Amazing Mammatus

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Announcement: Columbus Day Storm 50th Anniversary Gala at the UW: Oct. 11, 7:30 PM

On Thursday evening, October 11 at 7:30 PM, the UW will host a gathering to review and remember the 1962 Columbus Day Storm (October 12th will be the 50th anniversary).  I will discuss the major aspects of the storm and windstorm chronicler Wolf Reed will tell even more.  The Mt. Hebo radar dome broke apart that night as winds gusted above 150 mph, and we will have an eye witness account.  And there will be time for your comments, questions, or stories.  Steve Pool of KOMO TV will MC.  This meeting should be great fun will take place in Kane 120 on the UW Seattle campus.  You need to register for this if you want to go, since I expect it to fill.  To do so, go here.  The gathering is free, but the expenses are being covered by my research fund, so any contributions to offset the costs are very welcome. 

Sometimes the atmosphere produces images that leaves ones jaw agape.  Yesterday was such a day.  Many of you noticed a huge thunderstorm along the eastern slopes of the Cascades...a storm so tall (reaching roughly 35,000 ft) that it was easily visible from much of western Washingtion. (here is a picture taken by John Caldwell from Seattle.

This storm had a very large and prominent anvil, under which there was the most extraordinary field of mammatus clouds.  Here are some stunning pictures sent to me by John Stimberis of these features:

Pretty amazing pictures.   Some of you also saw some mammatus clouds on this side of the Cascades associated with the modest mid-level convection that moved over Seattle mid-day.

Why do we get these types of clouds?    They represent upside down convection...clouds that get cooler or heavier than their environment and convect downward...that is they sink!  Mammatus cloud are often associated with thunderstorm anvils. As updrafts carry precipitation-filled air to the thunderstorm top, upward momentum is lost and the air begins to spread out horizontally, becoming a part of the anvil cloud. Because of its high concentration of precipitation particles, the saturated air is heavier than the surrounding air and sinks back towards the earth. Evaporation and melting at the bottom of the cloud layer can also lead to cooling and downward convection.

Well you can't say this blog is not titillating.

No thunderstorms today on the eastern Cascade slopes...and the coming week does not look very unstable.

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