Tropical Storm TWELVE Advisory Fri Jul 24

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (TWELVE) WARNING NR
06//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 12W (TWELVE), LOCATED APPROXIMATELY 270 NM
NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED EASTWARD AT 05
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY SHOWS FLARING CONVECTION SURROUNDING A PARTIALLY EXPOSED LOW
LEVEL CIRCULATION CENTER (LLCC). WATER VAPOR IMAGERY SHOWS THE
OUTFLOW BANDS FROM TY 01C APPROACHING TS 12W FROM THE NORTHEAST,
BEGINNING THEIR INTERACTION. A 240951Z CORIOLIS MICROWAVE IMAGE
SHOWS A TIGHT WELL-DEFINED LLCC WITH SHALLOW BANDING WRAPPING IN
FROM THE NORTHERN PERIPHERY. UPPER LEVEL ANALYSIS INDICATES A
MARGINAL ENVIRONMENT WITH MODERATE VERTICAL WIND SHEAR (VWS) AND
WEAK EQUATORWARD OUTFLOW. THE INITIAL POSITION IS EXTRAPOLATED FROM
THE LLCC IN THE MICROWAVE IMAGE AND SUPPORTED BY A PGTW SATELLITE
FIX WITH FAIR CONFIDENCE. THE CURRENT INTENSITY IS HELD AT 40 KNOTS
BASED ON PERSISTENCE AND NO SIGNIFICANT CHANGE IN THE SYSTEM'S
STRUCTURE. TS 12W IS TRACKING SLOWLY EASTWARD WITHIN STRONG LOW TO
MID-LEVEL WESTERLY FLOW TO THE SOUTH.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE. THE CURRENT INTENSITY HAS BEEN
INCREASED DUE TO THE AFOREMENTIONED SCATTEROMETER PASS.
   B. TS 12W WILL CONTINUE TO TRACK SLOWLY EAST AND THEN TURN
NORTHEASTWARD AS THE EXTENSION OF THE STEERING RIDGE TO THE
SOUTHEAST BUILDS IN THROUGH TAU 24. MARGINAL ENVIRONMENTAL
CONDITIONS WILL PROHIBIT SIGNIFICANT DEVELOPMENT OF THE CYCLONE AS
IT GAINS LATITUDE. IN ADDITION, INCREASED VWS AND SUBSIDENCE CAUSED
BY THE INTERACTION WITH TY 01C WITH FURTHER DETERIORATE THE UPPER
LEVEL ENVIRONMENT. THE SYSTEM WILL BEGIN TO ACCELERATE POLEWARD AS
ITS TRACK IS INFLUENCED BY TY 01C PASSING TO THE NORTH. TS 12W WILL
CONTINUE TO WEAKEN DUE TO THE POOR ENVIRONMENTAL FACTORS, LEADING TO
ITS DISSIPATION BY THE END OF THE FORECAST PERIOD. DYNAMIC MODEL
GUIDANCE IS IN FAIR AGREEMENT WITH A HIGH DEGREE OF UNCERTAINTY DUE
TO TY 01C PASSING TO THE NORTH. DUE TO THE CONTINUED MODEL SPREAD,
THERE IS LOW CONFIDENCE IN THE JTWC FORECAST.//
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