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Storm today, Christmas Eve 2016!

First of all, how did it get to be 2016 so fast?

Yep, a dramatic Christmas Eve storm, complete with rain and bluster, maybe even ending with a little snow, in case you’ve been in a cave for the past couple of days and haven’t heard about it. Media folks have been all over this, so am tuning it here just a bit, if, in fact, I can, for Catalina.

The wind today in Sutherland Heights will likely gust to over 40 mph from the southwest in 1-2 second bursts here , similar to the wind in the last big couple of FROPAs, so best to put loose stuff away.

In fact, the U of AZ mod from last evening sees winds of 115 mph above TUS at mid-day at just the 500 millibar level (15,000 feet or so above Catalina), a quite unusual strength of wind at that elevation, to give an idea of how strong the jet stream will be above us today. So, if it looks like the clouds are moving too fast, as in a time lapse movie, they are!

The core of that jet at 500 millibars passes over during the middle of the day, and that pretty much should coincide with the onset of rain as it usually does. So, look for rain to start around between 11 AM and 2 PM AST today based on that passage; the U of AZ mod output from last evening’s global data sees the start time somewhat later, between 3-4 PM. Be ready, though; it will come in a hurry! From IPS MeteoStar, this for 11 AM AST today, a real screamer of a jet is overhead:

Forecast of the flow at 500 millibars valid at 11 AM AST today. Its based on the global data, such as is available, from 11 PM AST last night, the most recent model prediction available.

We’ll have the usual “temperature slam” when the wind shifts to the NW here in Catalina during the FROPA late this afternoon or early evening. Looks like it will be a good 15° F drop, typically occurring within an hour, the first ten degrees in 15 min or so, with the temperature likely ending up in the mid-upper 30s. This is where some snow is possible. Imagine, a little SNOW in parts of Catalina on Christmas Eve is possible.

And with fronts/jets as strong as this, the rain band with the front should lead to at least moderate rain for a couple of hours. “Moderate rain”, probably “immoderate” in intensity for some desert dwellers and snowbirds, is 0.10 to 0.30 inches per hour. So rain will pile up pretty good during those periods of “moderate rain. ” Even a couple of hours of that intensity will lead to a substantial amount for our desert.

AZ mod (see link above) sees half inch to an inch here in the Catalina area to Mt Lemmon! That would give us a December total that’s above average, something we haven’t seen in a few months, an above average monthly total. A shot from hip from this keyboard yesterday to a friend was for a lesser total, 0.40 inches in Sutherland Heights¹. Truly hope it is LOW!

One of the best sights today will be the transition in the clouds from dawn today (if any) until the jet core gets here in the middle of the day. Typically, on the right hand side of the jet (looking downwind), which is also the warmer side of it, the air is stable and its a great environment for lenticular clouds (smooth ones that hold in place, such as downwind of Ms. Mt. Lemmon).

As the jet core arrives at mid-day, which divides that warmer air from much colder air aloft on the left side, looking downwind, the lower clouds deepen up or move in, merge with higher cloud layers, ice forms begins to form like mad, and you start to see virga and precip all around. So, a pretty dramatic sky change should occur in the middle of the day today; have camera battery charged up, and maybe video or time lapse cameras ready to go as well.

Some cloud shots from yesterday’s “in between” day:

12:45 PM. Small Cumulus clouds (humilis) dot sky.

4:26 PM. Stratocumulus clouds cluster around the Catalinas.

5:35 PM. Nice sunset of precursor to storm, Altocumulus perlucidus deck. But what’s that over there, far right corner? Let’s go zooming, take a closer look.

5:35 PM. Right there next to that tree on the right is virga, the only virga in this whole layer! And, though hardly visible, there’s a clearing above this patch of virga, a hole in the cloud deck. This layer was “seeded” at this point, that is, ice was caused to form in what otherwise were clouds composed of supercooled liquid water droplets, by the passage of an aircraft. This demonstrates what happens in any cloud of supercooled droplets when ice is introduced. The droplets evaporate, and the vapor deposits on the ice crystals, causing them to grow and fallout. You may recall that it was Catalina’s own Cloud Maven Person and Hobbs that brought this phenomenon to the attention of the airborne research community way back in ’83, something I wish I could point out everyday! (J. Appl. Meteor.) That’s why even the tiniest blip of virga caused by an aircraft is brought to your attention as often as possible!

The exciting possible weather WAY ahead

We have a penchant here for pointing out quasi-disastrous storms that appear in the models beyond the normal skill period of 7 days or so. Remember last year, when Cloud Maven Person was talking up those gigantic, Big Niño storms that would appear in the models, but not one actually occurred as shown? Typically, as we all do, we look at the NOAA spaghetti factory outputs to see if there is much credibility to those sometimes wild predictions. As in the current weather, the indications of frequent trough passages was well indicated in those crazy plots more than 10 days ago. (How much precip will come with them is very “iffy” but we’re doing well this time!)

Well, there’s another set of “doozies” showing up in the mods now, ones that roar out of the central Pacific and into California, just like we expected with last year’s Big Niño! How odd. Those kinds of trajectories over the warmer waters of the eastern Pacific lead to the heaviest of all rainfalls in California, and heavy amounts here in AZ. Here’s my talking point, this:

Valid in only 312 h from now! Look at that "low rider" trough off southern Cal! This is SO EXCITING to see. Something like this COULD happen. If so, a trough with this trajectory and magnitude would be one of those that can bring 10-20 inches of rain in a DAY to southern California mountains, and, as shown later, continuning on at lower latitudes, bring a few inches in a day to the mountains of AZ! — Valid in only 312 h from now! Look at that “low rider” trough off southern Cal! This is SO EXCITING to see. And something like this COULD happen. If so, a trough with this trajectory and magnitude would be one of those that can bring 10-20 inches of rain in a DAY to southern California mountains, and, as shown later, continuing on at lower latitudes, bring a few inches in a day to the mountains of AZ! These are the kind of model outputs that make life truly worth living. A key ingredient here, too, is that trough that would bring extremely cold air down along the Pacific coast from Canada. That would help energize and deepen the surface low under the big trough offshore of southern Cal as it got closer to the coast. (Kind of reminiscent of what happened in Jan 1969, cold in the Pac NW, super rains in Cal, and maybe reminiscent of the weather configuration during the truly gargantuan Cal flood of late December-Jan of 1861-62 when 35 inches or so fell in 30 days in the Los Angeles area, which, in normal circumstances would have meant 70-100 inches during that time in the higher mountains! The LA Basin was a lake at that time, reports said. Does that much rain sound crazy for southern Cal? Well, the DAILY record Hoegee’s Camp Ivy, is 26.12 inches in ONE DAY, January 1943! More than 25 inches fell in one day in January 1969 before the gauge floated away. So, you COULD have 70 inches in only three days or so! Man, I am filled with historical facts today!

But does “spaghetti” support these exciting model outputs? I don’t know because I haven’t looked yet. But let’s do look at a couple and see if catastrophic, well, heavy anyway, rains are headed to Cal, and maybe AZ, too. The onset of this “break through” pattern begins in about nine days or so (exact timing will vary a bit):

Valid for about nine days out from now, and shows a great beginning to this pattern. This says with pretty good confidence that the jet stream will break into Cal from the Pacific. — Valid for about nine days from now, and shows a great beginning to the pattern discussed above. This says with pretty good confidence (judged by the bunching of the red contour lines) that the jet stream will break into Cal from the Pacific. The red lines bound the southern edge of the jet stream.

Moving ahead into the distant forecast future….(wow, this is getting to be too long again!):

Valid for 14 days from now. Note says it all.

Will look at this in a few days, noting that the ACTUAL model outputs will bounce around this “solution” but SHOULD tend to gravitate back toward it if it does bounce away from it (producing what would be considered an outlier).

Fun times in weather following ahead!

The End

——————————–

¹Feel I have to ride that 0.40 inches rain prediction out since its “out there” and it was in the context of a friendly competition with a friend whose also big faculty member at a famous university in Fort Collins, CO, as well as a Catalina snowbird. In this regard, I have noted that some friends change their forecast with each model run, then in retrospect, select the forecast they made that was closest to the observed amount of the many they made, and then claim that they “really nailed” a rain prediction for Catalina.

Yesterday’s blog was re-written and re-organized some after finding several occasions of not such great writing and org.

Summer-like storm surprises with frequent thunder and a half inch of rain in 18 min

Here are the latest 24 h totals, ending this morning the 23rd at 3 AM AST from your Pima County ALERT gauge network. Our own amount over this period is embedded for comparison purposes:

Gauge         24         Name                        Location
    ID#             hours
    —-     —-       —-        —-       —-         —-       —————–            ———————
Catalina Area
    1010          0.71      Golder Ranch                 Horseshoe Bend Rd in Saddlebrooke
    1020          0.83      Oracle Ranger Station         approximately 0.5 mi SW of Oracle
    1040     0.87      Dodge Tank                   Edwin Rd 1.3 mi E of Lago Del Oro Parkway
    1050     0.59      Cherry Spring                approximately 1.5 mi W of Charouleau Gap
    1060     1.10      Pig Spring                   approximately 1.1 mi NE of Charouleau Gap
    1070            0.79      Cargodera Canyon             NE corner of Catalina State Park
    1080            0.79      CDO @ Rancho Solano          Cañada Del Oro Wash NE of Saddlebrooke
    1100            0.67      CDO @ Golder Rd              Cañada Del Oro Wash at Golder Ranch Rd
xxxx     0.58     Sutherland Heights, Catalina

Santa Catalina Mountains
    1030         1.14      Oracle Ridge                 Oracle Ridge, approximately 1.5 mi N of Rice Peak
    1090         1.34      Mt. Lemmon                   Mount Lemmon
    1110        1.22      CDO @ Coronado Camp          Cañada Del Oro Wash 0.3 mi S of Coronado Camp
    1130         0.87      Samaniego Peak               Samaniego Peak on Samaniego Ridge
    1140         0.79      Dan Saddle                   Dan Saddle on Oracle Ridge
    2150         0.71      White Tail                   Catalina Hwy 0.8 mi W of Palisade Ranger Station
    2280         0.71      Green Mountain               Green Mountain
    2290        0.35      Marshall Gulch               Sabino Creek 0.6 mi SSE of Marshall Gulch

Yesterday, with it many twists and turns, with that significant rain overnight providing a happy, moist beginning. Then, there was a sad middle of the day when two windshifts passed, the second a major, long-lived one one bringing a substantial drop in temperature and fronted by a dramatic arcus cloud, but there was no rain to speak of with either……at first.

Then the surprise, the unlikely resolution of the sad middle of the day just as a dismal clearing advanced from the west: a highly unusual thunderama and cloud burst beginning at 1 PM, one gushing a half an inch of rain in 18 min! This, just when it looked like a total dud was certain from the passage of that front. That “TRW++” (weather text for an extra heavy thunderstorm), provided the happy ending, thus making it a day truly out of Hallmark. The total rain was 0.58 inches, with the three day total at 1.03 inches! Yay, flower help! Rain table at bottom.

Though it was late December and at the winter solstice, the breezy 63° F damp air yesterday morning made it feel like you had awakened from your long vacation flight and found yourself in Hawaii or Miami. It was a truly remarkable, even a joyful feeling.

With that strong upper low WAY off to the southwest of us yesterday morning, and moving right this way, you KNEW that the rain wasn’t over, that thought adding to the joy of yesterday’s early morning. 0.34 inches had fallen mostly during the night before, adding to the humid feel.

Too, yesterday morning’s joy had a withering effect on all those dry weeks that had preceded these past few days with measurable rain, maybe even withering the hard feelings that remain in many of us about those disappointing Big Niño forecasts of a wet Southwest last year. You were finally beginning to feel that you could let go of those hard, grinding, grudge-holding feelings you had against weather forecasters, the ones that misled us so much last year about the Big Winter in the Southwest due to the Big Niño, a record Niño, they told us, indeed, a “Godzilla Niño.” Then, what followed was, “The Big Winter that Didn’t Happen.” And it will be years before we get another Big Niño!

But, let us move on from that tirade to current events; you can see that I am personally completely over the hard feelings of last year’s disappointing forecasts and have moved ahead, as we need to do in life…

Now, finally (!), for yesterday’s clouds, so fantastic in all their presentations and drama, that one really could finally forget the busted Big Niño forecasts of last year²:

Oh, yeah, the cloud diary for yesterday, probably more than you need to know, but, what the heck:

7:56 AM. A shower complex heads north toward Catalina, only to graze the city.

7:57 AM. Stratocumulus clouds topped Sam (Samaniego) Ridge as that shower approached, the lower bases telling you how humid the air was. Dewpoints were in the low 50s!

8:04 AM. Gettin' closer, gettin' pumped for a nice rain blast in tropical air! — 8:04 AM. Gettin’ closer, gettin’ pumped for a nice rain blast in tropical air!

8:22 AM. That complex of rain mostly slud off to the east of us, as so many have this year. However, note the lack of good shafting, just rainy areas that are a little thicker and thinner. This tells you that they're really not Cumulonimbus clouds, but rather shallow ones not having strong updrafts. Earlier, it appeared to be a complex with a Cumulonimbus in it, and in that case, you would see strong shafting. — 8:22 AM. That complex of rain mostly slud off to the east of us, as so many have this year. However, note the lack of good shafting, just rainy areas that are a little thicker and thinner. This tells you that they’re really not Cumulonimbus clouds, but rather shallow ones not having strong updrafts. Earlier, it appeared to be a complex with a Cumulonimbus in it, and in that case, you would see strong shafting. Wonderfully dismal scene, I suppose to those of you with normal sky values; sunny and blue are just fine. Those of you with sky values like that might just as well get the HELL off this page right now! There’s a lot more dismality ahead, except maybe for the next couple of photos…

10:24 AM. Sky breaking out more and more, probably some non-cloud maven people exulting over the clearing. But, it was still moist and humid, and no real windshift had occurred, something that woud presage descending air behind it, and a true clearing. Indeed, true cloud maven folk were exulting over the clearing since with the low aloft approaching, some warming of the ground might lead to real Cumulonimbus clouds while the air aloft was cooling! In this photo are Cumulus humilis and fractus (down low, darkish cloudlets) a riff of Altocumulus castellanus (indicating mid-level instability) and above those, a separate layer of Altocumulus with ripples (“undulatus”), and maybe Cirrocumulus adjacent to the higher Ac clouds. A Cu fattening on calories of sunlight can be seen on the horizon, center. I hope I can be done with this cloud story before dark today….

10:22 AM. Here we go! A line of Cumulus congestus and "soft-serve" Cumulonimbus clouds HAS to be associated with a windshift line. Its got to come through Catalina. This view is looking to the NW. Such a band is likely to extend to the SW from here, and beyond the SW horizon, so you won't see it yet over there. — 10:22 AM. Here we go! A line of Cumulus congestus and “soft-serve” Cumulonimbus clouds HAS to be associated with a windshift line. Its got to come through Catalina. This view is looking to the NW. Such a band is likely to extend to the SW from here, and beyond the SW horizon, so you won’t see it yet over there. Altocumulus perlucidus clouds overlay Catalina at this time along with a few puffs of Cumulus fractus. Its still humid.

11:44 AM. Pretty scene of course, but look carefully on the horizon below the bases of the clouds and you will see arc-shaped clouds curving back toward the NW. THis view is to the SW. Those arc-shaped clouds are that windshift line where air converges to form a line of clouds as was seen in the prior photo. Too many invervening clouds prevent seeing a line here, but as a cloud maven junior or expert, you know there will be a LINE! We hope to have a lot of good testomonials at the next club concerning who saw these arched clouds first. — 11:44 AM. Pretty scene of course, but look carefully on the horizon below the bases of the clouds and you will see arc-shaped clouds curving back toward the NW. This view is to the SW. Those arc-shaped clouds are that windshift line where air converges to form a line of clouds as was seen in the prior photo. Too many intervening clouds prevent seeing a line here, but as a cloud maven junior or expert, you know there will be a LINE! We hope to have a lot of good testimonials at the next club concerning who saw these arched clouds first. Right here, you KNEW something dramatic was about to happen to the sky, and almost certainly something to your rain gauge as well.

12:25 PM. Here it comes! No telling how many inches we might get! (However, the shafting looks weak to me... Not congruent with big "Cumulonims" with good updrafts....so some doubt creeping in.) — 12:25 PM. Here it comes across the OV! No telling how many inches we might get! (However, the shafting looks weak.. Not congruent with big “Cumulonims” with good updrafts in them….so some doubt beginning to creep in.)

12:31 PM. I feel like I am in Louisiana or Alabama awaiting a cold front. THis was SUCH a dramatic scene, I know you were having a hard time constraining yourselves, and not running to tell neighbors about it. — 12:31 PM. I feel like I am in Louisiana or Alabama awaiting a cold front. This was SUCH a dramatic scene, I know, like me, you were having a hard time constraining yourselves; not running to tell neighbors about it.

12:32 PM. Zooming in on a fantastic scene for Arizona! Camera can't fire fast enough! — 12:32 PM. Zooming in on a fantastic scene for Arizona! Camera can’t fire fast enough! I was getting light-headed here.

12:39 PM. The windshift to the NW has passed the house, but those arched clouds above the windshift are getting pretty ragged. And where's the rain? — 12:39 PM. The windshift to the NW has passed the house, the temperature is dropping like mad, but those arched clouds above the windshift are getting pretty ragged. And where’s the rain? Pretty scene, though.

12:45 PM. Within a few minutes, a few hundredths of an inch fell, propelled on gusty NW winds, but then it quit, the low clouds banked up harmlessly against the Catalinas, which still had sun on them! This was looking really bad. No rain was in sight, either. Pretty scene, though. We don’t want to lose sight of beauty when its in front us, even when we’re getting sad about the turn of developments, which in a Hallmark movie would be that point when the owner of the building that a bakery or flower shop is in, says he has to lick them out because he has sold the building. Yep, that’s how bad it looked right at this point.

12:50 PM. The arcus clouds and windshift had moved in from the west, and so this clearing out there HAD to be approaching, the day's rain likely over. I can only imagine how glum you all were out there in seeing this abyssal scene, "sunny skies just ahead", spoken sarcastically. — 12:50 PM. The arcus clouds and wind shift had moved in from the west, and so this clearing out there HAD to be approaching, the day’s rain likely over. I can only imagine how glum you all were out there in seeing this abyssal scene, “sunny skies just ahead”, spoken sarcastically.

12:53 PM. The Stratus clouds now hung even lower, as though wanting you to touch their empty innards, a truly humiliating scene. I have never seen such vacant clouds, so filled with portent only minutes before. This was, indeed the low point of the day. The sun would soon burn them off.

1:02 PM. Just after the most amazing thing, a blast of THUNDER overhead E or SE, And, it was starting to rain! But here you can see lower clouds (Stratus or Cumulus fractus) that are separate from a higher layer (top). So, where the HECK was the Cumulonimbus? — 1:02 PM. Just after the most amazing thing; a blast of THUNDER overhead E or SE, And, it was starting to rain! But here you can see lower clouds (Stratus or Cumulus fractus) that are separate from a higher layer (top). So, where the HECK was the Cumulonimbus?

1:09 PM. Heart of the blast, visibility is less than a quarter mile, thunder, close to overhead it seemed, had become more frequent, once every minute to two, unheard in winter storms. It almost exactly the intensity of our summer ones. Completely out of control here snapping photos of nothing but rain, hoping camera battery doesn't give out. But, then I know I would have had company with all of the CMJ's out there losing your minds over this as well. What a day, Mr. and Mrs. Catalina! — 1:09 PM. Heart of the blast; visibility is less than a quarter mile, thunder, close to overhead it seemed, had become more frequent, once every minute to two, unheard in winter storms. This winter storm, on the solstice, was almost exactly the intensity of our summer ones. Completely out of control here snapping photos of nothing but rain, hoping camera battery doesn’t give out. But, then I know I would have had company with all of the CMJ’s out there losing your minds over this as well. What a day, Mr. and Mrs. Catalina! Is this what “global warming” has ahead for us, as one Arizona scientist mused? Summer-like storms in the heart of winter? Maybe it would be so bad…. Hardest rain I’d seen here in nine winters.

1:18 PM. A few hundred photos, 18 min, and a half an inch of rain later, I ventured out to see what was the result. Here, ponding had occurred in a swale. I wondered whether toads would re-emerge after this warmish rain? — 1:18 PM. A few hundred photos, 18 min, and a half an inch of rain later, I ventured out to see what was the result. Here, ponding had occurred in a swale following the gush. Considering the warmish nature of the rain, would toads now re-emerge along with flying ants?

4:42 PM. One of the rewards of clearing skies, are the quilted-with-sunlight mountains sides of the Catalinas.

4:43 PM. While plump Cumulus clouds and dark skies abounded, these clouds no longer reached the level where ice could form, and were "dry" clouds as far as precip goes. — 4:43 PM. While plump Cumulus clouds and dark skies abounded, these clouds no longer reached the level where ice could form, and were “dry” clouds as far as precip goes.

5:16 PM. More evening color; note rain gauge. Such a pretty scene!

The End

New storm marches toward Catalina! Due in tomorrow afternoon.

¹Meteorologists, outside of Buffalo and Seattle, have inverted values regarding clear and cloudy.

²I hope we get 30 inches THIS water year, dammitall, busting this year’s seasonal forecasts of a dry Southwest.

Wasn’t expecting rain to arrive this soon (overnight Tues into Wed); much more in route

0.11 inches logged in Sutherland Heights. Amazing, considering nothing was expected last night in mods, but rather tonight.

This rain situation from the tropics is looking better all the time, with an inch between tonight and tomorrow night looking very possible. Next, let’s see what the AZ Uber model predicts, from the 11 PM AST run to get some constraint on a shot from hip one:

Total rain expected between about now and 7 PM AST tomorrow evening. Note something like 3 inches is expected atop Ms. Lemmon!

Annotated version below since no one will be able to find Ms. Mt. Lemmon….

Same as above except with arrows and writing on it.

Well, we know these tend to run on the the high side, so look for something between a third and three quarters of an inch here in Sutherland heights, a really nice rain! We need it so bad, too. Desert looks awful dry thanks to the deficient Oct and Nov rains.

The future is hopeful, though, for rain anyway in Catalina. Recall that spaghetti (the “ensembles” told us were we going to be in the area where troughs collect at lower latitudes like ours and Baja. Well now its looking more and more like they’ll have rain in them and not just “temperature fluctuations”! I’m pretty excited here, hope you are, too!

The End

(more later)

First measurable rain in recent memory falls in Catalina! Also, strange and regular undulations observed

“Recent memory” is, of course, only about three weeks, certainly not more than a month….

BTW, FROPA is occurring now (3:55 AM-4:10 AM, marked by the usual wind shift to the NW from the SW, heavy bursts of rain in this case, and a sharp drop in temperature–so far we’re down from 55-56° F to 45° F in about 20 minutes. Likely will hit the upper 30s before the cooling stops. The rain total yesterday morning by 7 AM from the first rain band, mostly fell from mid-level clouds, was but 0.02 inches. Today, the total is going to be over 0.25 inches by 7 AM. Excellent indeed.

(Update: 7 AM rain total here in Sutherland Heights is 0.51 inches, as measured in a NWS style 8-inch diameter gauge! Awesome. The U of AZ model really nailed this event, predicting 0.25 to 0.50 inches here.)

Let us begin the cloud marathon that led to “rain.”

12:52 PM, December 15. Altocumulus (perlucidus translucidus) announces the storm, sans the Altostratus that was actually expected.

4:36 PM. Now we’re getting serious with Cirrostratus on top of Altostratus and scattered Altocumulus clouds. Three separate layers whose appearance tells you that the atmosphere above is in gentle lift, the kind of thing that precedes the actual storm, though not so much in deserty climates like ours where such scenes may only lead to a pretty sunset.

Creeping toward the present….by yesterday morning, things looked serious. I hope you noticed how FAST the clouds were moving, ones just above Ms. Mt. Lemmon:

7:20 AM. Stratocumulus layer with undulations and concave bases zipping along at 50 kts or more from the SW. Did you notice the stationary clearing to the SW horizon? These clouds were forming by the lift provided by the Catalinas and other mountain ranges downwind from the lower SW desert areas. Sometimes steady rain falls for hours with this scene. Yesterday, only sprinkles around mid-day since tops at this time were marginal for ice formation.

Some sounding comments, this nice sounding plot from IPS MeteoStar:

Ann 2016121612Z_SKEWT_KTUS — The TUS sounding launched around 3:30 AM when rain was falling in Catalina, giving us eventually our 0.02 inches of rain. No doubt the clouds in the preceding photo had warmer tops than these did. The top of the lower, and mostly liquid layer was about -16°C, normally plenty cold enough for ice to form. The humidity element on these balloon soundings can measure the humidity with respect to liquid water quite well, and so when the temperature and dewpoint lines are on top of each other in these soundings (are the same temperature) you can bet that the balloon when through a cloud of mostly liquid water. When the lines spread apart, as higher up in the balloon sounding, but are still close, you can be almost sure its an ice cloud that the balloon went through. This doesn’t apply on partly cloudy days or broken layers when the balloon passes between clouds. But when the balloon went up yesterday, we had a solid overcast, likely in two separate layers, one being mostly liquid and the higher one mostly ice. The spacing between the two is so small, if it even existed, that ice likely fell into the lower cloud layer. Sometimes this is called the “seeder-feeder” situation, since the ice crystals have a chance to grow like mad and/or collide with droplets while falling through the lower layer.

Kind of a crummy diagram of a "seeder-feeder" situation. That lower cloud is CRITICAL for enhancing precip! Believe or not, most precip in winter storms is added in the last kilometer at the bottom of the clouds, essentially by what are Stratocumulus clouds below Nimbostratus decks, themselves considered "middle-level" clouds in our cloud nomenclature. — Kind of a crummy diagram of a “seeder-feeder” cross section for the Seattle area. That lower cloud is CRITICAL for enhancing precip! Believe or not, most precip in winter storms is added in the last kilometer at the bottom of the clouds, essentially by what are Stratocumulus clouds below Nimbostratus decks, themselves considered “middle-level” clouds in our cloud nomenclature.

But what about those strange clouds later, undulations and cave-like cloud bottoms? For the person still reading this tedious blog, here are a few shots of those extraordinary scenes, ones you might only see with the ferocious winds aloft yesterday:

8:00 AM. Strange scene, concave cloud bases–personally would call this layer Stratocumulus, but with a base height of about 8,000 feet above ground, so could also be considered an Altocumulus opacus layer.

9:33 AM. Was taking photos every few seconds as sky seemed to change.

9:35 AM. While scary clouds were overhead, you could see that a clearing was going to move in before very long, given the horrific winds aloft from this direction. Note again “undulatus”, waves in the atmosphere showing up in clouds! But, it took hours for a clearing to occur because that was a standing zone of cloud formation to our SW yesterday, something like a gigantic lenticular cloud that stands in place downwind from mountains.

9:36 AM. Having taken three photos in the past minute, each one looks pretty much the same. But, this one has a bird of some kind on the side of that bird feeder at the bottom. Was small, yellowish; maybe a canary. Its important to note that each photo was taken at exactly the same spot, but rather tens of feet from the prior photos. Moving around helps provide perspective in photos….

9:51 AM. More undulatus. Looks like its going to clear up now. Nope, it didn’t as clouds kept being added to the upwind end of these.

9:53 AM. Waves began breaking out over or just downwind of the Catalina Mountains. Would want to be flying in them!

9:54 AM. Zooming in. What is going on here? Fortunately, for the sake of having to explain this to his three blog readers, Cloud Maven Person set up his video camera and starting a film of this phenomenon. Here’s the result: dry waves of air are causing the concave bottoms of these clouds. The air in the cloud layer was moving faster than the dry waves pushing up into them, and so clouds were forming on the right side of those concave bottoms (upwind side), and dissipating on the left side (the downwind side). So those dry waves that pushed up into the cloud layer, were in effect creating cap clouds at their highest point, the kind of cloud that tops a mountain for minutes to hours (not the same as a “lenticular” cloud which is almost always downwind of the peak). Without video, I would not have known this, might have put forward something crazy in the way of hand-waving….maybe.

11:55 AM. As you can see, that clearing is still out there. Here some ice began to form in these Altocumulus opacus clouds (I would call them) and a few drops made it to the ground about this time. Eventually, it did clear up; “the clearing before the storm” as we see so often here in Catalina and Arizona where dense bands of middle and high clouds, this time thick enough to provide us with a little measurable rain overnight (that 0.02 inches), is separate from the thick, lower-topped clouds that produce the actual storm such as this morning’s blast of rain accompanying the cold front.

3:55 PM. The evening closed with “partly cloudy”, producing those nice scenes on the Catalinas. These clouds are Stratocumulus, tending toward lenticulars if that bit smoother. You no longer see any ice or virga from these clouds. Since mid-day, the tops lowered to around -5 to -10° C, a little too warm for ice formation, and the upper atmosphere dried out, so no higher clouds around either, as the main front approached.

The TUS rawinsonde balloon sounding for yesterday afternoon. The arrows denote cloud bases and cloud tops. Yesterday, there were no overshooting tops, so they probably were at -9° C as shown in this sounding. Here, following up on the prior sounding discussion, the balloon passed between clouds since if it had gone in them (droplet clouds) the two lines would have indicated the same temperature (water saturated conditions).

Well, at 6:41 AM, the rain is over, with nothing definite now in sight, though there are close calls since we seem to be in or near the “mean trough” where individual troughs and fronts like to collect and reach their farthest points south. While rain is “iffy” in these passing troughs, fluctuating temperatures from pleasant days to cold days following dry cold fronts passing by is virtually certain.

The End.

Measurable rain to fall in Catalina at last!

The chance of measurable between this afternoon and Saturday morning isn’t 10%, or even 50%, but 100% as seen from THIS keyboard. If you want a better forecast than that, go to the NWS, Tucson, or see Bob’s expert take. I like Bob. But we go for it here; don’t mess around. The last measurable rain, only 0.10 inches, fell WAY back on November 27th. I wonder if you remember it? Probably not. I don’t.

Rain hits after midnight tonight after a day of heavy middle cloud overcast (that would mostly be Altostratus opacus, probably with virga later, maybe some Altocumulus embedded or at the bottom or below that As layer, with mild temperatures. Don’t expect sunset color tonight since the cloud deck is likely to extend too far to the west for that.

These middle and upper clouds, whose bases will lower as the day goes on and during the night when the rain hits, are associated with a surge of moist air from the tropical Pacific. This chapter of rain will followed by an extremely sharp cold front passage (“FROPA” in weather speak) late Friday night or early Saturday morning with another round of light rain.

AZCat model output foresees quarter to half inch here in Catalina.

Wind will be a problem.

This situation will be accompanied by a really intense low developing to the north of us and the wind by tomorrow mid-day through early Saturday morning will be ferocious. We’re likely to see gusts here in Sutherland Heights to well over 50 mph from the SW as the wind bunches up against the Catalina Mountains, helping to increase speeds here in The Heights. CMP suggests putting loose stuff in the yard away somewhere. He might even do that himself instead of trying to find where all his baseball caps, left outside on the front porch, went the next day. Some composition shingles likely to come off, too.

The Weather WAY ahead

The good news here, if you like below normal temperatures and chances of rain or snow, is that the forecast models are indicating we’re in the mean trough position. Periodic fronts and troughs will affect the SW over the next two weeks, bringing with them at least a CHANCE of rain, while cooler than normal spells are virtually certain.

Check out the spaghetti:

From last night's computers, valid two weeks from now, Dec 30th at 5 PM AST. — From last night’s computers, valid two weeks from now, Dec 29th at 5 PM AST.

Notice the broad dip to the south in those red lines beginning in the eastern Pacific Ocean then down to Baja and then back toward the east-northeast into the southern Plains States. The 5700 meter height contour (red lines) is pretty much on the edge of the jet stream, and a dip like this would be considered a weakness, a vulnerability for troughs in these plots. Remember these are initial starting conditions in last evening’s global data with DELIBERATE slight errors put into those data to see how slight errors affect the outcomes. There are almost no differences at the beginning, the errors are so slight.

And there are ALWAYS slight errors in our measurements, of course, so spaghetti helps pin down what those errors might do to embarrass us forecasters. When those red (or blue lines) cluster somewhere into a band, it means that the errors introduced have little effect on the position of the troughs at this level (500 mb).

For example, over there off SE Asia, the cold continent and the warm ocean constrain the jet stream into a tight bundle of contours. Errors don’t have too much influence on where that jet stream will be off Asia; its pretty much locked into place.

Down stream, things are more of a mess, but you can still see, in this case, where there is kind of a bunching to the south in the red lines in our SW domain. So, there would be, oh, moderate confidence of passing upper level troughs during these latter days of December. At least that’s what I see from this from here.

Worried about wildflowers now, due to the paucity of fall rains….so really hope December can come through with some major rains!

The End

Strange sunset brew of clouds and color; but was it natural?

Cutting to the chase: I don’t think so.

Yesterday, after an ordinary beginning,, finished in a spectacular, if likely artificial way. Let us work our way through yesterday’s cloudulations:

7:39 AM. I thought this was a cute display by this little cloud, making its own little shadow rays as the sun made its way up from behind the Catlinas.

7:40 AM. But what kind of cloud is it? It, to these eyes, is all ice, but LOOKS like an Altocumulus cloud. But those clouds are all or mostly comprised of liquid drops. And you can see that this little guy is well BELOW a higher layer of ice cloud, we might call CIrrostratus, or a thin Altostratus. Oh, well, let’s move on to something explicable….

7:41 AM. Hmmmm. Quite a linear virga feature over there. There are THREE cloud layers evident here, a thin Altocumulus layer, that dark cloud on the left, and patch of what I could call, Altostratus extending from the left corner to the right corner, and a thin layer of CIrrostratus on top.

7:41 AM. Let’s go zooming and check it out…. Though we don’t know for SURE, anytime you see this kind of linear virga anomaly, you should be smelling aircraft exhaust. Now, when you think about our fabulous sunset last evening and what that looked like, take a closer look at this photo.

Later that morning…..

10:53 AM. 10:47 AM. It was nice to see low clouds topping Sam Ridge, the lower boundary layer air (where convection takes place) moist for a change. — 10:53 AM. It was nice to see low clouds topping Sam Ridge at dawn yesterday, the lower boundary layer air (where convection takes place) moist for a change. Later they devolved into small Cumulus (humilis and fractus).

3:29 PM. A day with mostly ice clouds on top of Catalina, but here, off in the distance below the Cirrostratus, is an invading layer of Altostratus and Altocumulus that will set the stage for sunset glory later. You may be able to detect a faint halo, upper center. By the way, Cirrostratus typically deepens downward to morph into Altostratus, usually an ice cloud, too, but is deep enough to produce gray shading, and when its really thick or has embedded droplet clouds, hides the sun.

4:02 PM. Yep, moving right in. This is a very complex scene. There’s aCirrostratus ice layer. upper right quadrant , on top of everything. Below that, what appears here as a distinctly lower separate layer, a mix of Altocumulus (those dark cloudlets composed all or mostly of liquid droplets) and Altostratus (mostly or all ice, the smudgy more diffuse dark areas) . We can never forget that Altocumulus can morph into Altostratus, which would then be called, “Altostratus altocumulotransmutatus.” Tell that to your friends! (Well, maybe not.)

4:15 PM. Caught this bumpy aircraft contrail at CIrrus levels. Look how how the exhaust and water vapor that formed this, though output from an aircraft in a steady state, how the wing tip vorices (apparently) get entertwined at regular intervals with more exhaust and water vapor in those blobs.

But let’s go zooming up to flight level and take a closer look for a second:

A mammatus (or as the ladies like to call it) testicularis contrail. Almost certainly this is due to combining wing tip vortices. Many aircraft now have devices to defeat wing tip vortices, phenomenon that reduce flight efficiency. — A “mammatus” (or as the ladies like to call it. a testicularis contrail (the resemblances are pretty good). Almost certainly this is due to combining wing tip vortices. Many aircraft now have devices to defeat wing tip vortices, phenomenon that reduce flight efficiency. In both cases above, the ice particles have not grown enough to produce fallstreaks. These images tell us that SOME aircraft that produce ice in supercooled Altocumulus clouds, as we in Catalina have seen lately, are likely to have bunches of ice trails rather than a continuum if produced in a uniform cloud, anyway.

Now, where was I? Got mammatus on my mind again. I love mammatus so much… Oh, yeah, that sunset yesterday…..

5:13 PM. Ran out to check sunset status, and saw this feature advancing rapidly toward Catalina.

5:18 PM. Zoomed view; getting close to passing overhead. You might be able to notice that these pretty regularly spaced trails are BELOW the Altocumulus clouds, and there's a clearing that's been produced. All evidence of an artificial production of these trails. But belng below the Altocu, you might also have started to wonder whether the setting sun would light them up.... — 5:18 PM. Zoomed view; getting close to passing overhead. You might be able to notice that these pretty regularly spaced trails are BELOW the Altocumulus clouds, and there’s a clearing that’s been produced. All evidence of an artificial production of these trails. But belng below the Altocu, you might also have started to wonder whether the setting sun would light them up….

And the sun did its job….producing one of the greatest sunset scenes we’ve seen in a long time, even if phony (haha):

5:23 PM. Not zoomed, still a few minutes away to overhead passage. Very exciting to think this was going to pass overhead!

5:23 PM. Zoomed view. Again the pretty regular spacing is circumstantial evidence that nature didn't do it. — 5:23 PM. Zoomed view. Again the pretty regular spacing is circumstantial evidence that nature didn’t do it.

5:25 PM. Thank you sun! Looks pretty round again, which is good.

5:28 PM. Another view of the same thing.

5:28 PM. Our trails compared to the rest of the Altocumulus deck. Not much going on elsewhere in the way of natural virga.

5:29 PM. Taking WAY too many photos of the same thing. Out of control... Here I demonstrate that with another photo of the same thing. — 5:29 PM. Taking WAY too many photos of the same thing. Out of control… Here I demonstrate that with another photo of the same thing.

5:30 PM. After the trail hoopla, it was time to concentrate on the fabulous sunset taking place to the southwest of Catalina.

5:30 PM. Zooming in on interesting features; long trails, one with a clearing above it. Was it another aircraft-induced trail of ice and clearing above it? Probably. The trails to the left aren't as obviously produced by an aircraft, but I do think so anyway in this burst of objectivity. Recall that I have been trained as a "scientist" and don't care if I am wrong, but only about truth, as best as I can make it out. — 5:30 PM. Zooming in on interesting features; long trails, one with a clearing above it. Was it another aircraft-induced trail of ice and clearing above it? Probably. The trails to the left aren’t as obviously produced by an aircraft, but I do think so anyway in this burst of objectivity. Recall that I have been trained as a “scientist” and don’t care if I am wrong, but only about truth, as best as I can make it out.

Finally, let look at the TUS sounding for last evening, see how cold those Ac cloud were with the ice trail in them:

The Tucson rawinsonde balloon launch yesterday at about 3:30 PM. Goes up at about 1,000 feet a minute, so takes about 100 minutes to get to 100, 000 feet. They pop somewhere around that height or a little above. THought you like to know that. They have a little parachute to that when they come down, they don't bonk you too hard. Once in awhile people find them in remote areas downwind. — Results of the Tucson rawinsonde balloon launch yesterday at about 3:30 PM. Goes up at about 1,000 feet a minute, so takes about 100 minutes to get to 100, 000 feet. They pop somewhere around that height or a little above. THought you like to know that. They have a little parachute to that when they come down, they don’t bonk you too hard. Once in awhile people find them in remote areas downwind. You can send them back in to the NWS, too!

The astounding thing here, something that goes against everything I believe about clouds, is that it is indicated that the Altocumulus, lacking much natural ice, was at -30° C! Yikes! No wonder aircraft were producing ice trails and stuff yesterday afternoon.

You have to conclude there were almost no natural “ice nuclei” up there at, oh about 24,000 feet above sea level. This is not the first time for such an occurrence of liquid clouds sans much ice at low temperatures¹, but they are rare IME. This would never occur in a boundary layer cloud, that is, one where material from the earth’s surface is getting into the clouds, like the omnipresent dust, or biogenic ice nuclei.

The weather ahead

Some “fantasy” storms with rain in them for Catalina, are now seen on the model predictions beyond a week. Spaghetti is favoring this new development now. So, something to keep an eye on.

The view from here? Precip here is “in the bag” because going on subjective feelings, I really want to see a good rain here!

The End

——————————
1The famous John Hallett said he saw an Altocumulus lenticularis sans ice at -35°C in a conference preprint! Rangno and Hobbs (1986) claimed to have detected droplets in Altocumulus like clouds at the top of a storm on the Washington coast at -44°C. Their claim, first published in a conference preprint, was later rejected by the J. Atmos. Sci.

In case you missed them…a 2008 full moon and, moving ahead, yesterday’s sunrise

The full moon of December 11, 2008. Thought maybe you'd like to see it again coming up over the Catalinas. — The full moon of December 11, 2008. Thought maybe you’d like to see it in case you missed it, or see it again if you did see it. Maybe you had a special memory with this moon.

7:09 AM. Altocumulus perlucidus with a little lenticular underneath.

7:43 AM. — 7:10 AM. Zooming and zooming.

7:14 AM. Iridescence is evident in the cloud ripples just above the mountain silhouette.

7:16 AM, Contrails were soon visible in our Altocumulus layer, the aircraft making it at the right edge of the photo. Appeared to be in a climb out going right to left. And, when you see these “high temperature contrails” in Altocumulus, you can be sure ice will form and rifts will develop as a little bit of light snow develops and falls out. The jillions of ice crystals in the contrail cause the droplets in the Altocumulus to evaporate, in a way, gutting it. An ice crystal is like a low pressure center when amid droplets; the droplets evaporate and those water molecules deposit themselves on the ice crystal, a process named after the discoverers, Wegner-Bergeron-Findeisen. Eventually the crystal is large enough to settle out and a clear streak results unless the air is rising rapidly and can replace the droplets (as generally happens in storms). Sometimes the lift in the Altocumulus layer is enough that a clear canal caused by an aircraft can fill back in after many minutes.

7:18 AM. Two aircraft contrails, about a minute old. After two or three more minutes, they will not be visible within the cloud, though ice is forming, decimating the droplets around the intense streamers of ice in the contrail.

7:28 AM. The small ice canal (the ice is hanging just below the Altocumulus clouds–kind of hard to make out, but its there.

7:42 AM. Those little clear streaks are hardly noticeable now, partly because they were quite narrow, and because of perspective and things bunching up in the distance.

From the Cowboys in Laramie, Wyoming, this TUS sounding for yesterday morning in the pre-dawn hours:

Suggested locations of cloud layers. The Altocumulus layer in which the contrails were embedded seems to be at -25°C, a "normal" temperature for this kind of "high temperature contrail". In general contrails are not supposed to occur until the temperature is below about -35° C and the air is moist, thus they are usually seen amid or near Cirrus clouds. not down in Altocumulus. — Suggested locations of cloud layers. The Altocumulus layer in which the contrails were embedded seems to be at -25°C, a “normal” temperature for this kind of “high temperature contrail”. In general contrails are not supposed to occur until the temperature is below about -35° C and the air is moist, thus they are usually seen amid or near Cirrus clouds. not down in Altocumulus. See usual contrail height at Cirrus levels in moon photo.

As the morning wore on, the Altocumulus deck faded away, moving east, and we were left with some Cirrus clouds, but what kind?

10:58 AM. Cirrus of some type, but notice there is absolutely no fibrous details (strands and such) as we normally see in Cirrus. Could be transverse waves in a Cirrostratus deck since Cirrostratus can be fog like, have no detail, in a version we call, Cirrostratus nebulosus. The up and down motions would cause clearings perpendicular to the wind up there. The lack of strands and uniformity in these bands suggests very tiny ice crystals, ones having very little fallspeeds.

2:34 PM. Some nice “hovercraft” clouds, Altocumulus lenticularis off in the distance SSW. Hung around out there for a couple of hours.

3:17 PM. This one appeared to be concave upward, which was a little odd. Zoomed view next.

3:17 PM. Looks like the inside is higher than the outside. Huh.

Well, that was it for photography yesterday.

Doesn’t seem to be any reliable indication of rain in sight. Oh, sure, rain here pops up in the models almost every day, but its about 12-15 days out. As the model gets closer to the day it predicted rain, it seems to go away like the “water mirage” on a hot paved road; always ahead of you, but you never get to it. We’ve had some major rains indicated in the models as of a few days ago, but spaghetti was never very high on those events (clustering those crazy lines in a trough over us), so it wasn’t even worth mentioning.

And, even that rain is a gonner in the model runs from last night!

The End

Rain, snow to stay in Arctic; not arrive in Catalina after all

“Can’t you see, I’m on a losing streak” Rolling Stones¹, 196x, in “I Can’t Get No Satisfaction”, a “PG” for radio tune from those days.

Well, it seems we “can’t get no satisfaction”, either, when it comes to rain

Being on a “losing streak” has been CMP’s fate as well as far as forecasting goes. A few weeks ago, right here on this blog is was reported that CMP was “on record” that November would end with a flourish of rain that would boost totals “to above average.” That statement has now been excised from that earlier blog; there is no longer ANY “record” that I said anything like that.

November ended up with 0.70 inches, whilst average is 0.96 inches.

Then, in a wild one, it was suggested strongly a ten or so days ago here that snow and cold would make the Catalina snowbirds feel right at home, the one they left to avoid snow and cold.

Well, that’s not gonna happen, either.

On the good side of things, distracting the reader from the many erroneous forecasts found here, CMP’s former employer’s fubball team, the University of Washington Huskies, are moving on to the Final Four of Division I fubball after bonking Boulder Buffaloes 41-10! This means a gigantic media paycheck for the U-Dub! As you likely know, Big Fubball supports all the little sports that can’t support themselves with revenue, like softball, cross country, volleyball, and the like, so many of those that come under Title IX. So, its a good thing for everyone, but in particular, especially women’s sports, when you’re university gets a big media paycheck, one that’s spread around the whole conference!

Now, where was I? Oh, yeah….bad forecasting.

The cold air, and any sign of precip will remain far to the north of southern Arizona. Spaghetti really let me down in that one, or my interpretation thereof. Not really my fault at all, when you get right down to it…

The current low spinning over southern AZ and northern Mexico was formerly a situation where precip was going to fall here according to computer models. Now, as our “losing streak” for storms continues, its going to end up as a “high, dry one” for us. Parts of Mexico, NM and points east will get generous rains and snow, so we can be happy for them, I guess.

On to clouds, for what its worth. There were some nice scenes again yesterday.

8:36 AM. Nice line of Cirrocumulus I would call it, some cirriform clouds in the background, maybe Cirrostratus fibratus (has lines, fibers in it).

9:57 AM. Action shot. This photo gives the feeling of clouds streaming at you, which they were; Altocumulus upper center, maybe Cirrostratus above it, and to the left and right horizon.

1:16 PM. Things started to look promising as distant light rain showers broke out to the southwest. Perhaps they would work their way into Catalina. Nope.

1:19 PM. The sun’s disk as seen through a cloud that is completely or almost completely comprised of droplets, hold the ice. Ice particles, if in any degree of concentration, caused the sun’s disk to blur, you would never be able to make out the edges due to diffraction of light by those larger particles. Droplets in clouds are mostly less than 20 microns in diameter, whilst ice particles are generally larger than a few hundred microns to millimeter sizes. Here, you could have told your tell your friends, if you have any, that this cloud is all or almost all comprised of droplets, probably no ice at all. Some kind of bird is passing off the frame of this photo, maybe a seagull.

3:54 PM. The day ended in disappointment, a word used a lot these days as those minimal showers rotated westward and stayed far to the south.

Now, there’s nothing in sight in the way of precip for southern AZ, not even an outlier model forecasts of some fantasy storm to dream about in the next two weeks. Oh, well, we can enjoy some nice sun and feel the warmth that sun brings

————
¹This is a really old R&B, rock band led by Mick Jagger. Mick will be 100 years old I think next year, and so they’ve cut back on touring; only 47 shows are planned in the US.

A stragne and wonderful day

Many strange¹ and wonderful sights were seen yesterday; I could feel the excitement out there as one cloud microstructural mystery after another regaled our Catalina skies.

7:24 AM. Here, a tiny highlighted flake of Altocumulus floating above a mass of light snow/ice crystals, maybe straight below it. This is one the classic mysteries we deal with in “cloud microstructure”; the oddity of nature preferring to generate a droplet before an ice crystal at least to somewhere in the -30°s C. Liquid clouds often are at the top of Altostratus and Nimbostratus (rainy or snowy days) providing the tops aren’t too much colder than -30° C. How strange is it to have liquid water at the lowest temperatures in a cloud system, with all the ice and snow underneath, as shown in this photo (though here they are no longer connected).

7:24 AM/ I think there is itty bitty droplet cloud at the very top bright dot there. A droplet cloud was likely much broader to have produced all the ice we see below that bright dot of liquid cloud.

7:26 AM. Looking afar, to the SW, there’s what appears to be an Altocumulus (droplet cloud) with a few ice crystals underneat it, especially to the right.

How cold are these clouds? Lets look at the TUS sounding, launched at about 3:30 AM yesterday morning.

The TUS rawinsonde balloon data for yesterday morning before dawn. That Altocumulus layer, and the other clouds above were likely at the pinched point above, topping out at -27°C and up around 23,000 feet above sea level (400 millibars), pretty darn cold. But, as you saw in the 3rd photo, not a lot of ice is being generated at this temperature by that patch of Altocumulus clouds to the SW. Not sure why, but its pretty remarkable and that is likely due to small droplet sizes AND a lack of ice nuclei, most of which are known to originate with soil particles When you see these rare occurrences of all or mostly droplet clouds at low temperatures (<-20° C in particular, get ready to see hole punch and ice canals produced by aircraft, a kind of inadvertent cloud seeding.

That bank of Altocumulus was racing at more than 50 mph toward Catalina, and so it got here in a hurry. And, as it got closer, it was also getting more into some airways at that height, possibly descents into PHX since the height of those clouds was below normal jet cruising levels at 23,000 feet Above Sea Level.

7:55 AM. This is one of the strangest sights I have ever seen. Why? On the left side of this photo, the clouds are completely glaciated, composed of ice, while along a line to the right, there's no sign of ice in Altocumulus clouds that appear to be at the same height (namely, temperature). I have no explanation for this scene, except those involving a lot hand-waving, so we'll just let go. — 7:55 AM. This is one of the strangest sights I have ever seen. Why? On the left side of this photo, the clouds are completely glaciated, composed of ice, while along a line to the right, there’s no sign of ice in Altocumulus clouds that appear to be at the same height (namely, temperature). I have no explanation for this scene, except those involving a lot hand-waving, so we’ll just let go, except that we speculate that the Ac layer was a little lower (warmer)? Could have been.

Now for the aircraft effects. Hardly a few minutes go by before aircraft began marking up this cold Altocumulus layer. Notice that it doesn’t seem to be producing much or any ice on its own, making aircraft inadvertent seeding lines and holes where tremendous numbers of ice crystals are generated immediately present. Here’s the first of many:

8:16 AM. An icy canal due to the passage of an aircraft rips through this pristine layer of Altocumulus whose temperature was around -25° C. The view is looking S toward Tucson, but is unlikely to have been an aircraft landing there because this layer was above 20,000 feet Above Sea Level. An aircraft lanidng at TUS would be much lower, this close. The passage of the aircraft was likely 10 or more minutes before this photo.

8:19 AM. The ice canal is broadening due to turbulence, and ice is not plainly evident to all Cloud Maven Juniors or we will have to go over discerning ice from droplet clouds at the next club meeting.

8:20 AM. A view of the northwest end of this aircraft-produced ice canal. Several others became apparent, too.

Heading for Catalina, this:

9:11 AM. Heading for Catalina, a whole mess of aircraft induced ice in that poor Altocumulus layer. The hole punch was likely due to an aircraft climbing out of or descending into TUS. The age of a hole that large, with ice below it like this would be something of the order of at least half an hour to an hour old. Just behind the hole is a new contrail in the Ac clouds,

9:23 AM. Hole punch area and ice canal arrive over Catalina! Losing control here, taking photo and photo, now looking for stragne optics, usually observed with aircraft produced ice particles because they are so numerous, compete for the available moisture and therefore remain tiny and perfect, prisms, plates, short column ice crystals, ones that can do a lot of optical stuff.

Here’s the south end of that ice canal:

9:24 AM. Also note iconic horse wind vane, and real wind vane atop a personal weather station. Doesn’t everyone have a “PWS”?

Looking straight up at the icy heart of a hole punch region caused by an aircraft. I am sure you have never done this before! This is gonna be a great blog with all these new things for you!

9:27 AM. Look at the detail in the ice, those fine, fine strands! Amazing. The thickest strand might be due to the higher liquiid water in the heart of one of those little Altocumulus cloudlets. ??? Look how much wind shear there is, those little itty bitty ice crystals falling so far behind the parent cloud, the streamers flattening out because the poor little guys, already undersized to begin with, are getting smaller and smaller, the fall velocity getting less and less until the strands are almost horizontal.

9:27 AM. Looking at this gorgeously uniform layer of Altocumulus perlucidus 9honeycomb of elements) translucidus (no shadows). To me this is a phenomenal scene, though maybe to u, not so much, which is understandable.

9:30 AM. The expected intense optical phenomena began to occur in these aircraft contrail remains. Here a parhelia, or sundog. More fireworks in a bit.

9:30 AM. While the parhelia was in its full display, very intense, this was the ice canal passing overhead. Look at the regular spacing of these strands of ice, Might be due to the spacing of the cloudlets in the Altocumulus layer, the spaces between them not producing much ice, or, as we know, contrails tend to clump behind the aircraft likely due to wingtip vortices interacting and combining masses of exhaust water and crud. This is now about an hour and fifteen minutes old, since we saw it way out to the west at 8:16 AM shortly after it formed.

9:37 AM. Here's what a new aircraft contrail in these clouds looks like, this one about 60 s old looks like — 9:37 AM. Here’s what a new aircraft contrail in these clouds looks like, this one about 60 s old looks like. Note all the irregularity in the contrail from the get-go.

As the south end of the original ice canal began to enter the refraction zone for simple ice crystals around the sun, usually at the 22° degree halo position, things began to light up with a particularly bright circumzenithal arc (more often observed on a halo) or colorful (in this case) partial “reverse halo”. The colors (iridescence) due to the refracting of light within very small ice crystals. Normally iridescence is seen near the sun in Cirrocumulus clouds or the then edges of other droplet clouds. Very exciting.

9:44 AM. Halo curving in the wrong direction, away from the sun! — 9:44 AM. A part of a halo curving in the wrong direction, away from the sun! (This is actually called a circumzenithal arc).

9:44 AM. Taking up you up thousands and thousands of feet via a zoomed view. Pretty cool, eh? Notice how much its moved in just seconds, You really have to let your coffee get cold if you’re a photographer and you want to get the best shots of this kind of phenomenon. You really can’t do anything but keep watching every second!

9:44 AM, again. All these changes took place within the minute between 9:44 and 9:45 AM! Here, the next grouping of ice strands is being lit up.

9:48 AM. Just a pretty scene. Altocumulus perlucidus translucidus, pocked with aircraft contrails, if you look real close. Make me move: $1 billion dollars…

9:54 AM. Its not even 10 AM and now this comes along, this fabulously complex zone of CIrrocumulus (at the same level of the Ac clouds) at the tail of the Altocumulus. You can see the much higher Cirrus going crossways, lower center. See TUS sounding for height of Ci.

Then this strange sight:

12:29 PM. A row of Altocumulus or Cirrocumulus, each formed by a little upward bump in the atmosphere of a layer just a hair below saturation. Just rising a few hundred feet or so causes these cloudlets to form. Why aren't they everywhere? Might be drier. Bumps like this are always present in the atmosphere, especially if there are mountains upwind. — 12:29 PM. A row of Altocumulus or Cirrocumulus, each formed by a little upward bump in the atmosphere of a layer just a hair below saturation. Just rising a few hundred feet or so causes these cloudlets to form. Why aren’t they everywhere? Might be drier. Bumps like this are always present in the atmosphere, especially if there are mountains upwind. Not taken while driving, of course, ; just looks like it thanks to photoshop.

The day closed out with a lower layer of Altocumulus moving in, this layer, according to the TUS sounding, at “only’ -17° C, and little ice detected. Below, at 2:09 PM:

2:09 PM. Altocumulus perlucidus translucidus. A natural conversion to ice is occurring on the right side of the photo.

4:41 PM. A strand of finely patterned Cirrocumulus shot out of the SW as the sun declined.

The Tucson afternoon rawinsonde . launched around 3:30 PM. The Cirrocu in the above photo was likely also at the Cirrus level indicated above.

U of AZ mod thinks so light rain will develop around here in the mid-later afternoon.

The End

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¹“stragne” above, originally an inadvertent typo, but left in place as another cheap trick to get draw the curiosity of readers who might wonder what stragne is.

A day with rare and regular clouds

Yesterday, whilst disappointingly dry, no rain fell here overnight was a day of rare cloud sightings, most of it involving the rarely seen, “Cumulo-cirrus¹“, a cloud fakery situation where extremely cold (less that -40°Ç, -40° F)and clouds at Cirrus levels appear to be ordinary little Cumulus fractus clouds. I hope you weren’t fooled by those impersonators. You’d be pretty embarrassed at the next meeting when we go over yesterday… Yesterday was, in essence, a test for you, and I hope you passed.

Along with the rare “Cumulo-cirrus” sightings, there were intricate patterns in Cirrocumulus clouds that may have caught you’re eye. However, with the wind aloft being so strong (around 90-100 mph at 18,000 feet) you didn’t have a lot of time to enjoy them.

Yesterday’s clouds

10:01 AM. These were the first “Cumulus” pretenders I saw yesterday, though I suppose the discerning eye might have called them “Altocumulus” as well. When they first formed they look hard and rounded like they might have had cloud droplets. But then within seconds, that brighter look caused by high concentrations of droplets or tiny ice crystals (sometimes called “germs” because they have no particular shape when just formed) fades as the concentrations decline rapidly due to evaporation and mixing with the dry environmental air around them. Eventually, they become transparent. Also notice that you don’t see trails come down out of them. This is likely because the concentrations are so high that competition for moisture keeps all of the ice crystals so small they can’t really fall out.

10:01 AM. Zooming in. The brighter ones have just formed. The faded ones are the older ones heading for extinction. Many more shots of “Cumulo-cirrus” to follow. Got kind of carried away, as usual.

10:18 AM. Another moist layer shot in, first showing up as Cirrocumulus, though this cloud was in the middle levels, not at Cirrus heights. The fine granulation makes it look higher than it really is. This was probably around 12, 000 feet above the ground, if that. One giveaway was the rapid movement of the cloud itself, and compared to the cirriform clouds above it. If they are near the same levels, they won’t move much at all relative to one another. Anyway, these patterns changed by the SECOND! It was amazing how quickly they devolved into something completely different.

10:27 AM. A wid angle view of another incoming group of “Cumulo-cirrus.” The thinnest clouds are the ghostly remains of those clouds. The more compact and brighter ones are the youngest ones.

10:27 AM. A closeup of a just formed globule. Everything around it was onece like that but now has the visual attributes of regular Cirrus.

10:42 AM. One of the strangest cloud sights ever seen by yours truly, CMP. Here a layer of Cirrocumulus (note fine patterns lower center) passes rapidly underneath those globules of fake Cumulus clouds full of ice.

Explanatory figure below:

11:22 AM. Another patch of fake Cumulus fractus at Cirrus levels comes by. Note the true Cirrus in the background, and was higher than the fake Cu fra.

11:36 AM. Was beside myself seeing this! Just incredible!

11:38 AM. Just two minutes later! Look what has happened to that puff ball of ice. The turbulence up there must have been tremendous.

11:57 AM. Some real fakery here. Ordinary people would have said, “Oh, those are just little Cumulus fractus over our Catalinas.” But not you. You would have chided them in friendly, gentle way, telling them they were WAY too high for Cumulus clouds and are mainly composed of ice, not possible for low Cumulus fractus clouds. You could have also pointed out that the cloud in the upper part of this photos were way below those Cumulus fakeries, and that they about to obscure them as this encroaching layer slid underneath them. Also, try not to be condescending, act superior like you know so much even though you do. You might lose your friend if you do that.

11:53 AM. Another zoomed view of one of those icy puff balls, not long after it formed.

4:01 PM. Altocumulus opacus underneath a Cirrostratus layer. A great sunset was in the works with that opening to the southwest. Also notice, no ice or virga evident. Guess that the temperature at the tops of this layer, likely only a couple of hundred meters thick, is warmer than -10° C.

5:31 PM. Altocumulus opacus at sunset. The height of this layer was about 8,000 feet above Catalina by the TUS sounding, top temperature about -5° C. “No virga, no cry,” as Bob Marley said.

The End

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¹Though it fits, I made this cloud name up. Probably would be Cirrus floccus, maybe Cirrus castellanus in the humped up cases.