Severe weather radar terms and what they mean

Severe weather radar terms and what they mean

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  • Doppler radar is one of the tools used to determine if a storm is producing severe weather.
  • There are several terms that meteorologists use to describe what radar shows.
  • Sometimes it indicates a devastating hurricane or strong winds.

Radar displays several visual cues to meteorologists when tracking severe weather and tornadoes. “Wrecking ball,” “hook echo,” and “bow echo” are just some of the terms you may have heard before on the Weather Channel or elsewhere.

We’re here to provide a little Meteorology 101 lesson on what that means so you can use this knowledge the next time severe weather threatens.

1. Echo hook

A supercell thunderstorm with a hook echo that did not produce a tornado near Lubbock, Texas, on April 29, 2012.

(Radar image: National Weather Service – Lubbock, Texas | Annotation by Weather.com)

As its name suggests, this refers to an appendage that appears as a hook on radar and usually emerges from the southwestern portion (bottom left) of some supercell thunderstorms. It is an indicator that the storm has a strong updraft and sometimes rotation. When tornadoes are produced by supercells, they are located near the tip of the hook echo on the radar. But a hook echo doesn’t always mean a tornado is in progress.

The example above shows a hook-echo supercell near Lubbock, Texas, which produced large hail and strong wind gusts but no tornado.

2. Wrecking ball

Radar of a debris ball from a tornado that caused EF3 damage near Crossville, Illinois, on February 28, 2017.

(National Weather Service – Paducah, Kentucky)

Now that we know what a hook echo is, we can move on to the next radar signature that is sometimes seen within it.

The mention of a debris ball on radar is an indicator of a devastating tornado. This means the radar senses an area of ​​higher reflectivity in the hook echo, which is often associated with debris that has flown thousands of feet in the air.

Above is an example of a debris ball (purple shading in the hook echo) from a tornado that produced EF3 damage near Crossville, Illinois, on February 28, 2017.

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3. “TDS”

A tornado debris signature appears in a correlation coefficient radar screen from a tornado that caused EF4 damage in Newnan, Georgia, on March 25, 2021.

(National Weather Service – Peachtree City, Georgia | Annotation added by Weather.com)

This is the abbreviation you may hear that stands for “tornado debris signature.” Like a debris ball, it means the radar has detected debris high in the air from a tornado in progress.

Upgrading National Weather Service radars to dual polarization technology earlier this century allowed meteorologists to see the TDS and report that a tornado is occurring and causing damage, even if it occurred at night or no observers have seen it yet. It is often seen using so-called correlation coefficient (CC) radar data.

Airborne tornado debris is made up of items of widely different sizes and shapes, and falls to the ground much differently than rainfall, which is what the CC lab detects. The example CC radar shot above from an EF4 tornado that struck Newnan, Georgia, on March 25, 2021, shows the debris it lifted as a blue dot amid the broader area of ​​red echoes.

4. Bu Echo

A bow echo appears on radar in northern Wisconsin on July 19, 2019.

(National Weather Service – Green Bay | Stocks added by Weather.com)

This is the name given to radar echoes that bend outward from a larger line of thunderstorms (see arrows in image above). It is an indication of a concentrated area of ​​harmful straight-line winds in a line of thunderstorms.

Bow echoes show where rain-cooled thunderstorms push to the Earth’s surface and spread horizontally. Wind gusts in bow echoes often range from 60 to 80 mph, sometimes higher.

One or more of these curved lines of thunderstorms can be long enough to be called a derecho, a large-scale wind damage event.

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Chris Dolce He has been a senior meteorologist at Weather.com for over 10 years after starting his career with The Weather Channel in the early 2000s.

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