WDPN32 PGTW 311500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 27W (BANYAN) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 7.2N 131.6E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 119 NM NORTH-NORTHWEST OF SONSOROL
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
OVER THE PAST SIX HOURS ANIMATED ENHANCED INFRARED (EIR) SATELLITE
IMAGERY INDICATES THAT TROPICAL STORM 27W (BANYAN) HAS CONTINUED TO
HOLD TOGETHER SURPRISINGLY WELL, AS THE SYSTEM HAS RETAINED A SMALL
CENTRAL DENSE OVERCAST OF DEEP CONVECTION OBSCURING THE LOW LEVEL
CIRCULATION CENTER (LLCC). THE OVERALL ENVIRONMENT IS
MARGINAL, WITH WARM (29-30C) SEA SURFACE TEMPERATURES (SSTS) AND
STRONG EQUATORWARD OUTFLOW BEING OFFSET BY STRONG NORTHEASTERLY
FLOW ALOFT AROUND THE SYSTEM. HOWEVER, IN THE MIDST OF STRONG AND 
PERSISTENT NORTHEASTERLY FLOW ALOFT, THE CONVECTIVE BURST HAS ENABLED 
A SMALL REGION OF RELATIVELY LESS SHEAR ALLOWING THE SYSTEM TO 
MAINTAIN A CURRENT INTENSITY OF 35 KTS. THE INITIAL POSITION IS PLACED 
WITH MEDIUM CONFIDENCE BASED ON ANIMATED EIR, AND THE PGTW FIX 
POSITION FIX. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE PGTW, RJTD, AND KNES DVORAK INTENSITY
ESTIMATES ALONG WITH A COMBINATION OF OBJECTIVE DVORAK INTENSITY
ESTIMATES.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTH. 


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T4.0 - 65 KTS
   CIMSS SATCON: 38 KTS AT 311043Z
   CIMSS ADT: 37 KTS AT 311140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM 27W HAS GRADUALLY TURNED AND
TRACKED TOWARD THE WEST-NORTHWESTWARD ON THE SOUTHERN PERIPHERY OF A 
DEEP-LAYER SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTH. BY TAU
12, THE SYSTEM IS EXPECTED TO TRACK TOWARD THE NORTHWESTWARD AS THE
STEERING RIDGE TO THE NORTH IS FORECAST TO REORIENT TO A
NORTHWEST-SOUTHEAST DIRECTION, THIS WILL ALLOW THE SYSTEM TO STAY A
NORTHWESTWARD TRACK THROUGH THE END OF THE FORECAST PERIOD. THE
JTWC INTENSITY FORECAST CALLS FOR THE SYSTEM TO MAINTAIN ITS
CURRENT TS STRENGTH OVER THE NEXT 12 HOURS UNDER MARGINAL
CONDITIONS. HOWEVER, THE UPPER LEVEL ENVIRONMENT IS FORECAST TO
BECOME LESS FAVORABLE DUE TO UPPER-LEVEL CONVERGENCE, ALONG WITH
MID-LEVEL DRY AIR ENTRAINMENT. THESE UNFAVORABLE ENVIRONMENTAL
CHARACTERISTICS WILL RESULT IN A SLOW WEAKENING TREND AFTER TAU 12.
THE ENVIRONMENTAL CONDITIONS WILL CONTINUE TO DEGRADE FURTHER WITH
DISSIPATION JUST TO THE EAST OF THE SOUTHEASTERN PHILIPPINES BY TAU
48.  

MODEL DISCUSSION: THE TRACK GUIDANCE IS IN OVERALL GOOD AGREEMENT
WITH THE EXCEPTION OF THE JGSM MODEL TRACKER WHICH REPRESENTS THE
EASTERN EDGE OF THE GUIDANCE ENVELOPE. THE MINIMAL SPREAD IN TRACK
GUIDANCE LENDS HIGH CONFIDENCE TO THE JTWC FORECAST TRACK. THE
INTENSITY GUIDANCE REMAINS MIXED, AS COTI, CTCI, AND HWRF INDICATE
A FLAT INTENSITY TREND THROUGH ABOUT TAU 12 FOLLOWED BY STEADY
WEAKENING BY THE END OF THE FORECAST. WITH THE DECAY-SHIPS (BOTH GFS 
AND NAVGEM) INTENSIFYING THE SYSTEM UNREALISTICALLY TO A PEAK OVER 55 
KNOTS. THEREFORE, THE JTWC FORECAST IS PLACED CLOSER TO THE COTI, 
CTCI, AND HWRF INTENSITY SOLUTIONS AND JUST ABOVE THE MULTI-MODEL 
CONSENSUS THROUGHOUT THE FORECAST.  

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