Altocumulus clouds – Page 9

About ice-in-clouds and APIPs (or high temperature contrails)

6:55 AM. A surnrise glow from receding CIrrus spissatus highlights Samaniego Ridge. Very pretty and dramatic.

8:19 AM. Forming uncinus, CIrrus that is. Note trails of precip beginnng to form under these tufts of Cirrus castellanus clouds.

9:06 AM. Jet contrails begin to show up in a Cirrocumulus cloud. You know what going to happen.... — 9:06 AM. Jet contrails begin to show up in a Cirrocumulus cloud composed of supercooled cloud droplets. You know what going to happen….something special for you to log in your cloud diary.

9:20 AM. Another patch of supercooled, very supercooled Cirrocumulus with evidence of a jet contrail. But, is the jet above or IN the Cirrocu? TIme will tell. — 9:20 AM. Another patch of supercooled, very supercooled for that matter, Cirrocumulus with evidence of a jet contrail. But, is the jet above or IN the Cirrocu? TIme will tell.

How cold were those Cc clouds? See below.

(Begin technical module)

The Tucson balloon sounding for 5 AM AST, November 19th with writing on it. — The Tucson balloon sounding¹ for 5 AM AST, November 19th with writing on it. The height of these clouds was slightly lower in the mid-afternoon, but (as Altomumulus then) were still about -23 C. As we know, cloud bottoms almost always get lower with passing time because the higher parts of cloud shields are moving faster.

In the mid- -20s C, around -15 F. Height, about 21,000 feet above the ground here in Catalina. Hope you got that estimate of cloud height right.

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Continuing…

9:21 AM. ANOTHER jet streaks by! This is going to be darn interesting, a rarity, like see a grey parrot in Catalina! — 9:21 AM. ANOTHER jet streaks by! This is going to be darn interesting, a rarity, like seeing a grey parrot in Catalina! The secret about what height the first jet was flying at is beginning to be revealed. Can you see what’s happening to that first contrail a little below the new one? This is a great test to see how far you’ve come as a CMJ (cloud maven junior)!

Here’s what happened in the Cirrocumulus cloud layer in yesterday’s special day, a pretty rare one, after the jets flew through it:

9:30 AM. OK, mystery's over. Even the average CMJ Joe can see that 1) the jets were IN the Cirrocumulus cloud, and more importantly, the aircraft contrails consist of ice. Yes, that's right, the passage of the aircraft has caused a phase change from liquid drops to ice crystals, a lot of them. — 9:30 AM. OK, mystery’s over. Even the average CMJ Joe can see that 1) the jets were IN the Cirrocumulus cloud, and more importantly, the aircraft contrails consist of ice. Yes, that’s right, the passage of the aircraft has caused a phase change from liquid drops to ice crystals, a lot of them.

9:47 AM. Now those contrails are looking like real and icy Cirrus clouds. In this case they're called "ice canals" but sometimes, when aircraft are ascending or descending and do this, they make round clear holes with ice in the middle, called "hole punch" clouds. — 9:47 AM. Now those contrails are looking like real and icy Cirrus clouds. In this case they’re called “ice canals” but sometimes, when aircraft are ascending or descending and do this, they make round clear holes with ice in the middle, called “hole punch” clouds.

Lessons to be learned from yesterday’s supercooled clouds and the aircraft interactions inside them:

Cloud seeding works! You CAN make a supercooled, non-precipitating cloud produce a little precipitation that would not otherwise have occurred.

But in those situations where the clouds, say, are topping the Catalinas, they are often quite thin, and whether there is an economically worthwhile amount of precip is not known. However, an experiment targeting those clouds would be the perfect “baseline” one in cloud seeding to establish how much we can wring out of non-precipitating clouds. Things become kind of a mess when even randomized seeding takes on already precipitating clouds.

“Overseeding”, as here in these clouds when aircraft produce prolific numbers of ice crystals in a small volume, it leads to tiny ice crystals with low fallspeeds. Sure, they fall out and leave a hole, but they virtually never reach the ground except in one a in billion cases when the very cold clouds are real low, practically on the ground.

The Wegener-Bergeron-Findeisen mechanism produces precipitation.

Alfred Wegener, 1911, and later Bergeron³ and Findeisen in the 1930s, came up with the hypothesis that adding ice to a supercooled cloud results in the growth of the ice crystal at the expense of the droplets. They’ll tend to evaporate while ice is being added to the crystal via deposition of water vapor that was once liquid. So, an awful lot, maybe most of the precipitation that falls on earth, involves “mixed phase” clouds. This process has also been called the “cold rain process.”

However, let us not forget the two other processes that produce precipitation, the all ice process (no liquid required–helps produce “powder snow”, and the all liquid process, where cloud drops collide and grow into raindrops–the biggest measured drops in the world (about 1 cm in diameter) have formed soley through this process. It is likely that most of the rain that falls in tropical locations like the Hawaiian Islands and in hurricanes is due to this process even when ice is present in the top part of storms.

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Later, we had some Altocumulus castellanus clouds with virga as the moist level lowered, though they were long gone before they could provide us with a nice sunset:

2:32 PM Bands of Altocumulus castellanus approach from the west. These clouds, while based at just about the same level as the Cirrocumulus clouds earlier in the day had three things going to produce so much ice, and really, convert to Cirrus clouds. The cloud bases were slightly warmer, meaning more water was available to the cloud, the tops were higher and colder, likely around -30 C (-22 F), and perhaps as importantly, the drops near the top of the Ac turrets were larger than those in the earlier Cc clouds. The larger the droplets, the higher the temperature that they freeze at. — 2:32 PM Bands of Altocumulus castellanus approach Oro Valley from the west. These clouds, while based at just about the same level as the Cirrocumulus clouds earlier in the day had three things going for them to produce so much ice (right side of photo–and really, convert to Cirrus clouds). The cloud bases were slightly warmer (the TUS sounding suggests, -22 C), meaning more water was available to the cloud, something that would impact the drop sizes in the turrets of the Altocumulus clouds (left side of photo); 2) the tops were higher than the Cc clouds (ones that were paper thin) and therefore, slightly colder (probably about -28 C) than those of the Cc clouds, and perhaps as importantly, the drops near the top of the Ac turrets before they converted to ice, were larger than those in the earlier Cc clouds. The larger the droplets, the higher the temperature at which they freeze. So, ice is more likely to form in a cloud with larger droplets in it than one with tiny droplets in it even though they are the same temperature. That might explain the difference ice-forming behavior of yesterday’s very thin Cc clouds which mostly had no ice (until an aircraft came along in them) and these prolific ice-producing Altocumulus clouds, ones that converted to all ice. Just educated guesses here.

Still looking for scattered very light showers in the vicinity tomorrow as a Mr. Troughy goes by.

The End.

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¹Through the oral history tradition I learned while viewing the Washington Husky meltdown² at AZ stadium on Saturday from a Mr. Mark Albright that the Tucson weather balloon launch site has been moved from Davis-Monthan Airbase to the University of Arizona campus next to their weather department.

²Late in the proceedings, with about 2 min left and the Huskies starting a play, and in the lead, CM was visibly moved to jump up and say, “Don’t hand the ball off!”, as a gift to Arizona fumble occurred simultaneously. But, being bifurcated in his loyalties now that CM is in Arizona and not with the University of Washington, he had to be somewhat “glad” that the Cats maintained their somewhat suspect but great win-loss record.

³From the Historic Moments in Weather collection:

Tor Bergeron and CM meet in Goleta. His head was gigantic! No wonder he was so smart. CM, not so much. — Your Catalina CM and Tor Bergeron meet for the first time in Goleta, CA, in 1968 at the headquarters of North American Weather Consultants. Yours for $2,100 dollars, today only. I remember thinking that his head was gigantic! No wonder he was so smart. CM, not so much.

Dull cool day and blog, book-ended by a nice sunrise and a nice sunset

Here we go…..some pretty, but also dull, photos, along with some novella-sized captions as mind wandered into the obtuse while writing them.

6:44 AM. Nice sunrise due to Altostratus/Cirrus ice clouds.

2:00 PM. Stratocumulus topped Samaniego Ridge most all day, but was too warm to have ice, and droplets too small to collide, stick together, and form misty drizzle. Misty drizzle? Could be a great name for a late night female vocalist. — 2:00 PM. Kind of a dull day yesterday, kind of like this blog. Stratocumulus (Sc) clouds topped Samaniego Ridge most of the day, below that gray Altostratus ice cloud layer. But those Sc clouds were too warm to have ice in them, and droplets were too small to collide, stick together, and form misty drizzle. Have to get to at least 30 microns in diameter before they stick to one another. Misty drizzle? Could be a great name for a late night female vocalist doing earthy songs like Earthy Kitt back in the ’50s. “Earthy” was much hotter than global warming.

3:29 PM. An Altostratus translucidus mostly ice-cloud with a dark patch of Altocumulus droplet cloud blocking the sun. If you look closely, you can see a that there's this Altotratus layer may be topped by a Altocumulus perlucidus droplet cloud layer. Yes, droplet clouds at the top of As where the temperature is lowest? Yep, happens all the time, up to about -30 --35 C. Been there, done that, in aircraft research. — 3:29 PM. An Altostratus translucidus to opacus, mostly ice-cloud with a dark patch of Altocumulus droplet cloud blocking the sun. If you look closely, (upper center) you can see a that there’s this Altotratus layer may be topped by a Altocumulus perlucidus droplet cloud layer. Yes, droplet clouds at the top of As where the temperature is lowest? Yep, this counter-intuitive finding happens all the time, up to about -30 C -35 C. Been there, measured that; in aircraft research. Ma Nature likes to form a drop and have it freeze before forming an ice crystal directly from the water vapor.

4:40 PM. — 4:40 PM, shot taken as we entered a local restaurant. You’ve got your two layers of Altocumulus, with some Altostratus translucidus above those, filling in the gaps. Gaps? Huh. I am reminded that I have a failed manuscript about “gaps”, these kind; *Cloud Seeding and the Journal Barriers to Faulty Claims: Closing the Gaps*., rejected by the Bull. Amer. Meteor. Soc. way back in ’99. It was an instruction manual, in a sense, about how to prevent all the bogus cloud seeding literature that got published in the 1960s through 1980s, and was not only published, but cited by our highest national panels and experts, like the National Academy of Sciences. Amazing, but true. I give examples. You can read about this chapter of science in Cotton and Pielke, 2007, “Human Impacts on Weather and Climate”, Cambridge U. Press, a highly recommended book. That cloud seeding distortion of cloud seeding science was due to many factors, of which perhaps the primary one was, “nobody ever got a job saying cloud seeding doesn’t work¹.” This was a great segue. Of course, we have similar stresses on those researchers looking for effects of global warming nee “climate change” now days. Nobody will ever get a job (a renewed grant) saying they can’t find evidence of global warming, “Can I have some more of that money to keep looking?” And beware the “Ides of March” if you criticize published work in that domain! Think of poor Judy C , a heroine to me, and how she’s been vilified for questioning climate things.

5:29 PM, took leave from Indian food there in R Vistoso for this. Its not just anyone who would excuse himself from dinner to do something other than visit the laboratory.

That’s about it. No use talking about the rain ahead again. Seems to be a couple chances between the 20th and the 30th.

The End

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¹You can make a cloud snow a little by seeding it with dry ice or silver iodide. This has been shown since the earliest days of experiments. Below, to demonstrate this, an aircraft inadvertently “seeded” this Altocumulus cloud layer. However, whether the small amount that falls out from previously non-precipitating clouds is economically viable is not known. Increasing precipitation due to seeding when the clouds are already snowing/raining has not been satisfactorily proven. As prize-winning stat man, Jerzy Neyman, U of Cal Berkeley Golden Bears Stat Lab would tell you, you need a randomized experiment and followed by a second one that confirms the original results, with measurements made by those who have no idea what days are seeded and evaluations done by those who have no vested interest in cloud seeding. Wow there’s a lot of boring information here. Getting a little worked up here, too.

Ice canal in supercooled Altocumulus clouds, bases -23 C, tops -25 C (from PIREPS). — Ice canal in supercooled Altocumulus clouds over Seattle, bases -23 C, tops -25 C (from PIREPS). Photo by the Arthur.

Rain to fall in Catalina! (as shown in this latest model run shown below)

Finally found some rain for you. Took awhile. Came from the 11 PM AST global data from last night using the WRF-GFS model, our best. The rain falls around the 19th, “only” 11 days from now and during the “sweet spot” for southern California rain in mid-November, 10-20th, which gives it a few more percent of credibility than it otherwise would have.

BTW, there is virtually no support for this pattern from the NOAA spaghetti factory. So, all of the discussion below about an upcoming rain in Catalina might erroneous, based on a personal hunch about an outlier model run being the correct “solution”, one based on experience, and to HELL with spaghetti¹, a study in forecasting subjectivity, etc.

Got that Bay Area rain timing info originally from C. Donald Ahrens, the big author of Meteorology Today and Essentials of Meteorology, both of which have about 400 editions out by now, while he and I were at San Jose State College University.

Don, a grad student then, and me, and undergrad, worked and sang together to Top 40 songs radiating from KGO-FM ^2,3 in a little corrugated metal building there by the San Jose State football stadium back in the late 60s, and it was somewhere between songs that he told me about his findings.

Don had done a rain frequency study for the Bay Area for a local insurance company and it turned out that he found that it was somewhat more likely to rain in the middle of November than earlier or later in the month. That rain fell more more often than earlier was no surprise, but more often than later in the month was. Later I found that it was also true for southern California.

Sometimes oddities like these are referred to by big professors of weather, like Reid Bryson at the U of Wisconsin Badgers, as “singularities”, a weather pattern that tends to recur year after year around the same time of the year, like the so-called “January thaw” in the East which I don’t think happened last year.

So, ever since Don told me about the mid-November peak of rain in the central and southern parts of Cal, I have looked for it year after year and it seems to turn out quite often, and this November seems to be no exception, though the models were resisting this pattern for quite awhile before “giving in.”

Well, anyway where was I? It seems that the southern California rain is now being foretold for around 18th of November, and a day or so later it trudges on into Arizona. From IPS MeteoStar, a Sutron Company, whatever that is, this wonderful map:

Valid the night of November 19th-20th. Colored regions denote those areas where the model thinks it has precipitated during the PRIOR 12 h. So, storm has arrived here during the day on the 19th.

Some clouds

we have known over the past few weeks while CM was re-hydrating mentally:

Some ice for you on a warm fall day (virga from Altocumulus castellanus and or floccus)

Pretty iridescence (or irisation) in a Cirrocumulus cloud.

The End

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¹1The non-supportive spaghetti plot from the 00 Z (5 PM model run from last evening):

Valid at 5 PM AST Wednesday, November 19th. Arizona is in a low amplitude ridge, according to most of the "members" of the repeat model runs with itty-bitty errors deliberately put into them. I have rejected this plot and look for validation of this action around the 19th of November. You will not hear about it further if I am erroneous in this action! — Valid at 5 PM AST Wednesday, November 19th. Arizona is in a low amplitude ridge, according to most of the “members” of the repeat model runs with itty-bitty errors deliberately put into them. I have rejected this plot and look for validation of this action around the 19th of November. You will not hear about it further if I am erroneous in this action!

²An odd, almost mysterious Frisco FM radio station with no commercials featuring, “Brother John.” We’d sing along to the Four Seasons, The Five Americans’, “Western Union” (about telegraph, the way people used to communicate before the Internet).

³We both had quite a talent for falsetto it seemed at the time.

While waiting for S, the (NASA) Diary of the Great O

While waiting for the remnants of former H. Simon to pass over us during the next couple of days, bringing some rain, starting overnight, got distracted while looking to see how many rainfall measuring stations they have in Baja Cal, and found this about the Great O from NASA. Its a pretty fascinating read I thought, which you will also find fascinating. Sure, intense hurricane O’s floody remnants missed us here in Catalina/Tucson, but it did produce some prodigious rainfall on its path across Baja and points northeast from there into NM. NASA’s Tropical Rainfall Measuring Mission (TRMM) radar estimates that over the ocean off southwest Mexico that about 33 inches fell over a ten day period while O was meandering around down there with some other disturbances, probably raising sea level that bit. And up to 5 inches per hour was falling in rainbands as it entered Mexico from the Gulf of Cal! O was deemed the strongest hurricane (tied with 1967’s Olivia) to ever hit southern Baja since sat images became available.

You will also see reprised in the “Diary of O” the huge rainfall totals that were expected in the TUS area but rains that missed us, the sad part of the story for some folks, who we will not mention. But, as Carlos Santana said, “Those who do not know history, are doomed to repeat it.”

For that reason, in view of the prodigious rains predicted in southern AZ again, but to the west of us, I thought we should be prepared for disappointment by recalling O’s “terrible” miss for TUS.

Here are some graphics from our very fine U of AZ Weather Department’s Beowulf Cluster computer outputs from just last evening at 11 PM AST, ones that can be found here, in case you don’t believe me again, a seeming theme around here. First, when the computer model thinks it will start raining, Figure 1, and in Figure 2, the expected gigantic totals expected along and near the US border where we really shouldn’t go unless you 1) go in an armored vehicle of some kind, 2) make prior arrangements with the appropriate ruling Mexican drug cartel for that part of the US that you just want to visit some rain, nothing more:

Figure 1. Valid for 2 AM AST tonight. The leading edge of the rain has reached Catalina. You might want to stay up for that. That wet desert aroma as rain begins is so awesome!

Valid for 3 PM tomorrow afternoon. One small area around Organ Pipe National Park is forecast to exceed TEN inches by then! — Figure 2. Valid for 3 PM tomorrow afternoon. One small, mountainous area around Organ Pipe Cactus National Monument is forecast have more than TEN inches by then, likely slowing the amount of incoming drugs. Organ Pipe Cactus NM is a US national park that you are warned not to visit, or if you do, you might be shot or have some other untoward happenstance if you go hiking. So you probably shouldn’t drive down there to see this once in a century rain. How sad is THAT?

Right now, as of 4 AM AST on Thursday, this model thinks Catalina and vicinity will get less than half an inch. Be prepared for more, though, rather than less. Note the streamer of heavy precip associated with Simon in Figure 2. Well, recall that O’s heavy precip streamer was going to be right over us, but then shifted eastward in the models and in real life at the last minute. The above prediction would only have a bit of a “westward bias” (the real streamer is EAST of where its shown now) to give TUS and vicinity a memorable, drenching October rain. This is what occurred with O’s streamer of torrential rain which was expected to pass over TUS, but ended up a little east of us. So, anyway, given all the little uncertainties in model predictions at this point, the watchword here is “watch out” which is actually two words. The view from here, incorporating a positive rain bias as you know, is somewhere around an inch for Catalina. The grassy green is gone, most annuals in serious wilt or crispy now, but could an inch bring some green back? Clueless on that score.

Yesterday’s Clouds

6:06 AM. Nice Cirrus sunrise. — 6:06 AM. Nice Cirrus sunrise, maybe some Cirrocumulus at far right, and off on the left horizon.

5:05 PM. Altostratus translucidus with an Altocumulus layer on the horizon.

5:07 PM. A “classic” view of Altostratus translucidus (sun’s position can be discerned through it), and here, an all ice path to the sun. Liquid cloud elements would appear as dark flakes, or would obscure the sun’s position. Sounding indicated that this layer was 26 kft above the ground in Catalina!

The End.

O, models, disappoint

Odile passed to the S and E of Cat land, leaving only 0.13 inches here in the Heights, the Sutherland ones. Didn’t even get the half inch I hoped for. Oh, well, we can be happy for the droughty areas of New Mexico that got the brunt of that tropical system as did portions of extreme SE AZ. You may know that for many days in advance and up until 11 PM the night before last (shown here), our best models had O practically passing right over us with prodigious rains indicated.

Unfortunately, we meteorologists often “go down with the ship” when this happens due to model forecast consistency. Only in the last minutes, so to speak, did the model runs get it right (but too late to be of much use) and finally indicated that the true path of the heaviest rain was NOT going to be over us, as was already being discovered via obs. O was such a cloud mess, the mods may have been off in locating where the center was. Not sure. Will have to wait for the panel report.

Seems to be preciping on the Cat Mountains right now, though doesn’t show up on radar, so its likely a RARE “warm rain” event here in AZ where the rain forms by collisions between larger cloud drops to form rain drops and the cloud tops are low¹. Maybe that’s O’s legacy; tropical air and a warm rain day sighting.

BTW, whilst Catalina and most of Tucson didn’t get much, it has continued to rain steadily in our mountains over the past 24 h with Dan Saddle, up there in the CDO watershed, leading the way with 2.09 inches in 24 at this hour (5 AM) and its still coming down lightly, as noted. Its been a fantastic rain since it was steady and soaking up there over that whole 24 h period, much like in our winter storms. Below, some totals from the PIma County ALERT gauges. You can see more totals here.

Gauge    15         1           3          6            24         Name                        Location
    ID#      minutes    hour        hours      hours        hours
    —-     —-       —-        —-       —-         —-       —————–            ———————
Catalina Area
    1010     0.00       0.00       0.00        0.00         0.16      Golder Ranch                 Horseshoe Bend Rd in Saddlebrooke
    1020     0.00       0.04       0.04        0.04         0.20      Oracle Ranger Stati          approximately 0.5 mi SW of Oracle
    1040     0.00       0.00       0.00        0.00         0.12      Dodge Tank                   Edwin Rd 1.3 mi E of Lago Del Oro Parkway
    1050     0.00       0.00       0.00        0.00         0.16      Cherry Spring                approximately 1.5 mi W of Charouleau Gap
    1060     0.00       0.00       0.00        0.00         0.16      Pig Spring                   approximately 1.1 mi NE of Charouleau Gap
    1070     0.00       0.00       0.00        0.00         0.04      Cargodera Canyon             NE corner of Catalina State Park
    1080     0.00       0.00       0.00        0.00         0.20      CDO @ Rancho Solano          Cañada Del Oro Wash NE of Saddlebrooke
    1100     0.00       0.00       0.00        0.00         0.08      CDO @ Golder Rd              Cañada Del Oro Wash at Golder Ranch Rd

Santa Catalina Mountains
    1030     0.00       0.04       0.04        0.08         1.73      Oracle Ridge                 Oracle Ridge, approximately 1.5 mi N of Rice Peak
    1090     0.00       0.00       0.04        0.04         0.75      Mt. Lemmon                   Mount Lemmon
    1110     0.00       0.00       0.00        0.00         0.43      CDO @ Coronado Camp          Cañada Del Oro Wash 0.3 mi S of Coronado Camp
    1130     0.00       0.04       0.04        0.04         0.31      Samaniego Peak               Samaniego Peak on Samaniego Ridge
    1140     0.00       0.08       0.28        0.35         2.09      Dan Saddle                   Dan Saddle on Oracle Ridge
    2150     0.00       0.00       0.04        0.08         0.71      White Tail                   Catalina Hwy 0.8 mi W of Palisade Ranger Station
    2280     0.00       0.04       0.12        0.16         1.02      Green Mountain               Green Mountain
    2290     0.00       0.04       0.04        0.04         0.47      Marshall Gulch               Sabino Creek 0.6 mi SSE of Marshall Gulch

BTW#2, true CMJs (cloud maven juniors) will want to photograph the rain from these shallow clouds, this rare, Hawaiian-like rain event², lining the Catalinas this morning as soon as its light enough. It would be like photographing a parakeet on your bird feeder here in Catalina, one migrating from South America. I think that’s where they come from. Anyway, your cloud-centric friends from other part of the world would be quite interested in seeing your photos of this.

Is the summer rain season over?

No way! (But you already knew that, though it sounds more exciting to put it that way, in the form of a question like the TEEVEE people do)

Now we get into some interesting weather times as we go back into the scattered big thunderstorms feeding on the moist plume that accompanied O. That moist plume will be around for the next few days. These coming days, with their thunder squalls, may well be the most “productive” ones for rain here compared to the piddly output of O here in the Heights. We have upper air goings on that are likely to make storms cluster more into big systems a time or two during the next few days instead just the one over here and over there kind of days, the ones you hope you get lucky on to get truly shafted. So, “fun times at Catalina High” ahead, to paraphrase something.

Yesterday’s clouds

11:15 AM. The look of a stormy sky, Stratus fractus lining Samaniego Ridge, overcast Nimbostratus producing R-- (very light rain). — 11:15 AM. The look of a stormy sky: Stratus fractus lining Samaniego Ridge, orogrpahic Stratocumulus topping the Ridge, overcast Nimbostratus producing R– (very light rain).

4:56 PM. By afternoon the deeper clouds were gone leaving Cumulus, a couple of distant Cumulonimbus clouds with their rain shafts, and an overcast of Stratocumulus or Altocumulus, no precip coming out of them.

6:28 PM. The sunset, while OK, like O was a little disappointing since more clouds could have been lit up by the setting sun but weren’t.

The weather way ahead

Cool weather alert: based on model consistency, which I have already discredited earlier, there are cold snaps now appearing for the end of September and early October. They’ve shown up in a couple of runs now. They have some support in the NOAA spaghetti factory plots.

The End.

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¹There’s a nice description of “coalision” , the warm rain process not involving ice, in Pruppacher and Klett (1998) if you really want a nice book about cloud microphysics in your library.

²Mostof the rain that falls in Hawaii falls from relatively shallow clouds with tops at temperatures above freezing, no ice involved, contrary to the usual situation here where ice is necessary.

Tattered “O” creeps into Arizona

Old Man O is kind of a mess now. Still hoping for half an inch here in Catalina/Sutherland Heights, but now even wonder it that will materialize as O goes by today and tonight. Darn!

But, even though O MIGHT be a rain disappointment here in Catalina, there are plenty of opportunities to get substantial rains AFTER O goes by due to lingering tropical air combined with the presence of an upper low pressure center along the Cal coast in the days ahead. Cloud Maven Person thinks (of course, as an “unofficial weather thinker”) that more rain will fall in the spotty thunderstorms here in the Catalina area in the five or so days after O than in O today. We shall see, won’t we?

However, before moving along, let us examine in the colorfully annotated map below those results produced by the truly great thinker inside the “Beowulf Cluster” at the University of Arizona’s Dept of Atmospheric Meteorology to compare the dinky amount CMP is dreading. Its only fair.

Shown below is more like a heavenly rain here, some 1-2 inches is predicted to fall over a number of hours, not in one dump. Hoping for what is shown below, but think it will be quite a bit less.

Total rain accumulation in the 24 h ending at midnight tonight, most will fall in the late morning to evening hours. This map from the model run at 11 PM AST last night, the very latest available. The reddish areas represent where the model thinks the center of O will go with its central heavier rains. Notice that it thinks some little areas of Mexico inland from the Gulf will get a mind-boggling TEN inches or more!

Besides, rather than having completely cloudy skies, as today’s sky will likely be, those heavy guys in the days ahead will be far more “photogenic” you might say with their black shafts and sparks. Rainrates will be greater, too, in those situations than from O’s clouds, which are a little too stratiformy and all mixed together for the blinding rains we see in our thunderstorm rain shafts. Also, since O’s little circulation will pass just to the east of us, the flow off the Catalinas will be a little downhill from the east, which helps to reduce what we might get here, too.

In contrast to the semi-steady rains of O later today, our summer thunderstorms can drop an inch or even two in 15 minutes (yep, its been recorded in gauges). The flooding rains we had a week ago last Monday, the rates were 1-2 inches. Makes quite a difference in erosion.

—-rambling aside below—-

Its interesting to me, stepping aside from direct weather commentary into a more philosophical one, how the story of O resembles life in general as happens to all of us growing up. All of the promise that O had for producing heavy, but mostly beneficial, rains here in Arizona, has been reduced, like that of a youngster growing up that gets straight A’s in the 7th grade, 8th grade, but then loses all of his focus when puberty hits and notices all those wonderful, endlessly intriguing, fascinating, “can’t take my eyes off of you”, creatures around you that seemed so boring and non-existent just a few years earlier. But now they have become the greatest conundrum in all of life! Instead studying, you, as I did, began making jokes in class as a way of getting the opposite sex (!) to notice you because you didn’t have any other social skills to interact with “girls” with. And, like me, you started getting kicked out of class and sent to the principal’s office for causing distractions. THESE humiliations after all those straight A’s and accolades we got from teachers just a year or two earlier. All of our promise, like O’s, dissipated: you’ve discovered that you’re a Saffir-Simpson Category 5 heterosexual, to continue a tropical theme here.

The life of O has been just like that; the once proud storm, so organized, so full of rain potential for Catalina, became “distracted”, disorganized, and torn apart by mountains, vagaries in the topography and lack of warm water to feed on. O’s life reflecting our own lives when hormones hit, blind siding us, deflecting us from the productive lives we thought were ahead but instead into poor grades and lack of self-control, which meant we had to go to a community college instead of real college. And even then, when you find you have a Spanish class there with Miss Wisconsin of 1961, the distractions and poor grades continue… You can’t even get into UCLA after seven years of JC!

Yes, O’s story IS the story of every man. Believe me, I understand what you went through and how hard it was to dissipate so much promise early in life, as tropical O has likely done for us here in Catalina.

—–end of RA—-

Here is a nice, but sad loop of radar and satellite imagery of O during the last 12 h or so from IPS MeteoStar, one that documents O’s decline.

Yesterday’s clouds

One size fits all it seemed yestserday, but I am giving you three anyway, so here they are, your cloud day.

8:03 AM. Light rain falls on the Catalinas and on Catalina, producing about a tenth of an inch here. The lack of variation in the rain intensity (“shafting” as we say here) along the mountains reflects small variations in the height of cloud tops; rain from stratiform clouds. The cloud? Nimbostratus.

1:56 PM. Those deep Altostratus/Nimbostratus clouds, typically with tops at CIrrus levels (30 kft or more), moved off after the rain ended, leaving Altocumulus opacus droplet clouds to continue the gray day.

4:41 PM. A few drops were falling off toward Tucson from this mostly ice Altostratus layer; some Altocumulus in the upper left corner, and in the distance.

Dial “O” for rain; Odile that is

Unless the younger folks watch Turner Classic Movies or something like that, they will be clueless about what ther the reference to “dialing” is in the title. Oh, well. Heck, who even remembers what a Walkman was these days?

The heavy cloud shield of TS Odile is moving in with some light, spotty rain hereabouts right now. It will be interesting to see if today’s rain amounts to anything. Seems it could be a very Seattle-like rain day with those heavy layer clouds over us (Nimbostratus/Altostratus) and intermittent very light rain all day. Boring! (Is “boring” with an exclamation mark an oxymoron of sorts?)

NWS is excited about Odile, as any meteorologist not having snow in his veins would be, and have posted some daily rainfall records for this week. Of course, we’ve already set some rainfall records for September; can it happen again? They seem to be concerned about that possibility. Many of those September records, as many of you will remember I am sure, were associated with tropical storm Norma that busted into Arizona in early September 1970 as you will see¹. Workman Creek got 11 inches in one day back then. You can read about Norma’s doings here and whether the NWS forecasts were adequate.

The meteorological situation was very different with Norma, and that may be why we precipophiliacs could be “disappointed” by rain amounts with Odile–Norma had help from the configuration aloft; Odile not so much. However, in the days following Odile’s passage, that upper level trigger does fall into place over southern Cal, and we’ll have to watch out for some big thunderstorms in the couple of days AFTER Odile goes by when that upper level trigger (trough) still has some tropical air to work with. So, some really “interesting” weather ahead, the kind of weather we’ve forgotten can happen here in the many droughty years we’ve had lately.

Here, just hoping for some nice steady rains, not just sprinkles, that add up to something significant like a half an inch or more, keeping the desert green that bit longer, and maybe, some good scattered thunderstorms for a few days after the big cloud shield of Mr. Odile fades away. That will pretty much do it for our summer rain season I’m afraid.

Now, since we don’t like to do work that can be done better by others, these ones and this one, for example, so on to yesterday’s pretty cloud pictures. (Can’t get over the thought I might be disappointed in Odile’s rain here, expectations not real high, so don’t want to express them and make you a little sad; keeping a lid on thoughts of a big Odile rain for Catalina, don’t want to get too manic, etc.) Will just lay back and enjoy it…whatever comes.

Yesterday’s clouds²

10:00 AM. Cumulus development looked promising in the mid-day hours, but none over the Cat Mountains produced ice. Was surprised that didn't happen. — 10:00 AM. Cumulus development looked promising in the mid-day hours, but none over the Cat Mountains produced ice. Was surprised that didn’t happen. Note glistening rocks dur to the recent rains.

: 11:59 AM. Towering Cumulus and Cumulonimbus clouds begin lining the International border. Warning: adult commentary included in photo, the kind you see every day on TEEVEE.

1:18 PM. High cloud shield from Odile’s advance creeps over Tucson from the south. Cumulonimbus clouds can be seen in the extreme distance.

4:06 PM. Cirrus and Altostratus have overspread the sky, and the darkening to the S-SW looks ominous in view of Odile’s approach after wrecking southern Baja.

Followed by a great sunset, one deserving of more than one example. No details, just enjoy.

The End

————————————–

¹The present Arthur was in Durango starting his first job as a weather forecaster for the great Colorado River Basin Pilot Project, a randomized cloud seeding experiment, when Norma’s remains hit and flooded the Animas River there. I was inside a vaudeville theater listening to the rain pound on the roof, the audience of that melodrama, too, distracted a time or two, and also being distracted by Durango school teacher, Janet James, whom I had taking a liking to. She was there that night, too, but not with me. Wonder what happened to her?

²Caution: one photo is annotated with adult humor.

Summer thunderama returns to Catalina for a day

Against the deepening blue skies over us as the sun continues its descent to overhead of the Equator, coming right up (September 22nd, AZ time), our late summer Cumulus and thunderheads become even more spectacular. You can see the whole cloud day here, courtesy of the University of Arizona, if you would like to avoid the tedium of examining photos and captions by yours truly.

I got very excited about a small thunderstorm that took shape almost overhead of Sutherland Heights, and you know what that means. Yes, too many photos of almost the same thing! See below. Captured it, too, BEFORE it even started to rain, or even thought about it. Produced a large number of cloud-to-ground strikes in the vicinity, too, more that you would expect from such a small storm. Also, if you could see them, you saw repeated split strikes, ones in the core of the rain, and at the same time a branch in clear air to the north, a mile or two quite a ways from the rain shaft. I had not seen that before happen over and over again. Samaniego Peak reported the only rain, 0.28 inches, in the ALERT Catalina Mountain gauges, like twice that in the core of the shaft.

Then, of course, we had a lot of LTG in the early evening and nighttime hours to the NE-S-SW as storms marched across Tucson, Marana and Oro Valley. Missed us, though. A place in Avra Valley got an inch.

That’s pretty much it for your cloud and weather day yesterday. Farther below, the details….

Mods see nothing for a couple of days, until Monday, when the moisture from now Hurricane Odile begins to work its way into AZ.

Yesterday’s clouds

10:30 AM. After a completely clear morning, Cu began to pop up around 9:30 AM. This size by 10:30 AM gave hope that the day would have full Cumulonimbus clouds later on.

DSC_0016-1 — 3:26 PM. Just a pretty scene. Note the contrast between the blue sky and the white glaciated top of this Cumulonimbus calvus. Note too, that there is only a faint rain shaft underneath (behind ridge top, that smoother area).

DSC_0022-1 — 3:48 PM. Here’s where you and me saw a lot of rain promise in this developing cloud base on our nearby mountains. Almost every cloud that had this much base or a bit more, eventually rained. Maybe it would explode into something really big with powerful winds! Well, “really big” didn’t happen, but it did do its job with nice, but small rain shaft a little later.

DSC_0036-1 — 4:01 PM. Excitement builds as base grows a little wider; rain excitement is now guaranteed. I can only imagine what you were thinking when you saw this, and how happy you were since it could lead to a nice rain on you. LTG and wind, just ahead.

Ann DSC_0038-2 — 4:05 PM. Bottom beginning to drop out now!

DSC_0039-2 — 4:06 PM. Graupel and/or large drop strand (center) just began to appear (look hard). This was taken just after the first cloud-to-ground strike near Samaniego Peak (center).

DSC_0045-1 — 4:11 PM. The gush reaches the ground amid frequent split cloud-to-ground LTG strikes, ones near or in the core, and repeated strikes a mile or two to the right in clear air.

4:17 PM. Our little rain shaft offered up a lot of wind, probably in the neighborhood of 50 mph, judging by the spread of the rain “plume” on the ground to the right. Some drops and gusty winds of 20-30 mph reached Sutherland Heights soon after this, making for an especially pleasant evening outside.

DSC_0089-2 — 5:42 PM. An isolated thunderstorm, rumbling to the west of the Tortolitas yesterday evening , offered up this dramatic shadow scene.Its remnant providing a sunset highlight.

DSC_0114-1 — 6:37 PM. The remains of the thunderstorm shown in the photo above provided a nice sunset highlight as they so often do.

4.63 inches; enhancing our historic storm due to “further review”

First, a tedious note about the Big One of two days ago.

While the Davis Vantage Pro 2 tipping bucket gauge registered a whopping 4.18 inches, a smaller plastic gauge from CoCoRahs here had 4.63 inches, after subtracting some rain (half an inch) I forgot to dump due to a brain cramp. A neighbor a couple hundred yards away here in Sutherland Heights, measured 4.65 inches in her gauge, and I now think that the 4.63 inches is the correct amount of rain for this spot. This goes with two other reports of 4.48 inches at Our Garden, and another one of 4.50 inches just a bit on the west side of Lago del Oro Parkway, and the 4.59 inches at the Samaniego Peak ALERT gauge just E of us. We seem to have been in the heaviest band of that storm! (Makes up for all the misses during the summer.)

The Vantage gauge is mounted above the ground, and some loss occurs due to wind, and also when the rain falls too hard, the tipping bucket can’t keep up. The CoCo gauge is ground mounted, and is protected from wind by surrounding natural desert vegetation (aka, “weeds”).

Below, from the University of Arizona’s rainlog.org, is a map of rain totals in our area and the northern areas of TUS. (The Our Garden and Samaniego Peak totals of 4.48 and 4.59 inches, respectively, don’t show up because they are not members of rainlog.org but probably should be so’s we can get all the rain we want to see in one site! I have added those values

Ann TUS rainfall 9-9-2014 fell prior day — Rain totals for September 8, 2014. The green values are for Our Garden and Samaniego Peak, along with the revised total for Sutherland Heights. Recall a neighbor here measured 4.65 inches!

In the meantime, from CDO at Wilds Road videos I took in heavy rain as the Sutherland Heights rain started to eclipse 3 inches, this larger wave that formed. I think it could have been surfed.

10:55 AM. From a frame of a video taken at the CDO wash and Wilds Road intersection, this monster. Must have been 6 feet high! — 10:55 AM. From a frame of a video taken at the CDO wash and Wilds Road intersection, this monster. Must have been 6 feet high in total height! So, you CAN “surf Arizona!”

Yesterday’s clouds

First of all, it was real disappointing to see so much haze in the air after so much rain! Not sure where it came from yet, will have to do some back trajectories to find out, but later…

6:54 AM. Crepuscular rays outline a Cumulus turret.

6:54 AM. Distant Cumulonimbus offers hope for a similar scene later in the morning over the Catalinas, a scene that was NOT realized.

8:17 AM. A great example of crepuscular rays and bad air.

12:53 PM. Promising Cumulus congestus that really went nowhere.

2:03 PM. However, it was not a completely rainless day. Some clouds got thick enough to rain lightly. In this Arthur's opinion, this rain was due to the collision with coalescence rain process, not the ice one which I deem with a 51% confidence level. — 2:03 PM. However, it was not a completely rainless day, as can be seen, “dead ahead.” Some clouds got thick enough to rain lightly. In this Arthur’s opinion, this rain was due to the collision with coalescence rain process, not the ice one which I deem with a 51% confidence level.

4:26 PM. Kind of losing interest in the whole day now as Cu disappear in favor of an Altocumulus opacus deck, one originating right out of Norbert if you saw the satellite imagery.

The weather ahead

Still pretty confident in more summer rains and tropical air after the current dry spell of a few days, this partly associated with the next tropical storm, likely to be named “Opal” or something like that with an “O” as it takes shape. Of course, we could look up what name it will be, but it will be named soon enough, so why bother?Its already a numbered tropical depression (a weak area of low pressure) down there off Guatemala now.

Special low cloud base day ahead; yesterday’s pretty cloud scenes

Today will be a special one in the desert. Cumulus bases are going to be really LOW for summer, maybe only 3-4 kft above the ground, and likely warmer than 15 C (50 F). Maybe 50 F doesn’t sound special, but it is. A base temperature of summer clouds that warm is rarely observed here. And with that, and all the posts here about the temperatures that ice forms (around -10 C, 14 F) are out the window. Ice will form at much higher temperatures than usual.

This is because on a day when the Cumulus bases are that warm, rain forms by collisions between droplets before clouds even reach the -5 C (23 F) level, the highest temperature at which Ma Nature can produce ice. Rain mgiht even form in our clouds today even before the freezing level itself!

This is so exciting for an Arizonan who has studied ice-in-clouds development over the years because today ice will form in clouds around the -5 to -10 C level, and the mechanism of Mssrs Hallett and Mossop will be heavily involved as well as other lesser understood mechanisms to form ice in clouds today. And, along with that high ice-forming temperature will be categories of ice crystals that are rarely seen here, needles and hollow sheaths, ones that form at temperatures in clouds warmer than -10 C! You can see how excited Mr. Cloud Maven Person is. For comparison, it would be like a bird watcher seeing a _________, something pretty rare go by.

Dewpoint temperatures are running in the upper 60s and was 70 F (!) at TUS earlier this morning! Indicative of a really, really moist day from a cloud standpoint even now is that line of Stratus fractus cloud halfway down on Samaniego (Sam) Ridge. And this is BEFORE rain has fallen. Not too unusual to see something like that AFTER a good rain, but before, its pretty rare.

All in all, a very tropical day ahead, very “Floridian” I would call it, and that means more water in the clouds above us ready to fall out, and more “fuel” to send those warm plumes of Cumulus turrets spaceward. That’s because heat is released to the air around cloud droplets as then form, and the more “condensate” the more heat. The warmer the cloud bases, the more condensate that occurs. Its quite a feedback loop.

The last time we had bases this warm and low, some “lucky” areas got “Floridian” dumps of rain, that is, 3 inches in an hour. (Three inches in an hour is pretty common in Florida in the summer.)

However, need some heating and/or a good symoptic situation to gather up the clouds today if we are to get more than just high humidity from Norbert’s remains. Last night’s model run from the U of AZ was not real supportive of a great day because while the humidity is here, and upper level situation is going in the wrong direction, is not going to help much. A lot of what we needed was expended over night in huge storms that are raking central and northern AZ now, with some sites in PHX reporting up to 2 inches since midnight! And as that upper air configuration responsible for their great rains moves away, what’s right behind it up there, will try to squash clouds.

So, while we have the ingredients down low for an exceptional rain day, its not in the bag. What’s worse is that drier air is now foretold to roll in from the west by tomorrow, further diminishing (not eliminating, though) the chances for a decent rain here in Catalina. “Egad”, considering all the promise that “Norbert” once held for us!

So, in sum, a bit clueless here as to what exactly kind of day we’re going to have. “Truth-in-packaging” portion of blog. I see rain has formed just now (6:41 AM) on Samaniego Ridge, AND to the S-SW, very good sign!

—a note on air quality—as inferred from visibility in a humid situation——–

Another thing you will notice is how clean the air is. We have tremendous humidity, and unlike smog-filled air back east, the sky will be blue, and the visibility good. If you’ve ever been back East, you’ll know that in most areas the sky between the clouds on humid days is pretty white, and horizontal visibility is reduced in the moist air, say ahead of a cold-cool front in summer. This is due to large haze particles that have become droplets before water saturation has been reached, a phenomenon called deliquescence. Its horrible. Really ruins the sky back there on humid days.

Enough semi-technical blather. We’re mostly about pretty cloud pictures here.

Yesterday’s clouds

There were some spectacular scenes yesterday, even though it was disappointing as a rain day, only a late afternoon trace here in Sutherland Heights. Here are some of the best.

6:34 AM. Altocumulus lenticularis hovers over and a little downwind of the Catalinas.

10:03 AM. First Cumulus begin to form on the Catalinas, later than expected. I will using the words, “expected” and “unexpected” a lot today.

1:21 PM. First ice seen, lower left top of blue sky and cloud border. Can you see it?

DSC_0097-1 — 1:24 PM. Soon after the first ice is seen, out pops the rain, that very faint haze in the center of the photo.

2:12 PM. Mt Lemmon receiving 0.79 inches of rain in about an hour from this little guy. Note that the peak is TOTALLY obscured by this rain shaft.

12:24 PM. Cumulus clouds kind of muddled around up there when yours truly was expecting a sudden eruption at any time. Really did not happen yesterday.

DSC_00870-1 — 12:26 PM. Mostly just a pretty scene, the blue sky, the Altocumulus perlucidus, and the Cumulus congestus erectus.

DSC_0116-1 — 4:17 PM. It was especially gratifying, after kind of a non event day, to have this unexpected late eruption of a Cumulonimbus NW of Catalina. Meant chances weren’t quite over for nearby developments.

5:03 PM. Cumulus cloud street trails off the Catalinas. Will it do anything?

5:21 PM. The ragged edge of the higher layer leads to a series of crepescular rays in the falling rain, while the Cu congestus turret sends a long shadow Catalinaward, A gap in the clouds allows the sun to shine on the rain falling in Oro Valley then. Can you imagine how great the rainbow was on the other side, say from the Tortolita Mountains? The rainbow isn’t seen in the forward scattering direction because its due to reflected light back toward the sun from within the raindrops.

5:22 PM. Nice lighting on Samaniego Ridge, rainbow imminent,

5:24 PM. Magnificent, the lighting, the rainbow. How lucky we are to be here!

6:56 PM. Just when you thought the day was finished, this surprise. Well, it was to me, that’s for sure!

6:58 PM. Ghostly-like late blooming Cumulonimbus calvus and Cumulus congestus clouds rise up against the falling temperatures. Pretty neat sight.[/caption]

6:58 PM. More unexpected strong developments to the west after sunset.

The End!

Heck, if I worked on this much longer, the answer to what’s going to happen today would be in!

Some clouds

The End

Yesterday’s Clouds

Yesterday’s clouds

The weather way ahead

Yesterday’s clouds

Yesterday’s clouds2

The End

Yesterday’s clouds

Yesterday’s clouds

The weather ahead

Yesterday’s clouds

The End!

Yesterday’s clouds²