Definitions – Page 42

Stagflation

Meteorologists have called stagnant pressure conditions with inflated temperatures “stagflation” for as long as I can remember, which is not that long. Anyway, that’s what we have before us, pretty much the same old thing, day after day, except for some really nice Cirrus patterns in the sky to go with those 100-110 F temperatures we get this time of year. You can see the upper level moisture stream coming over us here, from the Huskies, if you’re interested.

Mind-starting to drift off center now….

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Weather extreme note

If you noted the record-tying “trace” of rain at Vegas back on the 25th and were pretty happy about it, well, you’re going to be put out by this NWS message, passed along by climate guru and mischief maker, Mark Albright, just yesterday. Apparently, the NWS has been concerned over this record tying event for some time:

“RECORD EVENT REPORT…CORRECTED
NATIONAL WEATHER SERVICE LAS VEGAS, NV
1059 PM PDT THU MAY 29 2014
…NO RECORD DAILY MAXIMUM PRECIPITATION WAS TIED AT LAS VEGAS
SUNDAY...
DUE TO AN EQUIPMENT ISSUE WITH THE PRESENT WEATHER SENSOR AT THE
MCCARRAN INTERNATIONAL AIRPORT ASOS, A FALSE REPORT OF A TRACE OF
PRECIPITATION WAS REPORTED ON SUNDAY, MAY 25TH. AFTER FURTHER
INVESTIGATION, THIS WAS DETERMINED TO BE INCORRECT. THEREFORE THE
FINAL PRECIPITATION TOTAL FOR SUNDAY, MAY 25TH, IS 0.00 INCH AND THE
DAILY PRECIPITATION RECORD WAS NOT TIED.
THE ABOVE INFORMATION IS PRELIMINARY AND IS SUBJECT TO A FINAL
REVIEW BEFORE BEING CERTIFIED BY THE NATIONAL CLIMATIC DATA CENTER.
$$”

Hope I didn’t spoil your morning.

On the other hand, you wonder what the NWS meant, “after further investigation…”? What might they have done to remove an extreme weather event, one that tied a record?

Let’s “jump in” and see what we can find out about this record-tying mystery. First, let’s pull up radar-derived precip maps for May 25th and May 26th and see if there is any chance it rained on the 25th. We have to do two maps since the end time of each radar precip map is for the 24 h period ending at 5 AM, whilst the record is for midnight to midnight of the 25th. Below, from WSI Intellicast are those two 5 AM AST maps in chronological order:

:

We can see that it DID rain in the 24 h ending at 5 AM AST on the 25th at McCarran Field, LAS, but not AFTER 5 AM ending on the 26th (map on the right.

But when did the weather observing machine think it rained?

By pulling up the hourly observations in text form below, we can see that the machine thought that rain began at 1519 Central Universal Time (8:19 AM AST) and rained for 11 minutes, ending at 1530 CUT. “RAB” means “rain began, truncated to minutes after the hour).

25 1456 SA KLAS >120 SCT   10        1011.1 77 45   0    0          29.92         1 10   0    0             AO2
25 1556 SA KLAS >120 CLR   10        1011.3 79 44 160    4        29.93                T                    AO2 RAB19E30
25 1656 SA KLAS >120 SCT   10        1011.0 82 43        3           29.92                0                       AO2
25 1756 SA KLAS >120 SCT   10        1010.6 84 42        5           29.91 85 70 8 04   0    T          AO2

Looking further, we can also see the text words “SCT” and “CLR” for the time periods in which rain was reported. Furthermore, the the “numbol”, “>120” , means no clouds below 12, 000 feet above ground level.

Can it rain to the ground from clouds higher than 12,000 feet above the ground? Its fairly rare, but it happens, as we Arizona sunbirds know from just the past couple of days when sprinkles fell from such clouds.

However, investigating even farther, we find that the machine is also indicating “CLR” or “SCT” conditions, meaning CLEAR or SCATTERED clouds above 12,000 feet.

Can it rain from CLEAR skies, too few clouds for the sensor to detect overhead? Or SCT skies? It has happened that the machine reports SCT conditions on a RARE occasion when a little Cumulonimbus is passing overhead. I think it was reported from Douglas last summer; thunder, too. Very odd, but not impossible.

But what we don’t see is any “VCRA” report, that is, the coding for “rain in the vicinity” that would be inserted next to the column of “10s” above if there had been any as detected by radar.

So, after a few hours of investigation, we have absolved the NWS of having improperly removed an extreme weather event: the trace of rain was, in FACT, erroneously reported from the McCarran Field weather observing machine.

(Actually the point of this rather tortured writeup is to expose you to a little of our weather reporting language called, METAR. You can read about it here pretty good. You can get those METAR reports from many places, here’s one.

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A hodge-podge of cloud scenes from the recent trace of rain rainy day

(Counted over 100 drops on a wide area of pavement during the many, many sprinkle episodes two days ago; each one, I noticed, dried up in about two seconds, too.)

The End.

‘Manda rain

BTT you read this, rain oughta be falling or near by as the remnants of ‘Manda hurricane dribble into Arizona today. Looks like there’s just enough rain upstream right now (4 AM) to produce, hold your breath, a MEASURABLE amount here in Catalina! Likely will be just a few hundredths, though, as much as two tenths is about the top potential from this. At this point, anything measurable is a fabulous rain!

Mods have been oscillating on whether it would rain here for many days, but last night’s run ended pleasantly with a “correct” forecast of measurable rain. See green pixelation over Catalina below:

Valid for 11 AM AST today. Heart of rainband over us then, mod says. — Valid for 11 AM AST today.
Heart of rainband over us then, mod says. From IPS MeteoStar.

Your Catalina cloud day

(Also, another great cloud movie from the U of AZ here....)

5:15 AM. Cirrus, leaning toward “spissatus”, heavy dense patchy Cirrus.

7:42 AM. Cirrus fibratus/uncinus. “Cirrus” will do it.

4:35 PM. What would a day be like without Altostratus? Here, “translucidus” because the sun’s position is visible. When the sun can’t be seen, its “opacus”, like a lot of science can be.

5:27 PM. Walkin’ doggie and this seemed like a nice shot of the rustic neighborhood streets, the Catalinas, and up top, some glaciating Altocumulus, castellanus on the right side; hasn’t gone through the ice forming stage yet, or the ice hasn’t fallen out that’s in it.

7:18 PM, Crepuscular rays show up as the sun sets due to smoke and haze under the clouds. The clouds? A mix of flakes of Altocumulus and Altostratus (the solid blob), some Cirrus on top of it all.

The weather way ahead…

Not a lot showing up here for mid-June, so won't say anything about that. — Valid for June 12, 5 PM AST. Not a lot showing up here for mid-June weather, so won’t say anything about that. I suspect it will be warm, though.

Moon over the Tortolitas

7:09 PM. No visible sunspots on the “moon” either. Did you know that a long absence of sunspots, such as in the Maunder Minimum, was coincident with cold weather, such as that during the Little Ice Age, (though only a part of it)? A widely accepted causal relationship between sunspot activity and climate has not been established and findings of such relationships are usually considered controversial.

Remains of Amanda (Cat 4 hurricane) to bring rain to Catalina…maybe

The tropical fetch coming to Catalina (shown here yesterday) is from the remains of now strong hurricane Amanda, unusually strong for May for that matter, a month in which tropical storms in the Mexican Pacific are pretty rare, let alone have a Category 4 hurricane down there. Has sustained winds of 140 mph now, BTW.

When pointing out the tropical finches yesterday, was not aware that the low down there was, in fact, a hurricane. (Maybe I shouldn’t point things like that out, causing the one reader to lose confidence…. Too late now.) Check out this loop from the U of WA for the “pinhole” signature of strong hurricanes. Really happy to report that rain is on the way as May closes out (29th-31st are best chances for rain here).

Reprising yesterday’s cloud day…

1) Your day began with sprinkles from a cloud deck based at around 12, 000 feet above ground level (remember, too, that you can skip the “added value”, incremental approach below by just going to your great U of AZ time lapse movie. I thought it was really very pretty for yesterday):

5:32 AM. RW-- — 5:32 AM. RW– (very light rainshowers) were falling from what could be called a Altocumulus opacus deck with scattered taller turrets embedded in it, ones that produced the sprinkles.

2) clearing from the north:

6:24 AM. The shallow nature of most of the Ac deck is apparent as the backedge moves toward Catalina.

3) once the clearing arrived, small Cumulus began developing on the Cat Mountains and “?”:

9:36 AM. I have no idea. Move along now to the next photo.

4) nice small Cumulus all around, sometimes filling in to make it seem like a Seattle day in spring, with patches of Cirrus on top:

10:16 AM. Cumulus humilis and Cirrus. — 10:16 AM. Cumulus humilis and fractus (those shreds) and that beautiful Cirrus seemingly spreading its icy arms out (spreading likely due to perspective).

5) Was there artwork in the sky? You bet. A niche developed here I immodestly remind you, is that of cloud bottom photography, something I enjoy, and I think you do, too. Below is one of the best ones of the day from the Cloud Bottoms Collection:

10:16 AM. Cloud bottom of Cumulus humilis, maybe mediocris even, that was over ME. — 10:16 AM. Bottom of Cumulus humilis, maybe mediocris even, that was over ME. You look up, wondering, how deep is it? Will it form ice and rain on ME? Maybe graupel will fall out….since those are the first particles out the bottom of a growing Cumulus that is transitioning to a Cumulonimbus… So much to think about when a bottom is over you. Yours for $1,800, if you call now.

6) Late morning fill in:

11:23 AM. Cumulus and Stratocumulus dominated the sky for a time; looked threatening, but no frizzy ice seen around the edges, so as dark as they looked, no ice, no precip. — 11:23 AM. Cumulus and Stratocumulus dominated the sky for a time; looked threatening, but no frizzy ice seen around the edges. No ice; no precip or virga. Pretty, though, with those shadows and sun breaks on the Cat Mountains

7) Smoky sunset (not a western singer, though it would be a good name for one):

7:06 PM. Drifted down from the north. Likely hours old, judging by the striations in it (not well mixed out and homogeneous as would be smoke that’s days old). Could not find source in satellite imagery right off. I see that some of that layer is still visible to the SW this morning.

The End.

6) Wildfire smoke drifts down in a thin layer from the N to spoil our sunset. Note the reddish orange sun, a good sign of smoke and smog particles, tiny ones (typically, if you really want to know, that are 0.01 to 0.1 microns in size) that eviscerate the shorter wavelengths of sunlight so that only the reddish ones get through.

Tropical fetches

Flash: Very light rain (R–) falling at 5:30 AM! Amazing… Won’t measure though, as thickest clouds are already sliding away. But still, great to see, to smell the scent of rain in the desert, and feel the drops in this little surprise sprinkle!

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Forgetting about that last big bust, namely the last big trough of the season that let us down by producing no measurable rain, let us now consider tropical finches, or rather, FETCHES, since an example is coming soon, one that might well bring rain. (I know what you’re thinking; you’ve heard that before, wrongly, I might add as in the LBT-LBB). Hope springs eternal I guess, though rain is predicted by both the USA and Canadian models, so there is some mathematical backing to this hope. See below, as rendered by IPS MeteoStar:

Green pixelation approaches Tucson-Catalina urban complex. — Green pixelation approaches Tucson-Catalina urban complex on Friday, May 29th at 5 PM,

Yesterday’s clouds

You can see them all at once from the great U of AZ Weather Department time lapse video for yesterday here in case still shots with captions aren’t enough action for you.

5:59 AM. Virga falls from Altocumulus opacus. This can also be seen as like a little slice of the tops of many rainy days when cloud tops aren't below about -30 C or so. As here, those tops are usually still comprised of mostly liquid droplet clouds in which ice crystals form, grow, and fallout. If the air is not rising to replenish the doplet clouds, then you will be left with a patch of ice and virga, a patch that will eventually die. — 5:59 AM. Virga falls from Altocumulus opacus. This can also be seen as like a little slice of the tops of many rainy days when cloud tops aren’t below about -30 C or so. As here, those tops are usually still comprised of mostly liquid droplet clouds in which ice crystals form, grow, and fallout. If the air is not rising to replenish the doplet clouds, then you will be left with a patch of ice and virga, a patch that will eventually die. Estimated top temperatures, -12 to -15 C, a little colder than shown on the TUS sounding for yesterday near this time because we are farther into the cold air aloft than TUS is. Also, it would be unlikely that clouds like these would produce ice at the indicated TUS balloon sounding top of Altocumulus at -11 C. With their geerally small droplets, it needs to be colder than that. Egad! This is way too much info! But what kind of ice crystals would you expect in a water-saturated enviroment at around -13 to -15 C? Yes, that’s right, pretty Christmas tree stellar crystals, maybe some aggregates of dendrites. Remember, too, for aggregattes to form that concentrations of the crystals must be more than about 1 per liter. Too, since they are falling through a droplet cloud with droplets larger than 10 microns in diameter, you would expect those stellar crystals and aggregates of dendrites to exhibit some riming, that is, have impacted some of the cloud drops as they grew and fell through the cloud, though keeping in mind that the crystals must attain a diameter of about 200-300 microns in diameter before riming commences, helped by the fact that stellar crystals (planar ones) fall face down like a clown does when he’s trying to make people laugh and trips over something. Also, I think someone in that big house on the right is about to have a baby.

9:40 AM. With all the cool air over us, it wasn't long before Cumulonimbus clouds began boiling upward, giving someone some rain. — 9:40 AM. With all the cool air over us, it wasn’t long before Cumulonimbus clouds began boiling upward, giving someone some rain.

9:53 AM. While Cu boiled up quickly on the Catalina Moutains, and iced-out a plenty, they never really got the depth required to produce much more than sprinkles and virga. Can you spot the little bit of ice on the right side of this Cumulus mediocris?

10:30 AM. Nice example of the tremendous amount of ice being produced by such modest clouds (see right side here--nothin' but ice). — 10:30 AM. Nice example of the tremendous amount of ice being produced by such modest clouds (see right side here–nothin’ but ice).

1:01 PM. By early afternoon it was all over, the clouds too shallow, the tops too warm to produce ice even though they were still well below freezing. Just the way it is. Guess warmer than -10 C (14 F) at cloud top when you see a sky like this with no ice.

6:47 PM. Sunset so-so as high clouds to the NW blocked the sun so it didn't under light these clouds. Here, Cu flatten as the heat of the day, such as it was at 85 F, cold for late May, dies away, — 6:47 PM. Sunset so-so as high clouds to the NW blocked the sun so it didn’t under light these clouds. Here, Cu flatten as the heat of the day, such as it was at 85 F, cold for late May, dies away,

The End.

As close as it got

Like you, my heart started pounding when that bank of thick clouds on the horizon got close enough to see that there was a rainshaft to the ground with a minor Cumulonimbus on top of it (ignoring the fact that you could’ve been hanging out by the radar all day).

6:47 PM. Cumulonimbus with rainshaft to the ground slowly approached near sunset yesterday. Big dust plume also visible to the right of the shaft a little later.

Today, the heart of the cold air and best moisture are over us and TODAY we will get those local icing-out Cu and small Cbs with sprinkles here and there. Measurable? Not so sure. Will be lucky. LTG in the area likely today, too.

If you’re a low temperature anomaly centric person at this time of the year (in texting, “LTACP”, or just “LTAC” for short), you will likely enjoy today’s 10 degrees or so below normal afternoon maximum, chillier even with outflows from virga and the scattered light showers around.

More later, photos, too… Behind on animal chores now.

Yesterday’s clouds

I thought it was a pretty nice day for you, though a little disappointing due to the late arrival of the minor rain threat mentioned above. You had quite an array of clouds to discuss in your cloud diary, which was good.

Below, I reprise them for you:

6:30 AM. Altostratus, the State Cloud of Arizona I think; Altostratus. We see a lot Cumulus, of course, but sporadically in the winter following a storm or trough like today, and in our summer rain season, but Altostratus we see year round.

DSC_0087-1 — 8:49 AM. Mostly Cirrus uncinus (hooked, or tufted at the top).

10:03 AM. Accas: Altocumulus castellanus. According to my cloud chart, it could rain with 6 to 196 hours after you see these clouds.

Nice weather we’re having; snowbirds ejected to the north too soon

Sure, there was a little mischievous wind in the early afternoon, BUT, as a day in late May in Catalina/Sutherland Heights zone of Arizona, wherein the temperature is less than 100 F, well, it was pretty darn great. Another one is on tap today just like yesterday today, too. Feeling sad about the early, northerly ejections of “snowbirds” who thought because of the warm winter, May would be an inferno here and are missing some splendid weather. Doesn’t work that way. You just don’t know.

Lot of interesting clouds yesterday, too, real cold ones. Those Cumulus that formed in the late morning and afternoon started producing ice almost immediately. Wonder if you caught the first ones over there beyond the Charouleau Gap around 11 AM? They did not look as high-based as they were, thus, as cold overall, dad-gum, those cloud bottoms were running around -10 C (14 F)!

How high off the Catalina ground were they? Oh, about 13,000 feet, or about 16,000 feet above sea level (about 550 millibars). I woulda guessed, as you would have, about 8,000 feet off the ground when I first saw them forming (and not looking at the temperature and dewpoints, from which you can make a pretty good calculation of the cloud base height). From the Cowboys at the U of Wyoming, this sounding for TUS yesterday afternoon:

The Tucson balloon sounding for yesterday afternoon, launched around 3:30 PM, ascends at about 1,000 feet a minute.

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Weather Hints for Every Day Use by “Art”: You can calculate the height of a Cumulus cloud base by taking the difference between the temperature and the dewpoint, dividing it by 5, square that number, add the number you started with, and subtract the square root of 2.

DId I get the number you started with?

(Actually, stop at “dividing by 5”, multiply that number by 1000, and you’ll come out just about right. Yesterday, 85 F temp, 20 F dewpoint, leads to 65 F difference, divide by 5, you get 13, and times a thousand is an estimated CUMULUS cloud base of about 13,000 feet above you, not too bad).

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Continuing….. Since bases were so cold, tops were exceptionally cold, too, for shallow Cumulus and started producing ice when they were only about 1,000 to 3,000 feet thick, with cloud top temperatures of -15 C to -20 C (about 4 F to -4 F). Some of the highest tops, all east of us, and mostly on the east side of the Catalina Mountains, were likely as cold as -30 C (-22 F).

You can see yesterday’s small Cu spewing ice in the great U of AZ time lapse movie here. Only plays for one day, though.

You may also have noted in your cloud diary the bifurcation in the Cumulus array of yesterday. Almost no Cumulus west of Catalina, and plenty in the east half of the sky, appearing to be largest in the distance in the east. We were literally on the edge of the moist plume from the south that was hoped to end up been west, with us deeply embedded in it, and where measurable rain might have fallen here as it did east of us yesterday. Oh, well.

Today, with a low center passing over us tonight and a blob of Pacific Ocean air in it, and while that air is cold and pretty dry aloft, it will be a little more moist and so cloud bases today should be a little lower, and warmer, than yesterday’s. That means a little more water condensing in them than in yesterday’s clouds, and a greater chance of sprinkle here. Hoping for measurable, but its probably less than a 50-50 shot at that. Likely will be some thunder in the area of SE AZ, too. And, as always with high cloud bases, gusty winds that arise due to virga and rain falling through the dry air below cloud base. (Yesterday afternoon’s gales in the Sutherland Heights, momentary blasts of 40-50 mph, were NOT due to virga, but a rather to something I didn’t see coming, maybe a smallish low center–nothing really showed up on the maps.)

You can see the forecast trajectory of that upper low coming toward us, from the University of Washington’s Huskies, whose #14 softball team plays away, really away, at #1 Florida in Gainesville this weekend–how crummy is that except for the great Cu there and its important enough to be on TEEVEE Saturday?) computer output by clicking on this informative sentence.

You will also see in the above loop that our low takes its time moving along, and will keep the skies interesting with Cumulus and weak Cumulonimbus clouds today and tomorrow, along with temperatures below seasonal norms for late May (aka, less than 100 F) ((Snowbirds left too soon; ice still melting off some areas of the Great Lakes!))

From the cloud vault; yesterday’s clouds

10:28 AM. Small Cu began forming in the lee of the Catalinas during a horseback ride with a friend, in case you didn't think someone as cloud-centric as me could have a friend. — 10:28 AM. Small Cu with lenticular type tops began forming in the lee of the Catalinas during a horseback ride with a friend, in case you didn’t think someone as cloud-centric as me could have a friend. Calm winds, then, too.

11:08 AM. First ice! Can you spot it? — 11:08 AM. First ice! Can you spot it in the distance? Horse can’t believe that ice is forming already, and is rolling around in ecstasy, thinking about what it might mean for the afternoon.

1:43 PM. Approaching low with air moving upward ahead of it, triggers a batch of Cirrus and Cirrocmulus lenticularis (really high lenticularis) upwind of Catalina and above some Cumulus fractus.

3:18 PM. One of the more remarkable sights yesterday, were the small Cumulus clouds (humiilis or mediocris) that iced out. Look at ll the ice that formed in this small cloud, exiting on the left side, but dominates the whole cloud from this viewpoint. When you see this, it tells you how COLD those clouds are. First guess should be around -20 C at top when you see this much ice in a cloud this SMALL. Clouds having warmer bottoms, can have warmer tops that look this icy because ice forms in clouds at higher temperatures when the drops in them are larger. — 3:18 PM. One of the more remarkable sights yesterday, were the small Cumulus clouds (humiilis or mediocris) that iced out. Look at ll the ice that formed in this small cloud, exiting on the left side, but dominates the whole cloud from this viewpoint. When you see this, it tells you how COLD those clouds are. First guess should be around -20 C at top when you see this much ice in a cloud this SMALL. Clouds having warmer bottoms, can have warmer tops that look this icy because ice forms in clouds at higher temperatures when the drops in them are larger (see Rangno and Hobbs 1994, Quart. J. Roy, Met, Soc.) Oh, yeah, baby, have some pubs!

6:58 PM. Iced out Cu/weak Cumulonimbus beyond the Gap, the Charouleau one, end the day. Shoot, a slight change in trajectory from the south, and they woulda been here.

7:00 PM. Meanwhile, all quiet to the NW, no Cu whatsoever demonstrating the moisture edge we were on.

The weather ahead and WAY ahead

Now what I think is really interesting, which is almost everything to do with weather, is that the models are suggesting a tropical injection again at the end of MAY into early June, with a chance of a decent rain again. As you can see in the plot below from the NOAA spaghetti factory, a trough to the west of us and over California is a virtual certainty now at the end of May. That means the air above us will be, while quite warm, originating from the deep Tropics with the likelihood of clouds and precip coming up from there. Nice. Will keep me posted on these developments, in case no one else is reading this far.

The End.

Moist tongue failing

That’s pretty much it for the weather just ahead. Nice upper low passes overhead in the next coupla days, but it really needed an steroid-like injection of tropical air from way down south to do much for us in the way of measurable rain. Oh, sure, we’ll still get some clouds and isolated showers, maybe one or two with lightning somewhere in the whole state of Arizona, but our chances of measurable rain here in Catalinaland have gone way down because the moist tongue hasn’t materialized in time to reach us, but rather will be shunted to the east. But, the skies will be spectacular, even if they’re dry for us.

For a psychological lift, in addition to the one provided by large amounts of coffee, generous rains will fall in drought-stricken NM and west Texas as our little disappointing low approaches and moves over us. OUR tropical air will be just a little too far east, but great for them.

BTW, the Canadian model, the one that had so much rain in our area as late as 36 h ago, has bailed on rain here, as well in the past two model runs. Probably won’t be going to Canada now for any vacations in the near future; pretty bitter about those misleading forecasts. I think they smoke too much up there, too.

Yesterday’s clouds

First, in case you’re mad at me for predicting measurable rain, 0.05 to 0.25 inches, have some kind of “rain rage” going on now, a picture of a cute dog to help you get back in control of yourself:

10:04 AM. Flying saucers! Altocumulus lenticularis clouds sometimes trigger calls to the police department that a flying saucer is about. Had a real scare back in the 50s around Mt. Rainier, Washington due to an Ac len (true story).

12:12 PM. This one looks painful. Never seen anything like it before. — 12:12 PM. This one looks painful. Never seen anything like it before, a kind of yoga for clouds, “downward dog” cloud formation.

12:12 PM. Wouldn't want to be flying under this one; suggests extreme turbulence to me. — 12:12 PM. Wouldn’t want to be flying under this one; suggests extreme turbulence to me.

12:44 PM. That shredded. ragged base below the lenticular in the center also indicates heavy turbulence. The smooth cap is due to a temperature inversion that allows some give, a dome, a hump in it, but nothing more. — 12:44 PM. That shredded, ragged base below the lenticular in the center indicates heavy turbulence below it. The smooth cap is due to a temperature inversion that allows some give, a dome, a hump in it, but nothing more.

1:46 PM. An example of almost invisible Cirrus/Cirrostratus. Kind of a hot research topic, "invisible CIrrus", ice crystals floating around up there that are too low in number to be seen, but can be captured in aircraft instrumentation. This is about as close to invisible Cirrus as you can get. Look hard and you will see the faintest whitish haze above the flecks of Ac len clouds, one has a trail of fine ice coming out of it. Ac len remain stationary while the air flows through them, so the ice ejects on the downwind side. No sign of an Ac len having produced the whitish haze above those cloudlets, though. Personally I have never seen invisible Cirrus. — 1:46 PM. An example of almost invisible Cirrus/Cirrostratus. “Invisible Cirrus”, btw, is kind of a hot research topic since clouds affect the radiation budget of the earth. That kind of cloud is just ice crystals floating around up there that are too low, and small, in concentrations to be seen, but can be captured by aircraft instrumentation., which is how it was discovered. This is about as close to “invisible Cirrus” as you can get. Look hard and you will see the faintest whitish hazes around and above the flecks of Ac len clouds; the one a left center has a trail of fine ice crystals coming out of it. Ac len remain stationary while the air flows through them, so the ice ejects on the downwind side. But, no sign of an Ac len having produced the whitish haze above and to the left of that cloudlet, though. Personally I have never seen invisible Cirrus.

The weather way ahead

NOAA spaghetti plots suggesting that tropical air ahead of a trough may yet bring us rains in early June. Check it out.

Other than that, our only chance for measurable rain is in the next 48 h when MAYBE a rogue shower might hit. But, no matter what, pretty skies anyway for the next couple of days. Have camera ready.

The End.

Dewpoint rises above zero degrees! Upper low to pass over Catalina!

Moisture’s not flooding in quite yet, but just to see the dewpoint creep above 0 F lately has been satisfying. Here, from the U of AZ Weather Department, this plot from early this morning:

Plot of surface station data for 4 AM AST this morning. Numbers on the lower left are dewpoint temperatures; 18 F (!) at TUS, but 38 F over there in Yuma. Even higher dewpoints are headed our way!

Currently, ejecting out of equatorial waters toward Catalina, are banks of middle and high clouds, which, along with lower level moist air from the Gulf of California and waters to the south, will be moving into SE Arizona en masse tomorrow and Friday. You can see this process unfolding here from the University of Washington’s Weather Department’s western hemisphere satellite loop for the past 24 h. Take a look down in the lower right hand corner of these images, by the Equator, and watch those clouds begin to roll northward. Pretty exciting to think that clouds that were near the Equator will be here in 36 h or so.

US model has a paucity of rain, whilst the Canadian mod continues to have a much “juicier “solution for us as the big upper low now over southern Cal wobbles around for a day or then trudges east. The Canadian mod calculates, as it consistently has, that this low will be going slightly farther south as it passes over Arizona than the US model, with the center of the low eventually crossing directly over Catalina on Saturday at 5 AM AST.

A more southerly trajectory means more moisture is like to wrap into our low before it gets here. The best of the rain would fall just before the center arrives.

The start of scattered showers in the area is still later tomorrow and would continue through Saturday morning. The range of amounts for Catalina/Sutherland Heights is still probably “light”, in the range of 0.05 inches to 0.25 inches. However, with thunderstorms likely at times, a lucky hit might make that top end a much greater amount.

For quantitative predictions, go to the U of AZ mod output, ones that will be based on the US overall model, but downscales what the US model predicts a much finer grid of local terrain. So, those calculations, which weren’t done yet from the 11 PM AST data, are likely to be a little less even that what CMP sees. It will be interesting to see which of us has foreseen the more accurate future, the Beowulf Cluster at the U of AZ, or CMP in the game of “Beat the Computer.” (The human usually loses….) ((Oops, just saw now that there is no updated run from last night’s data, a shame, and may be due to lack of funding. How bad is that?))

Should have clouds similar to yesterday today, which is already what’s out there this morning.

Moving ahead to yesterday…

Yesterday’s clouds

Started appearing around mid-day yesterday, those non-Cirrus clouds we call Altocumulus. Some lenticularis here and there as well. I was pretty happy for you now that you could see some non-Cirrus for some excitement.

How high were they? Oh, about 17,000 feet above sea level, or about 14,000 feet above Catalina. Here’s the TUS sounding profile, launched about 3:30 PM. Where the two lines pinch together is where the clouds were, and, if you follow the sloping lines of temperatures to the lower left, you will see that the top temperatures of those clouds were pretty cold, -16 C, around 4 F, cold enough for some ice crystals to form, but not a lot. Below a few shots or your cloud day yesterday.

Tucson balloon sounding ("rawinsonde") for 5 PM AST yesterday. — Tucson balloon sounding (“rawinsonde”) for 5 PM AST yesterday.

1:02 PM. Altocumulus lenticularis dot sky north of Catalina. No ice visible.

1:02 PM looking south from Catalina. Altocumulus perlucidus patches with scattered lenticulars. Here’ where you should have been logging your first ice sighting. Look at the delicate, very transparent veils between the clouds. Of course, you would have been estimating less that one per liter concentrations of ice, too, in your cloud diary. The droplet clouds are easily detectable because “cloud condensation nuclei” are far more numerous than ice nuclei. Here, droplet concentrations are likely 100-200 thousand per liter; ice crystals, less than 1 per liter! Those factors make droplet clouds sharply defined, and ice clouds “wispy.”

4:38 PM. Droplet Ac clouds with ice falling out below. Interestingly, nature's ice nuclei like to form a liquid drop that then freezes rather than form a crystal directly (except at really low temperatures, like -35 C or so). — 4:38 PM. Droplet Ac clouds with ice falling out below. Interestingly, nature’s ice nuclei like to form a liquid drop that then freezes rather than form a crystal directly (except at really low temperatures, like -35 C or so).

7:24 PM. Ended up with a nice sunset again. Some ice falling from these Altocumulus clouds is visible, with a hint of a "sun pillar". — 7:24 PM. Ended up with a nice sunset again. Some ice falling from these Altocumulus clouds is visible, with a hint of a “sun pillar”.

Blazing heat still in the cards once our low passes on Saturday; temperatures will “recover” rapidly to max temperatures of 100 F or so for a good week beginning next week, but a an early June rain is also shaping up.

The End.

Canadian model wetting it up for Catalina and environs

http://weather.gc.ca/model_forecast/animateweb_e.html?imagetype=model_forecast&imagename=00_054_G1_north@america@zoomout_I_4PAN_CLASSIC@012_….jpg

Had maybe a pixel of “rain” over us prior to last night’s run based on global observations made at 5 PM AST yesterday. Now, from those obs there’s widespread rain in SE Arizona from the little low that drifts across SE Cal and just to the S of us. First showers now shown to move in overnight Thursday, continue off and on, for about 24-36 hours. Expect to hear thunder. Sticking with best rain total prediction, generated when the models had none, of between 0.05 to 0.25 inches. Tongue of moist air now seen to be injecting from tropics into that upper low!

Who cares what other mods calculate? We just hope the Canadian model results above are not some kind of confluxion.

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Off on another tangent:

The “strangely believe it” side of science, cosmology: Two weeks ago, in a Science mag editorial, it was pointed out that the entire Universe (!) as we know it today, even with those 50 billion new galaxies that the Hubble telescope disclosed back in the 90s, began with a particle SMALLER than a proton! The Science Editorial, however, did not disclose how that incredibly dense (!) particle got there, what was it doing before that, nor why, in 10^-35 seconds, it blew up to be a couple hundred light years across, the very parts I was hoping to learn about. This is, perhaps, a more amazing scenario than one that brings rain to Arizona in May!

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The End.