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发表于 2013-8-20 19:22
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WDPN31 PGTW 200900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01C (PEWA)
WARNING NR 16//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 01C (PEWA), LOCATED APPROXIMATELY 506 NM EAST-
SOUTHEAST OF WAKE ISLAND, HAS TRACKED NORTHWESTWARD AT 11 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS
THE SYSTEM HAS REMAINED COMPACT WITH MOST OF THE CONVECTION TO THE
NORTH OF THE LOW LEVEL CIRCULATION CENTER. THE CONVECTION HAS BECOME
MORE FRAGMENTED AND SHALLOW OVER THE PAST 12 HOURS. THE INITIAL
POSITION IS BASED ON THE ABOVE ANIMATION AND ON A 200511Z SSMI/S
MICROWAVE PASS WITH FAIR CONFIDENCE. THE INITIAL INTENSITY OF 45
KTS IS PLACED AT THE HIGH END OF DVORAK CURRENT INTENSITY ESTIMATES
FROM PGTW, RJTD, AND KNES AND REFLECTS THE WEAKENED STATE OF THE
STORM. UPPER LEVEL ANALYSIS INDICATES THE SYSTEM IS ABOUT 10 DEGREES
SOUTHEAST OF AN UPPER LEVEL LOW (TUTT CELL) IN AN AREA OF MODERATE
TO STRONG (20-30 KNOT) SOUTHWESTERLY VERTICAL WIND SHEAR (VWS).
THERE IS A MODERATE POLEWARD OUTFLOW CHANNEL, AS EVIDENCED ON
ANIMATED WATER VAPOR IMAGERY THAT IS HELPING SUSTAIN THE CONVECTION.
THE CYCLONE IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A
SUBTROPICAL RIDGE (STR) TO THE EAST.
3. FORECAST REASONING.
A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY FROM THE
PREVIOUS PROGNOSTIC REASONING BULLETIN.
B. TS 01C WILL CONTINUE TRACKING NORTHWESTWARD UNDER THE STEERING
INFLUENCE OF THE STR. THE TUTT CELL IS EXPECTED TO BEGIN MOVING
WESTWARD OVER THE NEXT 12 HOURS, DECREASING THE VWS AND INCREASING
THE POLEWARD OUTFLOW. THESE DYNAMICS, COMBINED WITH WARM ALONG-TRACK
SEA SURFACE TEMPERATURES (SSTS), WILL CAUSE THE SYSTEM TO GRADUALLY
RE-INTENSIFY. BY TAU 72, THE SYSTEM WILL REACH MODERATE TYPHOON
STRENGTH.
C. IN THE EXTENDED PERIOD, TS PEWA WILL ENTER A WEAK STEERING
ENVIRONMENT AS AN APPROACHING MID-LATITUDE TROUGH INDUCES A BREAK IN
THE STR. THIS WILL CAUSE THE CYCLONE TO TRACK ON A SLOW WESTWARD
TRAJECTORY. HOWEVER, LOW VWS AND A STRONG POLEWARD OUTFLOW OVER A
POOL OF EVEN WARMER WATER WILL ENHANCE FURTHER INTENSIFICATION. BY
THE END OF THE FORECAST PERIOD, TS 01C WILL BE A STRONG TYPHOON AT
100 KNOTS. THE AVAILABLE NUMERIC GUIDANCE IS IN GOOD AGREEMENT UP TO
TAU 72, LENDING HIGH CONFIDENCE TO THAT PORTION OF THE JTWC TRACK
FORECAST. AFTER TAU 72, THE MODELS SPREAD OUT SIGNIFICANTLY DUE TO
VARIATIONS IN THE SOLUTIONS TO THE IMPACT OF THE AFOREMENTIONED MID-
LATITUDE TROUGH. THERE IS LOW CONFIDENCE IN THE EXTENDED PORTION OF
THE FORECAST. //
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