Lenticular clouds – Page 4

Going inside the curl, again and again

Its not about hairdressing. Its about the “curl of the low” and its jet stream configuration, as shown here by here (IPS MeteoStar):

Valid for Wednesday, March 20th, 2013. Want to see if anyone reads the captions.

Oh, shoot, this is for a storm and cold blast about 13 days from now! (Secretly, with the storm tomorrow so well predicted at this point by all—might as well show you that it might not be the end of March storms.)

OK, lets try again to get a more timely forecast map:

Oh fer Pete's Sake. This is valid for 256 h from last night, or the morning of March 18th! — Oh fer Pete’s Sake. This is valid for 256 h from last night, or the morning of March 18th! But we’re in the curl AGAIN!

Oh, shoot, this ones for 256 h or almost 11 days from last night! What is going on here?

One more try for something relevant, well. its all relevant (suggests we’re in the “trough bowl”:

Finally, valid for 11 AM AST tomorrow morning, this from last night's WRF-GFS run. — Finally, valid for 11 AM AST tomorrow morning, this from last night’s WRF-GFS run.

Maps look kinda similar don’t they? Hence, talk about the “bowl” phenomenon where troughs “remember” where they’ve been like your horse does, and they know where they should be. There’s a long fair weather gap between the one tomorrow and the ones later; don’t get fooled by thinking winter’s over.

This last one for tomorrow suggests the rain is either here or imminent at 11 AM AST as the jet core at 500 millibars, is already deployed to the southeast of us by that time. The timing of all of what happens tomorrow is pretty good for rain amounts since with the chilling air aloft (making it easier for air to rise from near the surface), the cold front will blast across Catalina in the later afternoon. This means that the little heating that we will get tomorrow, limited by windy conditions and clouds, will work to plump up the Cumulonimbus clouds in the frontal band–oh, yeah, there should be some, and that means what?

Graupel (soft hail)! Shafts of them, here and there in the frontal band. The presence of graupel, and it’ll be bashing snowflakes and ice crystals on the way down (the latter can’t get out of the way fast enough) means the clouds will get “plugged in”, electrified, due to those collisions because they generate electricity and lightning is virtually certain in AZ tomorrow. Talk about excitement! Cbs, graupel, lightning, a strong frontal passage, strong winds, and a greater than 100-200 percent chance of measurable rain in Catalina! It doesn’t get better than that!

This pattern also favors better accumulations of precip here with the winds being more southwesterly to west at cloud levels. Amounts? Mod, the very excellent U of AZ mod run indicates Catlania-ites will get around half an inch! I am so excited since this is close to the median amount (0.60 inches) forecast from this microphone two and more days ago! Something must be wrong! Here’s the AZ cumulative precip map for Arizona. Look at all the precip in the State, about an inch and a half of liquid expected on top of Ms. Mt. Lemmon! This is going to be so good for our drought.

Valid for 3 PM AST on the 9th. Most of this falls on the 8th, but passing showers add that bit more into the 9th.

Yesterday’s clouds

They were great, such as they were, and before leaving for NM and points east. Take a look:

6:56 AM. I wanted to hug these little Cirrus uncinus clouds. So cute, just trying like anything to make a little snowstorm to water the ground. Just look at those long tails!

7:47 AM. Then you got to see a Catalina lenticular cloud. How nice was that? Note parhelia on the right.

8:04 AM. A nice, patterned Altocumulus perlucidus translucidus.

All in all, I thought it was quite a good day for you. As usual, thinking about others here.

Today’s clouds

Today we’ll likely see some precursor Cirrus, maybe a flake of Cumulus here and there. I will predict more clouds, if necessary, as they occur.

The End.

Smoke attack

It was hard to see all the smoke around yesterday morning after the two previous stunning days with high visibility. I was thinking I had never seen so much smoke in Catalina as I saw yesterday morning. Here is some photos of that awful event:

7:56 AM. Heavy dark smoke layer evident to SW. Some Stratus clouds also were present.

8:40 AM. Normally, in my experience here, such smoke is husbanded to that region south of Pusch Ridge. But no, not yesterday, its HERE! What an awful view this was!

8:45 AM. In this photo not taken while driving, you can see that there are TWO plumes the lower one drifting south from the area of the Golder Ranch-Sutherland Wash development of expensive custom homes that might have been burning wood for heat, while aloft is another plume. I could not tell where that came from, even in this time lapse from the U of AZ. Note how the Stratus clouds in the morning change direction in movement. — 8:45 AM. In this photo not taken while driving¹, you can see that there are TWO plumes the lower one drifting south from the area of the Golder Ranch-Sutherland Wash development of expensive custom homes, some of which might have been burning wood for heat, or something else woody, while aloft is a second, separate plume. I could not tell where the higher one came from, even in this time lapse from the U of AZ. Note how in the movie the Stratus clouds in the morning change direction in movement. The movement at first is from the west-northwest (left to right), and those clouds contained the higher smog layer. So, could it have been from PHX??? ———– ¹Smokey the Bear reminds drivers that only you can prevent smoky, well, a lot of it anyway.

In the afternoon, the smog was gone, mixed through a greater depth, the layering destroyed by the convection, those rising currents and compensating downward ones, that cream any morning layering. The dilution effect, and it also could have been that the aerosol load (smog) decreased with time, made things look much more clear. To this eye, there was still a lot of smog present, just diluted in the space between the ground and the bases of these small Cumulus clouds shown below. Still, there were so many pretty scenes on this horseback ride with a friend that I took more than 100 photos! Some water was present in some of the little washes, always nice to encounter, and some vividly green spots of of emerging growth (shown last).

The final point worth mentioning for pedantic reasons, is that yesterday afternoon’s TUS sounding indicated the same cloud top temperatures as the day before, about -12 to -13 C. Yet, there was no ice dropping out of those clouds. The day before, with the SAME cloud top temperature, ice and virga were widespread.

What’s up with that?

Ah, the complexities of ice formation in clouds!

When clouds are small and have a lot of droplets per liter in them, likely hundreds of thousands yesterday, given all the smog around, the drops end up being especially small because so many form on some of the smog particles (called “cloud condensation nuclei”).

In repeated flights at the University of Washington, we found that the resistance to form ice is dependent on not just on temperature, once thought to be the sole controller of ice formation, but droplet sizes in clouds as well. Small droplets sizes in clouds meant they were less likely to form ice, given the SAME cloud top temperature. Altocumulus lenticularis clouds are the poster child for ice formation resistance in clouds with their tiny drops, often having to be colder than -30 C before ice forms. On the other hand, clouds in the pristine Arctic around Barrow in the summer time, over the oceans away from continents, and in deep, warm based clouds even polluted ones, form ice at temperatures higher than -10 C when the drops in the clouds are large and have reached precipitation sizes (more than 100 microns in diameter to millimeter sizes).

So, it seems likely that yesterday, our shallower, pollutted clouds had smaller droplets in them than those deeper, less polluted clouds of the prior day in which we saw so much ice form in the later afternoon with about the same cloud top temperatures as yesterday. It is also the case, that when clouds are in large patches as they were the day before, that ice formation has more time to take place, and that, too, may be a factor.

Complicated enough? Yep.

2:18 PM. In the Catalina Mountains on the way to Deer Camp trail. Cumulus humilis dot skies. No ice evident. — 2:52 PM. In the Catalina Mountains on the back from the Deer Camp trail. Cumulus humilis dot skies. No ice evident.

2:18 PM. Cumulus humilis sitting around over Sutherland Heights, and the Oro Valley

The weather ahead

After another round of cold, this one dry cold just ahead for us, the heat is on by early March, and along with that heat in most of the West in early March, likely record cold in portions of the East. Check this 500 mb map out for the afternoon of March 2nd, produced by last night’s WRF-GFS model run at 5 PM AST, rendered by IPS MeteoStar:

Look at the size of that cold trough and low center! Huge!

That isn’t the only weather news ahead, cold in the East, warm in the West in March. Our upcoming cold shock that hits on Sunday, is caused by an unusually powerful upper trough that dips down into Texas after it blows by us, then roars northeastward across the South on Monday and Tuesday. Expect to read about godawful tornadoes in the South on Monday and/or Tuesday.

The End.

Another big day; scattered amounts around us of more than THREE inches again; we only got 0.18 inches!

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:

SONY DSC — 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.

Yesterday’s drama, forecasting for picnics, etc.

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.

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.

The End.

Windy, windier, windiest

Pretty much like that title will be the scene for Catalina for the next three days, particularly during the afternoons as temperatures moderate slightly to more normal values in the mid-upper 90s today, while the series of “Tonopah low” pressure centers that will form in Nevada and then move away, are stronger and stronger. The strongest one one is expected to form on Friday. Of course, “as always”, there was a low over Tonopah, NV, earlier today; now its down around Blythe, with cooler air following behind it.

Check our NWS excitement here where you’ll see maps and warnings galore. Also, here, where you can see the 24 h temperature change, a good tool for where cold fronts have passed. At this point, the major invasion of cold air stays to the north. Its later on the weekend it barges down thisaway.

Here are the current satellite and surface pressure map, and the “jet stream” maps (for 500 mb), both from the U of WA. What’s pretty unusual in our domain at 500 mb is how “warm” it is south of the jet stream (where the contours are bunched the most) over central California and Arizona. Its only -5 C at Tucson right now, hardly below freezing, up around 20,000 feet! This suggests that the racing around and outside the jet core on the south side has been subsiding like mad, and in doing that, compressing and heating up.

So what you might say?

Well, thinking of others here, normally, gobs of precip break out in the central and southern Plains States when these big troughs settle into the SW and Great Basin, but this one, on the models for the next few days, hardly produces ANY precip! Its pretty upsetting, really, because this could have been a real soaker out there in those droughty regions; instead the rain is mainly in Montana, the Dakotas and Canada.

And the likely reason is that the air is too hot above all warm and humid air from the Gulf of Mexico that is racing northward in the southern Plains right now to allow deep convection except in isolated areas. So, as warm as the Gulf air is, there will be an inversion that just won’t break down as they often do when they are not so strong as this one will be.

Nice sunset yesterday due to some passing Cirrus spissatus. Today will likely see more examples of those, along with Altocumulus or Cirrocumulus lenticulars, probably more off to the north of us because I see some over there to the north now (6 AM AST).

Cooler now, but windy, ovenly conditions just ahead

Here is the temperature change from yesterday morning at this time to today at this time, courtesy of The Weather Channel and due to that dry cool front that went through yesterday. Its about 8 degrees cooler this morning here in Catalina compared to yesterday at this same time. Nice.

But, its back to above normal temperatures for a few days after this respite. Normal is around 90-92 F here in Catalina for this time of year, but a 100 F is just ahead I’m afraid. No rain seen in mods for the next 15 days, too. Feeling glum.

Yesterday’s clouds

Had some nice supercooled Altocumulus translucidus clouds yesterday after the Cirrus departed. Here’s a shot that was taken as an aircraft flew through a patch of it. Note fine contrail. These clouds, from the Tucson sounding at 5 AM AST, appear to have been at temperatures between -15 and -20 C, ripe for aircraft to produce icy canals or holes, and that’s what happened. Below is the rest of the sequence, taken from different locations. In the last shot, the tip of that icy contrail began to light up and I thought I might see some color due to refracting ice crystals, but it didn’t happen. These aircraft effects on supercooled clouds are receiving more attention in the scientific community, BTW.

For a time, too, we had our lenticular cloud friend downstream of the Catalina Mountains in its normal position.

Powerful, but dry system progged for later next week

Check this “four panel” out, bottom of blog, from the Canadians from their model run last night. Its valid for the afternoon of Thursday, May 24th at 5 PM AST.

My first thoughts: Egad! Holy Smokes!

Looks like low temperature records will be broken in the West and Pac Northwest as this comes through those areas. However, the thought of the ovenly air over the Southwest at this same time, being drawn into the western High Plains States was alarming. This is because it could get superhot over there as our hot air comes down out of the Rockies. Fortunately, the models don’t show the 120 F temperatures in the Plains my alarmist mind was generating.

What WE will get here in Catalina as this giant trough settles in the West for several days is a LOT of wind and dust in a lot of hot air before the cooler air arrives sometime after May 25th.

This period of wind and hot air will be awful for the fire situation. No rain is indicated with this giant low, too.

I dread these days because you’re thinking about how much is on the line as far as our forests go.

The End.

Clouds of yore, well, those on Thursday, April 26th

Kind of got distracted with chores after the big trip to NC and didn’t get to this until today… If you can remember as far back as April 26th, we had a “FROPA” (“frontal passage” in weatherspeak) that day. The U of A weather model indicated beforehand that the bases of the clouds last Thursday would lower to the tops of Samaniego Ridge.

Well they did, though it seemed in doubt for a time, and occurred a bit later than the model had predicted.

Also, a few drops came down here late in the morning; more precip was visible to the north of us and that was reflected in the NCAR precip estimate for Arizona the following morning, an estimate that suggested the heaviest rains were up to half an inch just 150 miles away.

Here are a few of last Thursday’s clouds with some commentary.

These clouds came in two separate segments, the first batch were at Altocumulus levels, some 12,000 feet above the ground according to the TUS balloon sounding that morning at 5 AM AST. Those were the clouds that produced the sprinkles around 5:30 AM. Poor snowflakes melting into drops had to fall such a long way!

After a brief clearing, a surge of lower Altocumulus and Stratocumulus came in. For a time, they looked awful threatening, and appreciable rain could be seen falling from them to the north. They produced a few sprinkles here in the late morning and early afternoon about the time the clouds had lowered (as predicted by the UA model, to the tops of Samaniego Ridge to the east).

Why didn’t they rain more?

The answer, as always here, is that the tops were much shallower, and therefore warmer, than those early Altocumulus clouds sporting considerable ice at times. You can be sure that those Stratocumulus clouds over us had tops warmer than -10 C (14 F), a general threshold for ice formation around these here parts. (Over the oceans, where the drops inside the clouds are larger, the threshold temperature for ice formation is higher.)

Just to the north of us, where rain was occurring, you can be sure that the tops sloped upward in that direction, becoming colder than -10 C.

That second batch of lower clouds looked dark and threatening, but lots of times with lower clouds its because they have higher concentrations of drops in them, not because they’re especially thick as you might guess at first. The droplet concentrations in those dark Stratocumulus might have been twice as high as in those early higher, Altocumulus clouds.

Drops in clouds with higher droplet concentrations, say due to smog, reflect more of the sun’s light off the top. That makes them darker on the bottom, and because they are then also harder to get precip out of, they last longer.

This is a real problem, BTW, for climate models, since longer lasting clouds reflect more light back into space and in that sense, and help counter the global warming expected from trace gases like CO2. But, would you rather have ugly clouds and smog infested skies and a cooler planet, or clean skies and clouds and a warmer planet?

The weather ahead

No rain in sight. But a big heat wave, probably temps around 100 F now looming toward mid-may. May is our driest month, BTW, averaging only a quarter of an inch.

The lenticular that came for breakfast and stayed for dinner

Some of you already know that there is a favored position for a lenticular cloud downwind from the Santa Catalina Mountains. Yesterday, a little fluff of Altocumulus lenticularis kept reappearing all day! It didn’t have the “classic” look of a lenticularis early on, but that’s what it was, hovering over the same spot, changing size some, disappearing then reforming over the same spot. That rough bottom early on suggests turbulence. You don’t want to fly there. Often, flying IN lenticular clouds is, as the smoothness suggests, completely lacking in turbulence. Its when you come out the downwind end of those clouds that you can experience some nauseating bumps.

Why was the lenticular cloud there all day?

Because there is a standing wave, or hump in the airflow downstream of the mountain that raises a moist layer to its saturation level where a cloud must appear, and not much changed in wind direction and moisture all day up there. The morning and evening sounding for Tucson were almost the same. Also, while that lenticular cloud was nearly always there, it was often “buried”; obscured inside that sometimes thick layer of Altostratus with its virga that moved in during the afternoon hours.

Some photos. (BTW, since I started adding captions, WYSIWYG has gone bonkers in the Word Press edit page. So excuse the strange organization and text in odd places–still learning here.)

Below, photos of some of the other clouds of yesterday. I have to say if there was a disappointment, it was that there wasn’t as much Altocumulus as I thought, and virga trails were not as long as I expected, either. They were barely hanging down from that Altostratus layer, an indicating of smallish snowflakes in the Altostratus layer as well as very dry air below it.

DSCN1173 — "Altostratus over horse arena".

Lastly, a sunset shot, indicating the back edge of these high and middle cloud layers was over the horizon to the west.

Cloudy with snow above 15,000 feet

On deck, this cloud stream for today, as presented by the University of Washington Huskies Weather Department. As you will see, the whole stream rotating around that low off southern California has been thickening up overnight, a process that will continue, and so it looks like it will be a frequently gray day with Altocumulus, Altostratus, and Cirrus of various types piled on top of each at times. Don’t look for much direct sunlight today. Virga (snow), too, but no rain beyond the slight chance of a sprinkle. Most of the clouds you see will be composed of ice crystals and snowflakes. Also, with the wind picking up aloft today, lenticular clouds are likely again. Look to the NE of Mt. Lem.

Don’t miss a nice sunrise shot this morning.

Yesterday’s clouds

Below, after you have read all the captions, yesterday afternoon’s sounding from our friends in cowboy-on-a-bucking-horse-license-plate-land which, BTW, I think is a pretty cool looking license plate since I’ve been bucked off horses myself a few times and when I see that license plate can say, quite haughtily, “been there; done that”, and tip my hat to the driver. In fact, the horse I was bucked off most recently kicked about as big as the one rendered on that WY license plate, and while I ended up in the hospital with a big bill, HELL it was worth it when you can say things like this and show that you are truly embedded in western culture, which I love after leaving the Temperate Rain Forest-Starbuck’s culture of Seattle:

What do you see in this sounding?

The pinching together of the two heavy lines (temperature to the right, dewpoint to the left) tells you the height of the moist layer in which these clouds formed.

How high was that, you ask, or not?

The “300” line (refers to millibars of pressure) is about 30,000 feet above sea level (27,000 feet above Catalina) and the top of the moist layer, about at the “200” line, is 40,000 feet above sea level, 37,000 feet above Catalina.
So, they were damn high yesterday, running between 27,000 and 37,000 feet above the ground. The bottom temperatures were about -35 C (-31 F), and the top about -63 C. What’s interesting is that lenticular cloud was almost certainly comprised of liquid water drops on its upwind edge before glaciating (turning completely to ice a short distance downstream from that upwind edge.) One of the mysteries of ice formation in clouds is that Cirrus clouds don’t generally form until the conditions for a droplet cloud have been met. This means that when ice is present, it is in a highly supersaturated environment with respect to ice and in spite of the very low temperatures, the crystals can grow and fall out producing trails or fallstreaks as you could see in the Cirrus uncinus clouds.

Rain today, clouds yesterday

Yep, that’s right, rain IS imminent! In case you forgot what they looked like, there’ll be a display of “hydrometeors” before 7 AM here in Catalina. Should last the whole morning at least. If you don’t believe me and think I just made this up, go here.

BTW, “hydrometeors”; what real meteorologists, well, maybe pretentious ones, call rain drops; remember, we’re METEORologists, we like to see things falling out of the sky.

Not raining now at 4:38 AM, but its on the radar here for the Catalina area from a great weather provider, Weather Underground. Amounts here likely to be around an inch in the next 48 hours. Still looking for a drop in temperature enough to bring our current (5: 1o AM) mid-fifties temperatures into the upper 30s in the rain as the cold front goes by, maybe tomorrow morning as well as a second little pulse of clouds and precip keeps things going for a second day. That temperature drop should lead to a little snow in the heavier periods of rain.

Second pulse?

Racing from the north central Pacific is a little blob of clouds down the “backside” of our humongus trough. Here, from the University of Washington Huskies, still playing basketball in the NIT tournament, is a 500 millibar map. The blob of clouds that will extend our rainy spell is located, on this map, a few hundred miles west of San Francisco. It is CRITICAL to us to get that second day of showers after the current front goes by with its strong rainband today.

The green lines on this map are contours along which the wind blows. Here you can see a HUGE fetch from the north central Pacific to Oracle Road, Catalina. To demonstrate this more clearly, click on the map below to get the full version, and place a finger on one of the green lines in the north central Pacific, say, just south of the Aleutians. You might want to pick the one labeled, “5580”. Then with your finger on that line, follow it southeastward (“down” toward the lower right), maintaining contact with the montior screen, until you exit the right hand side of the map. I hope you haven’t had a peanut butter and jelly sandwich before doing this.

If this map pattern was stationary, that’s where the wind would go, forever, “down” and then “up”. Where your finger reached the point farthest to the south on this map, and where the wind makes a sharp turn around San Diego, is what we call a “trough”. And, if you were to see a map at a LEVEL in the atmosphere, there would be a long extension of lower pressure from the Pacific Northwest to San Diego at the time of this map. But no, we meteorologists complicate things by using constant pressure surfaces which go up and down in height all over the map instead of constant level surfaces instead of an easy to understand constant level map with highs and lows on it. Oh, well.

This “second pulse” of clouds and precip is moving so fast, it will get to the “bottom” (south end where the wind curves to the north) of the trough before it has a chance to exit Arizona. That will add a whole second day of showers and rain with a very low freezing level tomorrow. Its a bit rare to see something like that catch up so fast to the main trough and, in a sense, delay its passage.

Yesterday’s clouds

Okay, you had yer flying saucer clouds here and there during the day, that is, in proper cloudspeak, Cirrocumulus (Cc) lenticularis (first photo), Altocumulus lenticularis (second photo, is lower, has shading, compared to Cc–that short flat cloud below the Altostratus layer), you had yer Altostratus band (3), followed by yer clear slot, beginning at 4 PM -hope you planned a picnic around it, or trip to the beach (4), then quickly followed by heavy, dense Altostratus layer, (see second shot with saucer cloud).

No sunset color due to the solid cloud banks to the west. Should be enough breaks in “post frontal” low clouds for sunset color today, however.