The Arizona 500 – Cloud-maven

Its not about car racing…. though that might be more exciting than what I am going to write about. This is a discussion about 500 millibar maps and what you can get out of them.

Here’s this morning’s 5 AM AST 500 millibar pressure map below. Knowing that sea level pressure averages 1013.6 millibars, then 500 millibars, around 18,000 feet or so, is about halfway through, in pressure anyway, ALL the air above us that we have on this planet. Thins out, of course, as you go higher; 10 millibars, for example, is around 120, 000 feet above sea level. You don’t want to be there. Thought I would check around for that height of the 10 millibar level, and here’s what I came across

At this link on the web, however, it is calculated that the 10 millibar level is reached at “5.48 miles” above sea level, and at 4 miles above the sea level, about 21,000 feet, the pressure is but “13.44 mb”! I started laughing because you’d need a space suit to be at the top of our Mt. Lemmon with a vertical pressure distribution like theirs. Yikes! No wonder our math and science scores are behind those in the developed countries!

The pressure at 4 miles above sea level (at 21,000 feet) averages about FOUR HUNDRED FIFTY millibars, not “13”, fer Pete’s Sake, and its still about 320 millibars at the top of Mt. Everest, about 5.5 miles above sea level. I guess these folks don’t do any hiking above about 1,000 feet above sea level. Might be too dangerous without an oxygen bottle in the atmosphere they’re making calculations for. (Looks like someone mixed units; English and metric in their calcs.)¹

Now, where was I?

Oh, yeah, this morning’s 500 millibar map… Note where the wind maximum is around a cold trough that is about to pass over us, the one that extends across Utah to Vegas. The peak wind is just about over us, and as the day goes by, it drifts farther south. So what, you say?

Check below where the moisture is at mountain top level, or around 700 millibars, 3 km or about 10,000 feet above sea level.

Temperatures and moisture at 700 mb, about 10,000 feet above sea level, also for this morning at 5 AM AST. See how the moist air at mountain top level is contained within the wind maximum at 500 millibars. Its just how it is here in the interior of the SW–doesn’t work so well along the coast or north of Salt Lake CIty, UT, or much east of Denver in the wintertime, but it is a pretty solid relationship for hereabouts.

Later today, that green area will be over us and there’ll be some scattered showers. Cloud bases will be high, higher than Mt. Lemmon, and so the precip is going to be pretty marginal. Will be very happy if even a few hundredths of an inch falls in Catalina this afternoon or evening. BTW, with the freezing level so low again this afternoon, soft hail (graupel, tiny snowballs) falling from these clouds is a certainty this afternoon or early this evening. (I’ve repeated some of this in the caption below…. Hmmm. Mind going.)

Here is the latest surface map of obs and infrared satellite imagery on top of the obs from the U of AZ. And, if you look out the window now, adding this at 6:45 AM, you’ll see the first clouds with this trough, likely good enough for a bit of sunrise color here in Catalina.

5 AM AST this morning. Good thing this trough and its minimal amount of moisture is swinging over us in the afternoon since a nightime passage would not have the scattered glaciating Cu and small Cbs we're going to see later today. — 5 AM AST this morning. Good thing this trough and its minimal amount of moisture is swinging over us in the afternoon since a nightime passage would not have the scattered glaciating Cu and small Cbs we’re going to see later today. And, by the way, the skies should be real pretty, too; big long shafts of virga falling from high based convective clouds. And, as you can see, some jet stream layer clouds–Cirrus, high Altocumulus in advance (near tip of arrow at bottom. Likley another day for lenticular clouds before the cold core gets here. Lots to look forward to today!

What’s ahead? Storms

Storm world, that’s what’s ahead because we’re in the bowl now, the trough bowl, resulting intermittent periods of storminess, broken by deceptively nice weather for several days; the latter, times of some trough fakery, one that make you think the “bowl” is gone. But then its BACK! So, don’t be afraid when the weather turns nice again after today.

Here is a sequence of maps from IPS MeteoStar ones that document what I am trying so poorly to explain, the overall spell of storms that we’re in, where one cold trough after another is drawn to Arizona like metal filings to a magnet. First the “interruptus”, now on deck, a map for about five days from now. For some reason, I put all of what it means in the caption.

Valid February 16th at 11 AM AST. No trough nowhere near Arizona. In fact, it looks like the trough bowl might be relocating to the Ohio Valley down to Natchez, MS. This is pure trough "trickeration", the latter a term used in football for trick plays where somebody looks like they're doing one thing and then they do something entirely different. So at this time, you're going la-dee-dah, no more storms, just nice weather now for quite a while and at the same time read about bad storms and cold in the eastern US. But you'd be so WRONG, as we like say around here. — Valid Saturday, February 16th at 11 AM AST. No trough nowhere near Arizona. In fact, it looks like the trough bowl might be relocating to the Ohio Valley down to Natchez, MS. This is pure trough “trickeration”, the latter a term used in football for trick plays where somebody looks like they’re going to do one thing and then they do something entirely different. So at this time here in Arizona, you’re thinking, “la-dee-dah, no more storms, just nice weather now for quite a while”, and at the same time reading about bad storms and cold in the eastern US. But you’d be so WRONG, as we like say around here. Look at that trough coming into the Pac NW. Guess where its headed? By the time that one gets here, you’ll realize that you went for the “fake”, and that all is not well weatherwise in Arizona, and more troughs after that one piles on top Arizona, bringing bountiful late winter rains, one after another. Finally, you go back to Michigan, you can’t take it any more, because you only came here for the good weather, not to stay and be one of us for the whole year….

Valid for 5 PM AST, the 20th of February. Now look who's bowlling! Its Arizona! Lot of great rain foretold with this one. — Valid for 5 PM AST, the 20th of February. Now look who’s bowlling! Its Arizona! Lot of great rain foretold with this one.

Valid for 5 AM AST, Sunday, February 24th. More rain on the doorstep.

Valid for 5 PM AST, Tuesday, February 26th. The grandaddy, the Big Bopper, a crescendo of troughy-ness occurs.

In conclusion, and remembering that these exact depictions above are not going to be realized as such, they will vary in intensities and positioning; nevertheless, the prediction from this keyboard is that February 2013 will have ABOVE NORMAL precip in just about all of Arizona due to storms that occur in the last 15 days. I am really happy for you, and its always great to conclude things like this, conclusions that bring so much happiness to others.

The End

————————

Mr. CMP, in a twinge of conscience, realizes that the error he goes on about today is one that he himself would like have made during his struggles in math and physics in HS and college.

By Art Rangno

Retiree from a group specializing in airborne measurements of clouds and aerosols at the University of Washington (Cloud and Aerosol Research Group). The projects in which I participated were in many countries; from the Arctic to Brazil, from the Marshall Islands to South Africa.

View all of Art Rangno's posts.