Tropical Storm FRANCISCO Advisory Thu Oct 24

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 26W (FRANCISCO) WARNING NR 30//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 26W (FRANCISCO), LOCATED APPROXIMATELY 197 NM SOUTHEAST
OF KADENA AB, HAS TRACKED WEST-NORTHWESTWARD AT 07 KNOTS OVER THE
PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS
THE LOW LEVEL CIRCULATION CENTER (LLCC) HAS REMAINED TIGHTLY WRAPPED
BUT THE DEEP CONVECTION HAS CONTINUED TO STEADILY WEAKEN. A 230413Z
AMSU-B MICROWAVE IMAGE ALSO SHOWS SOME DEVOLVING STRUCTURE AS THE
CORE CONVECTION HAS WEAKENED AND THE LOW LEVEL STRUCTURE HAS STARTED
TO OPEN. THE CURRENT POSITION IS BASED UPON THE MSI LOOP AND RADAR
FIXES FROM RJTD WITH HIGH CONFIDENCE. THE CURRENT INTENSITY HAS BEEN
HELD AT 70 KNOTS BASED ON THE DVORAK INTENSITY ESTIMATES FROM PGTW,
KNES, AND RJTD. UPPER LEVEL ANALYSIS INDICATES A STRONG POLEWARD
OUTFLOW CHANNEL CONTINUES TO BE ENHANCED BY THE MID-LATITUDE
WESTERLIES ALTHOUGH VERTICAL WIND SHEAR (VWS) HAS STARTED TO
INCREASE TO MODERATE (15-20 KNOTS) LEVELS. THE POLEWARD OUTFLOW
CONTINUES TO BE THE DRIVING FORCE FOR THIS SYSTEM AS DRY AIR BEGINS
TO WRAP AROUND THE OUTER PERIPHERIES AND MARGINAL SEA SURFACE
TEMPERATURES (NEAR 26 DEGREES CELSIUS) ARE LOCATED NEAR THE LLCC. TY
26W CONTINUES TO TRACK UNDER THE INFLUENCE OF A DEEP LAYERED
SUBTROPICAL RIDGE (STR) LOCATED TO THE NORTHEAST OF THE SYSTEM.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING.
   B. IN THE NEXT 24 HOURS, TY 26W IS EXPECTED TO SLOW AND TURN
NORTH TO ALONG THE SOUTHWESTERN PERIPHERY OF THE STR AS AN
APPROACHING MID-LATITUDE TROUGH, CURRENTLY LOCATED OVER THE KOREAN
PENINSULA, IS FORECAST TO PROPAGATE EASTWARD TOWARDS JAPAN AND BEGIN
TO PRESS ON THE WESTERN EXTENT OF THE STR. AS TY 26W BEGINS TO GAIN
LATITUDE, THE TROUGH WILL TRACK FURTHER EAST AND PRESS ON THE
MODIFYING STR, WHICH WILL ACCELERATE TY 26W TO THE NORTHEAST.
FURTHER DECREASING SSTS AND INCREASING VWS FROM THE TROUGH WILL LEAD
TO A SLOW WEAKENING TREND THROUGH TAU 72.
   C. AFTER TAU 72, TY 26W WILL CONTINUE TO ACCELERATE TO THE
NORTHEAST UNDER THE INFLUENCE OF THE MODIFYING STR AND PRESSING MID-
LATITUDE TROUGH. FURTHER WEAKENING IS EXPECTED WHILE THE SYSTEM
TRACKS TO THE NORTHEAST AS ENVIRONMENTAL FACTORS CONTINUE TO ERODE
THE SYSTEM. INTERACTION WITH THE BAROCLINIC ZONE AROUND TAU 72 WILL
BEGIN THE EXTRA-TROPICAL TRANSITION PROCESS, WITH COMPLETE
TRANSITION TO A COLD-CORE SYSTEM EXPECTED BY TAU 96. DYNAMIC MODEL
GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 48, LENDING TO HIGH
CONFIDENCE IN THE EARLY PORTION OF THE FORECAST. AFTER TAU 48, THE
MODELS BEGIN TO DIVERGE AS THERE ARE SLIGHT VARIANCES IN THE EXTENT
OF THE STR AS THE TROUGH MOVES INTO THE AREA. DUE TO THIS, LOW
CONFIDENCE REMAINS IN THE EXTENDED FORECAST WHICH IS LAID CLOSE TO,
BUT SLIGHTLY FASTER THAN, MULTI-MODEL CONSENSUS.//
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