Tornadic mesovortices in LEWP/bows
- Thread starter Dave Gallaher
- Start date
Kevin Bowman
EF4
take a look at this, im not sure if your picture is what they are talking about though
http://ams.confex.com/ams/pdfpapers/115155.pdf
http://ams.confex.com/ams/pdfpapers/115155.pdf
Nigel Bolton
EF0
Is a relatively new idea in the UK, and has been subject to intense discussion.
Downburst on cell at southern end of bowing segment is prevented from spreading out by angular momentum within a misocyclone between two segments.
Weakly developed bowing squall line will produce just downbursts and fanning out of surface wind.
Stronger bowing squall line will develop short-lived 'misonadoes' that last a few tens of seconds and produce a path of severe damage, a few tens of metres wide and a few hundreds of metres long with little or no damage elsewhere. These can be thought of as a 'hybrid' between a downburst and true tornado, where angular momentum of low level helicity prevents fanning out of downdraft, and draws in the downburst into a short-lived vortex.
Very strong bowing squall line likely to generate short-lived, but potentially strong tornado, such like Kensall Rise London 07/12/06; strength EF2. strong for the UK.
N.
Downburst on cell at southern end of bowing segment is prevented from spreading out by angular momentum within a misocyclone between two segments.
Weakly developed bowing squall line will produce just downbursts and fanning out of surface wind.
Stronger bowing squall line will develop short-lived 'misonadoes' that last a few tens of seconds and produce a path of severe damage, a few tens of metres wide and a few hundreds of metres long with little or no damage elsewhere. These can be thought of as a 'hybrid' between a downburst and true tornado, where angular momentum of low level helicity prevents fanning out of downdraft, and draws in the downburst into a short-lived vortex.
Very strong bowing squall line likely to generate short-lived, but potentially strong tornado, such like Kensall Rise London 07/12/06; strength EF2. strong for the UK.
N.
Martin North
EF4
Yes, we are tackling this one with some 'robust' discussion in the UK. Funny, I meant to start a thread about this several days ago but was too busy what with one thing and another post-christmas business-wise.
I remain unconvinced about Kensall Rise, I think there was a mesocyclone in there. I know for a fact that that Reading doppler site was looking at it (the storm).
Why do they keep this stuff under wraps?
I remain unconvinced about Kensall Rise, I think there was a mesocyclone in there. I know for a fact that that Reading doppler site was looking at it (the storm).
Why do they keep this stuff under wraps?
Dave Gallaher
EF5
Thanks, Kevin--interesting doc. I don't think my photo is what is be referenced here due to the fact that it carried a tornado warning for a few minutes before I saw it. It was positioned on a bow, however, that had a narrow front before the rain and outflow came in hard. On the video from which this view was taken, there's only a few seconds of the open vortex (and the odd angle is due to my hurrying into the van to avoid the rain).
Nigel and Martin: it's funny, but when I first posted the question I thought 'this sounds like something the UK guys might discuss in depth.' Thanks for the responses--I'll be interested in reading your comments. The misocyclone events sound unchaseable, only interceptable...
Matt Ziebell
EF0
Your view of that was pretty narrow, so it's tough to say. If you recall radar showing an S-shape in the reflectivity near your area then I'd say there's a better chance of it having been an example of a LEWP. Below is what a well-developed LEWP looks like on radar. Granted, the same processes that produce these can occur on a smaller scale and are not always this apparent.
Attachments
Dave Gallaher
EF5
I was in the field without radar support, and have never attempted to retrieve an archive of the date (5/9/06 5:46pm central).
Thanks for the LEWP image.
Thanks for the LEWP image.
Nigel Bolton
EF0
It was a strong LEWP pattern that gave the Kensall Rise EF2 tornado in London on 7th December 2006. Despite being strong for the UK, the tornado path was relatively short, such is normal for a LEWP induced tornado.
In the UK, LEWPs are usually weaker than that which gave Kensall Rise, but can spawn a significant amount of small tornado damage. A very active cold front on 23rd November generated 105 damage paths attributed to tornadoes. In reality, probably only a very few actually manifested themselves into true tornadoes, the rest being 'misonadoes', these generating path damage normally no more than a few tens of metres long and a few metres wide. However, damage even with misonadoes can be severe.
N.
In the UK, LEWPs are usually weaker than that which gave Kensall Rise, but can spawn a significant amount of small tornado damage. A very active cold front on 23rd November generated 105 damage paths attributed to tornadoes. In reality, probably only a very few actually manifested themselves into true tornadoes, the rest being 'misonadoes', these generating path damage normally no more than a few tens of metres long and a few metres wide. However, damage even with misonadoes can be severe.
N.
Stephen Levine
EF4
In April of 2007, a large bowing line of thunderstorms moved through the DFW metro area.
Some rotation was noted and a tornado warning was declared for North Dallas. We were living in McKinney, about 25 miles north of the warning, but decided to spring for it and give chase. As we drove South, I noted the bank of shelf cloud, punctuated by several funnel shaped lowerings to our SW, and fast approaching. The storm and us met in the Plano area. A low hanging swirling vortex moved directly over our car at a high rate of speed, which was awesome and too brief. We later saw power flashes in a series approximately 3 miles in front of us (Richardson area).
In any event, the cloud was low hanging and swirling cyclonically. Tornado? no. However it probably fits the description of what is being discussed in this thread.
Some rotation was noted and a tornado warning was declared for North Dallas. We were living in McKinney, about 25 miles north of the warning, but decided to spring for it and give chase. As we drove South, I noted the bank of shelf cloud, punctuated by several funnel shaped lowerings to our SW, and fast approaching. The storm and us met in the Plano area. A low hanging swirling vortex moved directly over our car at a high rate of speed, which was awesome and too brief. We later saw power flashes in a series approximately 3 miles in front of us (Richardson area).
In any event, the cloud was low hanging and swirling cyclonically. Tornado? no. However it probably fits the description of what is being discussed in this thread.
Nigel Bolton
EF0
Apologies folks. Date in post above should have said 23rd November 1981.
N.
N.
Sam Barricklow
EF1
Bow Echo Tornado Photos
Last year, I photographed a weak tornado associated with a bow echo system. This feature was located just north of the nose of the bow echo. See:
http://www.k5kj.net/20070502.htm
Last year, I photographed a weak tornado associated with a bow echo system. This feature was located just north of the nose of the bow echo. See:
http://www.k5kj.net/20070502.htm
Stephen Levine
EF4
This was the particular storm that I referred to in my previous post. Thought it was in April but it's this one where we chased from McKinney and saw the rotating vortex overhead.
Chris Foltz
EF2
The image Matt provided was from an F3 that struck Columbia, MO on November 10, 1998 shortly before 2am. It formed on the northern end of the LEWP with a weak anti-cyclonic couplet on the southern end that did not produce a tornado. I lived in the subdivision that was struck with the main tornado missing my duplex two blocks to the north. Here's a link to a page with damage photos and the PNS issued by Ron Przybylinski at LSX.
http://www.gocolumbiamo.com/EM/Natural_Disasters/Tornadoes/southridge.php
Unfortunately, the WSO that had been at the Columbia Regional Airport had been decommissioned in 1995 with the WSR-74 radar shut down. Both the 88D from EAX and LSX are more than 90 miles from COU which presented a problem with detection of the meso.
Dave Gallaher
EF5
No expertise here, but it looks to me like Sam's images have a somewhat classic meso/rfd appearance, if on a small scale. I am wondering if both this type and the front line type such as I posted are considered the same phenomenom, or if mine is more of a frontline gustinado-type vortex.
Dave Gallaher
EF5
We were damned lucky to get ours reopened in HSV.
