Earth Science: Geology, the Environment, and the Universe

Chapter 13: The Nature of Storms

Problem of the Week

Doppler Radar: A Key to Tracking Severe Weather

Go to this site for background material on Doppler Radar. An Investigation of Doppler Radar

An Investigation of Doppler Radar

Radar

The three radar images in this exercise are fairly straightforward and give students an opportunity to practice the skills of interpretation and analysis.

Radar is dependent on the degree of reflectivity of the objects hit by the radar waves; in general, the larger the objects, the greater the reflectivity. Reflectivity is dependent on two factors - the number and diameter of the precipitation drops.

The radar can detect swarms of bugs, birds, dust, and buildings or it may "see" several drops in close proximity and show it as a small hailstone. Because of this, meteorologists must evaluate all the atmospheric data in the area to determine, if what they are seeing in the radar image is consistent with the other recorded conditions before they report a storm.

The "DBZ" seen on the key, in Problem 1, is the measure of the energy level of the returning radar beam that is reflected back by the precipitation. The higher DBZ levels indicate more intense precipitation.

The "DBZ" seen on the key, in Problem 1, is the measure of the energy level of the returning radar beam that is reflected back by the precipitation. The higher DBZ levels indicate more intense precipitation.

The Keys:

The colors used in the keys of these three images are fairly representative of the variety seen in radar images. There is not a set standard. However, greens and blues tend to be low intensity precipitation, yellow, reds, and pinks higher intensity, and gray is sometimes used to indicate hail (very high reflectivity).

Answer - Problem 1:

There is a line of intense storm activity that runs from the southwest part of Texas to the northeast part of the state. The reds and the pinks indicate the high intensity areas. There is one particularly intense area of precipitation near the center of the state. A forecaster might describe this system as a "squall line," as a "frontal system," or as an amateur, a line of severe thunderstorms that extend across the state, from the northeastern part to the southwestern part. It appears to be moving in a southeasterly direction. (The intense areas of precipitation are often nearer the leading edge of a moving storm system.)

A forecaster might describe this system as a "squall line," as a "frontal system," or as an amateur, a line of severe thunderstorms that extend across the state, from the northeastern part to the southwestern part. It appears to be moving in a southeasterly direction. (The intense areas of precipitation are often nearer the leading edge of a moving storm system.)

Answer - Problem 2:

The tornado signatures are shown within the pink circles.

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