Category: Definitions

Another summer thunderstorm day!

We’re on the cusp, of course, for the end of the summer rain season, and so every day like yesterday is a particular treasure.  Take a gander here at the bulging morning Cumulus congestus and Cumulonimbus (albeit, marginal ones) clouds early on over the Cat Mountains.  Note detached top of small Cb to left with virga.   Some science:  note, too, that it appears to be a droplet cloud with snow virga underneath.   The presence of a droplet cloud tells you that the cloud top did not get excessively cold, probably no lower than about -20 C.   Those big boys of the afternoon and their all ice, spreading anvils would have tops colder than at least -30 C.

Did you notice, too, how much lower the cloud bases were yesterday than the prior day?  (Com’on!  You’re supposed to notice things like that as a nascent cloud assessor!)  So, all in all, I was very happy yesterday.  Note in the second photo, this tiny start up Cumulus cloud seems to be making an unseemly gesture to the clear sky above, as though it will alone fill in that overly blue sky.  Well, it was joined by its big brothers later in the day to produce some nice showers, 0nly 0.05 inches here in Catalina “Heights”, but 0.16 inches just a mile N in the Sutherland “Heights” district.  Here’s what it looked like later on yesterday afternoon from Sutherland Heights:

Lastly, another one of our glorious sunsets to top off another exciting weather day.

Scattered rain in AZ forecast next ten days!

Last night’s model runs continue to indicate a showery spell of no less than 10 days duration in the State of AZ.  IPS Meteostar, a private weather provider,  has repackaged the National Center for Environmental Prediction numerical model predictions here.  No one cannot be excited by this prospect in view of our droughty August.  What’s REALLY interesting, though likely in some error, is that a tropical storm moves up the Baja Coast , dies, but its remnant moves into AZ in 10 days (see model forecast below valid for September 14th).   As a forecaster type of person, as well as a cloud-maven kind of person, this would be like Christmas in September to have something like this happen where maybe an inch or two of rain spreads over parts of the State.  This is because we are supposed to be getting drier and drier as the summer rain season withers in September, and so this would be an anomaly.  I’ve always liked weather anomalies, and this might be a real good one.  However, as mentioned in prior writeups, these kinds of things come and go in the models, and so its best to think of it as like in a dream right now, but a pleasant one.

Some cloud shots below from yesterday.  It was SO NICE to see that first little Cumulus cloud pop up over the Catalina Mountains in the early afternoon!  While the depth of the Cumulonimbus clouds locally was limited by dry air and an inversion (temperature reversal aloft) and they could not produce strong rainshafts as a result, still in was nice to see ANYTHING dropping out of those clouds!  Here we were lucky enough to register 0.o2 inches, enough to cut the dust some on our gravelly neighborhood roads.

 

 

Rain dump truck; 0.73 inches

As per my photographic niche, I began to capture some promising bottoms of clouds yesterday afternoon around 2 PM.  The first shot shows a promising cloud (so-so sized Cumulus congestus) drifting westward over Mt. Sara Lemmon.  The next shots show the progression in the appearance of the bottom (my specialty) before the dump truck was emptied.  Nice!  Its always satisfying to document the bottoms of clouds BEFORE the dump truck is unloaded.  Before it was over, visibility was momentarily less than 50 yards in swirling winds and blinding rain.  Unbelievable moment.  According to our tipping bucket gage, rain rates got up 8.4 inches per hour at that peak moment.  (The record, Btw, is over 12 inches actually recorded in less than an hour in Missouri!).  A few minutes after the last photo is when the rain started.

Well, it was a great rain, and the desert veggies seemed to respond to this one event by propping themselves up overnight and looking noticeably greener.

Thunder-rooskie

With a thunderstorm at 7 AM LST yesterday mainly toward Saddlebrooke, you may have thought, “What a thundery day this will be!  It will be like Cherrapunji during the Indian-Bangladesh monsoon season when it rains and thunders all day and inches of rain pile up!”

And of course, it wasn’t going to be like that at all, rather it was the famous deceptive weather “play” called, “thunder-rooskie”, whose first derivative was executed in a Nebraska in a fubball game in which the ball was not hiked by the Big Red offensive team, but was left on the turf for some lineman to pick up while all of the other players were too busy pushing each other around to notice the “egg” just lying there.   (Actually, the name of that trick play was “fumble-rooskie”, as students of the game will know.)  At least here in Catalina, we did get measurable rain in the morning, pretty refreshing, too, of 0.04 inches.  Lots more toward SB.

So wha-happened?  First, that mostly stratiform overcast helped keep temperatures down; only 91 F in Catalina yesterday.  100 F have sent volcanic explosions of Cumulonimbus clouds into the sky, but, except in a few isolated areas and on the White Mountains, that didn’t really happen.  Too damn cool.

Also, when you have a disturbance strong enough to produce rain and the rare morning thunderstorm, more often than not it is replaced during the daytime by dryer air asscoiated with an attendant couplet of descending air motion, and a little of that happened yesterday, too.  So, rain and thunder at dawn are often associated with disappointing afternoons here in Cat Land.  Naturally, I hoped for more, seeing those low cloud bases topping Samaniego Ridge, even during the afternoon.  But other than an occasional, and very brief tower, they did not even make it to the height where ice forms and rain falls out.

Here’s the rest of our muggy, but dry day:

 

Drops away!

As a photographer, you like to develop a niche.  My niche, of course, if you follow this site, is gray matter overhead, an amorphous, gray balls.  Now yesterday was a great day for adding something to my collection since a Cumulus base, one that was clearly headed for better things than just being a Cumlus cloud, developed almost straight overhead, giving me a great chance for another “signature shot.”  See below.  I don’t know of any other photographer that specializes in this kind of shot; kind of sad, really.

Once again, you’ll have to click on the image to get a proper size, and hold your monitor over your head.  People seem to enjoy doing this.  Make sure your plugs and connections to the monitor are long enough to do this maneuver.  Sometimes I forget to tell people this, and then they get mad when an external hard drive falls on the floor when performing this maneuver and it won’t work anymore.  Sorry.

Of course, I monitored this base and kept shooting ( you never know which one will be the best) it, and then, there came the strands of the first drops out the bottom, that fabulous moment so few photographers catch because it is VERY subtle.  Next photo, if you can detect it!

OK, this is probably too hard for you to see much in the second shot, though I can see something.

How about a bit later, when its obvious?

Pretty cool, huh?

I was really hoping for those giant drops, but the initial shaft was just a hair to the east, and so while it rained HARD, the main load was dumped toward Sutherland Wash to the east.  But, we did get 0.16 inches here. See next photos

What were seeing in this emergence of a fall streak is the overhead transition from a Cumulus congestus to a Cumulonimbus calvus to Cb capillatus.  Eventually only the “hair”, that is, the fibrous ice cloud is left up there.  The whole bottom two thirds of the cloud has rained out.  Since there were so many Cumulus clouds that went through this transition yesterday, we were left with a huge amount of what would be called, probably should stretch your tongue before trying to say this so you don’t injure it, “Altostratus cumulonimbogenitus.”  Here’s the great sunset shot showing mostly that mass of ice cloud up there (underlit by the ray of sun).  Enjoy once again!

 

 

 

 


 

Everywhere but here

What a great cloud day yesterday was with thunder on the Catalina Mountains by 10 AM. It seemed so promising for a major rain here in Catalina. But no, shafts to the left, shafts to the right. In fact, we were “surrounded” on three sides by shafts at times, but only residuals of those shafts got here to produce a measly 0.04 inches!  Still, it was nice to see those cloudbursts out there drenching something.

Here are a few photos of yesterday’s clouds, beginning with a 9:44 AM morning shot, once SO FILLED WITH PORTENT.  I remember how happy I was!  Look, the bases of the Cumulus clouds are touching the top of Table Mountain!  Think how warm they must be, maybe 12 F (50 F)!  And we remember that the WARMER the cloud base, the more easily they rain!  Also note ice falling out of the right side of the top of this cloud in the first photo.  Imagine, at 9:44 AM, those towers were already able to ascend to the level where its cold enough for ice to form, and you know what that means, RAIN falls out! Yay!

Below, is an example of that assertion about rain and ice.  First, a cloud (cumulus congestus) whose top has already reached that level where ice forms–look how different it appears in that highest sprout in the middle of the photo, how smooth it looks compared to the crenellated, cauliflowery look in the turrets below.  But there is NO rain falling out yet.  That conversion to ice has just happened.  The much higher concentrations of cloud droplets are being replaced by much lower concentrations of ice particles, and that’s why you can visually detect this change in appearance.  The lower concentrations of ice make the cloud look a bit less detailed in top structure.

While that highest portion is already converting to ice, you still see no shaft. This is a great moment to impress your friends with some razzle dazzle conversational meteorology:  “Hey, guys, that cloud is gonna have a helluva shaft of rain in just a coupla minutes!”  It would be a magical moment for you.

How long will it be before you see a rain shaft?  Only about two minutes! And here, in that first shaft shown in the next photo two minutes later,  are where the largest rain drops and sometimes hail will be found. You don’t want to go over the speed limit, but under this type of cloud BEFORE the shaft is out the bottom is where you should be to see some real rain excitement, that is, rain bouncing about 6 inches off the pavement, but you’ll have to pull over, maybe some close lightning strikes, too.

Finally, a typical afternoon shot of the rain shafts around Catalina, in this instance, looking toward Twin Peaks.

Man, that was a fun day yesterday for cloud viewing!

The End.

Promising fizzle

 

If you looked outside to the south and upwind of Catalina later yesterday afternoon, after a disappointing day of Cumulus development over the Cat Mountains, you saw this behemoth of a top protrude out of a mass of cirriform clouds beyond Pusch Ridge.   Excitement begins.  Can it hold up long enough to reach us?  This complex of thunderstorms that trudged slowly toward us was around Green Valley at this time (4:29 PM).  It faded almost from the moment this photo was taken.  Go here to see the radar imagery of this from IPS Meteorstar.  Alas, all we got from it was sunset color by the time it got here 3 h later.   The colorful underlit bubbles of downward moving air are called “mammatus” if you care.

We continue to be on the edge of the main summer rain areas to the south, and so we will be lucky to get anything again today other than sunrise and sunset color today. “Dang”, as a friend would say.

 

Sprouts, and not much more

Here they are, reflecting the heat island of Mt. Lemmon yesterday, repeated narrow surges of heat and cloud sprouting upward, and only one reaching the level where ice formed, and a little snow fell out–second photo.  Go here to the U of A fubball-practicing Wildcats Atmospheric website to see the whole interesting sequences of pulses yesterday.

Note frizzy stuff at left and below residual cloud patch in the second photo.  That’s ice that formed because the top of the cloud reached temperatures well below freezing, and is a good example of the threshold level at which ice formed yesterday because there is only a small amount coming out of this cloud.   Had that top ascended another couple of thousand feet, it is likely that it would have been all frizzy and fibrous; completely ice.

The height at which cloud tops begin to form substantial ice tends to change day to day and much of that due to how warm the bottoms of the clouds are.  The warmer the bottoms of the clouds, the higher the temperature at which ice first forms in clouds!  The highest temperature at which ice has been observed to form in any cloud is around -4 C (25 F), and then only when the cloud has formed rain already by an all liquid process called coalescence where cloud droplets merge to form bigger droplets, and eventually those colliding-merging drops reach sizes where they qualify as drizzle or rain drops.    Here in Arizona, clouds occasionally form ice in clouds with tops  warmer than -10 C, but mostly they have to be below -10 C.  It happens, too, but it is rare that clouds here form rain by the collision-coalescence process.

It may seem odd that ice does not form in clouds when they get colder than 0 C (32 F), but rather at lower temperatures, sometimes much lower.  This is a mystery that is still being investigated to this day.

When did we find out the complexity of ice formation in clouds, to continue a bit of a lecture?

We really found this out in Project Whitetop, a large, sophisticated and randomized cloud seeding experiment in Missouri carried out in the early 1960s under the aegis of the University of Chicago.   When researchers went up in aircraft to examine clouds on not seeded days,  they they found that the Cumulus clouds already had some ice in them in cloud tops that had never been colder than -10 C.  This was quite a surprise since nobody really thought ice formed much in all clouds until the tops were at least around -20 C (-4 F).  This was because measurements on the ground of artificial clouds in cloud chambers chilled to -20 C were almost always ice free until that temperature.  Nature’s trick?

We had a hint of a nice sun pillar, faint vertical column, at sunset, here for something more accessible.

 

The End.