Cloud-maven – Page 80 – About real clouds, weather, cloud seeding and science autobio life stories by WMO consolation prize-winning meteorologist, Art Rangno

Tropical whoppers

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.

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.

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!

The End!

Five days of rain ahead; interpreting probability forecasts

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).

How to interpret precipitation probability forecasts

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:

Down and (traced) out

A quiet day most of the day with no sign of the explosive developments that were indicated to occur in the U of AZ models, causing some excitement in the Dept there. Not a shred of Cumulus clouds appeared on the Catalina Mountains until mid-afternoon. Then, fairly quickly things looked more promising for rain, as in shots 2, 3 and 4 showing a Cumulus turret that exploded upward. The instability of the day, indicated in the models, was finally being unleashed! The time lapse movie from the U of A is even more dramatic (here).

But this Cumulus congestus cloud quickly converted into a long, thin Cumulonimbus, and was not followed by others as hoped for. Only its glaciated head survived, drifting non-chalantly across Oro Valley. No rain made it off the Catalinas, either, as can happen with this type as the mid and upper portions dribble light showers away from the mountains.

So, nothing in the daytime…

But then during the early nighttime hours, things began to happen. By nightfall lightning was occurring to the NE, and a cell developed right over Catalina/Oracle Road about 8:30 PM. An extremely close lightning “pop and explode” strike hit here about 8:45 PM, but no rain was falling! Odd, since the radar indicated the edge of the thundercell was in my neighbor’s yard practically.

The cell drifted away toward the west, its intense rainshaft visible in the night light of Oro Valley. You can see from the rainlog.org site that some folks got blasted, one site in Rio Vistoso reporting 0.70 inches. The Pima ALERT data, showing amounts in the mountains, is here. Pig Spring, a little northeast of Charoleau Gap was the “winner” at 0.43 inches.

Sprinkly rain occurred a time or two overnight; in fact, its raining right now (R—, “R triple minus” for exceedingly light rain, 6:07 AM.) And check this cloud-radar 12 h loop from IPS Meteostar. You will see how the rain was all around us last night, though light, something the U of AZ model (WRF-GFS) had picked up on yesterday in forecasting an active night rain situation in SE AZ.

One factor that kept things at bay, and my Seattle friends won’t believe it, was the “cool air” yesterday, the high temperature only reaching 95-97 F here, about 10 degrees cooler than the previous day. Really, it felt quite comfortable I thought. That cool air really put the damper on convection, or, restrained the damper conditions than could have been.

Today?

Of course, these model breakdowns have to do with how accurate the initial conditions are. The U of AZ experts, in their late morning assessments of data that have arrived at 5 AM AST and later, or other local data from water vapor sounders, spend a lot of time seeing which of the two models they run on their Beowulf Cluster had the best starting conditions. They can then estimate what the differences might be in the model output imagery, and which model did the best job given the starting errors, always present to greater and lesser degrees.

Today, the model run from last night’s data have little rain in the Catalina area today, though storms approach from the Ne in the evening hours similar to yesterday. But the mods don’t think they survive the trip from the White Mountains and Rim to here, dying out about the time they reach the Catalinas.

As we have seen, this kind of close call can’t be taken too literally. So, the best forecast has to be generalized, in my opinion, to a chance of a thundershower in the mid-afternoon through the early nighttime hours. If you see Cumulus clouds piling up over the Catalinas by noon, the chances will be much greater for rain in the Catalina area today or early tonight (he sez).

Tomorrow is thought to be a wetter day here. Always, “tomorrow” it seems.

The End.

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…

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.

Lots of bluster, little rain except at Sutherland Heights where 0.39 inches fell last evening

Another day with hours of thunder, but with those high and cold cloud bases, not much rain reached the ground. Also hurting the rain situation, too much ice. An afternoon sprinkle, a very close, rogue lightning strike, followed by an early nighttime “chaser” storm that, with all of its bluster, wind and vivid lightning, produced only 0.02 inches here, but a lot more at Sutherland Heights, a robust 0.39 inches (new knowledge, gained after dip sticking gage up there at around 7:30 AM) To see how remarkable that Sutherland Heights rain amount is, go here to the U of AZ rainlog network.

Here’s a smaller, but typical example of yesterday’s generally “low output” Cumulonimbus clouds:

Here’s another quite bad cloud (shown below), though it was good one one hand, because it was an early afternoon, frequently thundering cloud which gave promise of rain later in the day. But that rainshaft? Pitiful.

It was also a forerunner of the kinds of storms we would have. Again, with high and cold bases (and oddly to me), there seemed to be an awful lot of lightning for the size of the Cumulonimbus cloud at 1:55 PM, much of it in vivid cloud to ground strokes. You may have seen a another example of that last evening around 9 PM on the Catalinas when there were a series of frequent and spectacular cloud-to- ground strokes, but little rain. The most that fell up there was 0.28 inches at Oracle Ridge. Map here. BTW, you can see the “1:55 PM”
Cb in the U of AZ time lapse movie at the far left beginning around 1:40 PM.

Well, how high were cloud bases? Rendered by the Cowboys, this 5 PM sounding for Tucson:

Reading this sounding, it makes bases appear to be around 16,000 feet Above Sea Level (subtract our elevation for above ground level) and a few degrees C below freezing. With bases that high and cold, the amount of water condensing at the bottom of the cloud is less than on days with bases, say, at 5 C and at 10,000 feet ASL.

So, less condensed water input means less rain coming out the bottom later.

If there is “too much ice” for the amount of water coming into the bottom of the cloud as we saw yesterday, its like a glass of water filled with ice cubes in which only a tablespoon of liquid water can be contained in it. The analogy is only somewhat representative since with “too many ice crystals” competing for the available water vapor, you end up with high concentrations of smaller crystals that hang in the sky rather than fall out.

So you get big anvils and debris clouds with little rain to the ground even in the peak stage of the storm.

Since the best rains in the shafts we see are due to melted graupel and hail, icy particles that generally start as an ice crystal at high elevations in the cloud, if there is little “supercooled” water there isn’t much graupel or hail, the type of precip that can make it to the ground from high bases (melting snowflakes wouldn’t from bases as high as we had yesterday because they’re essentially like Rice Krispies, there’s not much mass in them).

Well, this is pretty boring, so will end here with a sunset photo from last evening:

Today?

The U of AZ WRF-GFS rendering of rain in the State of AZ sees early afternoon Cumulonimbus clouds breaking out over the Cat Mountains today.

Why not?

Starting out with pretty similar sounding this morning, but a bit more moist than last evenings above 600 millibars (about 14,000 feet ASL).

Longer view?

Hector marches slowly toward the Southwest (Canadian model outputs), promising an enhancement of August’s meager rains so far in southern AZ.

The End.

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¹Reminded one of summers in Durango, Colorado, where high, cold cloud bases and “too much ice” is normal.

Massing bases, smiling faces

Yesterday’s surprise thunderstorm, rolling off the Catalinas, provided relief with 0.22 inches here. More rain tables/maps here and here. This sight in the first shot, showing it in the formation stage yesterday, was cause for joy:

Due to global warming-induced extra heat over the past few days here, as all extra heat must be automatically assigned (go here to a critical commentary on recent claims like mine above by a still-employed University of Washington Atmo Sci. prof.–wonder how long he’ll last?) combined with a break in the summer rains, our grasses, amaranth, pig weed and such were looking pretty stressed out; wilted, turning yellow due to global warming. One felt helpless to see the green of summer fading so fast due to global warming. (Want to make sure I am on the RIGHT side of this issue, you can’t be too careful these days about what you say in this domain; who might be watching.)

Then, after a near miss to the north yesterday around noon, an initially small thunderstorm that dumped on Saddlebrooke, moved off to the NW, multiplied, and became a real giant on the north side of the Tortolita Mountains, this new, large cloud base (at left) began forming over the Catalinas upwind of us. Time for hope.

Rain was already falling out of the downwind leaning upper portions of the cloud (arrow), shown in the second shot. You might recall that rain that falls out like this is not going to be what it could be, all that it could be.

Imagine dropping a cup of water out of that cloud where the bottom is (arrow), to drift away from the main discussion for a second. What will happen? Since the humidity must be less than 100 % all the way to the ground after it leaves the cloud, a lot of that water from that cup will evaporate. If you could capture the water that originally came out of that cup, it might be 10% of what came out.

How high was that “base” that’s not really a base but an overhang (above arrow in second shot)? Probably at the freezing level, or about 12,000 feet above us. So, if you’re storm chasing, and want to collect the most rain, avoid rain from overhangs!

The next shot shows where you want to be to get the most rain, and in a hurry. Those dark bases managed to hold together and keep reforming as rain fell on the Catalinas. A new strand of rain has overcome the updraft associated with new dark bases, and is beginning to fall out this side of Samaniego Ridge. An arrow has been added to point out this new rain streamer. It reaches near the ground beyond the dead yucca stalk in the foreground. This is where you want to be to collect the most rain, should you be trying to do so.

This time, pouring out a cup of water at the same height as in overhang rain, but inside the cloud, several thousand feet above the bottom, means that there will be no evaporation, and MORE IMPORTANTLY, the cup of water will grow in volume until near the very bottom because the falling drops will bump into and collect floating cloud drops that got in the way. So, if you could collect that water somehow, there would be more of it than what you dropped originally. So, those rain streamers, forming high in the cloud, are doing the same thing, pulling water out of the cloud on the way down, growing in amount.

This was a heartening sight since this new shaft, and the movement rate of the storm as a whole, meant that it would reach ME and Catalina in general) before it dissipated. As it turned out, probably another such shaft dropped right on top of us, judging by the low visibility in the intense rain. Air, rudely pushed out of the way by all that water, created winds to estimated 50-60 mph for a brief time, followed by an almost instantaneous reversal to 5-10 mph. That reversal was really something, as was as the lightning strike back behind me about 100 yards.

Today?

Expected to be dry. End of story. I really don’t enjoy talking much about dry air.

What about Hector-Ernesto, that schizophrenic tropical storm that has come all the way into the eastern Pacific from a birth place in the West Indies, home of calypso music, some weeks ago?

The Canadians think Hector-Ernesto is going to end up as a big rain producer southern Cal, with some rain enhancement here as well. The USA! models think its going to drift north and die before getting much past Baja, where it drifts off to the west. Due to a rain bias, I am only showing the Canadian model result with a tropical storm approaching San Diego and a huge crescent of rain over the Southwest, including over ME (oops, I mean us).

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.

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:

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.

Bulimic Cumulus clouds, filled with portent, disappoint

Why would such skinny, towering clouds be filled with thundery, gushing portent? Its really hard for a cloud to be tall and skinny. Why? Because too much dry air comes in as it rises, both from the tops and sides, and if that air is dry, it can’t go far without evaporating. Too, the drop in temperature with height has to be larger than normal for clouds like yesterday’s to shoot up to well beyond the level where ice can form (glaciate). But they did off and on all day. Mt. Lemmon functioned as a smokestack for Cumulus and even skinny Cumulonimbus, clouds all during the late morning and into late afternoon. There was some thunder here as ONE got big enough to rain that bit toward Charoleau Gap. So, you do get to record a TSTM (thunderstorm) in your log book. No rain fell here.

If you missed those bulimic clouds, here’s yesterday’s movie from the U of AZ. If you watch that time lapse, you will see some of the tallest turrets shooting up awfully fast; I thought they were rising about fast, at times, anyway, as any turrets I have seen in these movies, a marker for how rapidly the air cooled with height yesterday.

Also, here are a few shots of those skinny clouds from this angle here Catalinaland.

OK, quiting visual cloud displays here. You’ve seen enough disappointing clouds, ones that did not live up to their potential like so many of us.

You would have thought massive clusters of Cumulonimbus clouds were about to roll in, spawned over the Rincon Mountains or from the high terrain near Pie Town, NM, rolling westward to pummel the townlet of Catalina again. Some of our more gigantic area storms have been preceded by morning “long tall sallys” like these.

But no.

Looking at today:

The boys in the weather club, like Bob and Mike, were talkin’ good storms today based on their very great and decades-long experience. I, too, am riding the Bob-Mike wave.

Way out ahead; major rain joy, maybe…

I am more excited about the longer term view, one in which when it gets here, will remember what I said with enthusiasm now. Remember our logo, one just like the big TEEVEE stations have:

“RIght or wrong, you heard it here FIRST! Live!”

What “first”?

Tropical storm remnant has been probably unreliably, but hopefully, forecast to come into southern Arizona in 192 h or so. Could be worse; what if it was a forecast that was 360 h from now?

Here it is, courtesy of those folks at IPS Meteostar who have rendered the 00 Z (think Olympics Time Zone) time maps for us. Here’s the low, shown on the first map, on Baja coast. The next map shows that the ENTIRE remnant has moved into AZ! Could be great.

What gives this storm a better chance of getting here than some? The upper level steering is set up to draw tropical storms northward should they drift too far northwest, like a bug getting caught in a spider web; the spider then hauling the bug to its hiding place. Gee, I never thought I would write about spiders here, but there it is; it just kind of popped out.

But, you ask, how do we KNOW, have any CLUE, that the steering, as by an upper level trough, is going to be properly placed to draw tropical storms northward so that they get caught up like a bug in a spider web which after being caught in the web, the spider comes down and takes it back to its hiding place. I really liked that metaphor. We are like that place where the spider is hiding!

Of course, you say, we go to the NOAA spaghetti factory and try to discern how likely it is that a trough will be along the West Coast, positioned to draw storms up thisaway.

The last image is a spaghetti plot of trough contours using what be called, “the bad balloon” approach. Hard to imagine, but the starting points for the model is deliberately altered a bit just to see how wild a few of the contours get. The wilder they get, the less reliable a longer term forecast is.

20120809002012080800_NAM_GFS_SFC_SLP_THK_PRECIP_WINDS_192 — Valid for August 15 at 5 PM AST. Note all the green, denoting rain that fell in the preceeding 6 h.

NOAA “spaghetti plot” valid for the SAME time as the first map, 5 PM AST, August 15th. Shows that a trough along the West Coast is virtually assured. But the “devil”, the storm here, is in the details. While it is a necessary condition, it is not sufficient, since the flow might not exactly draw a tropical storm right to ME. Oops, “us.”

Tracey day

Two maybe three sprinkles occurred in the early afternoon between 1:30 and 2:40 PM for a total accumulation of “trace.” The first from our very own Catalina cloud street off Ms. Lemon. Here it is in mid-afternoon when it was was still right over us, but the clouds in it not tall enough, as earlier, to have something in them that causes precipitation to fall out. (What is it? Hint: Think of the Beatles’ anthem about something that is, “all you need¹.”)

Bubble Cu drifts away, later becoming a “quarter pounder”… Watch the sequence below.

So, what did we get out of this sequence?

Even small clouds, really modest ones at the start, can boil upward and produce a useful amount of rain, albeit in a short-lived life. Between the time it began to rain from this cloud and the end of it from this little cloud was barely more than six minutes, maybe ten. But don’t overlook them; they can still get you wet.

And with that happy ending, let me leave you with this happy ending to our day; yesterday’s sunset Cumulonimbus cloud, and the thought of more of them today! (The weather service says so…here.)

¹ice

Rainbow? Or, after THAT storm, was it the “‘Arc’ of the Convenant”?

What an amazing, Biblical sight¹ that came across the Catalina Mountains yesterday evening, that shaft of intense rain and attendant rainbow! After a day where it looked like rain might not happen here, those earlier Cumulus clouds being pretty lazy really, this behemoth powered across Tucson and the Catalina Mountains dropping 0.56 inches in momentarily blinding rain blown on 60-70 mph gusts, with numerous cloud-to-ground lightning strikes, taking down power lines, and causing a 6 h plus power outage in Catalina. 0.51 inches fell here in 10 minutes!

Oops, forgot to remind you: Don’t forget to go to the movies. Shows the backside of what hit us just as the day ends.

How great this rain will be, too, for our stressed desert-thornscrub vegetation after almost a week of dry conditions. (Only 0.17 inches at Sutherland Heights, though.)

For me, yesterday evening produced the most dramatic sights I’ve seen here in four years in Catalina. I hope you caught it, but if you didn’t, here are a few of the most dramatic ones. The first, penultimate shot was from the front porch about three minutes before bedlam hit Sutherland Heights. Below this, those shots leading up to it.

A repeat of yesterday today? Not bloody likely.

Oh, well, any rain will be great, but drier air is moving in. Check it out here from the University of Washington Huskies’ (some former of whom, if that is correct english which I doubt, are in the Olympics, for example, women’s volleyball, but not in beach volleyball which I seem to be watching a lot of) Weather Department here.

Note the drier air moving in from New Mexico and west Texas in this loop. Just the same, it can still rain here some because while drier, it’s not dessicated air and so the usual isolated Cb should be around. So, keep watching, keep cameras ready and charged.

The End.

^{————————————————————————————————————————————————————-1}Biblical allusion is to the “ARK of the Covenant” whose activity was demonstrated in a movie with Harrison Ford some years.