Category Archives: Lightning

Lots of thunder and bluster but only a trace in Catalina

Heard thunder for about 12 h it seemed yesterday, but little came of it.  Even the rainshafts looked anemic for the most part for the second day in a row.

Current 24 h rainfall totals from the Pima County ALERT gages here.  U of AZ network here.  “Coco” for Pima, here.

Got hopeful after a disappointing afternoon when an evening shelf of Stratocumulus with buildups spread westward from the northeast, shown in the first photo.  Rain shafts began to appear in the upwind direction as the sun set with occasional cloud to ground lightning strokes, ones that continued until after dark.  Those showers grew and then were almost dead by the time they passed over Catalina.  So another disappointment.  Seems you end up saying that a lot when you’re living in a desert and wanting some rain…

6:58 PM. Looking north
6:59 PM. Looking NE.
7:33 PM. OCNL LTGCG NE (weather texting example for “occasional lightning cloud-to- ground northeast”).
4:48 PM. Got hopeful here, too, looking at this dramatic sky toward Charoleau Gap.  But no;  instead it went down the Catalinas, didn’t spread southwestward.
5:27 PM. This is the same complex, now moving away into TUS.  Dumped nearly an inch on the wealthy Catalina Foothills district where they probably don’t even need it because they can afford so much irrigation.  It had missed us completely. I included this one with lightning because sometimes it seems like you are a people that enjoys fireworks more than a lecture about how graupel forms.

 

 

 

 

 

 

 

Canadian prediction mellowing.

That Enviro Can model isn’t going to win a Gold Medal, another clever play on the Olympic Games now underway in London, with its forecast track for Hector-Ernesto.  In our last episode, the Enviro Can mod had H-E drifting northward in a timely manner, and it had been that way in model run after run, so that portions of its remnant produced significant rains in southern Arizona.

The medalist in the H-E track forecast?  The USA! WRF-GFS model.  It had tropical storm Hector-Ernesto staying far away until it was dead, drifting glacially northward off Baja until it disappeared (as it is shown to do today) with only modest effects here.   That USA forecast was better forecast all along.

We just did not get that upper level trough along and off the West Coast, required to steer H-E rapidly northward before it faded over the cool waters off Baja.

The good news is that there is no real droughty days ahead either, which means a steady diet of scattered thunderblusters for another week or so, and if we can get the cloud bases down from 14,000 feet above seas level to 8000-9000 feet (at the top of Ms. Lemmon), we could be back in the 1-2 inch rains in those scattered intense rainshafts.  This morning’s sounding from TUS suggests they will be a couple of thousand feet lower than yesterday!  Yay!

Here is the hour by hour forecast from our weather friends at the U of AZ and their local model run from last night’s data.

A quite active day is forecast for us today, beginning in the early afternoon rather than mid to late afternoon as has been the case.  The first shower/Cumulonimbus cloud is forecast to form today on the Cat Mountains is by 1 PM, hours earlier than prior days.  That would go along with the 5 AM sounding just in which has is more moist than previous days.   Note that last night’s model run would not have had this new data.

So, chance of a hard rain in the afternoon if we’re lucky.  But what could be really nice is that rain (in the model) continues here off and on overnight at a moderate rate, pretty unusual.

Fingers crossed that the “initial conditions”, the starting point for lat night’s run, are accurate, one of the biggest bugaboos in our models.

The End.

Royally “plugged in”, big and small

Yesterday’s higher based Cumulonimbus clouds were hyper-electrified for some reason.  Their bases were running about 11-12 kft above the ground over Catalina at 5 C (41 F).   Here’s are two examples of the tiniest thunderstorms I have ever seen (and I seen a lot of ’em, having chased them in the southern Cal deserts in the late 1950s and early 1960s, and for a few days here in the summers of 1964 and 1965. (Egad, you’re thinking; me, too.)

Here are those “tiniest thunderstorms” in the first two shots.

3:13 PM. Thunder in progress, slight rain shaft to the ground.
3:41 PM. Thunder from this seeming marshmallow (two rumbles I think there were).  Glaciated tip top of this guy, center.

At this point in mid-afternoon, even though the temperature was a baking 104-105 F here in Catalina, hot enough to send plumes of warm air into the ionosphere you would think, the cloud situation for rain was not looking so great upwind toward the northeast.

But those big rollers came, didn’t they!

What these little thunderstorms were telling us about the big boys that grumbled in from the NE eventually, and the ones that developed near us later, was that they were going to throw a lot of electricity at us.

They did not disappoint, though we only received 0.04 inches here in Catalina at this site.

The frequency of cloud to ground strikes was incredible, I think the most frequent I have seen.  Here are some shots, in case you were inside watching TEEVEE and Olympics’ beach volley ball from London, which is somewhat understandable:

5:08 PM. Here they come, puffin’ up, shootin’ sparks, like drunken cowboys in some western movie!
5:25 PM. Looking towards Charoleau Gap.

 

 

 

 

 

 

 

6:02 PM. Looking toward Saddlebrooke. Got an inch of rain from this just northeast of SaddleB.
6:34 PM. Strike across the Oro.

Some rainfall tables for you to peruse for yesterday:

Pima County Alert gages: http://159.233.69.3/temp/pptreport.txt

U of AZ rain network rainlog.org

Cocorahs” for Pima County, another, but national rain collecting network

Why were our Cumulonimbus clouds so hyper-electrified?

The simple answer is, I don’t know.

We know that electrification is related to updraft speeds in clouds and separation of hail/graupel (soft hail) and smaller ice crystals like dendrites, which leads to separation and build up of charge centers in clouds because, after bumping into one another, they collect in differents areas of the clouds.  They build up charge and spark to one another, and to the ground.  I am really oversimplifying this, but that appears to be the main source of cloud electrification, and why stratiform (“flat”) raining clouds and clouds that produce rain without ice, do not spark.

There was nothing in the lapse rate from the TUS sounding yesterday afternoon to suggest higher updraft speeds would develop that I could see.  Was it the extreme heat that drove this occurrence?  Also, crystal type in the clouds may have something to do with it.

Idle speculation:  It has seemed to this observer, that the warmest based Cumulonimbus clouds have not been highly electrified here, at least, not like the ones yesterday.  Warmer bases lead to different collections of ice crystals in the clouds, such as huge concentrations of columnar types (rods) called needles and sheaths (hollow columns).  At lower cloud base temperatures, these do not occur except at very great heights, and very low temperatures, not in the middle of the cloud as needles and sheaths might.

The weather ahead…

Today:  I could not find a single model that had rain here in Catalina today.  It’s supposed to dry out due to dry air invading from the east.  You can see that here in this water vapor loop from the U of WA Huskies.  That dark area in New Mexico and extending into the central Plains is how the imagery represents dry air as seen by a satellite.  You can see that while we are moist air right now, i.e., dewpoints are high, we have mid-level Altocumulus castellanus around, distant Cumulonimbus clouds to the WSW as I write, this moisture over us will thin.  Still, I have to think we’ll see something in the way of a Cb off somewhere, probably not here, though.

Tomorrow:  About the same as today, the mods say.  Darn.

The End.

 

68 F dewpoint in Catalina now; 0.31 inches overnight

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.

You can get the regional values of rain here from the Pima County Alert gage network and also here from the U of A’s rain measuring network.   Three Alert locations had over an inch, and many more in the U of A network!  What a great start to the summer rain season!

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 PM
3:44 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).

Whence graupel?

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

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

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

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

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

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

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

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

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

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

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

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

The End I think.