HCR?

[Bob Schafer]

At 1845Z last Saturday (day of Tulia/Cactus storms), as the upper-level trough approached me in Los Alamos NM, I discovered this from my SW to W of me (almost directly above me):

http://new.photos.yahoo.com/scudstudbob/photo/294928804350347119/0

At the time, IIRC, the strongest 500mb winds were still somewhat W of this location, but clouds were streaming by SW-NE at a pretty good clip. Since the elevation here is 7300 feet, or about 770mb, I would estimate that that feature in the photo was at approximately 550-600mb, oriented just about due N-S. The Jemez mountains are just W of here, which may well have contributed to its formation.

Would anyone say that that was a Horizontal Convective Roll?

If you look at the photo closely, you'll see that most of the cloud appears dark, as in shadow, but the interior, appeared white and convective. Look at it about 1/3 from the right edge.

Here's another look, facing further N:

http://new.photos.yahoo.com/scudstudbob/photo/294928804350330978/1

This was not a jet contrail. Anyway, it was pretty darn cool! Looked like a horizontal roping-out tornado. It persisted for about 3 minutes after I first discovered it. (Pics edited a bit to enhance contrast and brightness)

BTW, would someone please point me to some instructions about how one goes about getting photos to appear in the posts at full size? I made it work once some time ago, but can't seem to figure it out anymore.

 

[Adam Atkins]

Bob, if I'm not mistaken...aren't HCR's boundary layer phenomena? Products of convective mixing in the boundary layer methinks. Can't quite tell what that is because I didn't know its motion, but it's a cool striation in the cloud deck. If you were east of the trough axis there was forced ascent...maybe an elevated inversion layer can cause that striated feature.

 

[Jeff Snyder]

Bob, if I'm not mistaken...aren't HCR's boundary layer phenomena? Products of convective mixing in the boundary layer methinks. Can't quite tell what that is because I didn't know its motion, but it's a cool striation in the cloud deck. If you were east of the trough axis there was forced ascent...maybe an elevated inversion layer can cause that striated feature.

Yeah, HCRs are the result of vertical wind shear in a stable boundary layer, which explains why HCRs rolls tend to break down during the day as the surface warms and static stability decreases (buoyancy increases w/in the boundary layer).

It looks like some sort of wave, perhaps a sort of gravity wave atop cooler air (e.g. a strong inversion). Is there a nearby (in time and space) sounding?

 

[Bob Schafer]

Is there a nearby (in time and space) sounding?

Short answer: No to both. ABQ is about 60 miles away, and it was 1845Z. 60 miles might not be much, but there is mountainous terrain all around here that (I assume) would really make a sounding analysis moot. Have a look, if you like, anyway:

12Z:

http://vortex.plymouth.edu/cgi-bin/...y=07&mm=04&dd=21&hh=12&pt=parcel&size=640x480

4-22 00Z doesn't seem available.

Also, this was in a spot where sfc elevation decreases rapidly W to E. Pajarito Ski area, at 10,000 feet, is about 10 miles W, and the Rio Grande river, about 12 miles E, is at about 6000 feet.

E of trough axis at the time.

 

[Jeff Snyder]

Short answer: No to both.

I don't know a whole lot about topographical effects on meteorology. However, looking at that sounding, there does appear to be a layer that's nearly isothermal (a layer through which the temperature is constant, which means that the potential temperature increases rather quickly with height, indicating high static stability). This very stable layer (~450-400mb) is also at the base of a deeper layer that is nearly saturated. Perhaps this can account for a wave atop a stable layer, above which there is near-saturation (indicating potential cloud cover). The difference between your guess of 550-600mb for the height of the feature and the 400-450mb isothermal layer could be attributable to the change in elevation and different atmospheric conditions between the two locations. Just an "educated guess".

 

[Bob Schafer]

Impossible to say what caused it. Impossible to analyze what happens atmospherically around these orographics. The sounding was obsolete given the encroachment of the trough, as well as the time and distance. etc., etc.

But I do like your observation of the two air masses there, Jeff. Maybe some shearing there..... maybe not?

Anyway, it was, as I said, cool. Something I've never seen before.

 

[Jay Bell]

Hey Bob!

I mostly lurk here, but I'll chime in. That looks like a Mountain wave...also called a Lee wave. Check this link out:

http://en.wikipedia.org/wiki/Lee_Wave

As an airline pilot, i have seen many of these...and it makes for a very bad day. Rather than trying to get into a long explanation, refer to the above link as it does explain the feature pretty well.

Hope this helps!

Jay Bell

 

[cdcollura]

Could be a horizontal roll (or even a horizontal vortex) but at MID levels. These can and do exist, but are above the boundary layer.

HCR's exist more in a sheared boundary layer as it is beginning to heat up / mix.

It could even be non-meteorological, like a turbulent wake / vortices from a jet aircraft flying through the cloud layer (the vortices are the two lines that appear in the right side of the feature in the picture) - Not a contrail, but the turbulence / votex left behind a passing plane.

Just another possibility.

 

[Bob Schafer]

Good job, Jay! I'd be willing to bet that it was a rotor as described on the Wikipedia page.