Coming; Derechos or not. …
The USA (and, for all I know, Mexico and Canada) are going to be getting some tornadoes and or derechos. Derechos are the kind of weather you would experience on top of a skyscraper in Chicago on a windy day.
The word is Spanish for straight line winds; that is, there is no vorticity with them, they are not twisters. I have never studied them before and I hope you will join me in my first attempt to armchair-chase these.
If you want some serious meteorological discussions on this sort of thing, here are some good places to start. The moon is up north (10th December, 2011 @ 01:35 pm, it will decline +22:33 to the equator) so let's start with Chicago:
If you have a camera I would advise you keep it with you all through the next spell. It starts tomorrow so you have the weekend to prepare for the full blast:
You might want to keep an eye on this page too:
What will happen is that the storm systems will flow through the states west to east (I am expecting most reports to be along the east coast but you never know.)
So much for derechos, tornadoes are far more likely with a spell at this time: 02:30; 08:30; 14:40 and 20:30. We could even have them in Britain, I don't know what we have just had but from the comments on Usenet it WAS something to talk about.
With a time of phase on the half hour, a Greenland High will dominate the North Atlantic. This is what it looked like to a satellite last week:
And here it is in all its glory:
Well that's about it. To anyone caught in this stuff, good luck.
I hope I am wrong.
But I know I won't be. (And it's not just the way I tell 'em.