Tropical Storm SANVU Advisory Thu May 24

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 03W (SANVU) WARNING NR 12//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 03W (SANVU), LOCATED APPROXIMATELY 375 NM
SOUTH-SOUTHWEST OF IWO TO, JAPAN, HAS TRACKED NORTH-NORTHWESTWARD AT
08 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS TIGHTLY WRAPPED CONVECTIVE BANDING AROUND THE LOW
LEVEL CIRCULATION CENTER (LLCC). RECENT MICROWAVE IMAGERY SUGGESTS
THAT THE PERIOD OF INTENSIFICATION 12 HOURS AGO HAS LEVELED OFF,
WITH SLIGHTLY LESS DEEP CONVECTION SURROUNDING THE MICROWAVE EYE.
THE INITIAL POSITION WAS BASED ON THE ABOVE ANIMATION AND
EXTRAPOLATED FROM A 242026Z SSMIS MICROWAVE EYE WITH FAIR
CONFIDENCE. THE INITIAL INTENSITY WAS HELD AT 65 KNOTS, BASED ON THE
KNES DVORAK CURRENT INTENSITY ESTIMATE OF 65 KNOTS. UPPER LEVEL
ANALYSIS INDICATES TY 03W IS DIRECTLY UNDER A RIDGE AXIS IN AN AREA
OF LIGHT TO MODERATE (10 TO 15 KNOTS) SOUTH-WESTERLY VERTICAL WIND
SHEAR (VWS). ANIMATED WATER VAPOR SATELLITE IMAGERY REVEALS THAT THE
APPROACHING MID-LATITUDE TROUGH TO THE NORTHWEST IS ENHANCING
POLEWARD OUTFLOW. THE EQUATORWARD OUTFLOW, WHICH WAS VERY ROBUST SIX
HOURS AGO, HAS STEADILY DECREASED. TY 03W IS NOW TRACKING ALONG THE
WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) TO THE EAST. THE
FAVORABLE VWS, FAIR OVERALL OUTFLOW, AND WARM SEA SURFACE
TEMPERATURE (SST) OF 29-30 DEGREES CELSIUS SHOULD ALLOW FOR
CONTINUED DEVELOPMENT.
3. FORECAST REASONING.
   A. THE FORECAST PHILOSOPHY HAS NOT CHANGED SINCE THE PREVIOUS
PROGNOSTIC REASONING BULLETIN.
   B. IN VIEW OF THE FAVORABLE CONDITIONS MENTIONED ABOVE, TY 03W
IS EXPECTED TO CONTINUE INTENSIFYING AS IT ROUNDS THE WESTERN EDGE
OF THE STEERING STR AND BEGINS TO RECURVE TO THE NORTHEAST OVER THE
NEXT 24-36 HOURS. THE STRONG WESTERLIES ASSOCIATED WITH THE
SUBTROPICAL JET STREAM WILL PROVIDE EXCELLENT OUTFLOW PRIOR TO AND
IMMEDIATELY AFTER RECURVATURE. ADDITIONALLY, LIGHT VWS AND WARM SST,
WILL FUEL THE INTENSIFICATION THROUGH TAU 36, AFTER WHICH INCREASING
VWS AND A SHARP DROP IN SST WILL RESULT IN A RAPID DISSIPATION OF TY
03W.
   C. AFTER TAU 72, TY 03W WILL ACCELERATE NORTHEASTWARD AND BEGIN
INTERACTING WITH THE BAROCLINIC ZONE, LOCATED POLEWARD OF 30 DEGREES
NORTH DUE TO A VERY ZONAL SUBTROPICAL JET. THE SYSTEM WILL COMPLETE
EXTRATROPICAL TRANSITION AND BE COMPLETELY EMBEDDED INTO THE
BAROCLINIC ZONE BY TAU 96. THE AVAILABLE NUMERICAL GUIDANCE REMAINS
TIGHTLY PACKED WITH EGRR REMAINING THE SOLE EXCEPTION, WITH A LEFT
OF CONSENSUS DEFLECTION. THIS TRACK FORECAST REMAINS VERY CLOSE TO
MODEL CONSENSUS (CONW), BUT SLIGHTLY FASTER THAN CONW AFTER TAU 48.
THIS IS TO ACCOUNT FOR EGRR'S UNLIKELY LEFTWARD MOTION AND FOR THE
KNOWN TENDENCY OF MODELS TO SLOW DOWN DURING RECURVATURE. THERE IS
HIGH CONFIDENCE IN THE FORECAST TRACK BASED ON MINIMAL SPREAD IN THE
DYNAMIC AID GUIDANCE AND THE ECMWF ENSEMBLE MEMBERS.//
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