Re: Hmm - pre-Human-influence global...

Fingal wrote:
> That I find genuinely interesting and more than a little scary. Do
> you get more or less "used" to them. or is it a pretty serious fright
> every time?

Tornadoes are always associated with thunderstorms. The bigger and
taller the thundercloud - the more likely it is that a tornado will be
formed underneath it. (other considerations, such as temperature
differentials, water vapor density, and jet stream position apply
also).

When severe thunderstorms approach cities the local authorities set off
civil-defense sirens to warn the people. This happened maybe 20 times
in 2005

It's the degree of organized structuring of the air currents that set
up the vertical airflows which determines whether a thunderstom will be
just a thunderstorm - or will change into a twister. Most of the bad
ones trail behind a storm front (squall line) hidden in a trailing
cloud formation that they call a 'J' hook. (the tornado being in the
cup at the bottom of the 'J').

You can usually tell how bad the storm will be by the appearance of the
'wall/roll' cloud that forms at the base of the approaching
thunderhead... besides using modern definitive doppler radar..usually.
And also by the amount of hail that falls. Last year in March one storm
dropped 3-4 inches of hail. I never have seen anything like it before,
and took pictures.

I said usually..
A few years back, I went outside to check out the appearance of an
approaching thunderstorm and was briefly confused because I could not
locate its wall cloud. I just saw a light grey *** (of what I thought
was rain) about 500 meters down the road. The problem was that the
'rain' was *completely* opaque and had dark things moving in it
-sideways, and was coming towards me much too fast. The edge of that
wall hit my place before I could run inside and slam the door.

It later turned out to be a (not typical) half-mile wide tornado that
flattened a number of farm houses and killed a few people to the south
of me in a line that ran over 10 miles long. But it was not typical.
Most of the tornados are more distinctive - with the signature cone
shape extending partially or completely downwards from a pitch black
anvil cloud. They almost always come from the west.

But sometimes you only find out that a tornado went over you - only
after it has passed. By spotting the cone shape against the eastern
horizon, or sometimes by the color that the sky takes on -often an
eerie color tinge (usually light green, sometimes pinkish or orangish).


> I grew up in a place where very serious blizzards were a fact of life,
> but the nightmares I remembered from the time I was a kid involved
> being caught in a tornado. Well, and one with a dinosaur, but that's
> a subject for creationists.

PS. A tornado hit Latvia this last summer. They will probably become
more common.

.