WDIO31 PGTW 260900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 04B (SENYAR) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 3.9N 98.2E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 939 NM SOUTHWEST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE 04B WITH PERSISTENT BURSTS OF CONVECTION ALONG THE NORTHERN
PERIPHERY OF A SMALL LOW-LEVEL CIRCULATION CENTER JUST OVER LAND
WITHIN NORTHERN SUMATRA. ANIMATED RADAR IMAGERY REVEALED THE SYSTEM
HAS TRACKED SOUTHWESTWARD, ALONG THE COAST RATHER THAN FURTHER
INLAND. THIS SOUTHWARD TRACK IS LIKELY DUE TO DEFLECTION FROM THE
MOUNTAINS TO THE WEST OF 04B. THE INITIAL POSITION IS PLACED WITH
MEDIUM CONFIDENCE BASED ON THE SMALL LLCC IN ANIMATED RADAR
IMAGERY. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH LOW
CONFIDENCE BASED ON THE T2.5 ESTIMATE FROM DEMS AND GENERAL
WEAKENING TREND OVER LAND.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: STEERED PRIMARILY BY THE LOW TO
MID-LEVEL STRONG WESTERLY INFLUENCE TO THE SOUTH OF THE VORTEX.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   DEMS: T2.5 - 35 KTS
   CIMSS D-MINT: 48 KTS AT 260651Z
   CIMSS D-PRINT: 44 KTS AT 260700Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 20-25 KTS
   SST: OVER LAND
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: LAND INTERACTION

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE FORECAST IS EXTENDED TO 48 HOURS,
NOW CALLING FOR BRIEF INTENSIFICATION WITHIN THE MALACCA STRAIT
BEFORE MAKING LANDFALL ALONG THE WESTERN COAST OF MALAYSIA

FORECAST DISCUSSION: 33W IS FORECAST TO MAKE A TURN EASTWARD AS THE
LOW TO MID-LEVEL WESTERLY STEERING INFLUENCE TAKES THE SYSTEM BACK
OVER THE MALACCA STRAIT. A LANDFALL ALONG THE WESTERN COAST OF
MALAYSIA IS THEN FORECAST TO OCCUR AROUND TAU 48. THIS FORECAST IS
PLACED WITH LOW CONFIDENCE AND A COMPLETE DISSIPATION OVER LAND IS
STILL A POSSIBILITY. 04B IS FORECAST TO KEEP A DISTANCE FROM THE
MOST MOUNTAINOUS TERRAIN OF NORTHERN SUMATRA, ALLOWING THE SYSTEM
TO MAINTAIN INTENSITY THROUGH TAU 24. AFTER TAU 24, THE MORE
FAVORABLE ENVIRONMENT BACK OVER WATER IS EXPECTED TO INTENSIFY 04B
AS IT APPROACHES THE COAST. THE SYSTEM IS THEN EXPECTED TO RAPIDLY
WEAKEN AS IT MAKES A FINAL LANDFALL OVER MALAYSIA. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE CONTINUES TO BE IN
POOR AGREEMENT, BUT GENERALLY AGREE ON AN EASTWARD TRACK TO VARYING
DEGREES. THE JTWC TRACK FORECAST IS PLACED CLOSER TO THE GFS
ENSEMBLE MEAN WITH LOW CONFIDENCE. HAFS-A, HWRF, AND COAMPS-TC (GFS
BASED) MODELS ALL ACTUALLY DEPICT A SIMILAR TRACK BACK OVER WATER,
AND SHOW REINTENSIFICATION TO AROUND 40 KTS AT TAU 36. THE JTWC
INTENSITY FORECAST FOLLOWS THE HAFS-A AND HWRF MODELS WITH LOW
CONFIDENCE. 

FORECAST CONFIDENCE:
   TRACK 00-72 HR: LOW
   INTENSITY 00-72 HR: LOW//
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