0.73 inches

Bullseye thunderstorm off the Catalina’s between 12:30  and 1:30 PM really did it, dropping a miraculous 0.55 inches.  I suspect that 300 yards N and S got less than our driveway did where the gage is located.   The smells, the puddles, the water running down the road; it was all so marvelous, and seemingly it has been decades since we saw this kind of sight.  And then, after it looked like it might be “all over”. that dramatic darkening of the lower cloud bases pushing over the Catalinas from the east suddenly began to occur around 6 PM, followed by another nice rain of 0.14 inches.   While we did not get the core of that massive system, it was great to see all the rain fall in western Tucson from here, knowing how dry it is everywhere.   Finally, that little bit of rain after dark, plumped the gage another 0.04 inches to bring the total to a wondrous 0.73 inches, every drop so necessary now!

Below, a sequence of the cumulus building off the Catalinas, beginning around 10 AM, ending with the approach of the main “dump” just after 1 PM.  Sometimes seeing this happen, and being so close to it reminds me of being in an airplane meandering among the Cumulus.  The second shot is a great indicator for the rest of the day, a tall, skinny little cloud1 that shows just how ready the atmosphere is to allow huge clouds like yesterday to happen.  Seeing that type of cloud should really get you excited about what the rest of the day holds.

An even better way to view yesterday, in a cross section mode, is from the U of AZ time lapse video here.  You’ll be amazed by these “volcanic eruptions” of Cumulus and Cumulonimbus clouds over Mt. Sara Lemmon.  Better hurry though.  Movie is overwritten by today’s later on!


Finally, the “icing on the cake” to be quite unoriginal; that wonderful sunset.

The End except for the footnote.

1You might well call the cloud in the second shot,  “Cumulus castellanus”, though technically there is no “castellanus” variety for Cumulus as there is for other cloud genera like Stratocumulus.  You could just call it a “towering cumulus”, the kind of remarks seen in airport aviation weather reports, though for some reason my mind always drifts into other domains completely;  paleontology, anthropology, and I think of that early man, Homo erectus.  Perhaps it was too risqué for those naming clouds to use that modifier as a variety name.

Rainy portent in a scruff of cloud

….that scruff of cloud topping Mt. Sara Lemmon around dawn this morning, to finish the thought.   This:


Because seeing a cloud topping Mt. Lemmon instead of well above it indicates that the air is very moist and cloud bases are going to be realtively low, substantially lower than yesterday.  This in turn means even more rain will reach the ground after falling from cloud base today, more of the terrain will be involved with launching deep clouds later this morning,  with their crayola black bases and impenetrable rainshafts scattered around the area this afternoon and evening.

Will we get one of those rainshafts?

Well, no one knows exactly where they will be, but my best guess, based on a few summers here, is that Catalina will at least get measurable rain today, and a real dump of a half an inch or more is well within range.  Yesterday, two brief light showers only gave us a “trace” of rain.  Darn.  But, if you noticed, the rainshafts from the clouds yesterday were denser than the day before, and that trend will continue today.  Sometimes these dumps, just like the 4 PM shower yesterday, are invigorated and started by the gush of winds from dead showers off in the distance.  One of the patterns here is for a gush of wind to blast out of the N or NE, and suddenly, the clouds overhead start filling in in response to the gush of air.  The gush causes the air over it to be pushed up.   And, this can happen very rapidly, going from clouds that draw a yawn, to “Oh, my gosh, look how dark it is over us now!”  Better lie down now for a moment until this gush of excitement passes over.   But, this is going to be a GREAT day for Cumulus and Cumulonimbus clouds!

And what a sunrise display of lightning and a cumulonimbus clouds!

Invasion of the water molecules

At least more of them….   Overnight (take a look here), the dewpoint temperature, a measure of how much frost would build up in your refrigerator freezer and/or drip down the walls of it if you left the doors open and the refrigerator on, climbed a whopping ten degrees early this morning!  

Yay,  “mo better” humidity for storms!  This will mean lower cloud bases today, and that in turn means that the rain that falls out of the thunderheads with their anvils (aka, “Cumulonimbus capillatus incus” clouds, if you want to impress your friends) will reach the ground in torrents; the  rainshafts will be opaque under those clouds.   This will be quite unlike yesterday, where rain fell,  grudgingly it seemed,  from the isolated, high-based, and rather shallow Cumulonimbus clouds seen around Catalina.   This is the first day that, to focus on MYSELF for a second, I….have waited for all year!  I am not one of those little babies that can’t take a little heat and humidity of the Arizona summer and have to head off to his/her mountain palaces or shacks, as the case may be.

Now, of course, if you have any photographic documentation inclinations, you’ll definitely want to get some “before” shots of dusty cacti, dust-covered mesquite trees, your car, check the amount rocks around the little hill your house is on (I don’t think we have enough, for example) and be ready to get some “after” shots once our summer summer’s rains begin and the dead desert springs to life, one of nature’s big miracles around here.  In fact, it would be that bit better if you had a time lapse camera set up so that we could see this change take place over a period of a month or two.  Thanks in advance for doing this! I look forward to seeing your work.

Below, an example of dead desert taken during a horseback ride yesterday.    Also note in the second photo,  some large black birds in formation on the top of telephone poles, wings out.   Sometimes they extend for miles on top of telephone poles.   They do this when the relative humidity is about to go up in some kind of homage.  (OK, I made this up.)

How much rain can fall in our most intense rainshafts, the kind that you can’t see through, are virtually black, and also have just dropped down from the cloud?  (In “conversational meteorology”, when this happens, you might exclaim to dinner guests, “What happened to the view of the Tortolitas?  Just a minute ago there was only a dark cloud base over them, and now, 2 minutes later you can’t see them at all!  Man, look at that shaft of rain over there!”  A murmur develops among your guests…  They’re impressed by your interest in natural events.

Well, we have our measurements here in Arizona.   And once in a great while, something extraordinary like this “bottom drops out” situation hits a hi res gage.  Well, Floridians, you don’t have that much on us.  Our gages have indicated that a whopping  1-2 inches of rain can fall in but 15 minutes!  Unbelievable!  In those cases, its pretty much a whiteout inside the heart of that newly fallen shaft, and your roof will become the equivalent of Bridal Veil Falls, Yosemite.

Please note black dots on top of telephone poles in second photo.  They’re birds.  A close up follows, so that you can see I did not just make this up.  The clouds?  Center:  Altocumulus opacus virgae (has some stuff falling out it) with some “perlucidus” thrown in.

The End, except for the photos below.

First thunder

While only a disappointing trace of rain was observed here, it was so stimulating to see that evening lightning flicker beyond the Catalina mountains for the first time this summer.  And then see more lightning, unexpectedly, close enough to produce the first thunder early this morning between 2-4 AM.   A few large, sparse drops fell for about 8 seconds I think.  Here is are the local rain reports for the past 24 h for our region.  Almost an inch fell in parts of “Greater Tucson”!  How nice!

But perhaps the nicest part of yesterday was that little cloud that sprung up toward sunset to the south over Pusch Ridge.  Here is a sequence of shots from that pretty, narrow little thing that climbed high enough to reach the “glaciation level”–where the cloud top converts to ice, and voila, a little precip falls out.  These were taken at about 5 min intervals.    The first shot would be a cloud classified as a Cumulus congestus, the second might be Cumulonimbus calvus (“bald”), the crenelated top in the first shot is disappearing as ice takes over from the former mostly droplet composition,  and the last, Cumulonimbus capillatus (with “hair”).   Note:  Bald grew hair!  This is a common sequence for larger Cumulus clouds.  The frizzy top in the last photo is completely comprised of ice.  What made this so nice was how isolated and “photogenic” the cloud was.   It fizzled out a little later, and I thought we were doomed for a dry overnight.  The weather here can always surprise you!

“Pyrocumulus”, an awful sight yesterday evening

There may have been some sharp eyed folks that saw a great looking Cumulus congestus in the distance off to the NNE of Catalina yesterday.   The shots below were just before 7 PM LST.  Perhaps there was a shower or thunderstorm on the Mogollon Rim.

Sadly, even I was fooled for a few microseconds until you notice that there is NOTHING even slightly resembling the size of that cloud anywhere in the sky.  Then,  it dawns on you that it must be a “pyrocumulus”, the kinds of artificial Cumulus clouds that form atop the highest, and hottest portions of fires when there is a bit of humidity in the air. Once the fire dies down some, then all you see is smoke, the last evidence of the trees and the plant life consumed below.  Likely was a new fire, too, dammitall.    It was probably 50-75 miles away;  also just visible in the satellite imagery.   The second shot is an attempt at a close up, marred a bit by some kind of large insect that happened to fly by as I was shooting.  Just above the horizon of that second photo, you can JUST make out the telltale smoke below the bottom of the pyrocu.  The last photo, from Hornepayne, Ontario, Canada, is an example of a pyrocu up close, just as it was forming.  This was due to a prescribed burn by the Canadian government.  The cloud droplets are white while the smoke is black.   The cloud droplets are about 100 to 1000 times larger than the smoke particles, and reflect (have a higher albedo) more of the sun’s light than do the smoke particles.


Rain update:  Still looks like a great onset of the rainy season after a little “hip fake” today and tomorrow, that is,  a slight insertion of tropical air ahead of an unusually strong, winter-like storm in northern California.  That weak insertion of tropical air should lead to a few weak, high-based showers and thunderstorms on the high terrain.  And with high bases, there will be the chance of exceptional winds near showers due to the virga and rain falling into otherwise pretty dry air.   After this little episode,  the normal summertime anticyclone aloft rears up from the Tropics and after a couple of dry days and plants itself to the north of us.  This allows more humid tropical air to arrive pretty much on time, around the 3rd and 4th of July.  So, get ready!  It will be so great to see all the dust washed off the cacti, the stupendous sunsets, the lightning, the rainshafts, the whole works.  I’ve waited a year for this season to roll around again!  There won’t be a living thing that is not “happy” by the middle of July I would think, unless there has been too much flooding, always a possibility here.


Thinking about ice on a HOT day

Good grief, its already 88 F at 5 AM here in Catalina!

With a whole stretch of 100 F plus days ahead, maybe it would be good if we looked at some ice and thought about it.  Below are some ice crystals, as photographed by Magono and Lee (1966), a publication that is thought of as the “bible” of ice crystal classifications.   If you did or do field work on snow, in the air or as it fell to the ground, you likely classified the ice crystals that you saw as suggested by these venerable researchers.

Ice crystals have different shapes and different temperatures and saturation levels in clouds.   Magono and Lee classified those shapes by temperatures and saturation levels at which they formed, and you can see some that in the pages shown here:   Magono and Lee When you saw an crystal with a particular shape, or if it had frozen cloud drops on it, you then knew something about the temperature and humidity at which it formed;  that crystal’s history so to speak.

“Factoid”:  Nearly 100 percent of all rain that falls on us here in Catalina is that due to snowflakes, hail, soft hail (called “graupel”) that have melted on the way down.   For example, those huge drops that first fall out of that big, dark cloud base right above you are without doubt melted hail or “graupel.”

As you examine at these natural ice crystals in detail, thoughts of cool air should come rushing over you.   This is because the air in which these crystals formed would have to be cooler than  about -4 F (24 F), the highest temperature at which a natural ice crystal can form, and even then, those only under special conditions.

I suggest meditating on each photo.

In general, the ice crystals shown below go from higher formation temperatures to lower ones.    The first ice crystals shown, for example, are “needles.”  They form at temperatures between -4 and -6 C.  These are temperatures that moderate-sized Cumulus congestus tops sometimes reach, or winter Stratocumulus clouds. An example of using this knowledge in our module of “Converstional Meteorology” would go something like this.    Lets say on a winter’s day, deep and dark in December (why does that phrase sound familiar?) that you saw some “needle” ice crystals falling on your dark jacket at the top of Mt. Sara Lemmon.   The sky is cloudy in low Stratocumulus clouds, witih higher Cirrus clouds visible through the breaks in the overcast.    I have made this a bit complicated to test your knowledge.    It would be quite embarrassing for you and everyone who knows you if you then said, looking at those needle ice crystals (or even “sheath” ice crystals,  “I think these fell from those higher  Cirrus clouds we can see through the breaks in the overcast.”   Instead, you would likely know that they must have originated within the lower, warmer shallow clouds and NOT  from the Cirrus clouds overhead since the ice crystals in Cirrus clouds are mainly short stubby columns, and pointy ones called “bullets”, and sometimes in deep Cirrus clouds,  bullet rosettes, ones that look like a “bouquet of bullets”, p55 in part 2 below.  (Part 1 is ice former at higher temperatures, and part 2 are those ones that form at lower temperatures in general.)

Copies of the original photos here:




May add a bit more later, but gotta go walk a horse now…..

The “greening” of Arizona

In the numerical weather models, that is.

IPS Meteorstar, regurgitating the National Center for Environmental Prediction’s (what happened to simple titles like,  “The Weather Bureau”?) model output from last night has come up with MORE GREEN in that run over prior runs in the State of Arizona.  This,  over the next two weeks!  Caveat:  Might mean this run’s WRONG because of having changed quite a bit, but personally I am getting pretty worked up now.  Kinda tired of the dust here in Catalina, AZ, the cloudless skies,  etc.,  so there are a lot of reasons to want to believe this last run is absolutely correct.

Take a look.  Here are a couple of panels from that run.  You can almost smell the desert after the first rains!  See the impassable roads and washes!  Feel the moss starting to grow under the mesquite trees!  It would probably be of interest for you to take some pictures of dusty plants and stuff before the rains hit, and then the same views afterwards to document the wonderful changes that are going to take place in the next week and two.

BTW, I hope you are not afraid of maps like those below with “isobars” on them, lines delineating (hmmm, is that redundant?) where the pressure is the same, circling around highs and low pressure centers.  You see, most media people and TEEVEE weather presenters think you’re afraid of “isobars” and so they don’t show them.  Too much for you.   They only show you an “H” for a “high” and an “L” for a “low.”

I think you’re better than that;  I will not dumb this down.  I will insert maps with isobars more or less “willy-nilly” as I think would be interesting for you.

Also, I like the expression, “willy-nilly.”

The End

Attention: We interrupt this drought with some (forecasted) summer rain

The numerical leprechauns that spread green (our ancient weather map code for areas of rain) have put a coupla green pixels in the State of Arizona!   The first green pixel from last night’s run appears on Monday evening, June 27th in extreme SE AZ.  Its not much, see  first map below, probably only enough rain to give an ant a drink of water, but, just think, we will have some CLOUDS!  The cloud drought will be over!  

After this itty bitty possibility, and as the jet stream buckles in the eastern Pacific, our bloatful upper level high, normally in place during the first week in July,  is in its normal place in the first week in July!  Imagine, after all the weather “discrepancies” around the country, a normal map!   This means that the tropical air will spurt northward as that ridge develops over and to the north of us and we’ll get into some real nice Cumulus and Cumulonimbus clouds for a few days!   Think of those cool breezes blasting out of the rainshafts, even if you don’t get that rain yourself!  Think how nice that will be.

So when does that little preview of the summer rain season begin after the 27th?  Two days later, on Wednesday evening of the 29th, and then we should be set for several days of clouds and scattered thundershowers.  Check it out here at IPS Meteostar.   Here are some examples below.   Now the first couple of green areas in the State of Arizona will require a magnifying glass.   The mods also suggest it will dry out again after the evening of July 8th.  Phooey!

The End.

Dust in the wind; model rain on the distant horizon

“All it was was dust in the wind” , recalling that tuneful song about large aerosol particles by the rock group, Kansas.    Note: Their first album was incredible!  (This lead in, in case you thought that yesterday evening’s haze was smoke from our awful fires.)

Here’s the change from two evenings ago to last evening.   Cold front went by late yesterday afternoon, pressure began to rise, the dust moved in, and temperatures were 5-7 degrees cooler than it was at the same time the day before.   I guess we only get dirt now with our fronts.  I guess we should be happy;  we have that bit more top soil as well a lower temperatures for a day or so.  BTW, dust particles causing this gritty haze at right usually run a few micrometers in size, HUGE for aerosol particles, so, unlike smoke particles, mostly 100 times smaller, dust don’t hang around for long.

A happy surprise in the overnight National Center for Environment (NCEP) model run, as shown repackaged by IPS Meteorstar a nice weather browsing web site.  Water from the sky in the model runs!  Right here in SE Arizona!  Its only 12 days away!  Start your calendars!  It wasn’t there on the prior NCEP run!  (Sad,  “truth in advertising” note:  These forecasts are mostly unreliable this far in advance, but…what the HECK!  It feels great to see possibly bogus rain here and let the mind wander toward the presence of giant Cumulus clouds, ones that transition into Cumulonimbus capillatus incus ones, cloud to ground lightning, the aforementioned dust washed off the cacti and mesquite trees, fires put out by gully washers!  Its like thinking about Christmas or other gift receiving holiday!  OK, calming down now.  Could just be a numerical mirage.  We have to keep that in mind.  Feet on ground now.  Not having unrealistic expectations as I sometimes do.

The end.

First hot air Cumulus over the Cat Mountains, Friday, June 17th

Small now, but what portent for the summer weeks ahead when it’s big brothers will show up over the Catalina Mountains;  a real milestone, so pretty.  This photo was yesterday, at 2:45 PM, when it was 101 F!  Cloud name: Cumulus humilis or Cumulus fractus.

Later, smoky Altocumulus filled in before and at sunset as a wisp of tropical air also drifted into Arizona.  Unfortunately, that was it for our hint of the summer rain season as this morning there were no clouds in sight.

If you look carefully at the orangish sky around the Altocumulus, you can see something that looks like very faint cloud ghosts, patches of whiter sky.   Those are moist areas at the same level as the Altocumulus where the air is nearing saturation, and some of the aerosol (smog) particles have fattened up as they “deliquesce”, absorb some water vapor, and when they get larger as a result, scatter more of the sun’s light.  That produces a faint ghost of a cloud that may be ready to appear if the air gets more moist.  Typically the relative humidity is 60-80 percent when particles begin “deliquescing.”    Some of our greatest summer days are humid, with low cloud bases on the Catalinas, and yet there is no evidence of haze whatsoever.  That means the air must REALLY be clean!

There was a suggestion of virga in clouds downwind of the Catalinas at sunset, but it was marginal if even there.  So, what was the temperature of those Altocumulus?  Those clouds could still be below freezing, but a good guess would be warmer than -10 C (14 F).  The TUS sounding indicated that they were at -12.5 C, marginal for ice crystals to form (and precipitation to fall out).