This blog provides commentary on interesting geological events occurring around the world in the context of my own work. This work is, broadly, geological fluid dynamics. The events that I highlight here are those that resonate with my professional life and ideas, and my goal is to interpret them in the context of ideas I've developed in my research. The blog does not represent any particular research agenda. It is written on a personal basis and does not seek to represent the University of Illinois, where I am a professor of geology and physics. Enjoy Geology in Motion! I would be glad to be alerted to geologic events of interest to post here! I hope that this blog can provide current event materials that will make geology come alive.

Banner image is by Ludie Cochrane..

Susan Kieffer can be contacted at s1kieffer at gmail.com

Friday, April 13, 2012

Severe tornado outbreak predicted for the weekend; record outbreaks

Storms on Friday, 4/13/2012
From weather.com
In a very unusual move, NOAA issued a severe weather/tornado alert two days in advance for this upcoming weekend. I first read of this from Dan's Wild Wild Science Journal on the American Geophysical Union Blogosphere. Dan (Satterfield) is a meteorologist on air who writes a blog for AGU aimed at junior high-school audiences and up.

Unfortunately, Joplin, Missouri, so hard-hit just a year ago, is getting pummeled again with severe weather today and forecast into the weekend.

Here's the NOAA detailed description.

My simplistic view of the spring storm system in the midwest is that cold air from Canada collides with warm air from the Gulf of Mexico, leading to our spring thunderstorms and tornado season.  The scenario for this weekend seems much more complicated.  An "impressive upper-level low" is moving out across the four-corners region (where New Mexico, Arizona, Colorado and Utah come together) at the same time as a powerful mid-level jet stream moves northeastward into the southern and central plains. This means that there is abundant moisture available in the lower layers of the atmosphere, and strong shearing winds at low levels to spin up parts of the storms into tornadoes. The third ingredient in place is a "cap" to hold the warm moist air near the ground until it "explosively" breaks through the cap in severe storms.  The "cap" in this instance is provided by warm dry desert air coming in from the desert southwest four-corner region. The geography then of Canada to the north, the Gulf of Mexico to the south, and the dry desert to the southwest makes the U.S. the tornado capital of the world.

The tornado outbreak from April 25-28, 2011 was the largest tornado outbreak recorded, with 358 tornadoes. In 1974, 148 tornadoes occurred in the U.S. and Canada (see this post on "tornado alley" in Canada.) That earlier outbreak has the distinction of severe tornadoes with 6 F5 and 24 F4 tornadoes.

Other posts on tornadoes: multivortex tornado, Monster Alabama tornado, February 2012 tornado, brutal weather April, 2011.

No comments: