01.31.11

Strengthening Tropical Cyclone Yasi

Posted in Non-US Weather, Tropical Weather at 2:47 pm by Rebekah

Yesterday I posted forecasts for a new tropical cyclone, Yasi, that had formed near Vanuatu. Yasi has strengthened considerably over the past 12 or so hours, and is currently a Category 3 severe tropical cyclone on the Australian scale (Category 2 on the Saffir-Simpson scale), with a maximum 10-minute wind speed of 98 mph (156 kph) and a minimum pressure of 960 mb. Maximum wind gusts are estimated to be near 138 mph (221 kph). Yasi is moving westward at 25 mph (40 kph).

Infrared satellite image of Yasi at 1830 Z (4:30 am Australian Eastern Standard Time), from UW-CIMSS (see this website for the latest data such as sea-surface temperatures, wind shear, satellite images, etc.)

Yasi’s track has shifted a bit further north, so the tropical cyclone is now forecast to make landfall Wednesday night / Thursday morning (Australian time) near Cairns/Innisfail, Queensland. Yasi is over some pretty warm waters and a low shear environment (see this blog post for info on how tropical cyclones form and strengthen), so more strengthening is expected.

The Australian Bureau of Meteorology is calling for Yasi to peak in strength late Wednesday afternoon (Australian time) as a Category 4 cyclone (on both the Australian and the Saffir-Simpson scales) with maximum sustained winds of 121 mph (193 kph) and a minimum central pressure of 939 mb. The cyclone may weaken just a bit before making landfall, but it is likely that it will make landfall as a Category 4 storm.

Yasi’s forecast strength and track, issued by the Bureau of Meteorology at 4 am Australian Eastern Standard Time

Surface map forecast for the next few days, from the Bureau of Meteorology

GFS model’s 12Z run (valid at 18Z Wednesday, or 4 am Thursday, Australian Eastern Standard Time), showing a more southern track, more towards Townsville (map from Weather Online UK):

ECMWF model’s 12 run (valid at 12Z Wednesday, or 10 pm, Australian Eastern Standard Time), from Weather Online UK:

To keep up-to-date with the Bureau of Meteorology’s latest forecast tracks and tropical cyclone advice, see the tropical cyclone section of their webpage. Another good website with tropical cyclone tracks and information, that I have yet to mention, is Weather Underground.

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