOW OVER VIETNAM AND SHOWS 35 TO 40 KNOT SOUTHERLY TO EAST-
SOUTHERLY WINDS OVER WATER. THE CENTER APPEARS TO BE LOCATED WEST-
NORTHWEST OF DA NANG, WHICH IS REPORTING SUSTAINED SOUTH-SOUTHEASTERLY 
WINDS AT 10-15 KNOTS. HUE'S SURFACE WINDS HAVE SHIFTED FROM 
NORTHEASTERLY TO NORTHERLY BUT ARE RELATIVELY LIGHT. RADAR IMAGERY 
SHOWS CYCLONIC TURNING WEST OF DA NANG AND INDICATES A WEAK LLCC AND 
QUASI-STATIONARY MOTION. A 270226Z MHS 89GHZ MICROWAVE IMAGE SHOWS 
LIMITED CURVED BANDING OVER THE WESTERN QUADRANT OF THE LLC, 
SUPPORTING THE INITIAL POSITION WITH MEDIUM CONFIDENCE. THE INITIAL 
INTENSITY IS ASSESSED AT 40 KNOTS WITH MEDIUM CONFIDENCE BASED ON THE 
ASCAT DATA, CONSISTENT WITH THE WEAKENING TREND.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: WEAK, COMPETING STEERING ENVIRONMENT WITH 
A SUBTROPICAL RIDGE (STR) TO THE WEST AND NORTHEAST, AND A SWATH OF 
WESTERLIES TO THE SOUTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   RJTD: T3.0 - 45 KTS
   RCTP: T3.0 - 45 KTS
   CIMSS SATCON: 46 KTS AT 270500Z
   CIMSS AIDT: 34 KTS AT 270500Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 20-25 KTS
   SST: OVER LAND
   OUTFLOW: MODERATE WESTWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 22W IS LOCATED WITHIN A REGION OF WEAK
STEERING AND IS EXPECTED TO MAINTAIN QUASI-STATIONARY TRACK MOTION 
THROUGH TAU 24. STEADY WEAKENING WILL OCCUR THROUGH THIS PERIOD DUE TO 
INTERACTION WITH LAND AND PERSISTENT EASTERLY VERTICAL WIND SHEAR. 
AFTER TAU 24, THE SYSTEM IS FORECAST TO DRIFT EASTWARD ALONG THE 
NORTHERN PERIPHERY OF THE LOW-LEVEL WESTERLIES AND SHOULD MOVE BACK 
OVER WATER BY THE TAU 36 TO TAU 48 PERIOD. THE SYSTEM WILL LIKELY 
DISSIPATE BUT COULD LINGER NEAR TROPICAL DEPRESSION STRENGTH.  

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE SHOWS A SQUASHED SPIDER
PATTERN WITH DETERMINISTIC GUIDANCE GENERALLY INDICATING A HIGHLY
UNCERTAIN, ERRATIC TRACK MOTION THROUGH THE FORECAST PERIOD. ALL 
GUIDANCE EVENTUALLY BRINGS THE SYSTEM BACK OVER WATER BUT THE EXACT 
TRACK MOTION VARIES CONSIDERABLY. THE MOST RECENT EPS AND GEFS 
PROBABILISTIC GUIDANCE ALSO SHOWS A SIMILAR TRACK PATTERN WITH THE 
BULK OF SOLUTIONS TRACKING THE SYSTEM BACK OVER WATER AS A WEAK 
TROPICAL DEPRESSION OR TROPICAL DISTURBANCE.   

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