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SPEAKER 1: Cooler Northwest, Wednesday, highs near 70 North to near 80 in the Southeast. Wisconsin--

SPEAKER 2: That's the voice of the National Weather Service, the 24-hour continuous weather broadcast, originating, in this case, from Minnesota's weather service headquarters at The Twin Cities International Airport. Officials there want people in the upper Midwest reminded that the approach of June means the beginning of this region's prime tornado season.

Nearly 3/4 of all Minnesota tornadoes occur between May and July, but it's during June that the greatest number are likely to occur. And statistics show that while tornadoes are erratic and can touch down at any time, during late spring and early summer, the most dangerous period is between the hours of 4:00 and 8:00 PM. While we're only now entering the most dangerous part of the year, the tornado season begins and peaks earlier to the South in the Eastern and central Gulf states.

You may recall that during early April, more than 100 tornadoes swept an 11-state area, from Alabama and Georgia to the Canadian border, claiming hundreds of lives and destroying hundreds of millions of dollars in property. Fortunately, Minnesota and surrounding areas lie just outside of the country's principal tornado belt. John Graff, the Weather Service deputy chief of forecasting, explains.

JOHN GRAFF: Minnesota sits on the edge of an area of the greatest frequency of severe thunderstorms and resultant tornadoes. And we're on the Northwest edge of this. The strongest convective developments and the most frequent convective developments are in an area from Texas and Oklahoma, across Kansas, Northeastward towards the Great Lakes, and, of course, that passes through your Missouri area, your mid-Mississippi River Valley, Indiana, Ohio, lower Michigan.

That's the centroid or the center of the belt, and we sit on the outside of that, and, therefore, we probably pick up as far as both in terms of total intensity and frequency, maybe 60% or 65% of what they would be receiving in the center area. So we're not prone to be in the strongest area, nor in the most frequent area of severe thunderstorms and/or tornadoes.

SPEAKER 2: While we are less susceptible than many other states, we do have enough tornado activity to be seriously concerned. Over the last 20 years, we've seen more than 350 tornadoes, and tornadoes resulting in a total of 67 deaths and 1,185 injuries.

One of Minnesota's most notable tornadoes touched down in North Minneapolis in May of 1965. That event resulted in the loss of 14 lives and an estimated $57 million in property damage. Last year, one life was lost in one of 22 tornadoes, five more than the seasonal average.

Even if you've never witnessed a tornado, the statistics alone suggest a destructive force sufficient to recall terror in the hearts of those who have. Under what weather conditions are they likely to occur? I asked Joe Strube, the Weather Service meteorologist in charge.

JOE STRUBE: Well, actually, it's the thunderstorm that produces the tornado. We must have a severe thunderstorm. Once we do have the thunderstorm, and it's reached the severe category, then we start looking for the tornado. We know that in the Metropolitan area in the South half of Minnesota, that we can anticipate about 45 thunderstorms in a given spring and summer season.

Now, out of these 45 thunderstorms, we can expect 17 of them to be severe. And then out of these 17, as far as the South half of Minnesota is concerned, we can look for about maybe eight or nine tornadoes.

SPEAKER 2: OK, Pat, what are you doing now?

SPEAKER 3: Well, I'm utilizing the height finder scope of the radar. Actually, what happens is the antenna goes up and down and physically raises and lowers the antenna.

SPEAKER 2: What are we looking at on this screen here?

SPEAKER 3: Well, this scope here, we-- excuse me, you can see the height of the clouds, the tops.

SPEAKER 2: In 1961, Minnesota's National Weather Service headquarters acquired radar, and the equipment's ability to see cloud formations helped in forecasting possible tornado conditions. A radar, though, does have limitations, so Joe Strube, John Graff, and others have, on their own, developed special electronic equipment, equipment designed to measure sferics or the electrical activity of the atmosphere.

The sferics equipment, used in conjunction with radar, now represents a highly accurate forecasting system known as GenCon or Genesis Continuum.

JOE STRUBE: The sferics gear gives us a little bit of advantage over radar because with radar, we send a signal that's dependent on the moisture that's in the cloud. So until you get real good cloud development, a lot of moisture, or rain, you don't always get the best signal.

Now, with the sferics gear, we know that there's electricity in the system and the atmosphere. This will start to record this, and this will pick up before our clouds reach the severe category. So this will give us maybe about a 35-minute advantage. So with our GenCon, Genesis Continuous method, we hope to be able to pinpoint the area that we expect the severe weather to occur.

SPEAKER 2: The GenCon system, used in Minnesota only, has been in operation for the last three years, and while another new tornado predicting system is currently being tested around the country, GenCon has a much greater range and may well prove to be the most accurate tornado warning system anywhere.

According to Joe Strube, GenCon means enough accuracy, so that when he issues a tornado warning for a particular area, we can be sure a tornado is likely. He says, two, if people take heed, he's certain of fewer tornado-related deaths.

JOE STRUBE: We want some type of action. See, our forecasts are only as good as the action that you take. If you don't take any action, even if they're 100% right, they're not worth the paper they're printed on. So our prime goal is to be able to locate where this is, and then to warn you as to how much time this is going to take.

SPEAKER 2: This is Greg [? Biren. ?]