Tropical Storm HAISHEN Advisory Mon Apr 06

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 05W (HAISHEN) WARNING
NR 10//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 05W (HAISHEN), LOCATED APPROXIMATELY 103 NM
NORTHWEST OF CHUUK, HAS TRACKED WEST-SOUTHWESTWARD AT 03 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
(MSI) SHOWS THE SYSTEM HAS MAINTAINED LIMITED CONVECTIVE WRAPPING
INTO THE FULLY EXPOSED LOW LEVEL CIRCULATION CENTER WITH THE DEEP
CONVECTION SHEARED TO THE EAST. THE INITIAL POSITION IS BASED ON THE
MSI LOOP WITH HIGH CONFIDENCE. THE INITIAL INTENSITY OF 40 KNOTS IS
BASED ON AN OVERALL ASSESSMENT OF DVORAK ESTIMATES FROM ALL
REPORTING AGENCIES. UPPER-LEVEL ANALYSIS INDICATES A MARGINAL
ENVIRONMENT WITH HIGH (20 TO 30 KNOT) SOUTHWESTERLY VERTICAL WIND
SHEAR (VWS) AND SOME POLEWARD OUTFLOW. TS 05W IS CURRENTLY TRACKING
WESTWARD ALONG THE SOUTHEASTERN PERIPHERY OF A WEAKENING EXTENSION
OF THE SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. OVER THE NEXT 6 HOURS AND THROUGH THE END OF THE FORECAST
PERIOD, THE STEERING ENVIRONMENT FOR TS HAISHEN IS VERY COMPLEX. THE
STR TO THE NORTHWEST WILL CONTINUE TO BUILD AND PREVENT THE SYSTEM
FROM MORE WESTWARD MOVEMENT BEYOND TAU 24. ADDITIONALLY, A NEAR
EQUATORIAL RIDGE BUILDING TO THE SOUTHEAST WILL TRY TO FORCE THE
SYSTEM TO THE EAST-NORTHEAST. FINALLY, A DEEP MID-LATITUDE TROUGH TO
THE NORTHEAST FURTHER COMPLICATES THE STEERING ENVIRONMENT. AS SUCH,
TS 05W IS EXPECTED TO REMAIN IN A VERY SLOW OR QUASI-STATIONARY
MOTION, TRACKING A MAXIMUM OF 100 NM OVER THE NEXT 48 HOURS.
THROUGHOUT THE FORECAST, INCREASING VWS WILL ERODE THE SYSTEM, WITH
COMPLETE DISSIPATION BY TAU 48. THERE REMAINS A SIGNIFICANT
VARIATION IN THE DYNAMIC MODEL GUIDANCE LEADING TO LOW CONFIDENCE IN
THE JTWC FORECAST TRACK.//
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