Tropical Storm FENGSHEN Advisory mié, 13-11

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 26W (FENGSHEN)
WARNING NR 004//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 26W (FENGSHEN), LOCATED APPROXIMATELY
924 NM EAST OF ANDERSEN AFB, GUAM, HAS TRACKED WEST-NORTHWESTWARD AT
16 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI) DEPICTS A BROAD, EXPOSED LOW LEVEL CIRCULATION (LLC)
WITH AN AREA OF DEEP CONVECTION SHEARED TO THE WEST. THE POSITION IS
BASED ON MSI AND A 120621Z SSMIS 91GHZ COMPOSITE IMAGE AND IS PLACED
WITH FAIR CONFIDENCE. THE CURRENT INTENSITY OF 30 KNOTS IS BASED ON
A PGTW DVORAK CURRENT INTENSITY ESTIMATE OF 2.0/30KTS. TROPICAL
DEPRESSION FENGSHEN IS TRAVELING ALONG THE SOUTHERN PORTION OF THE
SUBTROPICAL RIDGE (STR) AND IS IN A MARGINALLY FAVORABLE AREA FOR
FURTHER DEVELOPMENT WITH WARM (28-29 CELSIUS) SEA SURFACE
TEMPERATURES, MARGINAL (15-20 KNOTS) VERTICAL WIND SHEAR (VWS) AND
EASTERLY OUTFLOW ALOFT.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TD 26W WILL CONTINUE TO TRACK GENERALLY WEST-NORTHWESTWARD
UNDER THE STR UP TO TAU 60 WHEN IT WILL BEGIN TO CURVE POLEWARD. THE
FAVORABLE ENVIRONMENTAL CONDITIONS WILL GRADUALLY INTENSIFY THE
SYSTEM TO 80 KNOTS BY TAU 72. NUMERICAL MODELS ARE IN GOOD AGREEMENT
THROUGH TAU 72 WITH ECMWF THE SOLE OUTLIER AS IT SHOWS VERY WEAK
DEVELOPMENT OF THE SYSTEM PAST TAU 48. OTHERWISE, THERE IS GOOD
AGREEMENT BETWEEN THE OTHER MEMBERS OF THE MULTI-MODEL CONSENSUS
LENDING A HIGH DEGREE OF CONFIDENCE IN THIS PORTION OF THE JTWC
FORECAST TRACK.
   C. AFTER TAU 72, TD 26W WILL RECURVE TOWARDS THE NORTH-NORTHEAST
AND GRADUALLY WEAKEN IN RESPONSE TO THE MID-LATITUDE TROUGH
APPROACHING FROM THE NORTHWEST AND THE STRONG WESTERLY FLOW IT WILL
ENCOUNTER. IT WILL THEN CREST THE STR AXIS AND ACCELERATE EAST-
NORTHEASTWARD ALONG THE NORTH SIDE OF THE STR. STRONG WESTERLY WINDS
WILL PRODUCE INCREASINGLY UNFAVORABLE VWS (25-40 KNOTS). THIS, ALONG
WITH SLIGHTLY COOLER SSTS, WILL RESULT IN A MORE SIGNIFICANT
REDUCTION IN INTENSITY. BY TAU 96, TD 26W WILL BEGIN EXTRA-TROPICAL
TRANSITION AS IT BEGINS TO INTERACT WITH THE BAROCLINIC ZONE.
NUMERICAL MODELS DIVERGE AND ARE IN POOR AGREEMENT LENDING LOW
OVERALL CONFIDENCE IN THE JTWC FORECAST TRACK.//
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