WDIO31 PGTW 261500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 04B (SENYAR) WARNING 
NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 3.7N 98.6E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 643 NM SOUTHWEST OF HO CHI MINH CITY,
VIETNAM
   MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE 04B (SENYAR) WITH FLARING DEEP CONVECTION RIGHT ALONG THE
COAST OF SUMATRA, OBSCURING THE LOW-LEVEL CIRCULATION CENTER
(LLCC). ANIMATED RADAR IMAGERY SHOWS A SMALL LLCC STRADDLING THE
COAST BUT HAS LOST SOME DEFINITION OVER THE PAST 6 HOURS. THE
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE
ANIMATED RADAR IMAGERY.  THE INITIAL INTENSITY OF 35 KTS IS
ASSESSED WITH LOW CONFIDENCE BASED PRIMARILY ON PERSISTENCE, THOUGH
CIMSS OBJECTIVE ESTIMATES SUGGEST A SLIGHTLY HIGHER INTENSITY.
ENVIRONMENTAL ANALYSIS INDICATES THAT 04B IS IN AN UNFAVORABLE
ENVIRONMENT CHARCTERIZED BY MODERATE EQUATORWARD OUTFLOW ALOFT,
MODERATE (15-20 KTS) EASTERLY VERTICAL WIND SHEAR, AND TERRAIN
INTERACTION.

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
   CIMSS D-MINT: 37 KTS AT 261109Z
   CIMSS D-PRINT: 41 KTS AT 261200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 15-20 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: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: 04B 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 IN
SUMATRA IS STILL A POSSIBILITY. IF THE SYSTEM IS UNABLE TO KEEP A
SOLID STRUCTURE OVER THE NEXT 12 HOURS, IT MAY NOT HAVE A CHANCE
FOR ANY REDEVELOPMENT. 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 GUIDANCE CONTINUES TO BE IN POOR
AGREEMENT THROUGHOUT THE FORECAST PERIOD. HOWEVER, GFS, HWRF,
HAFS-A, AND COAMPS-TC ALL TAKE THE SYSTEM EASTWARD BACK OVER THE
STRAIT. MANY GLOBAL MODELS LOSE THE VORTEX THOUGH, AND OVERALL
CONFIDENCE IN THE JTWC TRACK FORECAST IS VERY LOW. THE MESOSCALE
MODELS MENTIONED EARLIER ALL GENERALLY AGREE ON REINTENSIFICAITON
TO 40 KTS AT TAU 36 BEFORE DISSIPATING OVER LAND AFTERWARD. THE
JTWC INTENSITY FORECAST IS PLACED CLOSE TO THE MULTI-MODEL
CONSENSUS WITH LOW CONFIDENCE DUE TO THE POSSIBILITY OF AN EARLY
DISSIPATION.

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