Tornadoes - Nature's Most Destructive Winds. Facts and Causes
Tornadoes are a fact of life in North America, but a little understanding goes a long way towards reducing the risks.
Many of the pages in this site have suggested several ways of making the most of your home weather station by going a little further in observing those features of the weather beyond what your sensors are telling you.
The theme has been to get a little closer to the weather - take notes, take photos, make videos, and generally upgrade the experience of being able to record the physical aspects of the weather so easily and effectively.
The Oldest Known Tornado Photo
Howard, South Dakota, August 1884
Source; NOAA Archives
But there comes a point where you should step back, move aside,
or even head rapidly in the opposite direction to the
approaching weather, and that, most definitely, is the case
There's no doubt it would be a huge buzz to see a tornado at
close hand, but its not the best sort of exploit for the
But there are ways of reducing the risks which you can follow up
in the second half of this article, Watching Tornadoes.
Some Facts About Tornadoes
Meteorologists now know quite a lot about tornadoes and how
they form. But there is still a lot to learn.
As far as tornadoes go, the net is full of reports, fact
sheets, photos, videos and DVDs, and some of the best of them
are listed elsewhere - see More Tornado Resources . One of the most useful sources of
information is an article on frequently asked questions about Tornadoes,
written by Roger Edwards of the Storm Prediction Centre. Not
only does it answer just about every question you may think
of, but it contains numerous links to reports, research,
myths and forecasting.
Tornadoes are typically a North American phenomenon, with
most occurring in the USA, notably in Tornado Alley, a roughly
triangular area bounded by Louisiana and Texas in the south,
North Dakota in the north, and extending east to Ohio.
Tornadoes are always associated with thunderstorms, and as a
general rule, but not an infallible one, the bigger and more
complex the storm system, the more destructive the tornado.
The larger thunderstorm systems are associated with the
interface between warm humid air moving north from the Gulf
of Mexico and adjacent seas, and cooler air moving southward.
The interplay of these air masses has a lot to do with the
type and strength of thunderstorms, and the direction they
move in. Other storms and their tornado spin offs form
when western dry air interacts with moist air from the Gulf
Tornadoes usually begin to form in the southern states in
late winter, typically late February to March. The peak
tornado season gradually moves north during spring. May and
early June are the most active months in the southern
plains, while in the northern plains and upper midwest the
peak is in June or July. But if the conditions are right,
tornadoes will develop at any time and almost any place.
Overall the peak season on an all state basis is in
May/June, with both months experiencing, on average, over
Here are a few tornado facts
An important indication of imminent tornado formation is a
rotating wall cloud - a small area of cloud below the main
cloud base of a thunderstorm, and in a fairly central
Supercell with well developed wall cloud,
but no tornado. Source; NOAA Library, also
published in National Geographic
Of the 10,000 US thunderstorms each year, about 1000 will
produce tornadoes. 100 to 200 of these will be severe,
producing significant damage in populated areas.
Ballpark figures suggest that any given square mile in the
US can expect a tornado about every thousand years or so,
although some areas are more at risk than others. The
chance of your house getting hit is much less.
The busiest month ever for tornado touchdowns was May
2003 with 516 confirmed.
The busiest day was 3rd April 1974, continuing through to
the 4th. 147 tornadoes touched down in the US, plus one
more in Canada. Thirteen states were affected, 48 were
killers, and 318 people died.
The deadliest tornado was the "Tri-state" tornado of 18th
March 1925, which affected a 219 mile long path through
Missouri, Illinois and Indiana. It killed 695 people.
The average annual US death toll is about 60, and has been
decreasing as warnings become more accurate and emergency
plans and reactions have improved.
Maximum recorded wind gusts are meaningless - recorders
either get broken or just disappear. An estimated gust of
318mph (about 510kph) was derived from a mobile radar unit.
Modern forecasting techniques are still improving, but
high tornado risks can generally be predicted 12 hours
in advance. This doesn't mean a tornado will develop,
just that the chances are high.
So how can you gain experience in severe weather observation
without putting yourself at risk of injury or death? Follow this
link to the Watching Tornadoes.
This link will take you back to the Top, or, when you're ready, here's how to return to the Home page.
But just before you move on...
You may be interested to know that you can find out more about weather and home weather stations by receiving our newsletter ,"Watching Weather". It's published more or less weekly, and apart from tips on how to use your weather station and understand what it's telling you about the weather around you, it also covers many other weather related topics.
If this sounds interesting, just add your name and email address to the form below. When you join, you'll also receive, totally free, a 20 page guide to setting up and trouble shooting problems in home weather stations.
And I promise that you won't get spammed, and that your sign up details will remain totally confidential.
Sign up now and receive your first issue almost immediately.
ADD TO YOUR SOCIAL BOOKMARKS:BlinkDel.icio.usDigg FurlGoogleSimpySpurlTechnoratiY! MyWeb