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A basketball and a yard stick. Can you guess the weather connection?

Even though we have a state-of-the-art graphics system, sometimes a few simple props can get your point across. Today on News8@11, I used a basketball and a yar...
A basketball and a yard stick. Can you guess the weather connection?

All morning long, the Doppler radar has shown snow falling across the Quad City Region. But go about 30 miles in any direction and the radar is blank. Could it be that the snow is just developing over us? The short answer is no. That's where the basketball and yard stick come in.

A basketball and a yard stick. Can you guess the weather connection?

Picture a basketball as the world. The Doppler radar is the end of the yard stick. At the Quad Cities National Weather Service office, the Doppler radar beam heads out on the horizon at 0.5° of elevation. Since the Earth is round, that radar beam gets higher and higher the farther it travels. At 25 miles, the radar beam is about 1,800 feet up. At 50 miles, the radar beam is 4,500 off the ground. And at 75 miles, the radar beam is too high to see the lowest level of the atmosphere, under 8,100 feet.

In addition, the beam is also getting wider as it heads away.  According to the National Weather Service, the width of the beam expands at a rate of almost 1000 feet for every 10 miles of travel. At 30 miles from the radar, the beam is approximately 3,000 feet wide!

Today, the snowflakes are being produced in the lower 2,000 feet of the atmosphere. That's the reason why it appears we're the only ones getting snow right around the Quad Cities! We have observation sites showing snow in Dubuque and Waterloo, even though there's no blue on the radar. The Doppler radar beams coming out of Des Moines and the Quad Cities are just too high by the time they reach those cities to see the snow.

A basketball and a yard stick. Can you guess the weather connection?

To think there's actually a growing population of people in America who firmly believe the Earth is flat? Well, here's the science to prove that our Earth is indeed very round. It would actually be much easier to track storms and forecast the weather on a flatter planet.

-Meteorologist Eric Sorensen

 

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