What is this storm feature? From 12/31/2010 in Illinois

[Nick Nolte]

I was going to append this to the DISC thread for this day, but someone else mentioned it might deserve its own thread.

Here's the videos, first one is HD video of the feature, my camerawork isn't pristine, but you can see what I'm talking about. The second video is time lapse from my dash webcam, it's quality is poorer, but you get a sense of the direction of movement. The feature shows up around 0:12.




I was about half a mile northwest of Pleasant Hill, IL in Pike County at about 10:50 am CST on 12/31 parked off IL-96 looking SW when what looked like white smoke showed up and appeared to be connected to the storm base and in contact with the ground. I am 99% sure this was NOT a tornado, but it coincided with a radar indicated couplet at the same time. I am also positive it is not actually smoke as it coincides with the storm.

My original thought was (and after talking with others) that the updraft was grabbing cold air from the ground and it was condensing very quickly, or it was grabbing snow fog from close to the surface. However, the updraft would move NE with the storm and this feature moved S.

So, ideas? Discussion?

Here is a radar animation of the area/time in question: http://i55.tinypic.com/28vaal0.gif

Happy New Year!

 

[Scott Weberpal]

There are a few sloughs, lakes and the Mississippi River in the direction you are looking. My guess is the updraft was pulling much colder air off one of the water bodies and it was condensing immediately off the surface - or an outflow interaction with the colder air. But I'm willing to guess it absolutely has something to do with a cold water body or snowpack.

OR

There is a very quick 200'-300' elevation drop from the MO side of the river to the floodplain on the IL side. It's quite possible that had something to do with it, though I think my river/lake theory holds more water - pun intended.

 

[Rejean Boudreau]

It looks like the updraft from a localized front. A bit like in front of a shelf cloud where the air at the tip of the cloud is lifted straight up to the shelf cloud's border (lip) from the ground.

I've seen that often, but on a very smaller scale than what you got on the video - like scuds lifting from the ground up.

Might be caused by localised very humid air mass (a lake, snow haze), and then the phenomena becomes visible on a much larger scale.

 

[Olivier Staiger]

to me it looks like smoke rising after lightning hit the area and ignited fire

 

[David Wolfson]

The un-zoomed video seems to pretty clearly show the feature as a shelf/gust front cloud fragment IMO. Because of the foreshortening of the zoomed video I think the feature appears much larger than it really is ... unless there really are those high mountains in the vicinity!

 

[Nick Nolte]

It looks like the updraft from a localized front. A bit like in front of a shelf cloud where the air at the tip of the cloud is lifted straight up to the shelf cloud's border (lip) from the ground.

This makes the most sense to me, a localized gust front moving away from the storm causing air to rise from the ground and up along the interface. There was a lot of snow fog that day and I imagine there is probably some ice/snow along the edges of the Mississippi there.

I also agree that the zoomed out shot makes it seem more like a shelf cloud, I had viewed that video last and that was the first thing I thought when I watched it.

There are some decent hills there, the zoomed video might exaggerate them a bit. Here's a google streetview link looking downstream with MO on the right http://maps.google.com/?ie=UTF8&ll=...=s26IOFrabfXmiMAaH01w1Q&cbp=12,137.17,,0,7.81

 

[Sam Barricklow]

Gust Front Plume

Agree with the previous assessments, but wanted to add that I've seen similar features south of Amarillo near the Palo Duro Canyon after a storm has moved through the area, and new convection is forming. Rich, moist air flowing in through the canyon from the southeast is lifted and cooled, resulting in condensation occurring almost at ground level. The presence of an outflow boundary would enhance this effect.

 

[Skip Talbot]

I definitely agree with Scott and Sam's assessments. On yesterday's chase a bit further north, I saw a lot of fog patches from remaining snow drifts that were similar to this but on a smaller scale. River valley fog being pulled into the updraft makes a lot of sense, given how close temp/dewpoint spreads were already and that the air in these valleys was probably saturated. Maybe the slow southward movement is even a result of the river's motion?

 

[Andy Wycislo]

I grew up in Pike County and am familiar with the area. The "fog" is coming up directly off the river, as that treeline runs along the river down there and it is clearly behind it. It is also clearly in front of the hills, which are directly on the west side of the river. The river is fairly wide down there. As cold as it's been I'll bet the water temp is pretty cold, so the right wind pattern could probably cause that. Hope that helps!

 

[Donovan Gruner]

I saw some interesting fog/cloud features on my way down that morning... One was a big and very low roll cloud formed on the northern edge of a patch of showers. I would also assume that is fog rising into the updraft. There was definitely plenty of it.