Tuesday, May 27, 2014

How Radar Can Mis-Position Tornadoes

We've covered this topic one other time but a comment made on the air last week makes me think it is important to mention it again.
Two yellow lines represent the radar beam -- where the radar is sensing the tornado.
We often see "street-level" radar displaying tornado locations. When close to the radar (within about 15 miles) with the radar being operated properly, they are reasonably (not precisely) accurate.

However, at any significant distance, it is invalid to try to get the location down to a couple of blocks. Tornadoes are often not completely vertical nor is the earth's surface straight. The earth curves out from under the radar's beam so that when it is 120 miles away, the beam is about 10,000 ft. above the ground. At that distance, the tornadoes ground location may be a few miles from where the radar is sensing it.

To viewers: do not rely too precisely on television radar displays for tornado locations.

Television meteorologists: do not try to do more with your radar than it is capable of.

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