Now in a really good web site about weather, clouds and climate, we would have talked about May around the first of May. But let’s face it, this site really isn’t that great. So now we’ll talk about the climate of May on May 11th.
Below is the rain frequency climate, such as it is, for May here in Catalina. Surprisingly, to Mr. Cloud-maven person, there is no downward trend in the chances of measurable rain from the very first days of May until the end as was expected. Instead, each day of the whole month has about the same small chance of rain from the 35 year record mostly made by the folks (Wayne and Jenny) at Our Garden here in Catalina.
Where the rising temperature graph for May, you ask? Well, I don’t do temperature. I am cloud and rain person. A nice graph of the temperature trend for May, which we know is upward on average for the whole month, can be found here at the Western Regional Climate Center, housed at the cloud seeding-inclined Desert Research Institute of the University of Nevada which issues misleading PR pieces on cloud seeding which they conduct for the State of Nevada (no, you won’t find them, in spite of being an academic institution, doing proper randomized cloud seeding experiments, but rather bogus-style “operational” seeding. They’d be AFRAID of doing a proper long-term, double blind randomized experiment using independent evaluators! If I was them, I would be afraid, too, about what such an experiment might tell their long term funders! Don’t get me started on cloud seeding discussions!
Now, where was I?
Oh, yeah, climate. Don’t get me started about the parallels between some aspects of the purveyors of global warming info (I’m talking exaggerations, not the prospect of it which I have to grudgingly go along with, “grudgingly” because I really hope there’ll be an ice age tomorrow when I read some of the exaggerations that come out for the purpose of scaring people, like this or that storm or tornado was due to global warming.
Yes, there are parallels between cloud seeding claims and some of the GW ones, mostly, in this writer’s opinion, driven by the need for funding.
Now, an hour later, back to that graph at DRI…. You can see that the temperature at the U of A rises steadily throughout May on average. We knew that already, so there really wasn’t much point in showing it, but I feel a lot better now having exhausted some hot air myself.
When the massive dust cloud rolled in from Tucson-Oro Valley, I heard a neighbor screaming at the kids outside, “Go inside, the rain is coming!” A “humbug” is an imposter, meant to deceive, and for a time, I’ll bet many folks, like my neighbor, thought a good rain was coming along with the darkening sky (composed mainly of….”Altostratus cumulonimbogenitus”–kind of a silly name, some with areas of virga). There were also dark-looking Altocumulus opacus clouds, and Cumulus humilis at the bottom of the As here and there (e.g., see second photo). So, it was a threatening sky to be sure!
Go here to see dust storm roar through Tucson, courtesy of your University of Arizona Wildcats Weather Department. Very exciting! Plus you will see all the cloud movement that was going on before the dust hit.
Below are a few shots from yesterday’s dramatic dust cloud as it rolled and roiled northwestward out of the Tucson metro area and up the Oro Valley. First, a cloud shot that showed truly remarkable Cumulus-Cumulonimbus development east of the Catalinas just after 7 AM AST yesterday. You knew at this point, it was going to be an interesting day with so much so early.
Then, "whilst" in a local gym, this came round the corner of Pusch Ridge (2:59 PM AST)3:04 PM AST: Within 5 minutes it attained the classic "haboob" shape roaring into Oro Valley.By 3:10 PM AST, it had filled the valley.Finally, 4:33 PM AST, descending on Catalina from the NNE, a weak thunderstorm and a bit of rain to turn the deposited dust into mud. Cleaning all windows this morning.
All this was caused by the huge splash of rain to the east and southeast of Tucson yesterday earlier in the day. With high bases, and lots of dry air below, as you all know by now, the scene was set for a massive drop of cold air as the rain evaporated below the bottoms of those clouds.
Next: June preview in May
The total of maximum temperatures added together over the next 7 days will be HUNDREDS of degrees! This makes no sense at all, but it does sound dramatic. It will be hot for awhile.
But then what?
Pretty strong signal from the NOAA Spaghetti Factory that another cut off low or trough will barge into the State by the 25th of May. With that would be a strong cooling, and maybe some rain.
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!)
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!
I wanted to get your day going on the right foot, one filled with the thoughts of a few scattered Cumulus and Cumulonimbus clouds next week, with almost a certainty of hearing thunder in Catalinaland, along with brilliantly colored sunsets, and some shafts of rain.
How do I know this so confidently, and am feeling good about myself also having those thoughts whizzing around?
Model “convergence.”
Both the USA (!) and the Canadian model (a version of the European Center for Medium range Forecasting, “ECMWF”) are both showing rain around here, and the little baby low center that forms going along the same track, one to the south of us.
BTW, a quite illustrative cartoon discussion of models (USA vs European) after Dreamworks has been released recently. You’ll want to bone up on models here, perhaps before reading on. This cartoon was brought to my attention by Mark Albright, the former WA State Climatologist who wants to live in AZ but can’t make up his mind on a house, to give credit where credit is due. This is so funny; brilliant!
Contnuing on to what the models are saying, the chances of rain falling here are more better when the low center is a little to the south and moisture from the tropics can wrap around the low from the east side of it. Here are two prediction maps for about the same time. The first from IPS Meteostar for Wednesday May 9th, midday.
You can see a low center at 500 mb (18,000 feet or so in the atmosphere) is over the north portion of the Gulf of Baja California, Sea of Cortez. The green represents moisture at that level streaming in from the east on that day. Cool! We will certainly get a boatload of Ac cas with this, something that Mr. Cloud-maven person likes to see and frequently, as a result, forecasts its occurrence wrongly because he is not being objective, but SUBjective, which as the name applies, is below “objective” and being “disinterested” in what you are talking about, to go on and on about it. It happens in science. Remember when…, oh, never mind.
OK, below this chart, from Enviro Can, is also one for Wednesday, May 9th at 5 AM AST-PDT. The low center at 500 mb is shown by the little red dot in the upper left panel. You can see that both models have now (after being “divergent”) have put the low center in the same spot. The USA model had it farther north for several model runs, which were quite bad for rain here in Catalina.
Yesterday’s clouds
Just a few Cirrus ice clouds floated over as the upper level winds start turning from the southwest at high levels. These kinds of clouds should be seen over the next few days.
Something to blab about at last. The computer models show a small area of low pressure breaking off the main jet stream and setttling over Arizona for a few days. Arrives on Monday, May 7th, then hangs around for a couple of days before moving off. Rain here? Doesn’t look like it now, but there should be some high based Cumulus, and one or two high-based thunderstorms over the mountains, maybe some Altocumulus here and there, too.
The happy part of this is that this time of year weak lows aloft like this one can produce a boatload of rain in the droughty areas of eastern New Mexico and west Texas when they interact with that Gulf air sloshing northward and westward into those areas. That happens after this forecast map. Let’s hope so. See below from our friends at Environment Canada for the afternoon of May 7th:
However, and pretty confidently predicted a huge bubble of warm air arises over us in the days. This in the longer term NOAA WRF-GFS model rendered by IPS Meteostar below. The last of the snowbirds will be scurrying off to their northern climes when this hits since temperatures are likely to ascend to over 100 F for a few days (a preview of normal June weather). Get ready.
Errata
Mr. Cloud-maven person misspoke recently when he asserted that May was our driest month. Below he reprises the Catalina monthly rainfall averages for himself and his two other readers.
Kind of got distracted with chores after the big trip to NC and didn’t get to this until today… If you can remember as far back as April 26th, we had a “FROPA” (“frontal passage” in weatherspeak) that day. The U of A weather model indicated beforehand that the bases of the clouds last Thursday would lower to the tops of Samaniego Ridge.
Well they did, though it seemed in doubt for a time, and occurred a bit later than the model had predicted.
Also, a few drops came down here late in the morning; more precip was visible to the north of us and that was reflected in the NCAR precip estimate for Arizona the following morning, an estimate that suggested the heaviest rains were up to half an inch just 150 miles away.
Here are a few of last Thursday’s clouds with some commentary.
Row of Altocumulus castellanus top lower center.
These clouds came in two separate segments, the first batch were at Altocumulus levels, some 12,000 feet above the ground according to the TUS balloon sounding that morning at 5 AM AST. Those were the clouds that produced the sprinkles around 5:30 AM. Poor snowflakes melting into drops had to fall such a long way!
After a brief clearing, a surge of lower Altocumulus and Stratocumulus came in. For a time, they looked awful threatening, and appreciable rain could be seen falling from them to the north. They produced a few sprinkles here in the late morning and early afternoon about the time the clouds had lowered (as predicted by the UA model, to the tops of Samaniego Ridge to the east).
In the distance is Altocumulus opacus virgae, that is considerable precip is dropping out of them.Here the faint whitish cloud ghosts near splotches of the Altocumulus clouds are due to ice crystals, indicating that these clouds are colder than -10 C at cloud top.Our regular neighborhood cloud, an Altocumulus lenticularis formed downwind of the Catalinas in the usual spot after most of the Altocumulus had departed.After the brief clearing, a surge of threatening looking Stratocumulus invaded the sky. Rain can be seen falling above the horizon to the north.
Why didn’t they rain more?
The answer, as always here, is that the tops were much shallower, and therefore warmer, than those early Altocumulus clouds sporting considerable ice at times. You can be sure that those Stratocumulus clouds over us had tops warmer than -10 C (14 F), a general threshold for ice formation around these here parts. (Over the oceans, where the drops inside the clouds are larger, the threshold temperature for ice formation is higher.)
Just to the north of us, where rain was occurring, you can be sure that the tops sloped upward in that direction, becoming colder than -10 C.
That second batch of lower clouds looked dark and threatening, but lots of times with lower clouds its because they have higher concentrations of drops in them, not because they’re especially thick as you might guess at first. The droplet concentrations in those dark Stratocumulus might have been twice as high as in those early higher, Altocumulus clouds.
Drops in clouds with higher droplet concentrations, say due to smog, reflect more of the sun’s light off the top. That makes them darker on the bottom, and because they are then also harder to get precip out of, they last longer.
This is a real problem, BTW, for climate models, since longer lasting clouds reflect more light back into space and in that sense, and help counter the global warming expected from trace gases like CO2. But, would you rather have ugly clouds and smog infested skies and a cooler planet, or clean skies and clouds and a warmer planet?
The weather ahead
No rain in sight. But a big heat wave, probably temps around 100 F now looming toward mid-may. May is our driest month, BTW, averaging only a quarter of an inch.
Who can forget those profound words of Aerosmith and Steve Tyler, “I’m BACK in the saddle again”? Just the way he says, “I’m BACK…” is really something. Well, if you can’t remember anything anymore, here’s a reminder. Wasn’t that great “rockumentary” movie by Rob Reiner, “Spinal Tap” about these guys? BTW, pilots on VFR flew through cloud saddles between turrets all the time… So, there really are “cloud saddles.”
First of all to start today, you budding cloud-mavens out there should, as always, be reviewing yesterday’s skies here to make sure you got all the clouds down in your cloud log, a service provided for you by your University of Arizona Weather Department. Since this link is overwritten each day, you probably should go there now.
In the meantime, while you’re scrutinizing that time lapse film, a cool front will go by this morning. Nice, except no rain outside of isolated sprinkles from mid-level clouds like….Altocumulus opacus virgae, you know, those dense loooking clouds with little snowstorms under them meaning their tops were colder than -10 C (14 F).
Later, after a brief gap in those mid-level clouds, some honest to goodness LOW clouds are supposed develop just after the front goes by later this morning. How do I know that? I cheated by going to the Wildcat Weather Department model results produced by the MASSIVE Beowulf Cluster and saw that clouds are supposed to get low enought to top Samaniego Ridge by mid-morning. Check the sounding predictions here if you don’t believe me. You’ll see the temperature and dewpoint lines pinch together at sharply lower altitudes beginning around 9-10 AM AST, with cloud bases predicted to be down to about 7,000 feet!
Haven’t seen cloud bases (bottoms of Cumulus and Stratocumulus) as low as that since the last rain which I missed because I was driving mom all the friggin’ way to Asheville, NC, and back to see my brother in his “new life” there. There’s a lurid story behind that new life, one that you would naturally be quite interested in, but it shall remain hidden from view.
But why don’t those lower clouds that move in and top our Catalina Mountains rain/snow? Tops too warm, predicted to be warmer than -10 C, so, no ice can form, a necessary ingredient for stuff to fall out the bottom. You probably knew that already, and I am beginning to feel a little useless. Oh, well.
Here’s a nice plot of today’s weather around the SW and the satellite cloud scene at 5 AM AST from the U of A (again): Wow! Rain drops hitting roof now, 5:37 AM! Overhead cloud tops still colder than -10 C!
Remember, if you are an intelligent person you will NOT CALL THESE FEW SCATTERED DROPS “DRIZZLE”!!!!!!! Its a rain shower, a very very light one, that you might “code” as RW— (three minuses). Drizzle drops float in the air, and are close together; these are not. There are IMPORTANT cloud reasons for denoting this difference. Some day I will tell you the “science story” about a well-known scientist, really considered the best in his field, who told me to leave his office and never come back after I informed him it had been drizzling outside. So, I Mr. Cloud-maven person has some “drizzle baggage”…..he is carrying around.
Note the gap in clouds over us now and that little scruff to the west. Those are the lower clouds that will move in later. Below this, our Tucson sounding for 5 AM AST, where you can see that the tops of these Altocumulus clouds are around -20 C (-4 F). Bases are indicated to be around 15,000 feet above sea level, or 12,000 feet above Catalina. Poor drops have to fall such a long way in such dry air. No wonder only the biggest ones, likely HUGE snowflake aggregates, or maybe even “graupel” up there, made it down.
