WDPN31 PGTW 160900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 14W (BANYAN) WARNING NR
22//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 14W (BANYAN), LOCATED APPROXIMATELY 810 NM
NORTHEAST OF MINAMI TORI SHIMA, JAPAN, HAS TRACKED NORTHEASTWARD AT
28 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY SHOWS THE CENTRAL CONVECTION HAS BECOME MORE SHALLOW AND
SHEARED NORTHEASTWARD OF THE LOW LEVEL CIRCULATION CENTER. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A WELL-
DEFINED LOW REFLECTIVITY CIRCULATION FEATURE IN THE 160504Z SSMIS
MICROWAVE PASS. THE INITIAL INTENSITY OF 55 KNOTS IS BASED ON AN
OVERALL ASSESSMENT OF AGENCY AND OBJECTIVE DVORAK CURRENT INTENSITY
ESTIMATES AND REFLECTS THE WEAKENED STATE OF THE CYCLONE.
ENVIRONMENTAL ANALYSIS INDICATES AN INCREASINGLY UNFAVORABLE
ENVIRONMENT WITH MODERATE (15-20 KNOT) VERTICAL WIND SHEAR (VWS) AND
COOLING (25 CELSIUS) SEA SURFACE TEMPERATURES (SST). HOWEVER,
POLEWARD OUTFLOW HAS INCREASED BUT NOT ENOUGH TO OFFSET THE
WEAKENING TREND. THE CYCLONE IS TRACKING NORTHEAST ALONG THE
NORTHWESTERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR)
LOCATED TO THE SOUTHEAST.
3. FORECAST REASONING.
A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
B. TS BANYAN IS FORECAST TO CONTINUE TO ACCELERATE NORTHEASTWARD
ALONG THE NORTHWESTERN EXTENT OF THE STR. INCREASING VWS COMBINED
WITH COOLER ALONG-TRACK SST WILL GRADUALLY ERODE THE SYSTEM.
CONCURRENTLY, TS 14W HAS COMMENCED EXTRA-TROPICAL TRANSITION AS IT
GETS EMBEDDED DEEPER INTO THE BAROCLINIC ZONE, BECOMING A GALE-FORCE
COLD CORE LOW BY TAU 24. DYNAMIC MODEL GUIDANCE REMAINS IN STRONG
AGREEMENT, LENDING HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.//
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