WDPN31 PGTW 262100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (TRAMI) WARNING NR 
026//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.0N 109.8E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 105 NM NORTHEAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: WESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 32 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
HEAVILY SHEARED TROPICAL STORM 22W, AS IT APPROACHES THE COAST OF
VIETNAM. NEARLY 30 KTS OF VERTICAL WIND SHEAR, COMBINED WITH LAND
INTERACTION IS LEADING TO STEADILY WEAKENING WIND FIELD STRUCTURE
AND INTENSITY. AT THE SAME TIME, DEEP CONVECTION IS STILL
PERSISTENT, PARTICULARLY OVER THE WESTERN PORTION OF THE SYSTEM,
ENHANCED BY A MODERATE WESTWARD OUTFLOW. THE INITIAL POSITION IS
PLACED WITH LOW CONFIDENCE BASED ON ANIMATED INFRARED IMAGERY. THE
INITIAL INTENSITY OF 50 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON 261618Z OSCAT PASS, AS WELL AS OBJECTIVE AND AGENCY
ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.5 - 55 KTS
   KNES: T3.5 - 55 KTS
   DEMS: T4.0 - 65 KTS
   CIMSS SATCON: 58 KTS AT 261630Z
   CIMSS ADT: 43 KTS AT 261800Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   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 FORECAST TO CONTINUE TRACKING
TOWARDS THE VIETNAM COAST, PARTICULARLY THE AREA NEAR THE CITY OF DA
NANG, WHILE BEING STEERED BY A WEAKENING STR TO THE NORTH. AS TS
22W CLOSES ON THE COASTLINE, THE STEERING WILL TRANSITION INTO
ANOTHER STR, LOCATED TO THE WEST OF THE SYSTEM, WHICH WILL
EFFECTIVELY BLOCK ANY FURTHER WESTWARD PROPAGATION. MAJORITY OF THE
MODEL GUIDANCE SUGGESTS THAT THE SYSTEM WILL THEN RE-CURVE OVER THE
SOUTH CHINA SEA. INTENSE VERTICAL WIND SHEAR, LOWERING SEA SURFACE
TEMPERATURES, AS WELL AS LAND INTERACTION WILL CAUSE TS 22W TO
STEADILY WEAKEN THROUGHOUT THE FORECAST PERIOD.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT
ONLY THROUGH THE INITIAL 12 HOURS, AS THE SYSTEM HEADS TOWARDS THE
COAST. FURTHER OUT, UNCERTAINTY IS INCREASING, PARTICULARLY IN
REGARD TO THE TRACK OF THE SYSTEM, WHICH ALMOST EVERY MODEL PAINTS
A DIFFERENT PICTURE FOR, WITH SOME, LIKE GFS OR NAVGEM, TAKING THE
SYSTEM DEEPER INLAND, WHILE OTHERS ONLY GRAZING THE COAST AND
RE-EMERGING OVER WATER. INTENSITY GUIDANCE IS MORE CONSISTENT, WITH
NEARLY ALL MODELS PREDICTING STEADY WEAKENING, WITH POTENTIAL FOR
DISSIPATION TOWARDS THE END OF 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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