Category Archives: Definitions

“This (dry air) will not stand”

Pretty tough day, yesterday.  After a few altocumulus floccus shred clouds around dawn until around 7 AM, the sky became absolutely, totally clear.  Once again, I did not expect this.  (There are a lot of surprises in life when you are a weather forecaster.) I thought shirley1 a few small Cumulus would form later that morning.  Nope.  Absent clouds,  I had little to say to my riding partner yesterday on our mid-week ride.  I think she took it as a pleasant departure from the continuous stream of cloud commentaries she normally experiences. (hahaha, sort of).  It was wondrous seeing the carpet of green erupting from oven baked soil of this past late winter and early summer.  That has to be one of the truly great things about living here, that second greening when the summer rains come.

However, I am heartened by the presence of Cirrus from the tropics this morning and a clear push of tropical air back toward Arizony already,  as seen in the water vapor loop here.  Look to the south of us and see that massive “army” of water molecules (that whiter area covering northern Mexico) push westward against the bad dry air (darker regions) from the Pacific that invaded us yesterday.  Fantastic.   Maybe a storm chasing trip to Douglas tomorrow is in the cards.  I really dislike a day without thunder in summer! (Perhaps I should have moved from Seattle to Tampa-St Petersburg, the latter the lightning capital of the US, instead.)  Just kidding, though it would be fantastic to be there in June!

Mods say that the summer rains will begin recurring maybe as early as Saturday in the vicinity of Catalina.  How fine that will be.


The End

1I once knew a Shirley.  We were just friends, though, nothing lurid that’s worth re-tellling here.

“Groundhog Day” all over again

If you mainly focus on going to movies about weathermen, you will remember this classic along with Steve Martin’s “LA Story.”   Bill Murray, the weatherman, is condemned to live the same day over and over again until he gets it right. Since yesterday was a near repeat in many respects to the failed rain day of Monday, this seemed like an appropriate title.

1.   OK, morning:  some really nice Altocumulus castellanus (miniature Cumulus clouds with flat bottoms) and “floccus”–raggedy bottoms1. These indicate a nice drop in temperature as you go upward in the “middle-levels” (around 10-15 Kft above the ground) and that in turn helps the formation of thunderstorms.

2.  Clouds topping Mt. Sara Lemmon again indicating a grade of  “juicy” moisture hereabouts.

3.  Very early thunderstorm, first thunder heard a 10:40 AM in a mountainous Cb N of the Cat Mountains (shown below in its, “Cumulonimbus calvus” stage;  top is ice, but is not yet CLEARLY fibrous, striated).

Seemingly all is in place for large thunderstorms to be scattered hither and thither later in the day, rumbling and banging around, scaring cats and dogs with lightning sabres, blinding rain, puddles in the road, TEEVEES out of whack, missing your favorite show, “TV party tonight2” canceled.  OK, enough dramatics and songs2.

But it didn’t happen did it?  Why not?

One of those very circulations foretold in the numerical models slipped over us yesterday during the day, and as these circulations do (you can see it here in this long “water vapor” loop)-you’ll need a broadband connection to see this.   You’ll see a miniature low spin into SE AZ from Sonora, MX, late on the 11th-early yesterday morning.  The darker area rearward of this circulation represents horrible drier air in the mid-levels especially.    The whole point of this loop is to show that drier air moved in and desiccated the otherwise growing Cumulus clouds following the passage of this micro low above us.  The very raggedy tops of our afternoon Cumulus clouds was an indicator of this extremely dry air that did not allow them to explode upward with the afternoon’s heating.

You could see this happening since,  in a homogeneous air mass, there would be no full blown Cumulonimbus clouds just to the north semi-circle of Catalina, and only weak Cumulus with ragged tops spearing that dry air at the same time in the southern semi-circle from Catalina.   I started to get depressed.   Something was going wrong, the air was getting too dry upwind.

Still, the there were enough Cumulus and Stratocumulus around at sunset to produce another memorable sunset.  Maybe that’s reward enough.

The End.



1distinguishing between the two is a bit silly IMO.

2Who can forget the Black Flag tune, “TV Party Tonight”?  “We’re gonna have a TV party tonight!  All right!”


Kind of sad today.  Too sad to think of a title.  Thought you’d like to know that.  Yesterday was once so promising.  I almost had it all.   I was SO happy to see clouds topping Mt. Lemmon at dawn, and then later, cloud bases down on Samaniego Ridge east of Catalina.  How warm those cloud bases were (maybe 15 C)!   And how full of condensed water those Cumulus and Cumulonimbus clouds later on were going to be!   I opined from this very blog that we would have a big day in the area.

As the morning wore on, it was as though my thoughts were magical and could make things happen by only thinking them, the Cumulus that morning churned, roiled and boiled upward as though on command. The first shot below shows one of those boiling,  ominous clouds so full of promise at only 10:19 AM.  It was so GORGEOUS!  Then, but nine minutes later, in the second shot, a turret had powered up to through the “glaciation level”, where the highest portion (uppermost part) had become cold enough to convert to ice right before my eyes (that top 25% frizzy part).   As you know, this means that the Cumulus congestus had become a Cumulonimbus “calvus” with a strong rainshaft.  Minutes later, the “capillatus” stage was reached and an anvil began spreading northward!

Thunder was heard by 10:29 AM! This was perhaps the earliest occurrence ever for thunder  over the Catalinas as the day’s new Cumulus buildups began.  Really, I could not praise myself enough for having looked out the window at dawn for a few seconds, and then magically deduced from a perusal of the sky what the cloud future would hold.  It was really pretty remarkable; daring even.  I looked forward to the rest of the day.  Maybe Catalina would get another inch of rain from some massive complex that afternoon or evening.

But then things began to go bad.  It began to get cloudy, though admittedly there was a brief shower that brought 0.01 inches (third photo).   You could see that with the increasing “stratiform” (flat) cloud cover that things were going “south”–not really “south”, its just a figure of speech indicating a downturn.  The clouds were mostly going north.

There were no more new Cumulus clouds building up over the Catalinas due to this heavy cloud cover.  It “sprinkled-its-not-drizzle” for a coupla hours.   Seemed like Seattle rain, as a former Seattetonian.  Why was I experiencing Seattle rain in Catalina, AZ?  Finally, the afternoon ended dismally with this heavy overcast of Altocumulus opacus.  I usually love Altocumulus clouds, but not yesterday.   They were offensive to me.  I had been humbled thoroughly and completely; felt like a mashed down Cumulus humilis at the end of the day.  But then, humble is good, isn’t it?  I began to feel better that I had been wrong because I learned something and was now humble.

At least the day ended up with a pretty sunset due to those obnoxious Altocumulus clouds combined with the “topography” of a distant thunderhead that caused rays in the sun’s light to appear in the “cracks” of that distant cloud top.  Those rays are called “crepuscular rays”, as we weatherfolk call them.   But a friend recently told me that they were also called “stairway to heaven”; very poetic and much nicer than “crepuscular rays.”  Enjoy.

Not speculating on today’s weather except that we should still have a chance for a big day here in Catalina.  (After the word, “except”, you can say almost anything.)

The End.

Too much “Altostratus cumulonimbogenitus”

Yes, that really is a cloud name;  kinda silly really.  Oh, well….

First, since there wasn’t enough rain here to make me happy–there wasn’t ANY in Catalina yesterday, I thought I would start out by making people feel better with a “Clouds R Fun” photo from yesterday.  Here are two “puppy” clouds, side by side, ones I thought might grow up to be Great Danes, but didn’t.  Still, they’re awfully cute anyway.  You just want to cuddle them.

Now that we’re all feeling that bit better thinking about puppies, we can move ahead to solving what happened and why Mr. Cloud Person’s expectations of signicant rain in the immediate area were not realized.   If you are a really good sky watcher, off in the distance, large Cumulus and Cumulonimbus erupted explosively well before noon.  I was so happy!  This could be a “totally awesome” day, I thought!   Look at these photos taken  at distance “Cbs” to the south of Catalina before Noon.

In the first shot taken at 11:45 AM, to the right, a full blown “Cb”, to the left partially hidden by Pusch Ridge, Cumulus congestus clouds.  Now look at the next photo in that same direction.   That group of Cumulus congestus beyond Pusch Ridge have exploded into a massive Cb with a giant anvil (“incus”)!  Areas near Green Valley, toward which these photos are taken,  got 1-1.5 inches.

But there was something pernicious going on right in front of my eyes; those huge anvils (“inci?”) that were being ejected by these explosive thunderheads.  Those can actually be a BAD thing because if they spread over the whole sky, they tend to kill off the Cumulus clouds underneath them by shading the ground, often teamed up with a subsiding air pattern.  While the air rushes upward in hot spots in these complexes, there must be compensating downward and cloud killing motions somewhere around it. It seemed to be the case as that huge complex S of us yesterday afternoon fizzled out and left a giant mass of—you’ll want to exercise you tongue before trying to pronounce this—“Altostratus cumulonimbogenitus” spread over the sky in the afternoon (last photo of a Seattle-like sky over Catalina). This smooth layer cloud is really just the remains of thick anvil clouds from all those “Cumulonimbus capillatus incus” clouds earlier in the day to the south of us.

Were there huge storms relatively nearby yesterday?

You bet!  Take a look at this loop from IPS Meteorstar, one that combines radar echoes and shows the spread of the thunderstorm anvils, the “whitest” and coldest topped clouds in this loop.   Notice what happens near the southern Arizona border about the time the second two photos above were taken.  Just an explosion of grouped thunderstorms with their flash floods that we call “meso-scale” complexes.  With luck, a bit different weather pattern, we could have been under that. Darn.  We’re still having conditions to produce large severe storms.  Maybe today will be our day.

Here’s are the cloud signs for today for why it is especially ripe for high rainfalls:  Its moist through about 40,000 feet above the ground and the cloud bases are LOWER today than yesterday.

How could you tell that just gawking at the sky and our Catalina mountains?  Well, you got yer Cirrus (high level moisture), you got yer Altocumulus (mid-level moisture) and you got yer Stratocumulus, some of which are topping Mt. Sara Lemmon (low level moisture)!

Now this last factor is really good in indicating the chances of 1-2 inch rains under the main shafts of our thunderstorms today–nothing too unusual, however, for AZ .  Lower cloud bases means warmer cloud bases, and warmer cloud bases in the summertime is like adding a furnace inside those towering Cumulus clouds due to heat released when condensation occurs.  And the warmer the cloud bases, the more water that is being condensed inside them.  Is anybody still reading this? Better quit here; I’m even getting saturated.


The End.

Stormy, pretty weather

It’s great when things are as they are supposed to be.  Below, “the usual” kinds of scenes in July in southeast AZ from yesterday, such as Cumulus boiling off Mt Lemmon in the late morning, followed by dense rainshafts in almost every direction in the later afternoon.  I love these scenes!

Well, “usual” for SE AZ, except that high reaches of the Canyon del Oro wash watershed were deluged by 2-3 inches of rain (see two of those dumps in progress in the second and third photos below).   And Mt. Sara Lemmon had over 2 inches! (Must check washes out this morning to see if any are running around Catalina and environs, and how green it is already starting to get.

Here in Catalina land, after another 0.27 inches yesterday and overnight, we now have had 2.37 inches since the beginning of July!

The very pleasant news ahead is that the numerical forecast model by our friends in Canada, that can be seen here, is now suggesting, based on last evening’s data, that a series of itty bitty disturbances1 in the upper air are going to affect our region from now through July 13th.  These little lows/troughs arise from the tropics and their role is to take the underlying humid air and organize it into larger clusters of thunderheads (aka, “Cumulonimbus capillatus incus” clouds;  use this name if you want to impress your friends) so that the rains last longer, and might be heavier than on days with no disturbances aloft.  How cool is this forecast except for those times when the roads are impassable?

I have not yet checked other model outputs, ones that might be different, because I like this Canadian one the best already and don’t want to know other things that might ruin my current very good mood.  Ignorance truly IS bliss!  However, I do feel that the “pendulum” has swung back to the wet side here, as it always eventually does in climate, and so there is that pinch of intuition thrown in that wet forecasts are more likely to be correct.  Lets hope so.

Finally, even ordinary gray skies are pretty, even dramatic and interesting in weather like this.  Check out the last photo, taken in the evening after the first rains in Catalina.

The End.

1 In the perhaps unneeded technical jargon of atmospheric sciences, they might be described as “mesoscale”–namely, ones much smaller than the gigantic highs and lows we see on the usual weather maps for the whole US












Check this out for yesterday at 6:05 and 6:15 PM.  First, part of the precursor FULL rainbow to the east of Catalina.   (In most locales a rainbow to the east would mean the storm has passed.)  The second shot was taken at the height of this magnificent storm.  I thought I had seen it rain as hard as it could here, and with as low a visibility as possible  last summer.  But, no.   This topped them all!  Golder Ranch Road, only a few hundred yards north is gone, and I could hardly make out our horse, Jake, in his corral, only 50 yards or so away!     At this moment, too, the wind raged.  Everything was moving violently amid the occasional lightning strike.  The wind probably reached 50 kts (60 mph) during one of two of the violent puffs that came through at that time.  It was just incredible;  unforgettable.

The rain?  1.01 inches of which most (about 0.9 inches) fell in the first 20 minutes!  Lots of erosion apparent today in our modest gravel roads.  We’ve now had more that 2 inches of rain in only the first five days since the summer rains started.  Fantastic.   Even today, after only a few days with rain, there were traces of green at the bottom of otherwise dead looking grasses.  And, now some of the washes will start to run for awhile, too.

And, more days with strong storms here and there are ahead.  How great is this after our crummy winter?


Both the rainbow last evening, and in a momentary language lapse below….

A once-severe severe thunderstorm with warnings out at one time, whimpered into Catalina last evening giving us just sprinkles or, in aviation parlance, “RW–” (meaning, “very light rain shower”) And long with it, one of our memorable sunset views of the rocky faces of the Catalinas.  Total rain?  A “trace”; i.e.,  not measurable, but drops fell.

Once again I will take this opportunity in the event of very light rain consisting of sparse drops to educate:  Its not “drizzle”, DAMMITALL!

My apologies; probably shouldn’t cuss while educating.

What IS “drizzle” then?  The People of Earth, well those people represented by the United Nations World Meteorological Organization, have officially defined “drizzle” as “fine, close together drops that virtually FLOAT in the air.”   They are LESS THAN 500 microns (micrometers) in diameter (about five human hair widths) at their greatest size.   The smallest size is 200 microns, since drops much smaller than this do not fall fast enough to qualify as precipitation.  Note, some researchers have termed drops from as small as 50 microns to 100 microns, “drizzle” drops.

If any TEEVEE weather presenter uses “drizzle” in the context of RW– (sprinkles)  type of rain, please turn off the set immediately, change channels, send in some angry e-mails to this “pretender”.  Find a weather presenter approaching the status of a “real meteorologist” who knows his precipitation!  In this vein, let us recall the memorable words of the National Science Foundation sponsored program, “Bill Nye the Science Guy” and one of the little Disney Studios produced ditties, Water Cycle Jump:

“Your brain is on vacation, if you don’t know about precipitation.”

Feeling better now.

(This ditty,  my favorite one, of course, from that program….)  ((On second thought, I REALLY liked the “Smells Like Air Pressure”,  the Disney cover of Nirvana’s, “Smells Like Teen Spirit” too.  Very funny and yet educational!))

PS:  Remember in the olden days, when, say a baseball manager excoriated an umpire using “colorful” language?  Cussing was quite “colorful” back then.

Happy desert everyone!

I think it should be a holiday when the summer rains have crested over the inch mark, a “personal holiday” anyway, if you get one where you work.   With a second day in a row yesterday with THREE sets of thunderstorms going over Catalina, and hearing thunder from about 1 PM until 9 PM, it was a fantastic day.   And if you didn’t get goose bumps watching the sky darken over the Cat mountains around 5 PM (second shot), well, I feel sad.

Me?  I vacated dinner to make sure I didn’t miss anything as that started to happen. Its a matter of priorities.  I am a poor dinner guest in summer.   But what a dramatic sky that was in its greenish blackness rising over the Catalina mountains!

And with 0.36 inches total yesterday,  and a nice lightning show between 7 and 9 PM, the rain gauge in my gravel driveway has now received 1.09 inches over the past 48 hours.  Happy desert!

Some areas of the Canada del Oro wash watershed received over an inch in the past 24 h after having been largely bypassed by the previous day’s rain.  So, that is great news, too.  Is there anything better than seeing water in the washes here in the desert?

So, we have “inched” that bit closer to that happy happenstance, to be alliterative there for a second.  To the left, one of those intense rainshafts that did it.  Rainshafts are like tree roots in a way.  Sharp, vertical rainshafts like this one (looking toward the Charoleau Gap) are likely associated with tops right above it that are probably 40,000 feet or more above ground level.

And of course, with the outflow winds gusting to around 40 mph, there was some very local some storm damage as well along with some flooding (documented below).

Seems like another day with great clouds (like those in the last photo), rain and lightning around.  Enjoy!

0.73 inches

Bullseye thunderstorm off the Catalina’s between 12:30  and 1:30 PM really did it, dropping a miraculous 0.55 inches.  I suspect that 300 yards N and S got less than our driveway did where the gage is located.   The smells, the puddles, the water running down the road; it was all so marvelous, and seemingly it has been decades since we saw this kind of sight.  And then, after it looked like it might be “all over”. that dramatic darkening of the lower cloud bases pushing over the Catalinas from the east suddenly began to occur around 6 PM, followed by another nice rain of 0.14 inches.   While we did not get the core of that massive system, it was great to see all the rain fall in western Tucson from here, knowing how dry it is everywhere.   Finally, that little bit of rain after dark, plumped the gage another 0.04 inches to bring the total to a wondrous 0.73 inches, every drop so necessary now!

Below, a sequence of the cumulus building off the Catalinas, beginning around 10 AM, ending with the approach of the main “dump” just after 1 PM.  Sometimes seeing this happen, and being so close to it reminds me of being in an airplane meandering among the Cumulus.  The second shot is a great indicator for the rest of the day, a tall, skinny little cloud1 that shows just how ready the atmosphere is to allow huge clouds like yesterday to happen.  Seeing that type of cloud should really get you excited about what the rest of the day holds.

An even better way to view yesterday, in a cross section mode, is from the U of AZ time lapse video here.  You’ll be amazed by these “volcanic eruptions” of Cumulus and Cumulonimbus clouds over Mt. Sara Lemmon.  Better hurry though.  Movie is overwritten by today’s later on!


Finally, the “icing on the cake” to be quite unoriginal; that wonderful sunset.

The End except for the footnote.

1You might well call the cloud in the second shot,  “Cumulus castellanus”, though technically there is no “castellanus” variety for Cumulus as there is for other cloud genera like Stratocumulus.  You could just call it a “towering cumulus”, the kind of remarks seen in airport aviation weather reports, though for some reason my mind always drifts into other domains completely;  paleontology, anthropology, and I think of that early man, Homo erectus.  Perhaps it was too risqué for those naming clouds to use that modifier as a variety name.

Rainy portent in a scruff of cloud

….that scruff of cloud topping Mt. Sara Lemmon around dawn this morning, to finish the thought.   This:


Because seeing a cloud topping Mt. Lemmon instead of well above it indicates that the air is very moist and cloud bases are going to be realtively low, substantially lower than yesterday.  This in turn means even more rain will reach the ground after falling from cloud base today, more of the terrain will be involved with launching deep clouds later this morning,  with their crayola black bases and impenetrable rainshafts scattered around the area this afternoon and evening.

Will we get one of those rainshafts?

Well, no one knows exactly where they will be, but my best guess, based on a few summers here, is that Catalina will at least get measurable rain today, and a real dump of a half an inch or more is well within range.  Yesterday, two brief light showers only gave us a “trace” of rain.  Darn.  But, if you noticed, the rainshafts from the clouds yesterday were denser than the day before, and that trend will continue today.  Sometimes these dumps, just like the 4 PM shower yesterday, are invigorated and started by the gush of winds from dead showers off in the distance.  One of the patterns here is for a gush of wind to blast out of the N or NE, and suddenly, the clouds overhead start filling in in response to the gush of air.  The gush causes the air over it to be pushed up.   And, this can happen very rapidly, going from clouds that draw a yawn, to “Oh, my gosh, look how dark it is over us now!”  Better lie down now for a moment until this gush of excitement passes over.   But, this is going to be a GREAT day for Cumulus and Cumulonimbus clouds!

And what a sunrise display of lightning and a cumulonimbus clouds!