WDPN32 PGTW 312100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 27W (BANYAN) 
WARNING NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 7.4N 130.3E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 169 NM NORTHWEST OF SONSOROL
   MOVEMENT PAST 6 HOURS: WESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
STRUGGLING SYSTEM WITH DISORGANIZED CONVECTION TO THE
WEST-SOUTHWEST OF AN ASSESSED LOW LEVEL CIRCULATION CENTER (LLCC).
A PARTIAL 311252Z ASCAT-B PASS REVEALS WHAT APPEARS TO BE AN
ELONGATED CIRCULATION EXTENDING EASTWARD. COMPARISON BETWEEN THE
89GHZ AND 36GHZ 311636Z AMSR2 PASS INDICATES NO RELEVANT STRUCTURE.
THE INITIAL POSITION IS PLACED WITH LOW CONFIDENCE BASED OFF
MULTI-AGENCY FIXES AND EIR LOOP. THE INITIAL INTENSITY IS PLACED
WITH MEDIUM CONFIDENCE BASED OF MULTI-AGENCY DVORAK ESTIMATES.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF THE SUBTROPICAL
RIDGE (STR) TO THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   CIMSS SATCON: 42 KTS AT 311708Z
   CIMSS ADT: 35 KTS AT 311910Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG 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: TROPICAL STORM BANYAN IS CURRENTLY STRUGGLING
AS IT TRANSITS WESTWARD ALONG THE SOUTHERN PERIPHERY OF THE STR.
ALTHOUGH OVER WARM SSTS, ANALYSIS OF THE UPPER-LEVEL WIND FLOW
SHOWS A SMALL POCKET OF 40 KNOTS OVER THE SYSTEM. THE CONSISTENT
WIND SHEAR TS BANYAN HAS EXPERIENCED CAUSED THE MID-TO-UPPER LEVELS
TO TILT. THE MID-LEVEL (700 MB) AXIS IS NOW DISPLACED TO THE
SOUTHWEST WHICH IS CAUSING TS BANYAN TO LOSE SUPPORT. AS THE SYSTEM
TRANSITS TO THE WEST IT WILL CONTINUE TO WEAKEN AND BECOME FULLY
DISSIPATED OVER WATER JUST EAST OF THE SOUTHERN PHILIPPINES BY TAU
36. DRY AIR ENTRAINMENT ALONG WITH AN INCREASE IN VWS SHEAR (25-30
KTS) WILL ASSIST IN THE DISSIPATION OF TS BANYAN.

MODEL DISCUSSION: THE GFS VORTEX-AVERAGED SKEW-T MODEL INDICATES
MID-TO-LOW LEVEL DRY AIR BEING ENTRAINED INTO THE SYSTEM FROM THE
NORTH BETWEEN THE 500 AND 800 MB LEVELS. THE NUMERICAL MODEL TRACK
GUIDANCE THROUGH TAU 24 IS IN GOOD AGREEMENT WITH A 44 NM SPREAD BY
THIS TIME. HOWEVER, BY TAU 36, THE MODEL SPREAD SIGNIFICANTLY
INCREASES TO 100 NM WITH NAVGEM AND JGSI BEING THE OUTLIERS
SHOWING A MORE NORTHERLY TRACK. BASED ON THIS, THE JTWC FORECAST
TRACK IS PLACED WITH MEDIUM CONFIDENCE. THE INTENSITY MODEL
GUIDANCE IS SOMEWHAT SPREAD APART WITH GFS AND COAMPS SHOWING THE
MOST REASONABLE SOLUTIONS. DUE TO THIS, THE JTWC INTENSITY FORECAST
IS SET WITH MEDIUM CONFIDENCE.

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