7:12 AM. Action shot of bird with morning Altocumulus perlucidus translucidus.11:50 AM. Clouds topping Samaniego Ridge. Get ready for sprouts!12:38 PM. Amid the Cumulus “rubble” a glaciated top has emerged representing a Cumulonimbus calvus. Can you find it? Only the BEST cloud-maven juniors will be able to locate this tip of a tall cloud. Maybe you’ll get that special badge… If you don’t believe me that there was an extra tall top in this photo, you can go to the movies and see it here: http://www.atmo.arizona.edu/~leuthold/yesterday.mov.4:23 PM. While it was pretty and placid here, ominous Cumulonimbus clouds pile up on the S-WSW horizon.6:49 PM. Closer, spectacularly tall and pretty, but still over there, not here.7:05 PM. Time to give up and go to bed. Finely granulated virga from Cirrus/Altostratus deck was a bit of a treat. Suggests tiny cells of rising currents within that layer that produced tiny areas of larger ice crystals now falling out after the “updraft” (maybe 1ft a minute) weakened. The crystals? Likely “bullet rosettes”, of course, to extend the guesswork.
OK, enough of yesterday, a bit of a disappointment unless you looked at the models and saw that there wouldn’t be much here.
But TODAY….oh my. Those models have a MUCH more active day! Be ready; have camera charged, video as well. Don’t forget, you loggers out there, to note the time of your first Cumulonimbus sighting.
Should be a “fun” day with once again our very warm cloud bases (topping Sam Ridge now as I write at 6:02 AM) giving us, in essence a cloud travelogue to normal condtions in tropical countries near the Equator.
How much rain can fall from in these tropical boys? As we saw two days ago, 2 inches in an hour can fall; three is possible. 2-3 inches in an hour? Happens all the time in Florida in the summer. And with our upper sixties and low seventies dewpoints this morning, we are one with them (taking into account our higher elevation).
While “only” 0.42 inches fell here (a great rain, really), and 0.43 inches at the ALERT gage on the CDO bridge at Lago Del Oro, Sutherland Heights got whooped with a whopping 1.75 inches yesterday afternoon in a remarkably dense and windy rainshaft. But I am getting ahead of myself with this report and this sunset photo. First some more precip reports, here (ALERT gages) and here (U of AZ network). “And the winner is…” (as of 9:18 AM) for the greatest 24 h amount in ALL of Arizona, Bonita Canyon near the Chiricahua NM (2.06 inches) followed by Sutherland Heights!
Check the rainlog amounts above and here for CoCoRahs!
On to our story of the day, to be interrupted later by another learning module…
The day started like any other one, with our often observed morning Altocumulus perlucidus translucidus deck covering most of the sky. With the rising sun, Cumulus began to appear and grow rapidly with bases of those clouds topping the Samaniego Ridge line, something that is a rare occurrence. By 10 AM, showers were already appearing on the Cat mountains; those towering Cumulus clouds had already reached the precip forming level.
By 10 AM, you should have been VERY excited, talking to the neighbors about the low and warm cloud bases; alerting them to possible exceptional rains.
6:49 AM.9:29 AM.10:11 AM. Little acorns are turning into giant sequoias already!
At this point, I feel I have to insert a diversionary learning module. If you’re one of those people who doesn’t care about what’s going on “way down inside” these Cumulus clouds, as Robert Plant might put it if he was a nephologist instead of with Led Zepelin, then skip this module.
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Begin learning module.
With cloud bases as warm as 15 degrees C (close to 60 F!) almost certainly the first precip to form in yesterday’s clouds were drizzle drops (remember, to keep Cloud-Maven from getting mad at you, having “rain rage”, you have to remember that drizzle drops are between about 100 and 500 microns in diameter and that at that size, a few human hairs in diameter, they almost float in the air; umbrellas can be useless when it is drizzling.
Dirzzle is NOT a sprinkle of larger drops, dammitall, and its important to me that you know that!
Here’s the interesting part (he sez). Before drizzle and raindrops can form in a cloud without ice being involved, the droplets inside the clouds must reach 30-40 microns in diameter, maybe a third of a human hair in diameter.
Until they reach that size in the clouds, they will bounce off each other like itty bitty marbles or ping pong balls. After that “magical” size greater than 30 microns, they can coalesce, merge into one larger drop, which then falls faster, collects more drops, and, if the cloud is deep enough, fall out as a raindrop.
In the olden days, this was called a chain reaction process by cloud seeding nut and Nobel Laureate in chemistry, Irving Langmuir, who published a nice paper on this in 1948. Today most folks call it the “warm rain” process, because ice is not involved. Happens a LOT in the tropics, and places like Hawaii, but its rare here because our cloud bases are so warm as they were yesterday, and our clouds, being “continental”, that is, having high droplet concentrations (hundreds of thousands per liter of air) makes it hard for cloud droplets to grow up to be 30 microns in diameter. BTW, raindrops as big as 1 cm in diameter, the biggest known size, came out of a cloud in Hawaii that had no ice in it.
So, for me, a cloud-maven, it was quite interesting yesterday to see that our cloud bases yesterday were “Floridian”, and likely had a good deal of “warm rain” in them, even before they towered up to 50,000 feet, -60 C, and had a ton of ice in them. Its often the case that those raindrops are carried up to levels where they freeze and jump start the ice/hail forming process higher in the cloud via splintering (banging into drops and leaving fine ice shards in their wake) and shattering (they break up upon freezing).
End of learning module; you can wake up now…
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The payoff by those low, warm cloud bases? Exceptional looking clouds, a travelogue in the sky really, more like ones you’d see in Florida in the summertime, Bangladesh, Phillipines, Jakarta, etc. Here they are, before and during the Big Dump on the Sutherland.
12:49 PM. After a huge storm over the Torts, an ominous line of Cumulus clouds began extruding westward toward Catalina.1:07 PM. This is looking VERY good, but, with all the cool air, can these Cumulus bases really be hiding tall clouds? You never know until you see the streamers. Excitement level probably should have been around a 6-8 of 10 here, holding back that bit so that you’re heart is not broken by a later broken up cloud base.1:29 PM. “Thar she blow”s, though actually, its like an upside down spouting whale; the streamers begin to emerge in the distance.
1:28 PM. Just six minutes later!1:31 PM THREE minutes later. Excitement level 9 of 10.1:36 PM. Full blowed tropical Cumulonimbus shaft. Thinking about that “Rawhide” theme seeing this, after all, this is “Arizony”: Rollin’ rollin’, rollin’, though the streams are swollen, keep them dogies movin’, rawhide” rain and wind and weather, hell bent for leather….’
That last shot is of the one that rolled into the north Catalina area and Sutherland Heights, dropping 1-2 inches.
Tried to beat it up to Sutherland Heights but was late, visibility
was bad, lightning close by, so stayed in car with one of our (wet) dogs, Pepper.
As a result, in no “in the storm” shots. Sorry.
Oops, today?
Latest mod run from 11 PM AST last night by U of AZ here. Surprisingly, this model run thinks today is quite a down day, not much shower action here. Must be due to the cloud cover keeping the temperatures down all day (in the model) Or something else that is not immediately apparent to me, anyway?
But, temperature is NOT everything, as we saw yesterday. When the air is this humid, and deeply humid as yesterday, it doesn’t take blazing temperatures to launch Cumulonimbus clouds.
So, it seems likely, with the usual daytime thinning of these clouds, perhaps not enough of that in the model, that tropical Cumulonimbus clouds will once again arise here and there. I think Bob, our local scientist expert in these matters, will fill in some of my blanks on this later. He’s probably not up yet.
Only a marked change in the flow pattern at near the top of our Cumulonimbus clouds can really do much, and its not obvious any thing much is changing up there (is it helping air to rise, or to descend and dry out?) The latter can put a real damper on cloud development even if there is initial good humidity, and right now, it doesn’t get any wetter in AZ than it is right now, this morning!
Five consecutive days of afternoon and, or, evening rains are ahead. If you don’t believe me, go here, to the University of Washington’s model run from last night‘s GLOBAL data, showing where the rain areas will be (in color!) every three hours for the next FIVE days. You will see that EVERY afternoon and evening has regions of color in our area. I hope you’re happy now.
Instead of dwelling on yesterday’s drab conditions; all that water up there, and in the air around us as measured by those high dewpoint temperatures, air that produced almost no rain here in Catalina, I thought I would instead liven things up today with a learning module for you, delimited by a string of dashes for excitement.
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Below, is a link to the Environmental Science Services Administration (ESSA) pamphlet that tells you how to interpret today’s probability forecasts (10%, 40%, etc., chances of rain).
While I have provided this information as a public service, if you would like to obtain one of these pamphlets for yourself, you can get them for ten cents from the Superintendent of Documents, Government Printing Office, Washington, D. C.
Alert: there may be some questions in the days ahead to make sure that you read and understand this information. A sample test question:
“There is a large Cumulonimbus cloud on the Catalina Mountains but you can’t see them through the rainshaft coming out of that cloud. There is a flash flood warning for the CDO wash. The chance of rain is 10%?
True or false?
(The answer to this sample question will be provided in an upside down font when WordPress is able to to that.)
End of learning module. (I hope you’re happy now.)
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OK, here’s is a tiny sample of clouds from yesterday. I hope you recorded them correctly in your log book. Here they are, in case you miss them on some hot day ahead:
12:36 PM Sprinkles are around. Altocumulus opacus, could be labeled Stratocumulus underneath. Above the Altocu, Altostratus, the three layers helping to provide that Seattle drab look.
4:35 PM. Can you spot the Cumulus fractus under this Altostratus translucidus layer?
Trying to be excited for those around us who got all that rain yesterday while we received a paltry 0.18 inches here in the upper reaches of Catalina. Still it was another good little rain for our local desert.
The 24 h rolling archive from Pima County rainfall gages is here. Most seen here? 2.01 inches at Finger Rock and Skyline, Tucson. You’ll see that storm in the movies.
Also, check the more comprehensive U of AZ rainfall network here. In fact, you might as well join up, too. It would get you out of your rut. Think how exciting it would be to go out in the morning and see how much rain fell in your gage in the previous 24 hours! Maybe someday you might win the “rain lottery” and have the biggest amount anywhere in the State! The most reported so far this morning is a deluge of 3.17 inches over by Picture Rocks again. Good grief, have they been getting hammered.
What a July this is turning out to be!
Here we are in Catalina, its late afternoon, it has just rained again, the temperature is a chilly 70 F, dewpoint 68 F (almost saturated), with Stratus fractus just above eyeball level lining the hillsides! Its an amazing scene for an afternoon in Catalina and vicinity in July. And so DARK! Here is that odd scene from yesterday afternoon:
4:42 PM Stratus fractus is that low bar of clouds in the foreground just behind the tree. Makes you want to run over there and play hide and seek in it.
Relive yesterday, as though you were in the city of Tucson shopping possibly, here in this movie, courtesy of the U of AZ Weather Department. The movie is rated “R”, for violence since the sky goes WILD in the afternoon, winds going every which way.
Also, in this time lapse you will get a sense of how rapidly moist air is flowing across us from the east to east-southeast. This movie, comprised of still shots taken every 10 s shows movement, like the day before, that is phenomenal for summer, more like a winter scene when winds are normally strong. There are even Altocumulus lenticular clouds (almond shaped ones) hovering over and just downwind of the Cat Mountains! Amazing.
But check the CHAOS in the mid and later afternoon. Unbelievable. Areas toward the Catalina foothills, during this chaos, got another 1-2 inches again yesterday.
In contrast, let us now look at the very same day in a time lapse film in Seattle, Washington, where Mr. Cloud-Maven person spent 32 years, most with the U of Washington Huskies Weather Department. Here it is. I sum up the totality of that movie for July 29th below:
Bor-ring!
Those Seattle skies, for the most part, were like eating plain, cooked oatmeal everyday, all day.
Below, the start of our exciting day, the middle, and the end has already been shown above. Lots of nice rain shafts SUDDENLY collapsing down out of clouds. A sequence of the big northwest Tucson storm early in the afternoon that moved off toward Marana is included as part of the middle. That shaft really fell out fast, and how you could detect the icey tops BEFORE the shaft appeared. I try to point out how you might have been able to do that in this sequence, and thus, and quite importantly, impress your friends and gain status and some kind of weather sage.
Today?
Just looked at the latest AZ mod output, as you can here (forgot to past link until now, 8:08 AM). Colored splotches are where it is supposed to have rained that HOUR. That model has a much less active day today, but much more active tomorrow. Cumulonimbus clouds in sight today? Oh, yeah! But, none are SUPPOSED to get us today. But these mods are always slightly inaccurate, so keep watching this afternoon. Should be another photogenic day, if nothing else.
10:03 AM. What a pretty start!1:29 PM. Cumulus congestus converts into a Cumulonimbus calvus. While no rain is falling out the bottom, check the top peaking through above in the next shot.Also at 1:29 PM. Annotated. Icey tops barely visible, but reveal that this cloud is LOADED with precip, certainly would have a radar echo aloft now. In a perfect world, the flash flood warnings would go out NOW, even though it hasn’t gone out the bottom yet.
1:32 PM. The first fibers of rain are just starting to be visible at cloud base as the updraft collapses, too much weight up there in rain, hail, and snow.
1:36 PM. There it comes! Close up of the main dump.
1:48 PM. What was interesting was how huge this got in just a few minutes, how the initial outflow winds kicked off other cells around the first dump shown above.
Man, its tough to get rain here sometimes. Not sure why we seem to be in a death zone for Cumulonimbus clouds lately. Yesterday, a really great shower plodded toward Catalina and only to fade on the east side, and propagate off to the west and over the Tortolita Mountains (veered down the sideline, in football speak). I guess we should feel lucky that, due to the lightly raining “stratiform” (blanket cloud) residual cloud from this strong storm, we got 0.02 inches here last evening. Coulda been worse, of course. (BTW, if you’re an old rocker and want to hear, “Dazed and Confused”, to which I allude to in the title, go here.)
Here’s the photo record in thumbnails, which I thought was interesting enough because this moderate-sized shower really exploded into something large as it approached from near the Tucson Mountains. You can also go here to get the full version as seen from the top of the Wildcat Dept of Atmos. Meteoro.
4:54 PM. Nice and cute; its even heading this way, but way too far away to make it, given the short lifetimes of small Cumulonimbus clouds.
5:04 PM. Huh? Its STILL coming, and seems to be developing a new “crop”; those flanking, non-raining clouds that might grow to take the place of the raining one. Oh, it’ll never make it. Too small.
5:36 PM. Its not small anymore! Holy Smokes! And look at those “fountain-of-youth-required-for-new-life-new dump for Cumulonimbus flanking clouds! This could be great dump here!
6:04 PM. Here, the side of the storm approaching Catalina. The flanking lower cloud deck has disappearing and only light to moderate rain is upwind now. Without re-inforcements from below, that approaching rain will only get lighter and lighter as it approaches. Dang.
6:11 PM. Awesome, but somehow “wrong”, falling over there. An almost black flanking cloud, piled high on top, was forced there by the outflow winds from the original storm as it dropped its first heavy load in Oro Valley. Because those winds aren’t symmetrical blowing out from the rainshaft, it happened that the strongest winds and uplift over them went over there. Dang#2
7:07 PM. Its raining lightly here now, coded “R–” or “RW–” in your log book. The cloud would be termed, Altostratus cumulonimbogenitus (namely, debris cloud, trash clouds from our glorious Cbs).
To finish off with something more positive, this sunrise photo taken just now while a few drops of rain were falling.
The Weather Ahead.
Drying trend starts on Wednesday, the 25th and lasts a couple of days. The Enviro Canada model saw this coming some days ago, the US WRF-GFS not so much, but they agree now.
The clouds and Cbs return on the 29th with July finishing strong in activity.
In the meantime, another great day ahead, one with large Cumulonimbus clouds and scenes like the past few days are on tap.
More, later.
It is later.
Here is the U of A model output for today, hour by hour. Lots of activity seen for us in Catland beginning after 12 Noon with numerous showers developing by then, but nothing for tomorrow and the next day.
Maybe you should call in sick today, and enjoy the sky all day.
In case you missed it, and you probably did because you were still in bed while I was doing things for you, there was a pretty sunrise to start the day yesterday, one that would not disappoint later by being a dry one. After all, we’re here in the peak of our summer rain season.
Got 0.27 inches here, and 0.40 inches in Sutherland Heights. (The U of AZ rainfall network will have lots of data, some places getting over an inch yesterday. Pima County amounts here.)
BTW, as mind wanders, the real monsoon in India is a a little below normal this year so far. But, check out these forecast maps from IPS Meteostar and look at the west coast of India. It rains every day all day for the 15 days of the computer model run. Nothing really too unusual about that, rain every day all day on the western Ghats, 10-20 inches a week. Now THAT is a monsoon! Thought you might like a little distraction, get you out of any ruts you might be, get you thinking “outside the box” for a change.
OUR story, the long and winding one, continues below, though it can be seen in totality, in the short form in the U of A time lapse movie. This is a great U of A movie, with several “dump trucks” going by. Its amazing how much water can just suddenly be unloaded by a cloud!
Also, lenticular clouds (hover clouds) can be seen at the beginning and end of the movie downstream of the Cat Mountains, unusual for summer.
5:27 AM. Altocumulus opacus, no snow virga. What’s the top temperature? Hint: warmer than -10 C (14 F).7:27 AM. You’re finally up and you see this grayness due to Altocu/Stratocu. You start to fret over whether it can rain later in the afternoon with all these clouds keeping the temperature down.10:32 AM. Your mood begins to brighten just like the sky; the temperature is soaring while the mid-level clouds thin, and Cumulus begin arising over Ms. Lemmon, trailing overhead toward YOU. You feel special.1:32 PM. You’ve been patient, and FINALLY the clouds trailing off Lemmon are beginning to look like they might erupt into Cumulonimbus ones; bases are firming up, coalescing.1:58 PM. Its looking really good. Nice compact bottom almost overhead. You’re getting euphoric, well, hopeful.2:00 PM. Only TWO minutes later and the load is on the way down! This is the time you want to be at a picnic 2 minutes earlier and amaze people by saying, “RUN for your car! NOW!”, though they probably wouldn’t pay any attention to you unless you knew them and they knew you were cloudcentric.2:02 PM. Picnic’s over.2:03 PM. ONE minute later! The Fat Lady has sung.2:19 PM. Downspout from Cumulonimbus cloud moves on across to Oro Valley to “excite” other picnickers.2:22 PM. This beauty off to the north. Name? Cumulonimbus calvus (fibrous nature of top not yet fully evident, though a practiced eye can detected the cotton candy ice composition in the two pronged top. In front of it, a Cumulus congestus. Check that shaft! What day! Fantastic scenes all around.
The weather ahead.
U of A mod results not yet available at this hour (5:08 AM), but other model outputs suggest another three days, including today, of the kinds of scenes shown above.
Every day will be that bit different in shower coverage, of course, that governed by subtleties in the flow aloft, grade of moisture supply, dewpoints, etc.
But those days ahead will be great enough, our deserts being drenched here and there, the desert foilage exploding. Enjoy those clouds while they’re here.
Another dry day yesterday, a tough one to take, since it appeared that rain hereabouts was a virtual certainty. All the model runs I saw from the U of AZ had good rains at times on the Catalinas yesterday afternoon and into the evening, as they do again for today. Here’s one U of A model output for 2 PM yesterday (WRF Surface (Flash Animation) as an example.
So, when the dense Altocumulus clouds with their spotty sprinkles and light showers finally thinned and the sun burst forth in the afternoon, up went the Cumulonimbus clouds within the hour off in the distance from Catalina to the NE and SE. It was going to be a great afternoon and evening I thought. Tucson International AP reported lightning, thunder, off and on yesterday until after midnight, and even a few drops! Go here if you want to see all of last night’s action in the satellite and radar imagery from IPS Meteostar.
But none here. Check the radar-derived precip from Intellicast.com. You can see light rain was all around Catalina, dang.
Rainfall for the 24 h period ending at 5 AM AST today.
Cumulus started to form above Ms. Lemmon, and it seemed one of those was bound to explode upward as well. While a brief sprinkle/virga fell out of one of those clouds at one point when it reached the “Cumulonimbus mediocris” stage, one I made up, no full eruption occurred. It was incredible that didn’t happen, and so discouraging when you claim to be a Cloud-Maven, one who is supposed to know stuff.
The full discouraging day can be seen here, if you can stand to review it. Still, these films are pretty interesting no matter what happens when clouds are present.
By evening all Catalina threats were seemingly gone, with no promising, massive clouds approaching from the northeast as they often do here at that time of day in the summer, rolling down out of the White Mountains, blackening the sky behind Charoleau Gap. I missed a great sunset, too.
About today, in view of my poor track record, you might want to check out what Bob has to say. He is one of the premiere scientists in convection, and lives right here in Tucson! I think he has better graphics, too. Also, here is the forecast from our NWS for Catalina, better get that in there for more balance, and maybe more accuracy! They think the chance of measurable rain today in Catlina is but 10%.
However, being indefatigable, imperturbable, immutable, stubborn, I will press on with this forecast space: _____________________ (write in your own forecast; it will likely be better than mine). PS: I think it will rain today.
BTW, even the coarse (as in grid spacing) Nvironment Canada model has a wet Arizona week ahead. So, if not today, tomorrow!
Below, a photo reprise of yesterday.
6:59 AM. That promising morning sky. Light showers can be seen beyond the Tortolita Mountains.1:25 PM. As the Altocumulus clouds faded, large Cumulonimbus anvils began appearing in the distance. This was going to be a great day.1:41 PM. Mountainous Cumulonimbus tops rise up over the White Mountains to the NE!1:26 PM. Cumulus are beginning to pile up over Ms. Lemmon! Surely there will be a giant Cb in an hour or two!Later that day…. a painful sight.
(A note: I am not getting WYSIWYG in what I am writing and what is posted in WP. This is SO FRUSTRATING! True I am a bit of an amateur at WP, but those spaghetti plots that start the blog are SUPPOSED TO BE AT THE END OF IT as I see them in the draft, not absorbed in the “gallery” as well, dammitall!) Computers and sofware are going to kill me, I am sure. Where are my pills?!
Another promising start to a summer day today in Cat Land, as was yesterday since we have another cloud filled morning, some clouds having weak rainshafts indicating glaciation in the turrets sprouting from today’s layer. And, there’s been a slight uptick in moisture over us, which raises the chances for measurable rain in Catalina today. We also have support for this contention in the great U of A local model forecasts here, based on last night’s 11 PM AST run! Yay!
Below, the photographic diary for yesterday starts begins with the Altocumulus opacus layer, with more than one layer up there. Then, after the usual thinning-dissolution of that layer in the morning, the welcome sight of baby Cumulus beginning to appear over Mt. Lemmon by noon. Those Cu steadily inflated reaching the “glaciation” level by 1:31 PM, a welcome sight after the “dud” Cumulus clouds of the prior two days.
After our first thundery spell, several new thunderstorms developed to the NW and E-SE over the Catalinas late in the afternoon, but again, produced only another trace in a 20 minute or so of “very-light-rain-its-not drizzle” (one of the recurring themes here).
Since I can’t add more captions after the icy sprout, a WP problem, the times of the last few photos are, 1:53 PM, 2:08 PM, and finally, another great sunset sequence, some distant Cumulonimbus to the NW and another blazing sunset underlighting some virga from the remains of our last thunderstorm, these taken at 7:30 PM.
6:14 AM.
12:39 PM.
1:18 PM.
1:31 PM. That icy sprout on the top meant a rainshaft was already fully developed inside that cloud. There’s always some of it falling out.
The Weather Ahead, way ahead:
We’re always on pins and needles this time of year, hoping for the best summer rains we can get, at least I am. The transformation of the desert into green again during the summer, after the spring greening, is one of THE most rewarding aspects about living here in the summer, flying ant swarms aside.
Below are the “spaghetti” plots from NOAA that give us some clue about the reliability of the longer term model forecasts. These are for the afternoon of July 19th, some ten days from now, and the afternoon of July 23rd. Both plots below strongly indicate that the circulation pattern is ripe for good summer rains here between now and the 24th. Doesn’t mean that every day will have rain, but it does mean recurring summer rains are likely with no long breaks. That black region over the SW indicates a high probability (not certainty!) that our big fat SW summer anticyclone will be well positioned for good summer rains here. In contrast, if that black area was OVER southern Arizona, or to the south, it would be a horribly, hot dry spell here that the models were foretelling.
Thunderstorms in the distance crept toward the Catalinas late in the day, and after sunset, an approaching, but thinning anvil of a dead Cumulonimbus cloud (no updrafts remaining to feed the anvil) produced this beauty. With the death of this prospect, any hope of rain moving in here later in the evening went six feet under as well.
The anvil below looks fairly close, but if you go to the U of A time lapse, this anvil comes onto the field of view at about 7:40 PM, and you can get an idea of how much farther the anvil below had to go to be above the Cat Mountains.
For the second day in a row there were virtually no Cumulus clouds over our Catalina mountains, a real disappointment. But, undaunted, Mr. Cloud Maven person will anticipate Cumulus clouds over the Catalinas once again today, following in the same wrong footsteps of the past two days, and will again foretell that these will be ones that will rise high enough to “glaciate”, that is, have their tops convert from liquid droplets to ice crystals.
The result of this “glaciation” process is something coming out the bottom of the cloud, a dense shaft of precip, as a Cumulus cloud transforms itself into a Cumulonimbus one.
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Science Story: This is always an exciting sight and a process that Mr. Cloud Maven person (MCMP) spent some 25 odd years studying with a highly instrumented aircraft at the University of Washington but couldn’t quite figure out how it happened. In fact, MCMP (with his lab chief co-author) were criticized royally (i.e., Blyth and Latham 1998) for what they did report over the years (“royally”; they were two British guys, but working in the US). We “Reply” to their comments in quite substantial fashion in the same issue (Reply to Blyth and Latham)!
BTW, real scientists, like Alan Blyth, are still working on this problem; how clouds glaciate. Its pretty amazing when you think of it. These days the Japanese (asteroid dust Science-2011) can send a spacescraft to an asteroid named, Itokawa, land on it, pick up some dust grains, and bring them back, a process taking more than 10 years, but we really don’t know completely how ice forms in a cloud!
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Back to the local scene:
once again we have our high surface dewpoints, in the upper 50s (58 F here in Catalina) and even 62 F now at Douglas. So the bottom of our atmosphere is OK for Cumulus. And once again, we have an overcast of mid-level Altocumulus clouds. A problem yesterday was the extreme dryness above that surface moist layer, and below the Altocumulus one, a shallow moist layer that was completely obliterated after the sun came up and the dry one and razor-thin moist one mixed together. Its not so dry today above the low humid layer today, and so Cumulonimbus clouds should be able to develop in the area.
Besides the models told me so. Have been a little sloppy and a little, well, arrogant, about reading the early morning sky absent more information.
Here’s today’s TUS sounding, from the Wyoming Cowboys, so you can see for yourself.
The End, unless I find out I am going to be wrong again when more data comes in a couple of hours.
68 F dewpoint at TUS, too. With this kind of dampness, it should be an exciting day with clouds topping the Catalinas, and you know when that happens, its another sign of really heavy rain in the area. In fact, we have a little strip of Stratus fractus along the base of the Catalina’s now (5:29 AM).
Let’s go to the National Weather Service’s web page and see if they are excited about today… Yes! They are pumped, with “green” shading designating those areas of southeast Arizona in a NWS flash flood watch!
Here’s the 4 AM map below, courtesy of our University of AZ Wildcats National NCAA Baseball Champions Weather Department. What a great final game that was! (You can get their latest map here.)
After a mostly disappointing day, an unusual summer day in which there were no clouds being launched off the top of Mt. Sara Lemmon, and temperatures were unusually “cool”, there was finally a strong, whitish brightening of the sky to the east, with darkening to the northeast beyond Charoleau Gap, as the sun slid below the horizon.
And if you were looking at the Weather Underground (now having been absorbed by The Weather Channel in some kind of capitalistic power grab) web page for the Catalina area, you saw that the brightening beyond the Catalina Mountains yesterday evening was due to the anvils of an approaching complex of Cumulonimbus clouds. But as we know, they don’t always make it after dark coming from the east, only on some days. They often fade away, or only produce sprinkles.
It began to rain pretty hard right at 9:30 PM, but there had been no lightning preceding it. I was surprised at how hard it was initially raining, thinking earlier that the rain was going to be old stratiform rain from dead Cumulonimbus remains, very steady and light, maybe adding up to just few hundredths. Then “BLAM” this brilliant bolt nearby and two huge booms of thunder setting off a car alarm near us. How great that was! Rain continued to fall until about 2:30 AM. That lack of lightning suggests the rain producing cell was building right over us, finally climbing to heights and with updrafts strong enough to produce the first lightning. Sprinkling again now (for a couple of minutes) from Altocumulus opacus clouds… Very unusual to have morning rain here as you know.
Here’s a reprise of yesterday’s clouds starting with mid-afternoon and the remarkable absence of Cumulus boiling off the Catalinas. Instead, small Cumulus (“humilis”) were scattered helter skelter around the area as though there were no mountains.
3:04 PM3:44 PM. Also, looking toward the sun you could see a lot of smoke in the air here, a pretty sight.7:17 PM. Sky looked threatening, but at this time they were just shallow clouds, ones whose cloud tops were below the ice-forming level.
Below, “the brightening” as Stephen King might put it, showing that deep clouds were around, and they were approaching from the east. The anvils, well above 30,000 feet, are still in full sunlight, and the sun is shining through the thin, probably haze-free air up there. Its undiminished light remains white when striking those cloud tops, not having had the shorter wavelengths scattered away by aerosols (until the sun subsides farther below the horizon).
