Local Weather History: Asperitas Clouds Twice In 4 Days!

What causes these relatively rare clouds in our area?

Posted: Sep 6, 2019 4:55 PM
Updated: Sep 7, 2019 1:07 PM

Asperitas clouds moved through Greater Lafayette & part of the viewing area this morning.  This is the second occurrence of this type of cloud in 4 days.

They are relatively rare & particularly picturesque & interesting.

They exhibit a variety of dark, ominous hues with wrinkles, swirls, rolls & waves in the clouds.

I remember seeing these clouds on two occasions as a kid, but they were not classified until 2017, though a classification was proposed in 2009.  I do actually remember one other time I saw them & it was in June 1996 during State FFA convention up here in Lafayette.  We were staying at the old Days Inn off Sagamore Parkway & South Street & following an evening of heavy storms with a Tornado Watch, the next morning at 8 a.m., they were all over the sky.  They were so interesting & unusual that they have stuck in my memory all this time.

This is an image of them this morning near West Lafayette.

In our area, they:

1.  Often occur in the morning when it is cool & stable at the surface with rather dry, lower dew points near the surface while........

2.  .....there is elevated instability or unstable parcels aloft above such a stable surface layer.

3.  A pronounced inversion is present at low levels.

3.  They usually occur as remnant storms/convective activity penetrates an area that has that cool, stable layer with the strong inversion in the morning.

4.  The turbulence associated with remnant convective activity or gravity waves associated with it can make really interesting waves with that inversion (where the cloud bases are) like shaking a blanket as 5 different people hold it.  Or, it looks like a you are looking upward at the surface water waves & currents near the shoreline from the ocean floor.

5.  Strong winds & dynamics (with those unstable parcels) above that stable, drier layer can also make for the Asperitas clouds.

6.  Strong inversion is a key. 

Case #1:

Tuesday Morning.....

Wake low kept storms going with good dynamics Tuesday morning.  Unstable parcels were forced up & over stable, drier layer near the ground.  Storms passing just northwest of Greater Lafayette were on the edge of better instability that tended to be elevated above more inversion/stable layer.

The rising air & turbulence of the storms nearby & some gravity waves of the wake low with this stable layer produced this area of Asperitas on the edge of these storms from Benton to White & northern Tippecanoe counties.

Precision 18 Meteorologist Anne Brown caught this image of those Asperitas clouds.

Another shot of the Asperitas clouds on the edge of that storm was caught by Brett Wilcox in Benton County.

Case #2:

Friday Morning....

We were cool & stable from the overnight (with strong inversion), but shortwave with unstable parcels, the turbulence & perhaps subtle gravity wave from cluster of storms from Minnesota to Wisconsin to near Chicago caused the Asperitas to form this morning.  Those storms there produced hail up to golfball size.

Here, they just produced a few showers, including 0.01" at the Purdue Airport.

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