Category Archives: Cumulonimbus clouds

An extraordinary June 16th

Not only did Tucson set a daily record for rain on June 16th with 0.29 inches, breaking the old record of 0.20 inches that fell in 1918 (!), but here in Catalina, the 0.11 inches was the first measurable rain on June 16th in the 35-year combined record maintained at Our Garden, and then here for the past few years.

It was only the second day with measurable rain in Catalina since mid-April, and that prior rain was only a paltry 0.01 inches that fell in mid-May.

Regional rainfall totals for yesterday’s magnificent day can be found here, courtesy of the Pima County Flood Control District.  Two sites in the Catalina Mountains got hit hard, with 0.94 inches at Pig Spring, and a whopping 1.54 inches at CDO at Coronado Camp.  Those two gages are close to one another near the top of the CDO watershed.  Here is a map having those locations.  You can also get 24 h rain totals, ending at 7 AM today, from the U of A network here.

The best part, though, may have been those desert aromas that spring out of the desert when it rains,  and that cool air that rushed around Catalina yesterday afternoon and evening.  Makes you happy to be alive.  However, those two close lightning strikes were somewhat unsettling when you’re running around outside with a camera..

The drop in temperature as the rain hit was stupefying, about 35 degrees, from 100 F to 65 F!

Here are some photos, since I am still alive, the first ones of the Altocumulus perlucidus clouds that were mutating into Cirrus uncinus, a bit of an oddity.  The TUS sounding indicates that these droplet Altocumulus clouds were extremely cold, -30 C (-22 F).  And their presence was another live demonstration about how odd ice formation is in the atmosphere, still not completely understood.

By late morning the Cumulus were sprouting over the Catalinas, and the Altocumulus/Cirrus were gone. Those Cumulus clouds were a great sight since the models had very little rain indicated, and these were fattening up nicely suggesting those models might not have gotten “the scene” for yesterday right; there was more hope for rain after all.

Ice clouds on the left, droplet clouds on the right side.
Parhelia (sun dog) in the fallstreak of a former Altocumulus flake.
1:16 PM: Cumulus mediocris, center right, portends a good shower day.
2:11 PM. We are underway!
2:32 PM: Heavy rain falls on the upper CDO wash watershed.
3:01 PM: A strong shower complex appeared to the S toward TUS, giving hope of some rain here.
3:02 PM: Two very strong dust devils developed ahead of the outflow winds coming into Marana. They seemed odd since they were under the cloud cover and you start looking up to the base to see it there is a tube up there, and whether it is one of the dry tornado funnel cases.
3:09 PM. The thunderstorms over the Catalinas propagated to the west and here Saddlebrooke gets a dump.
7:33 PM: After our nice little rain, and as happens so often here in the summer rain season, we polish the day off with a spectacular sunset.
























The weather ahead

The next chance for rain, the best one I could find, of course, is next Friday and Saturday afternoons. For Friday afternoon, this, from the U of WA’s model.  The lightly colored, filled in areas represent rain.

Looking for just Cumulus today, maybe a very isolated Cumulonimbus cloud.

Fires and smoke

Yesterday afternoon smoke from the Gladiator-Crown King and Tonto fires began spreading toward Catalina.  Here are a couple of photos taken toward evening.  The first photo is of the Gladiator fire plume and the second has the Tonto fire plume on the horizon on the right.  You can see a bit of separation between the two plumes.

As is typical of fires, they flare up during the hot daytime hours as these did yesterday, and those plumes are the evidence from that.  This morning, like yesterday morning, the plumes are likely to be more like haze layers than plumes, but then the plume characteristic will likely return this afternoon and evening as the fires heat up again.

Plumes like these in the photos show fairly close origins of fires, where smoke that has drifted in from Alaska or Asian fires would not have the streaks and irregularities in density that you saw yesterday evening.  Those from very far away would be more of a whitish vellum over the whole sky in which the layer seems to be almost the same thickness as you look toward the sun.  Generally, you don’t see those “long-range transport” layers when looking opposite to the sun.

Below, a satellite image from the University of Washington showing where the two fires were as of 6:15 PM yesterday relative to Catalina (the circle).  You can just barely make out the plumes that were heading our way.

Also you can see how close a bunch of Cumulonimbus clouds got to us yesterday evening, ones moving from the N as a new round of rain spread over eastern Arizona, New Mexico and Texas.  Sadly, they will stay well to the east of us.













Earth on fire map

How does fire activity in the US and Arizona compare with worldwide fires?  Not so bad.

Below is a summary map of fires for the last ten days of this past April as detected by satellite. This image was provided by the University of Freiburg, Germany. These are not campfires, but full blown deliberately set or wildfires.

Kinda depressing. Those in the Saudi desert may just be those due to the burnoff of natural gas, yikes what a waste!

Also, you may notice not so much going on in the Brazilian rainforest, say compared with the jungles in central Africa-Zambia. This is mainly due to the fact that the rainy season is just coming to a close in Brazil,and most “biomass burning” takes place during the dry season, one that peaks in August, but also due to the Brazilian government’s attempts to reduce such fires in the “Green Ocean.”


The End.

Yesterday’s awful Cumulus clouds; better ones today!

From the University of WY Cowpokes, this awful sounding from yesterday afternoon at Tucson.  Where the two lines first pinch together, around the “500” label, is where the Cumulus cloud bases were yesterday afternoon (marked by the oval)!  To see why those Cumulus were awful ones with too much ice, check the temperature lines, the ones that slope upward to the right with the labels on the bottom, “0”, -10, -20, etc.   Yep, that’s right, the bottoms of those clouds were at 500 mb, and -20 C!  The Weather Cowboy sounding algorithm, the one that produces all the numbers in the column at right, thinks the bottoms of Cumulus clouds were even HIGHER, at 428 mb and nearly at -30 C (that “LCLP” number)!

So, the awful looking, dried out, Cumulus clouds have been explained.

Too high, too cold, too much ice.  Reminded me of the old days in Durango, Colorado, in the early 1970s.  Charming town, but awful place if you wanted to see Cumulus clouds without much ice.  Too high, too cold, and too much ice there, too.

What’s wrong with too much ice?

Too many ice crystals completing for itty bitty amounts of “condensate” (yes, Virginia, even at those temperatures, cloud begin as liquid droplets).  But when they are so cold to begin with, so many of the droplets freeze, that they all try to take the water from the ones that haven’t frozen (cause them to evaporate, the water molecules rushing to the nearest ice spec.

So when nearly ALL the droplets freeze, the ice crystals are all itty bitty as well, and can’t fall out, even though individually they may have a bit more mass in them than the droplets.  They just float up there and gradually die.

Stories from the field interlude

OK, gotta get this out…   In the domain of cloud seeding, where ice-forming nucleants are put into clouds, the phenomenon of having too many ice crystals would be called, “over-seeding”.  Believe it or not, deliberately “overseeding” clouds to make them look like the ones we had yesterday, and so that they wouldn’t rain has been tried!

Yikes.  Why?

The Coors Brewing Company, in the early 1970s,  did not want their hops in the San Luis Valley of southern Colorada (around Alamosa) spoiled by having rain fall on them at the wrong time.  The program was ended when alfalfa farmers in the same area, ones that WANTED RAIN, terminated the program prematurely with sticks of dynamite;  they blew up the seeding contractor’s radar, used to direct aircraft into the clouds to seed them.  Mr. Cloud-maven person, the writer,  was working in Durango in those days, on the other side of the mountains from Alamosa, on a scientific cloud seeding project (a randomized one) to see if seeding could cause more snow to fall from winter storms, so he was close to the “action.”

Yes, everyone gets excited about clouds and weather, especially alfalfa farmers!  Its so great.

Below a few shots of yesterday’s small, ice-ed out Cumulus.

The haze below this little Cumulus fractus cloud is due to ice having formed in it! Bad news from the get go if you're hoping for virga and rain later in the day.
Merely a Cumulus humilis, center, and having a bit of puffery. But its mostly ice. Quite awful-looking, really.

About today’s “better” clouds

Overnight there was an invasion of air from the east carrying increased lower level humidity. How cold will the bases be today after yesterday’s -20 C or so? Around 0 C our TUS morning sounding suggests. While that’s still cold, it should mean rain to the ground here and there in the fatter Cumulonimbus clouds that will be around even though they will be dominated by ice again. With these higher base temperatures, it means more water condensing in the clouds BEFORE ice forms. When that happens, you are likely today to get “graupel” forming in areas of the clouds where the condensation is greatest, and the ice just beginning to form. “Graupel” or soft hail, falls rapidly compared to ice crystals and aggregates of ice crystals (i.e., “snowflakes” to get away from jargon) and those graupel up there are likely to be what MAINLY gets to the ground today, melted of course, into raindrops. This because the “free air” freezing level is about 7,000 feet above us here in Catalina (3,000 feet elevation). Should be a fun day, reminding us of out upcoming summer rain season.

And, what do we think about when we think about graupel/soft hail forming in the clouds overhead?

Electricity, lightning!  Yes, these clouds will be getting “plugged in”, so to speak, this afternoon here and there.  Be watchful.


Nice display of Cirrus uncinus in the late morning as Cu began to form.

BTW, if you want a really expert discussion for today, go to Bob’s page here.  (He may weigh in on this later…) And,  of course,  our NWS here.  They seem to be getting pretty worked up and excited about today’s weather and all the wind that might blow out of our afternoon thunderstorms.

BTW, nice flowers out there in the desert now days; this on our “Arizona rose” (took about nine attempts to upload this!  Bad WP!)


The End.

Spinning on down from Glasgow to Rocky Point, a low

This is pretty interesting; don’t see this happen too often where a lobe of low breaks off and spins from Montana, back toward the south-southwest to pretty much over Rocky Point, MX, as you will see in this past 48 h water vapor loop.  In a water vapor loop, you pretty much see all that the movement that is taking place in the atmosphere and here you can begin to understand why it takes biggest computers on earth to model it.  Here’s a close up from IPS Meteostar.

Note, too, those white puffs exploding in west Texas as our little low spins thisaway.  Those are massive thunderstorms that our low has and will be triggering in west Texas and eastern New Mexico over the next few days.  This is great to see that happening due to the drought those poor folks have been experiencing over the past couple of years.  This little low, as tiny as it is, will make a huge dent in those conditions in some areas.  It really would be great to be there in some little town, like the well-named town of “Plains”, TX, and see how happy the folks are getting as the rains hit.  It would be like the end of a Hallmark movie where everyone is quite happy about how things have turned out.

Here are two shots showing what its like now in Plains-Floydada, TX, area,  First, you can see that the earth is quite flat there.

Note green along highway. It has been raining off and on in these areas for the past month, so things are perking up. There were occasional bursts of wildflowers, too.
These aren't horses. What are they?

But while Texans are getting happier and happier (and I hope they don’t complain about flooding because that would be just plain WRONG), what’s in it for us?

Well, the quality of moisture is less here toward the center of the low, maybe about 1/3 as much in the air over us as in Texas.  So, what does that mean we will see?  Maybe a few Altocumulus in streaks, maybe finely patterned Cirrocumulus, and then as afternoon comes on, some Cumulus with high bases because its so dang dry.  I better predict some Cirrus cuz I see some now!  Also, I think I will forecast that the low temperature this morning will be about 62 F here in Catalina because that’s what it is now.   Maybe some ice optics, too, now in progress!  Continuing, these clouds, too, mean some great opportunities for sunrise/sunset color and ice optics now that I see one (parhelia).

But with those high bases goes low temperatures, likely well below freezing, and you know what that means.  The tops are likely to be colder than -10 C to -15 C, 14 F- to 5 F), an ice-forming threshold hereabouts for small, high based Cumulus.   With the formation of ice, VIRGA, snowflakes and ice crystals come out the bottom.   You can see this by the hazy look around the clouds where it is evaporating–ice takes longer to evaporate.

In the higher terrain, the virga will melt into rain and reach the ground, and the clouds will likely get tall enough to produce lightning, but not here today, but to the north of us at least early in the afternoon and evening.  Our best chance of rain with thunderstorms in southeast AZ will be tomorrow as the moisture gradually increases over us from the backflow around the north of the low.  The low is forecast to pass to the south of us tomorrow and Thursday.  You can see all this happening in our local U of AZ weather model here.  (Note the local time is in the upper left hand corner.  You will see the precip is only forecast to occur in the afternoon and evenings with this system.

So, finally, some weather excitement in the offing!

Cold one on tap for Catalina; tubes in Cal

First, this is not about BEER!

Usually when you get carried away and expect something unusual to happen, it doesn’t, like that girl I thought liked me but didn’t (there have been a number of those…)  Yesterday, carried-away Mr. Cloud Maven person mentioned the possibility of tubes in Cal.  Here’s the report in the Big Valley near Merced, CA, from yesterday.  Big hail, too.  I am pumped!  Spiking fubball now!

0535 PM     FUNNEL CLOUD     ATWATER                 37.35N 120.60W
04/12/2012                   MERCED             CA   PUBLIC


0605 PM     HAIL             ATWATER                 37.35N 120.60W
04/12/2012  M1.75 INCH       MERCED             CA   AMATEUR RADIO

Official name of tube-producing clouds?  Oh, something like, “Cumulonimbus capillatus incus (has an anvil) tuba.”

Actually, its not terribly unusual to have tubes in Cal when the air is extremely cold up top over Cal in April and May, and that’s what we have now.  Take a look at this nice, compact map from San Francisco State Former US Hippiedom Capital Weather Department for last evening at 5 PM AST. At San Francisco, its -29 C at 500 mb, very unusual for mid-April.   (Actually, they got some real nice maps there.)  Combine that with the strong sun on land surfaces, and voila, Cumulonimbus galore!

Also, if you look carefully, you will see that where there is no data, over the Pacific Ocean, the 500 millibar pressure contours are nice and smooth .  But notice how “nervous” they get once crossing the coastline where there is data.  I think really it has something to do with the interpolation scheme that try to place the contours exactly at the right spot between the real data; that algorithm may be a little primitive.  Kind of funny in a way.

That cold core of air is heading for Arizona, and no doubt some April low temperature records will be set, such as lowest maximum, and likely a few minimum temperatures before this passes on into the Plains, with no doubt true severe weather there the result of that.  And we, too, will have some Cumulonimbus clouds, lightning here and there around the State.

Below the SFO State map is the forecast from IPS Meteostar showing where this mass of cold air will be later Saturday at 5 PM AST, northern AZ.  U of WA WRF-GFS mod thinks rain will be occurring here just about ALL DAY on Saturday after beginning around dawn!  That would be a heckuva cold day, winter-like, with temps in the 40s-50s here at 3,000 feet and we’d have those pretty white Catalina Mountains afterwards.  Sure seems like 0.20 inches is in the bag for the bottom of this rain event, with maybe 0.50 inches being at the top here in Catalina.

Yesterday’s line of enhanced virga in As deck at sunset

Now here’s an odd feature. Looked at first that it might have been due to an aircraft passage in that streak of Altostratus, but then I rejected that thought, as I can do.  I came to believe somewhat confidently, odd as it is, that it was natural.  Natural linear features in clouds are fairly common.  Here it is, in case you missed it:

Whence graupel?

What a fantastically gorgeous, if uncomfortable day yesterday was!  Such skies!  Such odd temperatures for March 19th.  And another day with ice falling from the sky, mostly “graupel”, but also some snowflakes (aggregates of dendritic crystals) at one point, too, when “stratiform clouds” came by (flat, layered ones) about mid-day.  The total water equivalent, 0.08 inches, 0.75 inches for both days combined.   With a high of only 50 F, it was also the fourteenth lowest high temperature ever at Tucson in March.

It was great, too, that “sample” day yesterday of the Last Glacial Maximum, imagining what it was like thousands and thousands and thousands of years ago when humans and dinosaurs co-existed on this cold planet.  I could almost see the dinosaurs coming down out of the snowy Catalina Mountains, being chased by hunters, or vice versa.  I have to say I haven’t researched this, but I have seen some movies about it.

What is graupel, you ask?  A form of German wrestling?  “Die zwei Männer  graupeling sich auf der Strasse”?

Well, no my friend, it is what we weatherfolk call a tiny snowball that falls from a cloud.  You can also call it “soft hail”, because we call it that, as well.  You can easily mash it between your fingers because unlike hail, it has a LOT of air in it.  We had a LOT of that “graupel”-soft hail off and on yesterday, once, around 7:38:36 AM AST with a roll of thunder.

Here’s what they looked like, up close, along with a raingauge measuring stick for size (its one inch between labels).  You may have also noticed some, many at times, looked like little pieces of space debris, having a definite conical appearance.  This is called “conical” graupel.  Its quite common actually. The third shot shows, and this was somewhat miraculous, an element of conical graupel on the way down.   I was stupefied that I had gotten such a shot by accident!

On the right side of this third photo you will actually SEE a conical graupel in flight, on its way down, and how it falls, wide end first because that is the heavy end.  Also note the heavy shaft of snow/soft hail up against the Catalinas downwind.   The graupel that fell in the photo came from the back side of that Cumulonimbus cloud.  The second cloud shot shows the bottom of the cloud from which the graupel was falling.  Many of you know that I specialize in these kinds of photographs, the bottoms of clouds, hoping to have a show someday.

But, what do you see in the cloud base photo?  Not much.  The best eyes will detect that slight, slight striated look due to falling graupel.  Falls in strands reflecting the complex nature of the organization of liquid water and updrafts, wake capture in clouds.  The first precipitation falls out through the heaviest concentrations of liquid water (at well below freezing temperatures), and that’s what graupel does.   This the same as when the largest and heaviest raindrops in summer fall out from a cloud base with not much else going on.  And, like our graupel, they are spread around, sparse compared with the heavy rain that likely will soon follow.  So, graupel is the first thing that falls out of large Cumulus clouds, ones growing up to be Cumulonimbus ones.

Also you may have noticed that the graupel almost always was associated with a Cumulus clouds yesterday, localized clouds in lines with dark bases over you.  Cumulus clouds are loaded with liquid water, at least in the rising portions.  In those rising portions, a few ice crystals, or cloud drops might freeze.  Thereafter, they begin collecting drops that freeze on them when they contact the ice.

Cumulus clouds at below freezing temperatures are avoided by aircraft because this is where cloud drops can hit the airframe, freeze instantly, and weigh down the plane, as happened with our little graupel.  In Cumulus such as we had yesterday, a half an inch of icing can build up on the leading edges of airframes in just a few minutes while flying in their upper portions.  Near cloud base, the drops are too small to build up much ice.

With some of the graupel up there in those clouds, at some point early on, the freezing of drops on it as it collided with them produced a side that was slightly heavier than the rest of it.   That heavier side began falling downward, collecting more drops to make it more lopsided, conical.  You can then assume that graupel that are not conical, collected drops pretty symmetrically, something that would happen only if they were spinning on the way down.

Associated with the formation of graupel, as on this day, is a sudden burst of ice formation in the entire cloud leading to “glaciation”.  The liquid drops at below freezing temperatures are completely annihilated during this process in the turret initially spawning the graupel, and along with the remaining graupel, a dense shaft of precip drops out of the bottom. consisting of graupel and large snowflakes (aggregates of single ice crystals, sometimes hundreds of individual crystals in them).  So, on the back of this Cumulonimbus cloud raking the Catalinas, graupel, on the forward side where glaciation has taken out the liquid water, aggregates, probably huge ones.

Gads, I want to go on, but this is getting to be a little LONG!  However, here are a few more shots from that beautiful day. Some dessert after the heavy meal.

The End I think.