Lots of tornadoes are hitting the United States this year. And lots of people are being killed in them.

The year 2006 is a world apart from 2005 when it comes to tornadoes.

After this weekend's outbreak, 40 people have been killed in tornadoes since the start of the year. That is one more than the entire tornado death total for all of 2005. Most of 2005's tornado deaths, 29, occurred in November.

Early reports suggest 226 tornadoes hit the United States in March. The U.S. has averaged just 50 tornadoes in March the past three years, and the record number of March tornadoes reported is 180 in 1976, according to data compiled by the High Plains Regional Climate Center in Lincoln, Neb.

Keep in mind that, as meteorologists with the Storm Prediction Center and local weather service offices examine these reports, the final official tally of tornadoes usually comes down quite a bit. This is because some initial reports are later determined not to be tornadoes, while others are multiple reports of the same tornado.

But even at that, it's impressive that during the first 90 days of 2006, there were 290 tornado reports in the U.S. At this time last year, there were only 102 ... and later analysis brought that number down to 92.

So what is so different?

The large-scale weather pattern is much different than last year. For much of spring 2005, high pressure set up in the western states, and the jet stream came over the top of it, dipping southward in the eastern U.S. This kept chilly weather in our part of the country much of last spring, and blocked the kind of storm systems that typically kick off storms in the middle part of the nation.

You can almost flip that this year. Low pressure in the West has frequently caused the jet stream to dip under it, then lift northeastward toward the Ohio Valley. This has swung a series of storm systems through the Southwest and into the Midwest that have brought cooler, drier air slamming into warm, moist air lifting from the Gulf of Mexico.

The jet stream itself has been extremely vigorous, really since late fall. This has kept systems moving rapidly through the winter, so we didn't get a lot of precipitation, and cold-air intrusions were not common or long-lasting.

The fast jet stream has supplied a lot of dynamic energy to the storms in the Midwest, and often a lot of spin with strong west or southwest winds aloft on top of south or southeast winds at the surface. It's like taking a baseball and spinning it by moving your hands in different directions.

Another factor I wonder about, and this is strictly my speculation, is how the long dry spell in the Southwest and southern Plains has played into the severe weather. A sharp boundary between dry and moist air is often an ideal environment for severe thunderstorms to erupt.

With extremely dry air in the Southwest being recharged over extremely dry ground, it would seem such a boundary between dry air and moist air would be sharper and more extreme, and therefore an even more intense area for storms to fire. The dry air is also charging far to the east with each passing front to push it, exploding large storms even into the Mississippi, Tennessee and Ohio river valleys.

So far, in our area, the best atmospheric dynamics have been moving northeast more toward the Great Lakes, so we've been spared the huge outbreaks of severe weather that have happened to our west. We got a little taste of it with some high winds on Monday, but not the destructive outbreak of tornadoes and large hail that have been pounding the folks to our west time and time again this spring.

Seeing the destruction suffered by our Tennessee neighbors, we can be thankful for that. We need the rain, but not badly enough to have that with it.