Tornado Hits North London, UK

[scott r currens]

I love rain wrapped "landspouts".

 

[Bob Hartig]

Mini-tornadoes

Looks like the term "mini-tornado" has come under fire, but I for one wish to defend it. I mean, there are a lot of respectable "minis" out there that we've all come to know and love: mini-skirts, mini-cars, mini-bars, Minnie Mouse...what the heck, what's not to love about mini-tornadoes? I think the problem lies in the lack of a clear definition. I propose the following criteria for a mini-tornado:

• It is five feet tall or less. Of course, this implies an extremely low cloud base. You'd have to squat in order to get a decent photo.
• Width: Two feet or less.
• The mini-synoptic setup can be contained in a city block.
• Damage (introducing the M Scale):
  • M 1: Damage?
  • M 2: No noticeable damage.
  • M 3: Okay, some damage now. Card houses knocked over unless securely glued together. Hair ruffled. That sort of thing.
  • M 4: Now we're talking damage. Well-built card houses scattered into a lawn-size version of 52-Card Pickup. Ill-fitting toupes snatched away. Nasty things happen when you spit into the wind.
  • M 5: Inconceivable inconvenience. Securely glued card houses swept entirely away and lofted across the lawn. Well-gelled hair twisted into impressive new designs. You want to get out of the way of this baby.

I hope this helps. Of course, according to these criteria, I suppose the UK has yet to experience a true mini-tornado. Someone should probably inform the press. And none of us should hold our breaths waiting for such an occurrence, because, truth be told, mini-tornadoes are extremely rare.

 

[Mike Birbeck]

Ah an empirical man and a fine definition. I am a fan of the M scale and will not mock the mini-tornado ever again!

 

[Andrea Griffa]

Guys, here in Europe there's the tendence to call every tornado that has not the shape of an american wedge, "minitornado". The medias used to think that the real tornado happens only in the United States: if a tube drops down in our country,even with substantial damage, you have no doubt that they will call it a "mini"(if the shape was not the one of a 2 km wide monster). The reason is that here there's not the culture of tornadoes; I make you an exempleften when I talk about tornadoes with normal people they ask me if tornadoes are the same of hurricanes. So, you can well understand. It's not the first time that in England they speaks about minitornado, but I could say the same for Italy.

 

[Karen Politte]

Actually I have been in contact with the paper who published the picture and this images has now been proved NOT to be the London tornado - I was fooled as well

It would seem at this stage that the tornado remains unrecoreded - given that it would appear that it was rain wrapped

Whoa whoa......hang on there. NOT the London tornado? So - where did our good, trusty, oh-so-real friends at The Sun get that picture? And what IS it?

Stu you got me excited there for a minute LOL.

KL

 

[Paul Austin]

It is five feet tall or less. Of course, this implies an extremely low cloud base. You'd have to squat in order to get a decent photo.
Width: Two feet or less.
The mini-synoptic setup can be contained in a city block.
Damage (introducing the M Scale):

• M 1: Damage?
• M 2: No noticeable damage.
• M 3: Okay, some damage now. Card houses knocked over unless securely glued together. Hair ruffled. That sort of thing.
• M 4: Now we're talking damage. Well-built card houses scattered into a lawn-size version of 52-Card Pickup. Ill-fitting toupes snatched away. Nasty things happen when you spit into the wind.
• M 5: Inconceivable inconvenience. Securely glued card houses swept entirely away and lofted across the lawn. Well-gelled hair twisted into impressive new designs. You want to get out of the way of this baby.

I love it, Bob, but you'll never get a damage survey team to actually rate a mini an M5; not with the new EM scale. The mini would actually have to STRIKE a securely gued card house, which almost never happens (No disrespect for survey team members intended here - just laughing at the post )

If we're going to define a minitornado, what about a Megadustdevil. Stands to reason, right? I'll leave it to the professionals. Oh, and let's add minitornado and snowspout to the tornado terminology pole and debate.

 

[Paul Knightley]

This event certainly provided us with a busy day - I got to talk on BBC News and Sky News, and Stuart was also on BBC news.

I posted some thoughts about the development of the storm(s) on the MeteoGroup website, in the news section here:

Obviously it's a website for anyone, and so I haven't used any particularly technical language!

These are the relevant paragraphs concerning reasoning:

Residents of a north-west London suburb were left shocked on Thursday morning, as a tornado ripped through. The tornado affected the Kensal Rise area, and occurred at around 11am. It was spawned from a line of strong thunderstorms which passed across the capital. This line had its humble beginnings across Cornwall, when they spread in from the Atlantic at around 0730. This line raced to the east-northeast, passing Salisbury at around 10am. As it did so, the wind gusted to around 40mph at nearby Larkhill. At the same time, there was a drop in the humidity of the air, and this may have had a bearing on subsequent developments.

As the storms continued to move north-east, the drier air behind the storm is likely to have evaporated some of the precipitation of the storm, and this would have caused the descending air of the storm to become colder, and thus heavier. This caused a surge in atmospheric pressure just behind the line of storms, and this surge appears to have caused the storms to accelerate forward.

A storm’s ability to rotate and possibly produce a tornado is partly derived by the amount of “spinâ€￾ in the inflow. That is, the more “helicityâ€￾ the inflowing air has the better chance the storm has of rotating. Helicity is a rather complex notion, but is akin to the air flowing into the storm in spirals, rather like the coiling cable of a telephone handset. The magnitude of the helicity is partly determined by the wind speeds and direction in the lowest 3km of the atmosphere around the storm, and partly by the motion of the storm itself.

In Thursday’s case, it is plausible that the increased motion of the storm as it raced towards London, combined with a slight change in wind direction ahead of the storm, helped rotation to develop. Had the storm moved at a different velocity, the tornado may not have occurred at all. In addition, the downdraught of air at the rear of the storm, called the “rear-flank downdraughtâ€￾, is seen as very important in tornado formation. This flow of air can concentrate the rotation in the storm, and is often present in tornadic storms across the Great Plains of the USA.