Tracking Downbursts on Radar

The last several storm complexes that have rolled through the state have produce strong downburst winds. You’ll remember the winds hit 90mph in Lahoma and 80mph in Perry, where there was substantial damage. It is extremely hard for meteorologists to track and accurately forecast downburst winds. Downburst winds can occur quickly and with no notice.

We use the terms downburst and microburst almost synonymously. But, there is a difference. A downburst wind is a strong downdraft which causes damaging winds on or near the ground. A microburst describes the size of the downburst.

What typically happens this time of the year is a line of thunderstorms form and produce an outflow boundary, a gush of air that races out ahead of the line of storms.

 

Downburst winds in this environment tend to form where the heavy rain is still occurring. Those are called wet microbursts or wet macrobursts (depending on there size). Just like a rain-wrapped tornado, they’re basically impossible to see ahead of time. Where as an outflow boundary is out ahead of the rain can pick up dust or dirt, making it easily visible on radar.

How would we see downburst winds on radar? By using our velocity products. Since downburst winds spread out in all directions from a single point, we look for winds that are traveling in different directions embedded within the heavy rain.

Here are some radar examples from an event in South Dakota:

With velocity, green is air headed toward the radar site (upper-right of screen), red is air going away. Notice with the outflow boundary, the air is unidirectional. Behind the outflow boundary, a downburst has developed. You can see the red and green pixels next to each other, moving away from a fixed point. Downbursts are so localized and happen so fast, they’ll typically only show up on one radar sweep, or perhaps even develop and dissipate between radar sweeps.

 

 

 Here are a few more downbursts from the same event. Many of the downbursts from this day produced winds of 50 to 80mph.

 Rusty

 

Advertisements

There are no comments on this post.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: