#66 Postby Chacor » Fri May 20, 2011 9:31 am
JTWC discussion:
WDPN31 PGTW 201500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 04W (FOUR)
WARNING NR 02//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
A. TROPICAL STORM (TS) 04W (FOUR), LOCATED APPROXIMATELY 180 NM
EAST-SOUTHEAST OF YAP, HAS TRACKED WEST-NORTHWESTWARD AT 06 KNOTS
OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY SHOWS
THE SYSTEM HAS QUICKLY CONSOLIDATED AS FORMATIVE BANDS WRAPPED
TIGHTER INTO THE LOW LEVEL CIRCULATION CENTER. THE INITIAL POSITION
IS BASED ON THE ABOVE ANIMATION AND EXTRAPOLATED FROM A 200758Z
WINDSAT SCATTEROMETRY PASS WITH POOR CONFIDENCE. THE INITIAL
INTENSITY IS BASED ON A DVORAK ESTIMATE OF 35 KNOTS FROM PGTW. UPPER
LEVEL ANALYSIS INDICATES THE SYSTEM IS JUST TO THE SOUTH OF A RIDGE
AXIS IN AN AREA OF LOW TO MODERATE VERTICAL WIND SHEAR (VWS) AND
GOOD POLEWARD OUTFLOW. THIS IS ALSO EVIDENT ON ANIMATED WATER VAPOR
IMAGERY. TS 04W IS CURRENTLY TRACKING ALONG THE SOUTHWEST PERIPHERY
OF A LOW- TO MID-LEVEL SUBTROPICAL RIDGE (STR) EAST OF JAPAN.
3. FORECAST REASONING
A. THIS IS THE INITIAL PROGNOSTIC REASONING AND SETS THE FORECAST
PHILOSOPHY.
B. TS 04W IS EXPECTED TO CONTINUE ALONG THIS TRACK FOR THE ENTIRE
FORECAST PERIOD. AS THE SYSTEM MOVES FURTHER POLEWARD, ENHANCED
OUTFLOW AND LOWER VWS UNDER THE RIDGE AXIS WILL FAVOR GRADUAL
INTENSIFICATION, FUELED BY WARM SEA SURFACE TEMPERATURES IN THE
PHILIPPINE SEA. AFTER TAU 48, THE STEERING STR WILL MOVE FURTHER
NORTHEAST CAUSING THE SYSTEM TO TRACK ON A MORE NORTHWESTWARD
TRAJECTORY.
C. TS 04W WILL REACH TYPHOON INTENSITY BY TAU 72. A SECONDARY STR
ANCHORED OVER SOUTHERN JAPAN WILL ASSUME STEERING AND CAUSE THE
SYSTEM TO TRACK MORE WESTWARD. GIVEN THE FAVORABLE CONDITIONS, 04W
WILL CONTINUE TO INTENSIFY, REACHING 90 KNOTS BY END OF FORECAST
PERIOD. THE LIMITED NUMERICAL GUIDANCE IS IN FAIR AGREEMENT WITH
THIS TRACK FORECAST.//
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