Tropical Storm ISIS
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TROPICAL STORM ISIS DISCUSSION NUMBER 21
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2 AM PDT MON SEP 13 2004
A 530 UTC QUICK SCAT PASS SHOWS THAT THE LOW LEVEL CIRCULATION
REMAINS ON THE EAST SIDE OF THE DEEP CONVECTION. ISIS REMAINS
SIGNIFICANTLY SHEARED BUT IS STILL A 45 KT TROPICAL STORM...AS
CLASSIFIED BY TAFB AND SAB ESTIMATES.
THE INITIAL MOTION IS 270/9. ISIS HAS BEEN MOVING DUE WESTWARD ON
THE SOUTH SIDE OF A MID-PACIFIC RIDGE. THE RIDGE IS FORECAST TO
INTENSIFY AND BLOCK THE MOTION OF ISIS IN ABOUT 36 TO 48 HOURS. THE
MODEL GUIDANCE SUPPORTS THIS SCENARIO AND THE BLOCKING PATTERN IS
REFLECTED IN THE...SQUASHED SPIDER...GUIDANCE PATTERN. ISIS SHOULD
BECOME QUASI-STATIONARY AFTER 48 HOURS AND IF THE SHEAR IS STILL
PRESENT AT THAT TIME THE SYSTEM MAY MEET ITS DEMISE AND BECOME A
REMNANT LOW. ON THE OTHER HAND IF THE SHEAR IS LIGHT...ISIS MAY BE
ABLE TO SURVIVE FOR SEVERAL MORE DAYS. I AM ASSUMING THE SHEAR WILL
BE LIGHT AND ISIS WILL ACTUALLY REMAIN A 45 TO 50 KT STORM AS PER
THE SHIPS GUIDANCE.
FORECASTER JARVINEN
FORECAST POSITIONS AND MAX WINDS
INITIAL 13/0900Z 17.4N 126.2W 45 KT
12HR VT 13/1800Z 17.4N 127.5W 45 KT
24HR VT 14/0600Z 17.4N 129.3W 50 KT
36HR VT 14/1800Z 17.5N 130.4W 50 KT
48HR VT 15/0600Z 17.6N 131.2W 50 KT
72HR VT 16/0600Z 17.7N 131.6W 50 KT
96HR VT 17/0600Z 17.8N 131.9W 50 KT
120HR VT 18/0600Z 18.0N 132.2W 50 KT
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