Ice crystals – Page 5

“Back in the (cloud) saddle again”

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.

Will quit here……

The End.

Dusty parhelia

No, that’s not a baseball player that played for the Dodgers or Giants back in the 1950s, that was Dusty Roads; though Dusty Parhelia would be a nice name for a baseball player. Yesterday, with our slightly dusty skies, and on the 22 degree halo ring, and horizontally from the sun’s position, was a couple of sun dogs (parhelia) late in the day associated with those cirriform clouds we had. You know by now that those high clouds are comprised of small ice crystals. Here’s a few shots of those clouds, which were often CIrrostratus with embedded other Cirrus cloud species like spissatus, fibratus, and uncinus.

SONY DSC — CIrrostratus fibratus with a faint 22 degree halo.

The ice crystals in those clouds are typically hexagonal (six-sided) plates, ones that fall face down. If you could be there in them, and see them falling, at eye level you would see only the sliver side of them, but if you looked down at one that went by, you would see the whole hexagonal plate. The way that they fall is why aircraft laser imagery, when the laser is oriented in the vertical, captures such beautiful, full images of plates and other flat crystals in ice clouds as the aircraft flies through them.

The sun’s white light is separated into its colored components in these hexagonal crystals (but only at certain specific angles) and for this reason, the bright spots are at the same locations relative to the sun. Since I am not an atmo optician, I am relying on the links above to provide more complete, comprehensible explanations.

Note: Caption function stopped working again in WP for the fourth photo, and after half a dozen tries, will write it here:

Photo 4 caption: An especially vivid parhelia can be seen just above the horizon at lower left. The brightest ones like this are usually associated with aircraft contrails since those have high concentrations of pristine crystals. A flying saucer, or a bird with its wings closed at the instant the photo was taken, is also visible.

Continuing….

Sat image loop from the U of WA weatherfolk show lots more cirriform clouds in route to AZ next few days with occasional breaks. So, keep your camera ready for optics and sunrise/sunset color.

The weather ahead? Dusty cold snap.

“Dusty” is kind of the word of the day today.

Long foretold big Cal storm on the 12th-13th affects southeast AZ mostly with wind and dust on the 13-14th followed by unusually cool weather for mid-April. A hint of rain excitement for Catalinians has begun to show up in model runs, such as this one from the U of WA for early Saturday morning on the 14th. Yay.

The End

Whence graupel?

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

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

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

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

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

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

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

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

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

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

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

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

The End I think.

Cloud quiz

While waiting for the rain, here are some of yesterday’s clouds. What were they?

Answers printed upside down at the bottom except that WordPress wouldn’t let me do that. It would be great if you turned your monitor upside down before you looked at the answers. One is a trick “question” because I took a picture of a cloud behind what appears to be an inanimate plant, focusing on the dead plant and so the cloud shown in the background is a little fuzzy to make it more difficult.

1. Cirrus spissatus, the only type of Cirrus allowed to have gray shading in the daytime. Note mammatus like feature in the center.

2. Contrail, unusually turreted one (hmmm, perhaps a part of some government conspiracy–hey, I am kidding the “chem-trail” people). There’s also a patch of Altocumulus floccus (or Altocumulus perlucidus would be OK, too) lower part of photo.

3. Cirrus castellanus-turreted Cirrus, don’t see that species too often because it is rarely so unstable at that height. “Unstable”-the temperature dropped a LOT as you went higher up there, more than usual.

4. Altocumulus floccus, horizon, upper right, Cirrus fibratus (pretty much delicate, straight fibers) middle.

5. Ocotillo (hahaha, its not a cloud!) ((Another example of the juvenile humor that the writer seems to be afflicted with). OK, it looks like mostly Cirrus castellanus in the distance.

What do these kinds of clouds tell us?

The atmosphere is moist, but only patchy moist, a frequent occurrence in desert areas because “patchy moist” at middle and high levels in the atmosphere is most often all you get on the southern periphery of the major storms to the north of Catalina in the cool part of the year.

The atmosphere over us, too, is only in ascent at an overall rate of maybe an inch or two a minute; a bit more inside the clouds, less outside the clouds. One way to KNOW how slight the air is rising, even in the clouds, is to observe that snow is falling out of some of them, tiny ice crystals, typically in the low hundreds of microns in maximum dimension (width of a few typical human hairs, which are about 100 microns in width.) Such tiny ice crystals have fallspeeds less than 0.3 meters per second, and so they wouldn’t be able to fallout with higher overall “slab” lifting, the rate of that the whole upper air is lifting at these cloud levels. Q. E. D.

What caused the lifting? When you see clouds scattered over such a vast area, they have to be due to a disturbance in the wind field, a trough is likely nearby, normally upstream.

I have not looked at maps lately, but will NOW to see if there is a bend in the winds (indicating a trough) at these heights (mostly Cirrus level). I don’t see one on the 300 millibar map (30,000 foot map) and so I am not going to show it. But anyway, I am right, I am sure. Now, I will begin a serious investigation to prove I am right. The models will know if there is lifting going on.

Yes! I have been saved in my assertion by my former employer, the University of Washington‘s MM5 model, and this was the first thing I looked at! Look at the predicted high “clouds” (those above 20,000 feet) over Arizona for yesterday at 2 PM AST! They can’t be there in the model unless it thinks the air is going up some. OK, past the exultation stage now. Moving on. Actually, the model predictions of Cirrus-ee clouds aren’t really that great, so it was quite a surprise to see this.

The End.

Whiff

How sad. A few contours to the south of us, that jet to the south of us, that is, and we’d have got our tenth or more inch of rain. But no. That trough over southern California and northern Baja had to zip out and “up” (that is, to the northeast) like a jet taking off from an aircraft carrier. Gone now. All we’ll have is leftover wind and a threatening looking, but too shallow a deck of…….Stratocumulus. Too warm on the top of this layer this morning for ice formation, and that, as you know here in AZ, means that nothing comes out the bottom because the droplets in the cloud are too small to fall out.

But yesterday afternoon, an ice bonanza!

Alas, those Cumulus and Stratocumulus complexes were too high-based for the considerable ice crystals and snow forming in them to reach the ground as melted drops, except for “sprinkles-its-not-drizzle” here and there¹. Heck, the drops that made it down around 5 PM AST weren’t even that big.

I wonder if you saw the rapid transition to ice-producing clouds yesterday. Not much going on up to 1:30 PM. Then, all of a sudden, it seemed, there was ice almost everywhere in those little clouds. It was fascinating since they did not appear to be deepening upward to lower temperatures.

Let’s review yesterday with a long cloud harangue, starting from that wonderful sunrise with an Altocumulus lenticularis undulatus (has something like ocean waves or rolls in it to produce this where the air is rising and falling to produce cloud, then clearing), here is yesterday. Hmmm. I wonder if you remember where THIS sentence started?

Next, that promising scruff of cloud (I would call it, Stratocumulus) topping Mt. Sara Lemmon. It was promising because with cloud bases lower than the top of Mt. Sara, there’s a better chance of rain reaching the ground. But, up they they went as it got warmer, a usual thing. Has to be a flood of water vapor coming in to overcome the rise of cloud bases with daytime warming. As boffo as that trough looked over southern California, it couldn’t really “bring the bacon” if bacon was moisture that is.

We did have a lenticular cloud, too, for awhile. Let’s see that, too. It will be good for you. Notice how it is near the same spot as the “undulatus” cloud? That’s what lenticulars do; they have favorite haunts. When the flow is from the southwest, this is where they are going to be, over and over again, downwind from Mt. Sara L.

By mid-day and early afternoon, Cumlus cloud bases were well above Mt. Lemmon, a couple of thousand feet at least. Here is a mid-day shot of those non-ice producing, Cumulus fractus and humilis clouds next.

The first Cumulus photo was taken at 1:50 PM, and if you were a real sharpie, you would have seen some tell tale vales, but probably only Mr. Cloud Maven person did, they were that faint. But here in this second shot of Cumulus humilis and such, you can PLAINLY see that in the center, one of those little guys has converted COMPLETELY to ice. It was pretty amazing to see that in such small clouds. Soon the whole sky was filled with clouds “icing out”, becoming nothing but ice crystals and snow flakes. Here are some more photos of that stage, including a short rainbow demarcating where the snow was melting into drops.

So what caused all the ice to appear in clouds that didn’t appear to be growing in height? Well, first of all, by the end of the afternoon, they were certainly colder at cloud top, so that would explain the late afternoon ice everywhere. Also contributing, was that is was getting colder over us as the day wore on as that trough approached. So, even if the cloud tops stayed the same height, they would have gotten colder. Finally, dust has been known to have a role in causing clouds to glaciate at higher temperatures than if there was no dust getting into them. This is something that we saw happen in Durango, Colorado during a randomized cloud seeding experiment when dust storms hit and “ice nuclei” measurements shot up. So, dust, too, may have had a role.

The afternoon TUS balloon sounding suggested that the tops were only about -15 C (5 F), maybe -17 C in one that momentarily bulged above the main cloud top level-Cumlus clouds do that.

However, the amount of ice is not commensurate with a temperature that “high” and so I reject the sounding temperature.

I think, with bases around -10 C yesterday afternoon, that for clouds to produce as much ice as we saw, they would have to be -20 C (-4 F). I think maybe the strong temperature drop to the northwest from the balloon launch site might have played a role, that the temperature of the balloon instrument was correct, but it was a few degrees colder over Calalina and to the northwest of us. That “surmision”, a deduction, you get from, say, the 500 mb map where it was far colder at Flagstaff than here. Of course, you might think I am lying, and just made that last part up because I am really clueless about what happened. Due to your doubt, I will now post the 500 millibar map from my home university so that you can see I did not make this up.

As you can see, while TUS is only at -18 C, Flagstaff is -23 C, and San Diego is -28 C! So going to the NW (a heading of 310 degrees) from the balloon launch site their at Davis-Monthan meant it was a LOT colder in that direction, mile by mile even maybe. Also, you can see by Flagstaff’s wind, that the jet core at this level had not passed over us, a key to wintertime rain here. Never did. Hence, a “whiff” on this storm, to use an old word right before a new word from baseball, as in, “he whiffed on that slider” (struck out). I can’t believe how I am educating you today!

The End.

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¹Sorry, have to carry on this theme about what is drizzle and what’s not. You should find another TEEVEE weather presenter if he or she calls what happened yesterday for a few minutes, “drizzle.” Rain and snow mixed is NOT “sleet”, by the way, either, another looming corruption of our weather terminology.

Dark clouds but no rain yesterday. What happened?

Quick answer: 1) drops too small to coalesce and form ones bigger ones ; 2) no ice in ’em, for the most part.

Read below if you want a LONG discussion about yesterday; dull photos way below

Let’s talk about it, though probably more than you want to. You’re probably a little down because it didn’t rain yesterday, hour and hour though it looked like it should, except for a couple of “sprinkles-its-not-drizzle” drops. You probably had to use your headlights in the middle of the day like people in Seattle do. It began to clear up some, gradually, in the afternoon. Here are a few of scenes below, beginning with the morning overcast, with the last two shots between 4 and 5 PM AST as the clearing was underway.

So, what kind of clouds are they? Well, Stratocumulus in the first shot, in the second shot a higher layer of Altocumulus or water-topped Altostratus¹ is underlain by Stratocumulus and Cumulus clouds (when the bases are more isolated, we call them “Cumulus”; when they are more connected together, we hedge the name toward “Stratocumulus”.)

The third shot, showing Stratocumulus looks particularly ominous, probably the darkest part of the daytime was here around noon AST. A shot toward the mountains next shows the underlying Stratocumulus and Cumlus below the higher layer of Altocumulus/Altostratus. These clouds can’t be “nimbo” this or “nimbo” that because there is no rain to speak of falling from them. (“Nimbus” means rain in Latin.) Note the good visibility under all of the clouds; no precip there.

Finally, with the breakup of the overcast, shown in the last two shots, we can get an idea of the thickness of the lower clouds, at least at that point, about 2,000 to 3,000 feet at most. Also in those last shots you will notice that the higher layer has moved away or dissipated, and with a bit more heating, the clouds are tending more toward Cumulus rather than Stratocumulus.

The higher layer, located at Altocumulus level, about 12,000 feet above ground level, was actually the cloud layer producing the sprinkles, and was a key player in how dark it was; two layers, naturally, stacked on top of each other, will make it darker looking than just one, especially, in this case, when they are both pretty shallow. And with a top at about -18 C, you can almost be assured that the top was composed of mostly droplets, not ice crystals. A droplet cloud reflects much more sunlight back into space than ice crystal clouds like Cirrus and Cirrostratus.

Anyone still reading? I’m doing my best here…

That last photo demonstrates that in spite of having a little rain overnight, and even during the day, there was a lot of haze/smog in the air. It wasn’t washed out by rain. And, the more clouds get bunged up with aerosol particles on which drops can form on, the higher the concentrations of cloud droplets are in them, and the smaller they are as a result. Smaller drops cause more sunlight to be reflected back into space, and when that happens, the bases look darker. In Seattle, in our airborne studies, it was usually the case to have darker based clouds downwind of the city, and light gray clouds near the coast and offshore, even when both cloud layers were about the same depth. However, there are natural sources, like volcanoes that can also affect clouds this way. For example, “VOG” (volcanic smog) in Hawaii darkens clouds there because VOG has particles that can form drops in clouds. I seen it myself and I know a dark, polluted cloud when I see one!

What happens when you get smaller drops in clouds, as smog produces in them? It makes it harder for something to fall out the bottom in two ways.

First, in smog filled shallow clouds, drops don’t get big enough to collide and stick together to form larger drops (something that happens when they get to 30-40 microns in diameter (about a third of a human hair in width). But, even in the event that could have happened yesterday, drops got that large, the result would have been only TRUE DRIZZLE, fine, close-together drops that go under your umbrella if there is a breeze of any kind. Very tough on people who bicycle and wear glasses.

The more important key to not raining clouds, was that the clouds did not have, IN GENERAL, cold enough tops to form ice crystals. The lower ones seem to have topped out around -5 to -7 C (23-20 F), temperatures at which smoggy clouds with itty bitty drops cannot produce ice.

The higher layer, seen in the second and fourth shots, was just cold enough, about -18 or so at top from the morning TUS sounding, to form a few ice crystals. Also, being higher, it was probably not impacted as much by smog.

Quitting here, brain exhausted. Hope this is somewhat comprehensible.

The End

¹The smoothness of that higher layer is due to ice crystals falling out the bottom, obscuring an Altocumulus-like cloud from which they are originating. Sometimes this has been called the “upside down” storm because the top is liquid like Altocumulus clouds where it is COLDEST, but underneath is all the ice, where the temperatures are higher. (Man, this is getting way too complicated to comprehend!)

Snow day February 25th; “webby” Cirrus

Remember, whether it happens or not, you heard about it FIRST here! Tell your friends.

Was pretty excited to see this 500 millibar map (about 15,000 to 20,000 feet above sea level) for the morning of February 25th below from our friends at IPS Meteostar. Pretty cool, eh? This from the model run based on global data taken at 5 PM AST yesterday.

Note on that map, we are encircled by the jet stream, indicated by the brownish orange regions at the outskirts of this behemoth of a trough, a requirement for winter precip here. How “be-a- moth-ian” is it?

Check out how abnormal this pattern is in the panel below this one, marked by the dark blue bulls-eye here in Arizona! So, its really an unusual pattern that is being calculated by the computer.

An aside: Oddly, we use contours of the height above the ground of a pressure surface for our upper level maps¹, and the LOWER that height is (such as over AZ in the top panel), the COLDER the air must be overall below that height. Low sea level pressure also adds to this height “deficit”, but mainly its the density of the cold air that does it. The more dense the air is, the more rapidly you reach above you any particular pressure level. (It really would be so much better to have pressure maps with highs and lows at a constant level above us than having to divert attention for this explanation.)

So, in the panel below, its the LOW HEIGHT of at which the 500 millibar pressure was reached (i. e., 5340 meters) that tells you this is a cold, cold, cold, cold system. (They say that redundancy is the key to remembering things. Remember, “534” (decameters) is COLD).

What DOES that the huge anomaly from normal in the bottom panel tell us weatherfolk?

The forecast map for February 25th is a real outlier model forecast, and so we shouldn’t be proclaiming a snow day or anything like that here 15 days in advance because it is such an extreme prediction and likely to go wrong. So, that’s what I have not done here.

HOWEVER, this outlier prediction shown below, is a part of a jet stream pattern that is developing RIGHT NOW in which low pressure systems and cold fronts will come zooming down into the Southwest from the northwest, one that is likely to go on for a couple of weeks or more. I would guess there might well be a hard freeze at some point, though not in the immediate future. Be ready!

This developing pattern also means more chances for rain here in Catalina over the next few weeks, and with the cool air ahead, holding our late winter vegetation together better even if there is not much precip because it won’t get burned out. So, overall, good news unless you came to AZ for consistently warm days. Ain’t gonna happen so enjoy the warmth we have now!

Webby Cirrus clouds

Yesterday, moving rapidly out of the north, were some “webby” looking Cirrus clouds. These are always seen only right after they have formed, maybe 10-20 minutes or so after that. They start out as tiny flecks (which for a moment might be termed, Cirrocumulus clouds), and, possibly, for the briefest moment, may be comprised of liquid. They then convert to ice and as the individual crystals grow and fall out, or are dispersed by turbulence, the tiny flecks become larger and larger and some of the ice falls out in strands.

After about a half an hour to an hour, they are usually just masses of tangled looking Cirrus without much cellular structure. Here’s what they looked like yesterday in that younger formative stage. At most upwind end (lower part of photo), the newest flecks have formed, while the older Cirrus elements are broadening and becoming “webby” looking. The likely ice crystals in these older Cirrus, for some additional annoying trivia, “bullet rosettes”, spikey-looking crystals having columns jutting out from the original “germ” ice particle. Nice images of bullet rosettes here at the beginning of a long article…

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¹In the olden days, weatherfolk liked to look at “isentropic surfaces” which helped them figure out where the air was sliding upward and likely to form clouds and precipitation before there were computer models. These areas were well represented on constant pressure maps where the cold and warm air was being pushed around.

Weather 10 days from now remains uncertain

Hahahahah. That is the funniest thing I have thought of in a long time, and its not that funny. Take a look at this “spaghetti” plot for 10 days from now based on last night’s global data. The map is for 500 mb, about 15,000 to 20, ooo feet above sea level.

“High predictability”, even as far as 1o days out, is indicated by those areas where the bluegreen and red lines are all close together. For example, in the upper left hand corner, or in eastern Asia and the extreme western Pacific Ocean if you can make those areas out through all the lines. Also, both the red and bluegreen lines themselves are pretty close together there, and that says the jet stream is extremely strong there, normal for that region in wintertime. That jet stream is geographically anchored in that region and so not much changes there, even from winter to winter.

But then look what happens to that compact jet stream as it approaches the middle of the Pacific! It comes apart, line a twisted speaker wire that’s been untwisted. The bluegreen lines, representing a colder portion of the jet stream, mostly head off to the NE, while the red lines, indicating a warmer portion of the jet stream, split off and continue more or less toward the east across the Pacific and into the Southwest. However, the details of both flows, the northern one and the southern warmer one, are pretty unknown, as evidenced by all the “scatter” in the lines, the “bowl of rubber bands” you see in the east half of the Pacific and into North America (and elsewhere). Note that the lines are tending to group that bit more over the eastern US, suggesting higher predictability, and the presence of an upper level trough (and cold in the East).

For the sake of contrast, here is the same kind of plot for just 48 h from now, showing high predictability. Of course, things always go to HELL in the longer term, but today’s 10 day vagaries are more than usual.

So, what seems to be ahead for sure is a split in the jet stream in the eastern Pacific with one of the branches coming toward us. That is the good part since that branch can be pretty wet if it is strong. But, as you can see, exactly where it is, and that’s crucial, is really anyone’s guess at this point. That warmer jet has to be south of us to have any rain with the disturbances that are shuttling along in it. And if you look over AZ, the red lines of the warmer jet are all over the map, literally.

Hence, to use an old word there, particularly uncertain times ahead. In fact the only thing that is certain, is with the southern branch of the jet in this area, there will at least be passing regions of clouds as upper air troughs go by. Will they, like yesterday, only be Cirrus? Or rainy Nimbostratus?

The second shot shows a nice “parhelia” or “sun dog” at the far right, caused by plate-like ice crystals falling face down, the normal mode. The final shot has some the rarely seen Cirrus castellanus, Cirrus clouds with little turrets or humps at the top.

Some more of that Catalina climo

Here is a 35 year record showing what days have had measurable rain in January. Sometimes “singularities” in weather show up in these kinds of charts of tempearture or precipitation, such as the “January thaw” that seems to occur with some regularity in the East but is “unexplained.” You would be looking at our chart for Catalina for example, a cluster of days with higher or lower precipitation and it MIGHT be a singularity, something that Nature likes to do at that time of the year rather than a statistical fluke that represents nothingness. Here’s January, a month that averages 1.65 inches in Catalina. These data are almost totally due to the careful measurements made at Our Garden organic orchard here in Catalina–only the last few years here are from measurements on East Wilds Road.

Not much to see here. That peak on the 6th looks more like a fluke rather than a singularity. You would never say that one day represents a singularity, but maybe 5-10 days.

The reason why I wanted to see this was because of the striking changes that were foretold by the “WRF-GFS” model 36 h ago and were shown here yesterday. Was there a singularity that might support a greater chance of rain in SE AZ in mid-January, and therefore, cast that bit more credibility on such a huge model change?

I would have to say “no.” And, not surprisingly, that huge change has gone bye-bye in the models. Nothing like it is shown now, though they do have a rain situation developing for here by the end of the 15 day run (around January 20th and beyond). But this rain comes out of the lower latitudes of the Pacific, a completely different direction than was shown just yesterday, and if the models are correct in this pattern breakdown, it means flooding in California as the flow breaks through to the coast from the Pacific.

Below, what the models came up with based on last night’s global data, again, from IPS Meteostar, whose renderings I favor.

These are exciting times for those of us who peruse the models.

Why?

These vast changes indicate that there is something far, far upwind, perhaps a data sparse zone, errors in reported measurements that is causing a problem for the models and that more changes in their outputs may come down the line until that problem is better “resolved.” (They are never perfectly resolved.)

So, every 6 h update of the models is a “must see”, with the persuser (me) holding his breath with excitement. In these cases, its all “good” because a rain situation is foretold for us. Take a look at where the jet stream is compared to where it is now, up around British Columbia. You can see it barging into southern California and major rains ALWAYS accompany this pattern. Also, you can probably count on at least two storms breaking through before this pattern changes much. The reservoirists in Cal will be very excited to see this pattern develop since most of their holdings have much below capacity. And these kinds of storms usually produce significant rain in Arizona, too, though here we would be a little far south to get the brunt of those storms in this scenario.

Pretty clouds yesterday

Can’t leave without a little cloud excitement. I wonder how many looked up and saw this little beauty go by (shown below)? So pretty and delicate-looking, as unusually thick virga (snow) fell from this little cluster. It would be called, “Cirrus uncinus” at this stage.

That snowfall probably began developing one-two hours before it came over us, and the cloud patch would likely have been fluffed up on top that bit and as a mostly liquid water cloud, that is, an “Altocumulus castellanus” before becoming this “uncinus.”

Below we saw the dying remnants of that patch, the snow to finally stop falling out with the parent cloud mostly gone, and that snow continuing to dry up on the way down. Lots of nice cloud sights yesterday, in fact.

Enjoy.

“(the reviewers)… are still unconvinced by these controversial claims.” A science story.

Alternate titles, choose one or all:

1) The story of APIPs (Aircraft-Produced Ice Particles)

2) They said it couldn’t be done, but they did it anyway

3) ‘An embarrassment for the airborne research community’–Dr. John Hallett, 2008

OK, “baby I’m bored” with the lack of clouds and precip, and so I thought I would share my boredom with this long tome on aircraft effects on clouds. Why not bore other people if you’re bored? I’ve thrown in some alternate titles above to peak and pique your interest. Speaking of “thrown”, Mr. Cloud-maven person was also thrown off his big (I mean huge¹), young horse lately; “JohnT”, as he is named, doesn’t like people to sit on top of him sometimes. Not easy to sit at a computer these days, hence the lack of “acitvity.”

OK, on to the story of APIPs. The title quote was written in 1982 by the Chief Editor of the American Meteorological Society’s, J. of Climate and Applied Meteorology (JCAM) summing up the opinions of the three reviewers at the bottom of a second rejection notice of a manuscript, one that had been fluffed up with more evidence of APIPs. However, the Editor allowed us (me and Peter Hobbs, director of the Cloud and Aerosol Research Group at the University of Washington) another crack at it, and by the THIRD submission (requiring a bit of chutzpah), a colleague and me had found photographic evidence of aircraft having produced icy canals in supercooled clouds, and that visual evidence really pushed our third manuscript, now as big as JohnT, over the top in getting accepted and published.

The phenomenon came up again last summer in a Wall Street Journal article, one in which Mr. Cloud-maven person was asked his opinion. This phenomenon (APIPs) is attracting more attention these days, so I thought I would pass this background story along. I hope will encourage authors with rejected manuscripts, which I myself have quite a few. You might have something really good.

Yes, that’s right, lucky Mr. Cloud-maven person was involved in this interesting chapter of science that happened way back in the early 1980s when he was part of the flight crew in the University of Washington’s Cloud and Aerosol Research Group (CARG). Occasionally, and mostly in studies of ice development in Cumulus clouds, I got to direct the University of Washington’s first research aircraft, a 1939 manufactured, Douglas B-23, into Cumulus and small Cumulonimbus clouds. It was heaven for me, a storm chaser type person, having done that here in AZ way back in the mid-1960s chasing summer thunderstorms all over the State with my camera and rain gauge.

We had a viewing dome on the top of the fuselage of that B-23 and I sat in a swivel chair, head protruding into the “bubble.” I was kiddingly referred to as the “bubblehead.” I think they were kidding, anyway… Those who know me will understand that title. Sitting there with head in the bubble, allowed me to see EXACTLY where we exited a cloud and could direct the pilot to EXACTLY that same cloud blob we had just exited. The pilot was fond of turning the plane sidewise for this return so that one wing was pointed straight down in the turns and we often got back in within 90 s to two minutes. It was an exciting as well as sickening experience.

We did that because we wanted to see how that element of the cloud had changed with time. Did ice form? Did the drops get bigger or smaller?

This viewing dome gave us a huge advantage over other research aircraft doing this kind of research. Below, that B-23 aircraft sitting on the tarmac at Boeing Field, Seattle². The second photo is a view from the “bubble” located toward the rear of the fuselage. Nice! I was so lucky!

One day, while looking over our Brush strip charts from the flights, I noticed some odd spikes in the ice crystal detector we had. Also, since we were one of the first groups to get a probe that produced shadows of the particles in the clouds as we flew in them, I was able to see that the particles producing those spikes were oddly similar sized, as though they had formed simultaneously, something not seen so much in natural clouds. Pretty soon it became apparent that these spikes and odd particles ONLY appeared after we had gone through the same cloud for the second or third time.

I remember walking into Professor Peter Hobbs grand office with a strip chart with those ice spikes and saying, “I think our aircraft did this.”

He was unfazed; did not have a particular reaction. Peter Hobbs was always open to new thoughts, and that helped allow me to go forward with a further investigation even if it meant some of our past data and publications might conceivably be compromised, ones however, I was not involved with as a fairly new (5-years in) employee at the U of WA. No vested interests here!

After awhile, after aircraft plots showed that the spikes were within tens to a couple of hundred yards (meters) of where we had been before in a Cumulus cloud, a very short paper was written up on it and submitted to JCAM in late 1981. It was quickly rejected.

Ours was a highly controversial finding due to both the high concentrations of ice that we found (hundreds to over a 1,000 per liter) but most of all due to the temperatures at which we were reporting this effect, -8 to -12 C. Our plane was, in essence, seeding these clouds with ice crystals, changing their structure. Since the volume affected was initially quite small, it was likely that only having the viewing dome allowed us to find them on the second and third penetrations of the clouds.

This inadvertent aircraft effect had even been looked for by our aircraft group leader, Dr. Prof. Lawrence F. Radke before I had arrived and after the University of Washington acquired the B-23. He didn’t find’em though. Larry was also aware that an aircraft COULD do this in those early days with the B-23.

So, when I found them and a paper began taking shape, the skeptical Larry Radke called them, “Art-PIPs.” It was so funny.

Later, with the skeptical Larry at the helm, we got some money from the NSF to try to produce them in various clouds, and sure enough, we did. It was amazing finding those crystals in those test flights since even I couldn’t be absolutely positive sure that this was real. Why hadn’t this phenomenon been reported decades ago? That, too, was part of our problem: why you, why now? And why hadn’t I seen the holes and canals of ice produced by aircraft as a cloud photographer for decades even by then?

Some ground observers had seen trails and holes in “supercooled” clouds like Altocumulus. Those holes and canals were occasionally reported over the decades (!), but not in the technical journals. A couple of really lucky observers had even seen the type of aircraft that had caused them. But the airborone research community, ignored or did not know about these reports, ones that appeared in non-technical weather magazines like Weatherwise, Weather, and Meteorological Magazine (the latter two in England).

Furthermore temperature data were nearly always absent in these visual reports. So, it could be reasoned they had occurred at very low temperatures, below -25 C or -30 C. Clouds that cold, but still consisting of only or mostly of liquid droplets do occur, the ones in which an aircraft could leave an “ice canal” or a “hole” with ice in the center, falling slowly out.

If we had been reporting our finding at cloud temperatures of -25 to -30 C, maybe we’d have got into the journal on the first try and reviewers would have yawned. But at -8 to -10 C cloud temperatures? No way!

Why?

Research aircraft had been going back and sampling the same cloud, usually a Cumulus one, for a couple of decades by the time of our report. Furthermore, those aircraft re-penetrations were almost always in the same temperature domain that we were reporting this effect, to about -5 t0 about -15C. And one of the main findings in those early days of aircraft sampling was that nature was producing far more ice in clouds than could be accounted for in measurements of ice nuclei, particles on which ice can form. Concentrations of ice nuclei were largely determined from small cloud chamber measurements made on the ground.

These early cases of high ice concentrations in clouds with tops that were not very far below freezing (greater than -15 C) were called cases of “ice multiplication” or “ice enhancement.” No one understood how such ice developed and many theories were put forward initially in the 1960s. The issue was largely explained by the “Hallett-Mossop riming and splintering mechanism”, a mechanism discovered in the mid-1970s and today is still believed to be the primary reason for high concentrations of ice crystals in clouds with tops warmer than about -15 C. Oh, yeah, ice multiplication is real and NOT due to aircraft penetrations!

But our paper on APIPs, if true and published, would cause researchers to have to go back and look at their research data (even us!) and investigate whether their own aircraft had contaminated their published studies with artifact ice crystals. An entire body of airborne literature would come under question. This was not a pleasant thought for anyone who had conducted such studies.

Why would you go back and sample the same cloud?

To see how it changed with time. How many ice crystals formed as time went by? Where, and when? These were techniques used in trying to get to the bottom of the “ice multiplication” phenomenon. In fact, the Chief Editor of JCAM himself was involved with numerous aircraft that sampled clouds in a huge summer Cumulus cloud study program in Montana in those days (called “CCOPE”-Cooperative Convective Precipitation Experiment) That study, like so many other airborne studies, was to determine how ice onsets in clouds, how high the concentrations of natural crystals were in clouds with various cloud top temperatures, and the potential of cloud seeding to increase rain.

While academic scientists did not particularly welcome these reports and were dubious and largely ignored them (did not change their aircraft sampling strategies), or when they looked could hardly find any APIPs, it was soon evident that purveyors of cloud seeding services were elated! Our finding suggested to THEM that all that natural ice formation reported in re-penetrated clouds in research articles over the years might be wrong, and rather due to ice produce by the aircraft! Maybe those clouds that had been reported with a lot of natural ice, which made them unsuitable for seeding, was because the researcher’s aircraft had produced it, not nature. Purveyors of seeding would like clouds that are below freezing, about -5 C and colder, with no ice in them. If the concentrations of natural ice crystals forming in clouds ice get to 10s to 100s per liter, those clouds are deemed unsuitable for seeding to add more ice. The crystals might be too small if you add more in those cases, and not fall out. If surveys of clouds in a region find that they have lots of ice in them, its “no paycheck” for commercial cloud seeding interests. (Usually, cloud surveys aren’t done before commercial programs begin.)

Thus, those who had interests in cloud seeding actually saw our result as a way to discredit findings of high natural ice concentrations in clouds, findings that made them appear unsuitable for seeding. It was a bogus argument since numerous FIRST penetrations of clouds had encountered high ice particle concentrations, still, they had SOMETHING to hang a hat on.

This was indeed an ironic twist, being supported by the cloud seeding community!

Me, usually with Peter Hobbs as a co-author, had been discrediting various published cloud seeding results in the literature via reanalyses and journal commentaries for several years (e.g., here) when our APIPs finding finally hit the “streets” in 1983.

Given these a a priori possible biases between academia and in the commercial cloud seeding world in detecting APIPs you can imagine where the major “confirmatory” studies of this phenomenon came from. Yep, those associated with cloud seeding programs! It took 8 years (1991) for our finding to be independently confirmed (the best way) using several types of aircraft in marginally supercooled clouds. Then pretty much the same workers amplified their findings with another paper in 2003 WOODLEY et al. 2003. For those of you who don’t know the cloud seeding literature, Woodley and Rosenfeld and Peter and I have had a major clash in the cloud seeding literature (i. e. and big i. e., and bigger still)

We loved it! They loved it! Even the great John Hallett got involved and found in lab experiments that the mechanism was the extraoardinary cooling at the prop tips, momentarily down to -40 C, a temperature at which ice forms spontaneously in high concentrations (here). It had also been suggested that prop aircraft could do this by the late Bernard Vonnegut back in the late 1940s in a less widely distributed report from a General Electric research lab and in the J. Applied Physics.

Today this phenomenon is taken pretty much for granted, and has been more widely detected from time to time in satellite imagery in thin clouds as here. In thicker clouds, the effects of aircraft go largely undetected. Recently, in a widely distributed news release that accompanied their formal publication, Heymsfield et al reported a case in Colorado in which aircraft-produced ice effected a snow shower on the ground instead of just being a hole or canal in some thin clouds as we normally see. They opined that aircraft could actually help delay flights from the airports that they were taking off from or landing at in special conditions. (That’s what the Wall Street Journal article was about.)

Why was it an “embarrassment” to the airborne research community, as John Hallett (of Hallett-Mossop) asserted? Because they should have found out about APIPs right from the get go, especially in view of the occasional lay publications that had photographs of ice canals in supercooled clouds even in the 1940s, ones that could only have been produced by aircraft. It turned out to be a major oversight.

Below, a cartoon I did before the paper was accepted making fun of how a researcher, thinking that natural ice multiplication processes were taking place (i.e., the Hallett-Mossop riming splintering mechanism) might overlook all those ice crystals streaming off, in this case, the Husky 1 aircraft.

Below, some photographic evidence of what aircraft can do to supercooled clouds, the last one taken about two weeks ago over the Cat Mountains.

Finally! The End.

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¹The 6-year old horse in question is about 15 hands, 1200 lbs, not really a Clydesdale. I have overemphasized our horse’s size for personal reasons. You don’t want to be injured getting bucked off a Shetland pony, but rather something HUGE! It just sounds better.

²That B-23 aircraft, wherever it went, brought a crowd out to see this antique “tail-dragger.”