Thought I would touch on just how steamy the air is from west Kansas to Delaware and from Louisiana to the UP of Michigan currently.

Chicago Just Got Its First Tornado in Almost 10 Years

ARTICLE FROM WEATHER.COM

A weak tornado called a landspout was seen over Chicago on Tuesday.

This is the first tornado in the city of Chicago since 2006.

A tornado touched down in Chicago on Tuesday, but apparently it produced no damage and wasn’t even accompanied by a thunderstorm.

The bizarre, dusty funnel, known as a landspout, was visible from Chicago’s Midway Airport just before 4 Thursday afternoon for about 10 minutes and was photographed by several commuters in Chicagoland.

According to the National Weather Service, the landspout touched down in about a two-block area on the city’s near southwest side, south of Ogden Avenue. No damage was reported.

It could be seen from the top of Chicago’s tallest skyscraper, the Willis Tower.

This was the first tornado of any kind in the city limits of Chicago since an F0 tornado downed trees and limbs on the Loyola University campus on Sept. 22, 2006, according to the National Weather Service.

From 1954-April 2016, there have been 54 tornadoes in Cook County, according to NOAA’s Storm Events Database.

While a landspout is technically a tornado, it differs from what you may consider a tornado.

Landspouts don’t need a parent thunderstorm with a rotating updraft. They form when a developing towering cumulus cloud occurs over any near-surface boundary of converging winds.

(WATCH: What is a Landspout?)

In Chicago’s case, it was the lake-breeze boundary separating air cooled by Lake Michigan with easterly winds from hotter air over inland locations with winds blowing from the west or southwest.

The boundary, therefore, features very slowly rotating air. Once the growing cumulus cloud’s upward motion passes over the boundary, that slowly rotating air becomes stretched vertically and accelerates into what became the landspout.

They are essentially waterspouts over land.

Most landspouts are fairly weak and short-lived. On occasion, they can do minor damage. They are most common in the High Plains, Colorado in particular.

One recent, photogenic landspout damaged a farm near Peetz, Colorado, in late May.

New photos from our WGN-TV west cam on top of Willis Tower of Tuesday’s 10 minute, lake-breeze-induced “landspout” tornado over Midway Airport–the city’s first twister since the Loyola University shoreline touchdown on the North Side Sept. 22, 2006

by Tom Skilling Yesterday at 11AM

My WGN-TV colleague Dave Harpe, our Vice President of Technology, was conducting maintenance on our west tower cam on top of Willis Tower when he caught sight out of the corner of his eye of Tuesday afternoon’s landspout in the distance from his perch high above Chicago. It had formed beneath a towering cumulus cloud along an inland-moving lake-breeze front on the southwest side of the city near Midway Airport. It appeared at first to be smoke, Dave reports. But as it continued, the circulation within it became quite evident. FAA contract observer Melanie Harnacke observed the landspout from its inception and reports it lasted 10 minutes–forming at 3:48 pm Tuesday and dissipating at 3:58.  My National Weather Service-Chicago colleagues note this was the first tornado to touchdown within the city limits since the brief EF0 tornado touchdown on the Lake Michigan shoreline of the Loyola University campus on the city’s far North Side on Sept 22, 2006—10 years ago.

So what in the world is a “landspout”? Landspouts are a form or tornado and bear a resemblance in appearance to waterspouts–i.e. tornadoes over water. The term landspout was coined by well known University of Oklahoma severe weather researcher Dr. Howie Bluestein back in 1985. It’s different than a tornado because, unlike a tornado, its circulation isn’t nearly as deep. As we say in the meteorological profession, there is no mid-level mesocyclone associated with a landspout. Put in English, that means it’s not part of the deep layered circulation observed with powerful tornadoes which can extend vertically through tens of thousands of feet of the atmosphere, reaching nearly the entire vertical extent of a rotating thunderstorm–and that can mean 10 or more miles into the atmosphere. So landspouts are generally much weaker than a devastating tornado. But having said that, there IS a rotating circulation which reaches from the ground into the base of a building cumulus cloud above. That was certainly the case with Tuesday’s tornado. A landspout begins as a horizontally rotating column of air near the surface which is “stretched” or pulled aloft into a vertically rotating column of air which reaches into the parent cloud above. There are rare landspouts which have produced EF3-level damage, the product of winds in the 136 to 165 mph range. And landspouts have been known to survive as much as 15 minutes. Kansas-based severe weather researcher Jon Davies, who joined us at our Fermilab Tornado and Severe Storms seminar years ago, has diagrammed a comparison between the circulation of a landspout and gustnado. Jon Davies post on landspouts versus gustnadoes is available by clicking here.

The National Weather Service Chicago, in its posting on Tuesday’s landspout near Midway, reproduces the National Severe Storms Laboratory’s definition of a landspout as follows:

A landspout is a tornado with a narrow, rope-like condensation funnel that forms while the thunderstorm cloud is still growing and there is no rotating updraft – the spinning motion originates near the ground. In the case of the Chicago landspout, there was no rain shower or thunderstorm, just cumulus clouds along the lake breeze.

Check out Dave Harpe’s photos of the landspout as viewed from the top of Willis Tower Tuesday afternoon.

See today’s video.