Tornado or something else?

[Steve Elzinga]

Yesterday in Mason MI at about 7:30 PM I witnessed what appeared to be an extremely weak tornado but I am wondering if it is possibly considered something else considering the conditions. It had been raining all evening as a cold front came through. I believe the temperature was in the 50's at the time. At the end of the rain the cloud base was extremely low and much darker. I saw a small funnel form from the cloud base and there was a visible very rapidly rotating updraft that descended low enough that you could see the tops of the trees moving from the wind. I was standing approximately 500 yards away and you could feel inflow pick up from behind me as it approached and you could hear the swishing from the wind in the funnel. I could see leaves from the trees getting pulled up into funnel along with the visible condensation. It picked up to a point that there was a very defined funnel to the tops of the trees and then started to dissipate. The entire event lasted only about 10 minutes. Is that technically considered a very weak tornado? A cold air funnel? Something else? Thanks.

 

[Skip Talbot]

Any pictures?

You're definitely describing a weak tornado as it had a surface circulation and associated funnel. I'd guess it was a cold air event too taking a quick peek at some of the 0z NAM analysis plots from last night:

Very cold air aloft pushing in from the northwest:
http://www.twisterdata.com/data/mod.../15/00/NAM_221_2011091500_F00_TMPC_500_MB.png
Marginal moisture by classic warm sector severe weather standards, but more than enough for a cold air event:
http://www.twisterdata.com/data/mod..._221_2011091500_F00_DPTF_2_M_ABOVE_GROUND.png

The models aren't showing the areas overlapping very well, and usually you'd see a negative lifted index over the area:
http://www.twisterdata.com/data/mod...1_2011091500_F00_PLI_30_0_MB_ABOVE_GROUND.png

There might have been a sweet spot where the two areas did overlap that the model is resolving. There was also a very strong trough ejecting over Michigan:
http://www.twisterdata.com/data/mod.../15/00/NAM_221_2011091500_F00_WSPD_500_MB.png
That probably had quite a bit of dynamic forcing that could have spun up some mini supercells

 

[Steve Elzinga]

I recorded the entire event on my cell phone and my cell phone somehow managed to not save the video. Frustrating. I do have a cell phone picture taken just after the funnel dissipated that I will try to upload from home. I don't know if that will tell anything at that point but you can still see the lowered cloud base. Thanks for the info.

 

[Steve Elzinga]

A friend sent a couple of captures that he had that are unfortunately from the very end of the event where it was breaking up. The last image is from my cell phone after it was completely gone but you can still see the cloud lowering. My cell phone made it appear much lighter than it actually was. Just 10 minutes before this we were playing golf in the exact area this went through and had quit due to darkness.

 

[Robert Dewey]

Could be a cold air funnel. Looking at the radar around that time, it's most likely non-mesocyclonic.

 

[Steve Elzinga]

I have a L3 radar app on my phone and I checked it at the time and didn't see anything either. The conditions were such that I was just shocked to see what I was witnessing. That is really why I was asking about the terms used for this type of an event. I also thought that the conditions potentially made it interesting for other people that like weather events.

 

[Patrick Marsh]

Have you contacted your local WFO? If it was a true cold-air funnel, it's fairly rare for them to reach the ground. I'm sure they would be interested in seeing photographs and/or video.

 

[Greg Stumpf]

That sounds like a bonafide tornado.

BTW - I'm one that does not believe in "cold-air funnels". I have yet to see any evidence suggesting that funnels/tornadoes in the "conditions of cold air funnels", are something other than mini-supercell or non-supercell tornadoes.

 

[rdale]

It clearly wasn't a mini-supercell, and every cold-air funnel I've seen is not even related to any sort of convection. I think that's what people (at least in this area) use as criteria for CAF.

 

[Zach Young]

Well there is this example of a cold air funnel: Leadville, CO June 13, 2010 (not my video)

Leadville is at 10,000 ft, and at the time this video was taken the temperature was 46F (the high later in the day was 55F), and the dewpoint was 35F.

 

[Steve Elzinga]

Have you contacted your local WFO? If it was a true cold-air funnel, it's fairly rare for them to reach the ground. I'm sure they would be interested in seeing photographs and/or video.

Yes, I posted a report and then the same pictures that I posted here to the Grand Rapids NWS Facebook page at their request. I posted the initial report just after the event.

 

[Steve Elzinga]

Although there didn't appear to be any damage from this it did reach to the tops of the trees and I did see some leaves going up into the funnel. The area that it passed over was mainly woods so I couldn't tell if it ever got all the way to ground level. I was approximately 500 yards from it at its closest point. One thing that I noticed that seemed interesting was that as the funnel was descending how rapid the upward motion was from the tops of the trees up towards the funnel. You could clearly see the condensation trails of air going up vertically that then became rotational once it reached the area of the funnel. It appeared that the air was being pulled in straight up very fast and then the rotation and the funnel descended to the tree tops. Even once the funnel and the rotation was at the tops of the trees it seemed that there was very rapid upward motion associated with this. I have never witnessed a tornado initiating in person before this so I don't know if that is typical or not but it was interesting to watch.