When some of you were weather browsing this morning, and you saw this forecast map from IPS MeteoStar, valid for next Tuesday, which shows a very late in the season tropical storm off Baja heading toward the Southwest US, while a vigorous winter storm bashes the West Coast, I had a feeling that it reminded you immediately of one of your early weather memories of a similar situation. First, the IPS map.
The map below is from an era when you were a little child and maybe you, too, were clipping weather maps out of the Los Angeles Daily News, if that’s where you lived:
Looking back, but a little closer, like yesterday and the day before…..
Nice storm we just had. 0.65 inches fell in Sutherland Heights. Would not have predicted that much over these past couple of days to be honest. Total for month now 1.10 inches or a little above the 38 year average of 0.97 inches.
After a long dry spell though at least the next week, November will close out on a dry or wet note, which is pretty encouraging.
Yesterday’s clouds, ice and sun: a soliloquy on ice
Fair amount of ice yesterday in our low clouds. As you would guess on your way to becoming a cloud maven, bases AND tops were especially cold for AZ. Afternoon cloud bases were running about -8° to -9° C, whilst tops were about -15° C. Still ice was not plentiful. How’s come? Well, it seems the amount of ice in clouds is dependent on both the cloud top temperature and the droplet sizes in the coldest parts of the clouds (see Rangno and Hobbs 1994, Quarterly Journal of the Royal1 Meteorological Society) (Hell, no one’s going to read this, though it is now available without having to go through a “pay wall” and the page linked to above has been updated with new pdfs!)
In sum, a cloud with a base of -10° C and a top of -20° C will have LESS ice than a cloud with a base of 0° C with the same cloud top temperature (-20° C) because with a warmer base, the drops near the top of the cloud in second example will be larger.
That seems to be the way it works. So, yesterday’s thin cloud with cold bases had smallish drops, and ice production was a little limited.
Also, if you monitored Ms Lemmon, and the Catalinas in general, you probably were thinking, “Where’s the ice?”, in those cold Stratocumulus clouds as they piled up against them.
Well, when you have strong winds at cloud level as we did yesterday, and with ice crystals taking a little time to appear from some of the droplets that freeze in the cloud stream, grow, and eventually fall out, you’re not going to see much evidence of ice on the windward side of the mountains in these kinds of situations. The ice is going to appear and fallout as snow or virga downwind a good distance downwind, and that’s what was happening yesterday to nearly all of those deeper clouds (with slightly colder tops and larger cloud droplets in them) that formed over the Catalinas.
If you don’t believe me, yesterday’s time lapse movie from the our great weather resource, the University of Arizona, shows this. You’ll see a lot of precip and virga falling of those clouds as they stream eastward from the Catalinas. So, we didn’t get to SEE much ice from those Stratocu clouds but it was there.
Lastly, the sun, as it appeared yesterday at sunset in the dust-haze kicked up by that powerful low that brought us our rains. The jet stream, as was pointed out by a friend, was about 200 mph overhead of TUS at 40 kfeet. Wow.
1″Royal”–that is so funny; “hey”, guys, wake up, its the 21st century!
Looks like CMP is low AGAIN on his prediction! Thought a third was the most that could fall in our present storm chapter (10% chance of more, that is), and best estimate, 0.165 inches. Now it looks like met friend and professor at a major university will be much closer with his half an inch prediction. Very painful. Kind of like Stanford with their brainy team beating the Washington Huskies in fubball . It really hurts.
Let us begin today with a look at desert grasses from this summer and falls rains. Pretty deep, knee high in some areas, but as we know here, full of nettles. Kind of a cool look though.
Was heading out to see, what from Google Space, appeared to be a new meteor crater near me, one maybe the astro boys missed. Turned out it was just a house under construction, pretty much underground as well. Kind of a cool thought to build like this, lots of energy saved, which is always good. Cell phone service likely compromised.
…and a dense discussion of detecting ice in them. I am hoping that my followers noted the time of the first appearance of ice in those Cumulus and Stratocumulus clouds that began to fill in during the middle and late afternoon. As that happened, a few raindrops sputtered down here just after 3 PM as that happened. You should have logged both these events, the first visual appearance of ice, and when those drops fell in your weather diaries.
The whole point of this blog is the detection of ice in clouds by layman and laywomen, or “laypersons” I guess it should be now days. This is because if you see ice developing in lower clouds, something will be falling out of them soon. Ice grows in water clouds at below freezing temperatures at the expense of droplets. Therefore, if they stay in a water cloud long enough, they will get heavy enough to fall out. Poor droppies disappear, unless the air is really rising fast.
An interesting side note is that the air FLOWS THROUGH clouds, exiting on the downwind side. A cloud does not just float along as is. It is moving slower than the air, even itty bitty Cumulus clouds the cloudy air is being replaced constantly. The cloud is really moving upwind relative to the air! The POSITION of the cloud moves downwind, but SLOWER than the air that goes into it.
However, if ice crystals form in a small cloud then, they will fall out as single crystals at the downwind edge; they are not going to reach the ground unless you’re on a mountain top. You saw a fair amount of ice exiting the downwind end of clouds yesterday, falling out and evaporating in the dry air there. Where the cloud is wide, then they can gain some mass, collide with droplets, or other crystals and fall to the ground.
You need clusters of crystals locked together, called “aggregates” or ones that have gone through riming, collisions of ice crystals with drops at below freezing temperatures that freeze on the ice crystal making it more massive to get rain drops to the ground. Riming is what leads to graupel (soft hail) and hard hail (the latter to crystals impacting larger, often precipitation-sized drops that freeze on them).
For air travelers, or those who examine tree icing after storms, rime ice is white and produced by small cloud drops; clear icing is caused by much larger drops, usually drizzle or rain drop sizes. If the drops are too small (much less than about 20 microns) they are too small to hit anything and rather go around solid objects. Let’s say you’re on the top of Ms Mt Lemmon, say at 8.000 feet in the fog. The temperature is 24° F. Its windy. You look around and you see no icing on the pine trees trees up.
Where are you?
Ans: at cloud base.
That’s because itty-bitty drops, too small to hit on pine tree needles are flowing around the needles. Some great comments to make that would enhance your stature as a cloud maven junior is to offer your companion the information, “Wow, look at those trees! Here we are ing the freezing fog, and yet they have no ice sticking to them! That means the cloud droplets are pretty small, smaller than about 20 microns! I guess we’re at the base of this cloud system above us.”
These would be really great things for you to say. Of course, as you drove up to Mt. Lemmon, you would know already how far above cloud base you are, but, what the HECK.
You’re at Ms. Mt. Lemmon again, You like it up there when its in the fog. This time the temperature is 25 ° F. Its windy. The pine trees are loaded with rime icing, the ice juts out in the direction from which the wind is coming.
Where are you?
Answer: At LEAST a few hundred feet, more likely a thousand feet or more above cloud base. Drops have reached sizes above 20 microns in size, as they usually do at these heights above cloud base in old Azy. Later, you notice that the clouds are topping Sam (Samaniego) Ridge at the 6500 foot level. Now, they can’t be disconnected layer clouds, but rather SOLID from base to where you are. Drops are tiny again at the bottom of each layer.
Here’s another example. You get up in the morning after a cold winter storm to see “iced trees” on Ms Lemmon. Another comment you could be making is that, “Wow (always begin with “wow”), those clouds must have really been low based last night, way down on Sam Ridge!”
Riming on trees is analogous to the collection of fog droplets by trees and vegetation along the west coasts of the continents in onshore moving banks of Stratus and Stratocumulus clouds that intercept hillsides. These can be significant sources of water. Some studies of droplet collections by trees have found that under the tree, something like 20-40 inches of “rain” can be collected by a tree in northern California.
Wow, I can’t believe all the information I am providing today! Its really incredible.
“Just Another Day“, btw, one of the many great songs by Oingo Boingo, if you’ve ever heard of them. We’re not just about clouds here. Trying to broaden your pop cultural knowledge with distractions like this.
Yesterday was remarkable in how exact it was to the day before in clouds, but ultimately disappoiting.1 There was supposed to be more cloud action, shafting around, that kind of thing, but there wasn’t. It was virtually identical in every way, including having only two clouds that got high and cold enough to have ice in them. I am sure you recorded them in your cloud diary, and this will be a little tedious as a result, but….what the HECK.
Here is your cloud day for yesterday, focusing on the detection of ice in clouds:
Today is another day. More hope for a shower late today or tomorrow, models say, then likely another dry spell as the summer rain season ebbs again for awhile until that possible super hurricane Dolores drags some moisture up this way. (Dolores, now just a tropical storm, was just born off southern Mexico near the coast. Will be interesting to see just how strong she gets.
1Some fans like to see misspelled words here. Amyone see that criminal who was sentenced to “life in person” as described in the AZ Star? That was pretty grate.
Won something of a cloud lottery yesterday. A trace of rain might have fallen only on ME…as a single rain-producing cloud went over my house. I felt pretty special. Here’s the story in photos:
Looks like an active photogenic one with dense rainshafts around. Lots of excitement for weather guys like me. Hope we get shafted reel good here.
In unrelated matters, an extraordinarily strong hurricane still set to develop off Mexico in the next few days. If nothing else, surf will be up along the coast of Mexico and southern Cal. Will let you know when the winds in it have reached 140 mph or more.
Well, those showers were a surprise to “me and my model” yesterday morning, at least the one I looked at just before going on the air. There were no upstream echoes in the clouds upwind of us, either, something normally seen before cool season showers get here. Fortunately, I was able to get in a prediction that rain would fall just as the drops began coming down.
However, there are a few times when that bit more lifting as the air moves from the lower ground to the southwest of us to here can trigger precip; the tops get that bit colder, form ice, voila, out drops the rain (and snow). That’s probably what happened yesterday to cause a sudden development of light showers, “all quads” it seemed.
Cloud tops may not have gotten colder than about -10 C yesterday, too, and so our rain likely fell from ice crystals rarely seen in Arizona, hollow sheaths and needles (columnar crystals), which have to be in big aggregates before they can form a drop big enough to reach the ground. So, not only are they rare here, but there also have to be a LOT of them )10s to 100s per liter in the clouds) for them to form big enough snowflakes so that a drop reaches the ground. In fact, when columnar ice crystals form in clouds, they often do so prolifically so that, at least at the University of Washington where the present Arthur worked for about 30 years in airborne studies of clouds, needles and sheath crystals were always associated with the highest concentrations of ice crystals that we observed. Some of those rare ice crystals were STILL forming in the clouds above us near the time of the second sounding, shown below, launched at 3:30 PM! That was really shocking!
This ice crystal happenstance, and the surprise light showers, made yesterday particularly worth commenting on from this cloud pulpit, if that’s what it is. Some nice examples of needle and hollow column ice are shown here at CalTech. These kinds of crystals are rare in Arizona because they require larger (greater than 23 microns in diameter2 in clouds at temperatures between -3 and -8 C. Like the needle crystals themselves. Since the clouds were shallow, one has to speculate WHY the cloud droplets might have been extra large. It may have been that there were few of them (seems kinda unlikely this far from clean oceanic air. More likely, those clouds had large (micron-sized) dust particles in them, known to help form larger cloud droplets. So, I’m guess those clouds were helped by dust so’s they could have larger droplets in them, ones big enough to help produce ice splinters consisting of needle and hollow sheath crystals at such high temperatures (higher than -10 C).
Our U of AZ model predicted soundings were pretty much what we saw, too, cloud capped by a stable layer that got stronger as the day went on, and the air drier above it. Below, from IPS MeteoStar, these TUS soundings from yesterday morning and afternoon.
But let’s drag this out and look at yesterday’s clouds now…
During the afternoon, a nice cloud “street” formed, came all the way from Mexico way, one that spawned a little more anomalous ice, and those few raindrops; see below for evidence if you don’t believe me.
BTW, here’s our cloud street as seen in the “visible” satellite imagery at 4 PM AST, just before the drops fell on my windshield. You can see that it originated near the border with Mexico, as many things do.
The End, except I think there will be some more rain tomorrow morning, trace to quarter of an inch are the bounds, meaning about a tenth is the most likely amount from this cloud pulpit.
The End, again.
1I prefer this spelling today; more “o’s” than “l’s” in that word make you think more of a thing full of air; maybe a few more “o’s” would help even more, too, like “baloooon”…
2That size is considered “large” for a cloud droplet, and lab studies have shown that they splinter when they hit something, like soft hail, also called “graupel.” Splintering is thought to lead to all those extra ice crystals at temperatures between -3 and -8 C.
First, you should always begin your day, not with the breakfast of champions, but by reviewing the prior day’s clouds in the University of Arizona time lapse movie. Here’s what you will see:
Lots of Cirrus, varies species, Altocumulus, Cirrocumulus, a high temperature contrail go through some Cirrocumulus just after 4 PM, and flocks of medium-sized Cumulus clouds emitting ice.
First, one interesting, but inexplicable Cirrus scene. I know you were likely going to ask Mr. Cloud Maven Person, “Hey, what gives here?” I get a lot of calls like that1.
“I don’t know how that happened; let look at a flower instead”:
In the meantime, after being flustered over a cloud in the early afternoon, those Cumulus clouds aroiund, only two or three thousand feet thick were beginning to snow away, first way off to the south of us, then downstream of the Cat2 Mountains.
Here is the rest of your interesting and learningful cloud day yesterday:
There’s still water in the Sutherland Wash. Its been running now since the end of January! Amazing.
1FYI, this is a lie.
2I suppose someone could posit that “Dark Magic”, oops, “Dark Energy” may have caused those trails to “come together over me” , by Lennon and McCartney. “Dark Magic”, OOPs. “Dark Energy”, dammitall, is invoked to explain a lot of impossible things, like how the Universe blew up from something smaller than the head of a pin (!) and was 200 million light YEARS across in the tiniest fraction of a ONE second. Clearly impossible without magic, oops, Dark Energy. This impossibility was deduced on cosmic microwave radiation measurements at the farthest edges of the Universe as we know it.
However, instead of checking their measurements, cosmos (not Cosmos Topper of early movie fame with Carey Grant, but cosmos scientists that study the cosmos invented Dark Magic, oops, Dark Energy, dammitall again, to explain how something that’s impossible happened.
Recently, cosmos scientists retracted that finding and said their measurements in retrospect were likely compromised by cosmos dust. How funny izzat? Sure, I am a weather man and make a LOT of errors myself, but that cosmos one is pretty big.
Just kidding, cosmos guys, the cosmos is tough. Science mag reported that only 4 % of the visible Univserse is made up of known stuff, 96% (gasp) is made up of Dark Matter (23%), and 73%, of “Dark Magic”, oops again, “Dark Energy”, that stuff that is still thought to be behind the increasingly rapid expansion of the Universe3. That is, 96% of the Universe is composed of stuff we’re clueless about.
3It was originally posited that the expansion of the Universe should be slowing down until around the 1990s, when measurements indicated it was speeding up. Hmmmmm. Will there be a retraction of that claim, too, in our future? Stand by for more measurements. Just kidding, cosmos guys. Try being a weatherman….
In fact, the chance of MEASURABLE rain in Catalina is at least 100%, maybe as high as 300%, between 5 AM AST, Sunday, March 1st and 5 AM, AST, March 4th. Namely, its gonna happen.
Now, its not gonna rain that whole time, likely starting later in the day on the 1st. Pretty darn exciting to have a sure thing in the future! Check out this 4-panel presentation of maps from Enviro Can, I really like them:
Perhaps going farther than one reasonably should, the likely minimum amount will be 0.33 inches (10% chance of less) and top amount, gee, this situation has a big top, 1.50 inches, due to this trough’s deep reach into the sub-tropics, meaning it could pulling extra wet air toward us if everything works out in the “best” possible scenario. The best guess, between these two extremes is the average, or about 0.9 inches during our rainy spell. Should keep the washes flowing, though this one being colder than January’s tropical rains, should pile up lots of snow on top of Ms. Lemmon, so
Moving ahead to yesterday……
A pretty nice 0.09 inches fell yesterday morning in The Heights. “Nice”, because some model runs a few days in advance of this had no rain as a dry cold front went by.
When did the cold front pass?
9 AM yesterday, marked by a freshet from the NW with gusts to maybe 20 mph, with a falling temperature. Fell from 51 F to 42.x F by mid-morning, snow down to about 5,000 feet on Samaniego Ridge, too, though it melted almost immediately.
A push of wind like that virtually always builds a cloud above it, and yesterday was no exception. Here’ the cloud associated with that “freshet”:
Of course, the best part of days like yesterday is the play of the light and shadows on our mountains:
It was a great day to hike to that wash, too. Began with a nice sunrise; missed the nice sunset, darn. Hope you didn’t.
But the highlight of the day was seeing that water was still running in the Sutherland Wash, some eight days after our great snow. Like so many things that happen to meteorologists, I didn’t expect it.
Your cloud day yesterday
Was an interesting day because at times it looked summer-like due to Cumulus formations over the high terrain, Kit Peak to the Catalinas. The scenes below are mainly from a hike1 out to some native rock etchings.
Detecting ice module below. I hope most of you logged this as your first ice sighting of the day.
While waiting for still more rain, The End.
1Two of the people I was hiking with are very important meteorologists; faculty members at big universities with big Ph Ds, Wikipedia pages, give lectures all around the world about what they know. While I myself am not important, if you can align yourself with important people, befriend them in some way, and then go on to tell your friends that you have befriended that kind of person and do things with them, YOUR own mediocre life seems greatly enhanced. Let us not forget the guiding words to a peaceful, successful life as told to us in “Deteriorata.”
In case you didn’t notice, there was a prolonged street of clouds emanating from possibly as far away as Kit Peak, or maybe just the Tucson Mountains. Lasted for a few hours.Happens only on days with relatively shallow clouds (cloud-topped boundary layer) with a little wind, meaning that the thermals from the surface heating ended up being capped by an inversion or other stable layer, and those thermals form clouds in some places. In this case, a long line of intermittent clouds formed from an initial air bump caused by those mountains far to the SW of us. CTBL is more often invoked as a term by cloud folks when the sky is much cloudier in low clouds than these shots from two days ago, such as when the sky is covered in Stratocumulus clouds.
These kinds of streets occur over the same places whenever a day like this comes along. Think of it, especially here in Arizona, as a row of shady air under which you might like to live compared to those areas on either side of this cloud “street.” In Seattle, where the “cloud topped boundary layer” is almost a daily occurrence, you want to avoid being under the cloud street, where it can block the sun, and instead find the clearer slots!
For those sharpies that day and logged in their cloud diaries that ice formed in those shallow Cumulus clouds, they will be a little chagrined by this TUS sounding. This sounding suggests the clouds around the balloon were topping at -8 C, too warm for ice formation in shallow Cu. Let us begin to explain this puzzle by presenting evidence of ice formation in those clouds on the 18th:
Simple answer to our connundrum; due to lifting of the air as it approached and went over the Catalina Mountains, the tops of the clouds reached those temperature below -10 C where is begins to form. We would guess even closer to -15 C in that cloud in the distance beyond Charouleau Gap due to the amount of ice. Ice increases with decreasing cloud top temperature, but the temperature at which ice onsets can change on a daily basis; higher onset of ice temperatures on days in which the clouds have larger drops in their tops (a phenomenon originally reported by Ludlam in 1952, then re-discovered by Rangno and Hobbs (1988) who did not, at that time, know of the Ludlam finding, and thus, did not cite it. Pretty embarrassing, really. Was cited later in an update, however.
The weather way ahead
Seasonal rains beginning to show up in southern Arizona now on models beginning around the 4th of July as a big anti-cyclone parks itself over the Four Corners area in the latest model run from 11 PM AST last night. Very excellent run.
As the day rolled forward in time as they do pretty consistently, I was really happy for you having so many things to log in your cloud diary and maybe report to neighbors who might not have been so observant as you yesterday; the various types of clouds you saw, fun dust devils here and there spinning their way across Catalina, Cumulus clouds, a couple of which grew into Cumulonimbus clouds, and even produced a thunderstorm way over there in Safford. You could see that one from here, too. And there was a spectacular chances for you to test your ice-in-clouds acuity score.
Let’s go over yesterday’s clouds and make sure you got them right; but remember, don’t feel bad if you missed something. Cloud maven person will always understand and forgive those who might call a cloud by its wrong name. Believe or not, even CMP has done so1.
No further weather ahead of any interest to a CMJ, anyway. Darn.
1As a kid, I think I once called an Altostratus translucidus an “opacus.” It was pretty embarrassing.
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