Kelvin-Helmholtz Disturbance: 9/19/15

My brother, James Price, took this photo in Socorro, NM, yesterday at 10:03 A.M. MDT. This is a Kelvin-Helmholtz disturbance. He said it had dissipated within about 5 minutes, so he was happy he got the photo, and granted me permission to post it on my blog.

While I am mostly a convective meteorologist and storm chaser, Kelvin-Helmholtz disturbances are one of those things that show that we are only scratching the surface of weather by discussing tornadoes and severe storms. Kelvin-Helmholtz disturbances are not something I look for when I am storm chasing; never have I seen one and thought, “Oh, today will be a great day in the field.” They are not typically associated with severe weather.

To see this visible representation, two things must happen:

1. We have to have the right combination of moisture and shear at the right level of the atmosphere. Without the moisture, there would be no clouds to see. Too much moisture, and the feature would be difficult to see because it would just mix in with clouds above it. With too much shear, the feature would be lost; but with too little, it would not take on the shape that it does in these photographs.

2. There must be a shortwave disturbance that causes the wavelike motion. This can come from any number of sources, including mountain wave pattern from air ascending and descending the mountains.

Looking at yesterday morning’s (12Z) sounding from Albuquerque, we can see that there was a moist layer near a dry layer at around 600 mb. There was also some slight directional shear about this layer, though not much.

However, given that this feature only existed for a few minutes, and this sounding was taken several hours earlier, 100 miles north, we will never know if this was the condition that was seen in Socorro.

My theory is that the conditions were similar; the dry layer on top of the moist layer would create the interface that was modified by the wave motion.

Instead of having stratified layers, we needed some oscillation to produce the wave pattern. Because Socorro is in a valley, and we had some upper level winds yesterday (due to the convergence of two jetstream branches), we might have been able to set up a mountain wave pattern. There would have been a slight breeze flowing up the western side of the mountains, as well as some sinking air from the 300 mb level (due to the convergence). Some combination of the two, led to a wave pattern that disturbed the interface between the dry and moist layers, leaving the cloud pattern we see in my brother’s photograph.

At least, that is how it could be generated from the Synoptic through Micro scale. There could also be explanations from the planetary scale as well.

It is a fascinating feature!

Thank you for reading my post.

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About highplainschasing

This blog is about my tales in storm chasing. My name is Seth Price and I am an instrumentation instructor at New Mexico Tech. My amateur radio call sign is N3MRA.
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