Author: Art Rangno

Retiree from a group specializing in airborne measurements of clouds and aerosols at the University of Washington (Cloud and Aerosol Research Group). The projects in which I participated were in many countries; from the Arctic to Brazil, from the Marshall Islands to South Africa.

Boffo storm bops Burbank before belting Benson

…and the rest of Arizona tomorrow.    Actually, at this hour, 5 AM, the storm coming here has not yet gotten to Burbank.   Its only close.   But, people get excited when you say things like that in the title, and that’s what we’re about here, weather excitement, not accuracy excitement.

Weather excitement?

Take a look at the NWS site here.  They are beside themselves with excitement, issuing what appears to be hundreds of warnings for the entire State of Arizona, and not one drop of rain/snow has fallen yet!  Imagine how excited they will be at the NWS when something actually happens!  (hahaha, just kidding; you’re doing a great job down their guys and gals.)   They just want to WARN us about this well-predicted, STRONG storm, one having the unusual characteristic of being well-predicted in the models more than a week in advance.  Hardly ever happens.

So, with the NWS all worked up about winds and rain and snow and cold and stuff like that in our IMMEDIATE Catalina future (next few days), here at this keyboard we will try to fill in a cloud appearance niche, or try to.

Examining the AZ station and cloud plot here posted by our friends at the University of Arizona Wildcats Weather Department, this nice map.  
You can see a sheath of clouds (whitish area) extending southward from southern NV and UT down past Yuma AZ.   There is no radar echo with it now, or will there be.  Your interpretation:  must be Cirrus and Altostratus (thick ice clouds), maybe with some Altocumulus at the bottom toward the back (west side).  You’ll notice, too, that it is COMPLETELY separate from the main frontal band that has not yet (5 AM AST) gotten to Burbank, CA.

Note cloud empty area or slot behind (to the west) this sheath of middle and high ice clouds over the Colorado River Valley.  A very common sequence in the Southwest interior in late winter and spring is to have a completely separate slice of high clouds, even thickening up to look quite gray, maybe with some virga, give a false impression that the storm is imminent, much closer than it really is, followed by a spectacular clearing from western horizon. Often, this sequence, as is possible today, leads to astonishingly colorful sunsets here if the timing is right. You won’t read about possible colorful sunsets at the NWS today! This why I am here, to warn you about a nice sunset while they warn you about winds and stuff.

However, at the current rate of movement, this band of high clouds will pass overhead in the middle of the day.  Drat.

What next?

After the high clouds go by, there is enough moisture around for middle clouds, though not decks of them.  So in the hours after the ice shield goes by, that is this afternoon and evening, we should see some Altocumulus and patches of Cirrocumulus.   As the winds increase over us, almond shaped clouds (flying saucers) are likely.

Update at 6:13 Am AST:  “Lenticulated sunrise” in progress now!  Check toward Mt. Sara L.  Here it is, in case you missed it.  Gorgeous.

Continuing….   Those kinds of clouds are good harbingers of storms.    Some small Cumulus are likely to start showing up in the afternoon as well I think, but will be high based and too shallow to produce precip.

It will be, I think, one of our most photogenic days so get yer cameras ready for some interesting, and finely granulated Cc, or Ac lenses.

The main slug of low based clouds, rain/snow, cold air, windshift to the NW, graupel, lightning, etc., comes in after mid-night with the front.  Temperatures are likely to drop 10-20 degrees as the front goes by tonight and the rain begins.  Check it out here from the great weather calculator at the University of Arizona.  And here for even more detail!  Even the Great Beowulf Weather Calculator at the U of AZ is excited about this storm, predicting more than 3 inches of water-equivalent snow on the upper regions of the Catalina Mountains, which is clearly too much!

But how great it would be if it was correct!

Hang on.  Breezes already at 6:37 AM, and you know what that means:  one heckuva windy day this afternoon and evening, dusty, too.

I think I need to rest now, maybe lie down for awhile, let the weather excitement dissipate.

The End.

 

 

 

 

The End is at hand…

…of the superbly pleasant days, that is.  Sure today and tomorrow, and Friday, with the except of afternoon breeziness that last day, will be quite nice.  Probably some Cirrus or Altocumulus clouds at times to make the sky look interesting.  You will still be able to brag to your friends elsewhere during these days about how nice it is in Arizona in the wintertime.

Below, an example of the kinds of clouds that might float by, yesterday’s Altocumulus clouds that appeared at sunset.  I’m sure you saw them, and recorded the event in your weather journal.  After all, it might indicate something and then later, you would be able to tell your friends that you knew that something was coming because you saw that cloud. Now, if you really have good eyes, you will see in this photo, a veil of ice that formed in the little sliver cloud that is farther away and to the left.  You really need to know about ice if you are going to be a good cloud person.

But by Sunday, you may want to go to Buffalo, NY, or Ottawa, Canada, to get warm after the cold front goes by.   It’ll be raining, maybe even snowing at some point.  Ski Catalina!  Its THAT cold in this mammmmmmmoth system approaching Catland that we are probably going to at least see some flakes in the rain Sunday or Monday.  (That my friend, is NOT sleet, dammitall!  Don’t let some silly weather presenter convince you that its “sleet” when rain and snow are mixed together.  Sleet bounces off the pavement; its frozen raindrops, ones that fell into a sub-freezing layer near the ground–takes about 2,000 feet  or more of sub-freezing air for there to be enough time for those drops to freeze, and typically, temperatures below about 28 F.)  Now, where was I?

Right.  Expectations are supremely high for this storm at this keyboard.  May set some storm precip records here in Catalina for the amount in 1-2 days.  I am expecting an inch of precip by Wednesday mid-day, but it COULD be 2 inches (water equivalent), that’s how much potential this storm has.  Almost certainly some of the rain will be accompanied by electrical displays.

Why so much confidence and take the chance that you will look very foolish if you are wrong in these extreme weather pronouncements?

This storm is, and has been, well-progged.   Remember that discussion about “spaghetti” a few days ago?  Now, only a few days away, this mammmmmmmmoth storm is “in the bag”; don’t even think about it missing us, even though its still more than 72 h before rain even begins to fall (likely sometime overnight Saturday).  You’ll have to deal with it.  Get used to it,.  You’ve seen it before:  the dust , the strong winds (at some point, probably more than 50 mph in a brief puff) Saturday or Sunday night and then the cold air and rain/snow.

Here is a sample from one of the best models, from our friends to the north, for Sunday afternoon when the storm is well under way in AZ:

Then,  once here, it moves VERY slowly, so that the duration of rain and snow will be extended.  Hey, we’re due for a break in getting a great, drenching storm. Poor desert spring weeds looking pretty sad these days around Catalina, which makes me sad.  Why can’t it rain more in the desert?

And with a trough of this magnitude (upper left panel of prog map) bringing such cold air down here, ahead of it,  east of the Rockies, extremely warm air will rush northward.  While low temperature records are likely to be set in the West by early next week, high temperature records are likely to be set in the East and probably in eastern Canada as well.

The folks at the NWS, Tucson, will be, and are, very, very excited, stimulated, really, by this situation.  So many advisories to be issued, so little time, when its upon you.  This is what we weatherfolk live for!

May hunker down for a couple of days, daydreaming about how great it will be.

The End.

 

Cloud quiz

While waiting for the rain, here are some of yesterday’s clouds.  What were they?

Answers printed upside down at the bottom except that WordPress wouldn’t let me do that.  It would be great if you turned your monitor upside down before you looked at the answers.  One is a trick “question” because I took a picture of a cloud behind what appears to be an inanimate plant, focusing on the dead plant and so the cloud shown in the background is a little fuzzy to make it more difficult.

 

 

 

 

 

 

 

 

 

 

 

 

 

1. Cirrus spissatus, the only type of Cirrus allowed to have gray shading in the daytime. Note mammatus like feature in the center.

2. Contrail, unusually turreted one (hmmm, perhaps a part of some government conspiracy–hey, I am kidding the “chem-trail” people).  There’s also a patch of Altocumulus floccus (or  Altocumulus perlucidus would be OK, too) lower part of photo.

3. Cirrus castellanus-turreted Cirrus, don’t see that species too often because it is rarely so unstable at that height.  “Unstable”-the temperature dropped a LOT as you went higher up there, more than usual.

4.  Altocumulus floccus, horizon, upper right, Cirrus fibratus (pretty much delicate, straight fibers) middle.

5.  Ocotillo (hahaha, its not a cloud!)  ((Another example of the juvenile humor that the writer seems to be afflicted with).    OK, it looks like mostly Cirrus castellanus in the distance.

What do these kinds of clouds tell us?

The atmosphere is moist, but only patchy moist, a frequent occurrence in desert areas because “patchy moist” at middle and high levels in the atmosphere is most often all you get on the southern periphery of the major storms to the north of Catalina in the cool part of the year.

The atmosphere over us, too, is only in ascent at an overall rate of maybe an inch or two a minute; a bit more inside the clouds, less outside the clouds.  One way to KNOW how slight the air is rising, even in the clouds, is to observe that snow is falling out of some of them, tiny ice crystals, typically in the low hundreds of microns in maximum dimension (width of a few typical human hairs, which are about 100 microns in width.)  Such tiny ice crystals have fallspeeds less than 0.3 meters per second, and so they wouldn’t be able to fallout with higher overall “slab” lifting, the rate of that the whole upper air is lifting at these cloud levels.    Q. E. D.

What caused the lifting?  When you see clouds scattered over such a vast area, they have to be due to a disturbance in the wind field, a trough is likely nearby, normally upstream.

I have not looked at maps lately, but will NOW to see if there is a bend in the winds (indicating a trough) at these heights (mostly Cirrus level).  I don’t see one on the 300 millibar map (30,000 foot map) and so I am not going to show it.  But anyway, I am right, I am sure.  Now, I will begin a serious investigation to prove I am right.  The models will know if there is lifting going on.

Yes!  I have been saved in my assertion by my former employer, the University of Washington‘s MM5 model, and this was the first thing I looked at!    Look at the predicted high “clouds” (those above 20,000 feet) over Arizona for yesterday at 2 PM AST!  They can’t be there in the model unless it thinks the air is going up some.  OK, past the exultation stage now.  Moving on.  Actually, the model predictions of Cirrus-ee clouds aren’t really that great, so it was quite a surprise to see this.

 

The End.

Coming to Arizona-Catalina on March 18-19th: wind and dust followed by RAIN!

Sounds more like something coming to your local googleplex movie compound…but I am pretty excited today to be able to report a great model prediction that the title alludes to, one that has a higher degree of reliability than we usually see for that far in advance.

Normally one would not fool with a forecast of rain here that far in advance, more than a week, with any rain at all!  How many times have we seen that predicted rain in the models that far and more in advance, evaporate as the predicted rain day gets closer?  Well, I have anyway.  Way too many times.

However, as it has been written, the reliability of a longer range forecast by the models, such as a week or two in advance,  is discernible in something we call “ensemble,” or more colloquially,  “spahgetti” plots.  (Skip to pictures if you don’t want to know about these…gets a little technical.)

Occasionally, there are patterns in the jet stream that have high predictability, and these patterns produce “ensemble” predictions that are pretty much the same for one to two weeks in advance, even though the initial conditions are perturbed-that is, deliberately changed on purpose (haha) to see how much difference there might be in those longer term predictions because of the little changes.

You might think of these “perturbations” as representing bad data, “bad balloon”, lack of data, etc.    These small changes are introduced at the very outset of the model run and the models are run completely over again out to one to two weeks or more, to see how differently they look as the predicted days days accumulate.  At first, a “bad balloon”, bad data point, won’t have much effect, and so model forecasts just a couple of days out usually change very little.

But, if the pattern looks pretty much the same after, say 10 days out AFTER these changes are put in, then such a prediction has high reliability, a strong signal; what will happen has a high confidence level.   When the pattern is changed drastically with these little changes, then there can be little confidence is what is predicted.

Now, why am I going into all this (maybe useless) detail?

The strength of today’s blog title is due to having one of those rare situations where a situation has such a strong “signal” in the data that the forecast of a very strong trough here eight days away, has is showing a LOT of reliability in those “spaghetti” plots (shown below).

Re-inforcing this prediction a bit, too, is that in our Catalina climo data, there was a suggestion of a higher chance of rain in the third week of March than in the second week.   There really could be something in the global circulation that “likes” to put a big trough in Arizona and the West in the third week of March.

Another factor is that troughs are more common in the interior of the West in the springtime than at any other time of the year.  In many locations in the West (e.g., Seattle, San Francisco, Grand Junction), because troughs are cold aloft, March is the coldest month of the year overhead!  So, we would expect these kinds of events, just based on our usual climatology.

OK, back to our Catalina rain prediction:

Finally, below, if you have made it this far,  is what we are REALLY interested in, the areas of rain being predicted for Arizona-Catalina on March 19th (see panel below from IPS Meteostar).

First the rain prediction in panel 1 and the configuration of the jet stream over this same domain in panel 2.  You can see a huge southward plunge of the jet stream along the West Coast toward Baja and then see that it curls to the northeast after passing overhead of Baja.

If you read this blog, you know it ain’t going to rain here in SE AZ without the maximum wind at 500 millibars being south of us, and so, when you see so much rain in all of AZ, as in panel 1, you could have already guessed what this jet stream configuration would look like!  You’re friends will be amazed.  And, voila, there it is, where the jet should be!  Unless you have a telescope handy, you’ll have to click on these to get a resolution that you can see what the HECK I am talking about.

 

Next, we go into the ethereal world of spaghetti plots, this last panel, from NOAA.  These lines, some representing perturbations in the models, are pretty darn compact over Arizona on March 19th, and that, in turn, means a pretty darn reliable forecast.

Some details on this assertion:  take a look at the red lines, indicating a contour height on a 500 millibar map of 5700 m.  Compare the spread of our red lines to those in the Atlantic, where in that domain, there can be little confidence in what is predicted eight days out.  That 5700 m line is pretty much near the edge of the jet stream here, and the 5520 m contour lines (turqoise lines) well within in it. So, we are nicely sandwiched by those contour lines, meaning there is high reliability that there is a jet here.   Also, the yellow lines and gray lines, indicating the times of different model runs, also converge over Arizona.  I am so happy!

Finally, if you can make out the green “climo” line, you will see that the long term climatology favors this “trough in the West” pattern at this time of year!  Its all good!

What else can be confidently predicted?  Cold in the West, but also likely record warmth in the East with this pattern on the 18th-19th.

It will be interesting to see if Mr. Cloud-maven person really knows what he is talking about in the week ahead.  Of course, nothing can be guaranteed, but it sure looks like a rain is coming, finally!  What’s really certain in this longer range prediction, is the dust and wind part, dammitall.

The End, at last!


Backspin ending; upper low moving off to east as big trough barges into West Coast

You can see all the action described above here and here:  first the water vapor loop from the Huskies’ Weather Deparment that lets you see ALL the action, dry and moist air moving around, and then from this IPS Meteostar loop, you can drill down and see the clouds with the itty bitty radar echoes they produced over eastern AZ and NM as the clouds spin around that backspining low.   Stopped moving this way, as you will see, early this morning as a big trough with its broad band of westerly winds moves into the West Coast pushing our low away.

Unfortunately, that “big trough” will only bring rain as far south as SFO in the days ahead while we warm up for a few days.  I would look for a string of nice sunsets as Cirrus clouds on the periphery of the rainy systems to the north are drug this way , however, as the week begins.  I guess that’s not so bad.

Here’s a nice weather map for you (more from the Huskies!), one for the 300 millibar level, 30,000 feet or so above sea level.  You can see our spinner over the AZ-NM border, and the “big trough” which is about to brutalize the Pac NW and northern California:

 

Since a couple of those radar echoes last night are in our Catalina domain (a 100 mile radius, and rain was falling at Safford (3 AM AST), an old mining town NE of us), I now recommend that all readers of this blog check their dusty cars for sprinkles-its-not-drizzle on their dusty cars for a possible drop images in the dust, and a journal entry of a rain occurrence.   And, yes, we had plenty of dust yesterday as the lower level winds came scooting from the east-southeast  at 20-40 mph over much of SE AZ yesterday.  The Catalina mountains protect the town and environs around Catalina from these events, so we only get to imbibe dust, not actually experience it being raised up around us as was the case in the city yesterday.  You can notice this blocking effect nicely by driving south on Oracle on days like yesterday until you get to Pusch Ridge, Magee Road or so on Oracle, and then hang on to your hat.  There’s a similar low level wind situation today, and so you could do that today, drive south on Oracle, and experience it for yourself, maybe log the event in your weather journal as well.  I think readers in the years ahead would find it of interest that you did that.  I did it yesterday, and it was pretty exciting to see that east wind roaring though the palms, etc., just as you passed Pusch Ridge!

Yesterday’s clouds

What would a cloud maven’s post be without clouds?  First, take a look at yesterday’s time lapse from the U of A’s Weather Department.  During this one day, you can see the Cirrus clouds first coming from the northeast (they take awhile to appear), and then by the end of the day, they are almost coming from the west as that upper level low center spun back toward Arizona from New Mexico.  This is really cool, something you won’t see very often at high levels, this amount of turning of the wind in one day at that level.  Also, you will see lots of Cirrus forming in dense tufts and then dispersing once ice has formed.  That, too, is cool!

Here are some shots from yesterday:  1) Cirrus, 2) scruff of Cumulus humilis to the north, and 3), a dusty, Cirrus-ee sunset shot.

In the first shot, you may notice that these Cirrus clouds more resemble Altocumulus with its little flocculent masses.  Since Altocumulus clouds are all, or mostly comprised of liquid drops, you have to be able to see that these little cloudlets are ice, not water, thus betraying the greater height of these clouds compared with the Altocumulus (Ac) clouds they resemble.  There is a slight possibility, that for a second, these clouds had a liquid drop, such as upper center in the first photo.  Those look suspiciously like little tufts that may have been liquid drops.  However, while nearly all Ac REMAINS mostly liquid, even when trails of ice fall out, these clouds do not.  One of the mysteries in our science is about the formation of ice.  Some liquid drops in Cirrus clouds have been detected by researchers at the University of Utah1 at -44 C!  These are NOT the same researchers that were associated with “cold fusion” reports, BTW, ones that came out around the same time as this one.

 

 

 

 

 

 

 

The weather ahead

Latest model run, from 11 PM last night, has, after having several days ahead with rain, dwindled them to just two, the 19th and 20th of March.   These are indicated to be, in totality, a good rain.  Hope they “maintain” in the progs!

The End.

——————————
1Sassen (1986, Science)

“Back door man”, synoptically speaking

Who can forget Jim Morrisey and the Doors, and their raw, lusty,  “Back Door Man“?  Speaking of weather, though, and lows going the wrong way, that is, sneaking in the “back door” as it were, check out this forecast from the Canadian model for the next 24-26 h, an upper level low comes back over us from the EAST!  First, its over Las Cruces, NM (last night at 5 PM AST), and then, as in a shell game, its over there! On top of Nogales, at 5 AM tomorrow morning!

This is great because as the little center retrogrades back over us, with the little water it has in it, we are guaranteed moderate temperatures that will delay the burning out of our wildflower bloom, 2) virtually guaranteed nice sunsets with a few scattered Cumulus clouds around today and tomorrow, 3) will say it again, they should be virgae-ing here and there (snowflakes falling out), 4) Virgae means one or two drops could land on the ground in Catalinaland, perhaps benefitting an ant colony somewhere, 5) but you always hope for a busted forecast in these situations, some errant injection of moisture that will lead to a real shower.  Its not out of the question in these situations, but you’ll have to be watching since I won’t be expecting it.  You’re on your own, especially tomorrow.

The best part of this odd movement?  All the rain that will fall in drought stricken regions like New Mexico and Texas.  Yay!

From the University of Washington Huskies’ Weather Department, this link showing what the moisture pattern looks like over us and the rest of the US.  In this loop you can see how complicated the atmospheric motions are because you are looking not just at the clouds, but also moisture in the air even where the skies are clear.  Enjoy.   And you can also appreciate how darn hard it is for a computer model to get all of this right.   You will see that a moist tongue of air is feeding into our low from the northeast.  By tomorrow, it should have wrapped all the way around, and with luck, a blob of showers somewhere in AZ.  Doesn’t look like it will be here, but rather to the north of us.   Let’s hope this thought is WRONG.   I love being wrong when I think it might be dry!

 The weather ahead model dreamland

The longer term 10-15 day forecasts continue to have a couple of rains here in Catalina.  Rain is indicated on the 17th, 19-20th, and 24th.  This from the Weather Research Forecast model (WRF) -Global Forecast System (GFS) usually pronounced “Werf-Goofus” for those forecasts beyond about a week, which the last few are.  Don’t count on them except in our dreams for now so why did I even mention them?  I like dreaming about what could be.

Yesterday’s clouds

They really wasn’t what was expected yesterday from this viewpoint, scattered small Cumulus, some with virga.  Here’s what we did see, the second photo showing that there actually was one by Flagstaff:

When the jet goes by, the clouds, lower ones, roll in

And that’s pretty much what happened yesterday.   Here are some maps showing what happened as the jet stream in the middle troposphere (500 millibars or about 18,000 feet above sea level) went overhead while deploying to the east and south of us.  The sky change was pretty dramatic as you may have noticed.

First, how the forecast model had it timed, then the sky pictures as it was happening.  These panels, from IPS Meteostar,  are for 2 PM, 5 PM and 8 PM AST (these panels look almost identical, but believe me, that reddish area, indicating the strongest winds, is shifting eastward over southern Arizona!)  By 8 PM AST, the jet is completely past us (third panel).

The last panel, from the University of Washington, is the actual observations and “contour” map for 500 mb at 5 PM AST yesterday, that time when the sounding balloons (“rawinsondes”) went up.   That flag and four and half barbs at Tucson tell us that the wind was over 100 mph at 18000 feet above sea level over us at that time, likely the heart of the jet at 500 mb.  Its pretty unusual to see winds that strong so low.

You can also see in that contour map with satellite images of clouds that the clouds pretty much end south of that wind maximum at Tucson.  At the same time,  you can also see clouds puddled around inside the low in northern Arizona, encircled by a jet stream.  This sight, no clouds or just high and middle clouds, on the outside of the jet core, and low clouds with precipitation, is a common occurrence in the Southwest into the southern Rockies.  Scattered light snow showers were common in northern Arizona yesterday.  It is virtually required before any precip occurs in SW in the wintertime, that you have to be circumscribed (“inside”) the 500 mb jet.   BTW, this “rule” does not hold in coastal regions, such as southern California, or very far east of the front range of the Rockies, or in the summer months,  of course.  But its pretty solid here storm after storm.

And, of course#2, the sophisticated models of today know all about this “rule”, incorporating it in their outputs, and so we weatherfolk don’t really need to look for where the jet max is anymore like we did in the olden days of forecasting.  Still, its simplicity is appealing.

On some occasions, such as yesterday, when only brief virga accompanied those lower clouds, it is a “necessary” condition for rain here, but not always “sufficient.”  It was just too dry, even with this low’s little puddles of lower clouds filling its center.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


 

 

 

The cloud sequence:  1)  1:38 PM:  “nice weather we’re having.”  2) 2:18 PM:  wha’ happened?  Yesterday afternoon’s band of clouds accompanied the jet core passage overhead.  Cool, and it got even cooler.  Was hoping for a sprinkle, but didn’t get it.  There was a brief radar echo north of Catalina about this time.  That was it!

Since we’re still inside this jet/low this morning, there’ll be some lower clouds, Cumulus here and their, likely with a little ice, but too high and too sparse to have rain at the ground.  Most of the dust should be gone now, so a great looking day is ahead!

The weather farther ahead?  Some model fiction below, for March 19th.  Nice scoop jet rises up into southern AZ after scooping water out of the Pacific off California.  Would be a nice rain, if real.

Yesterday’s clouds, dust, and smoke; virga ahead

It was zero visibility in Parhrump, Nevada, yesterday afternoon with wind gusts to 85 mph, as the cold front was about to crash on by.   I guess we were lucky to only have 40-50 mph puffs of wind here in Catalinaland overnight, and not so much dust (yet).  A sharp, but dry cold front is bearing down on us, but the low center that was so intense yesterday over Nevada, then moved across Utah, has faded trying to move through the Rockies.  This means that the winds will be much less than yesterday.

Does that mean no dust around Catalina today?  Nope.  Those strong winds in Nevada and western Arizona yesterday raised a lot of fine (as in tiny) dust particles that are likely to be suspended for a day or two, and so we’ll likely see dusty skies today, without so much wind anyway.

We had some nice Altocumulus/Cirrocumulus lenticular clouds in the afternoon yesterday.  I wonder if you saw them?   They weren’t around for long.  Here’s what they looked like.

The last shot is of a cigar-shaped flying saucer with multicolored lights, OR, a Cirrocumulus lenticularis showing some slight iridescence (which are those rainbow colors near the edges of the cloud due to diffraction).    You have to look very hard to detect coloration in this cloud shot, but its there.  Diffraction is the bending of sun’s white light as it passes around the tiny (micron-sized) drops in the cloud and that leads to a separation of the white light into its components of reddish, greenish, blueish colors.

Take yer choice on what was photographed, but it is true that clouds such as lenticulars have been reported as flying saucers that “hover” then disappear.  This cloud was completely gone in one to two minutes after this photo AND was stationary, as lenticulars are in the face of strong winds aloft and at the ground, which also influences the observer’s reports of unexplained “hovering.”  This little cloud had been much larger ten minutes before reaching this size.

You can probably understand why such reporting might happen when you look at how smooth this little lenticular was.  And sometimes, when nearer the sun’s position, the colors caused by diffraction are quite vivid. 

Wildfire smoke

Also, in the late afternoon some smoke from the Nogales wildfire headed our way. It gave a great example of what young smoke looks like, that is, smoke recently emitted from a fire nearby. Its always got lots of gradations of the smoke in it because it hasn’t been around long enough for turbulence to mix out the smoke into a homogenous layer.   This happens when smoke has been around for days and days and has traveled thousands of miles, and so its one way of telling that a smoke layer has come from a long distance.

Sometimes high, smooth, long-range transport smoke layers can be mistaken for Cirrostratus, hold yer hat, “nebulosus”, a completely smooth ice cloud without much internal detail.  Below, the smoke from the Nogales area as it headed northward toward Catalina.

Rain possible?

It seems as dry as this system is, about all we can hope for is a trace.

It does appear that there will be enough moisture by tonight and for a couple of days as this cold air over us hangs around that we will see high-based (that is, probably based at or above the top of Mt. Lemmon) Cumulus and Stratocumulus clouds, and with the low temperatures aloft, ice should be able to form in them–which as you know, means virga, snow falling out and melting on the way down.

However, it would appear that only sprinkles are possible at ground level here in Catalina.

What to do?

You won’t want to miss entering the fact that a sprinkle occurred in your weather journal, one that might only last a minute or two, and so its best if you keep, say, your car parked outside where a layer of dust can accumulate, and then, when the rain drops fall, they will leave impressions in the dust.

The full moon of last evening, FYI.

Factoid:  it is thought that the moon was originally part of the earth, the result of a gigantic (!!!) impact that sent part of the earth out into space which then became our moon.  This theory would explain the synchronization of the moon’s face with the earth, that is, having the same face toward the earth.  Hmmm.  Hope we don’t have another one of those soon.  Two moons would be mind boggling.


Cirrus, maybe some lenticulars, and dust ahead

In case you missed it, the thin layers of Altocumulus clouds provided a bit of a sunset “bloom” around 6:30 PM AST yesterday.   Here’s what yesterday looked like, and I am doing this because I have a strong feeling some of you like to live in the past, like I do when I think about my best sports days in high school and JC R’s bat, and maybe a coupla others after that, so that’s why I am reprising yesterday below):

Here’s what we are looking at, in order of their appearance: 1) encroaching Cirrus (its not a cloud name, its what it was doing), 2) later, the Cirrus thickening (usually downward) into a nice example of Altostratus, a cloud normally composed of only ice crystals and snowflakcs, 3) Altocumulus perlucidus translucidus (honey-comb pattern, quite thin), with traces of ice falling out if you look VERY carefully, and 4) and 5), the Altocumulus as it was briefly (you only had a few minutes) underlit by the distant setting sun (its 93, 000, 000 miles away).

Moving on to the future, such as the rest of today

Its great, weather people can really do that, look to the future and say things that will actually happen with a great degree of confidence, like for the rest of today.  (HELL, an economist can’t even predict what will happen in the next few hours!)

What will happen in the hours ahead?  Cirrus clouds, patchy ones here and there,  and a good chance of some Altocumulus or Cirrocumulus lenticular clouds as the jet stream powers its way down here, shooting from the southwest over us by late in the day.  Sometimes, and I have predicted this before without a lot of success, you get these tremendously fine grained clouds (Cirrocumulus) that suddenly pop out of the blue overhead.   There’s an awfully good chance of seeing those today, too, with the strengthening winds aloft.   Of course, I’ll be watching for you if you miss them, and will replay anything “exciting” tomorrow.

Also, as the low in southern Nevada strengthens tremendously during the day, the winds will pick up as you all likely know by now, and the blue sky will start to wash out in a brownish dust haze.   Twin Peaks may not  be visible from Catalina late in the afternoon due to dust.  You can track the development of that low here, from the University of Washington.  Right this moment, 5:50 AM, there is not much there, so a lot of the development excitement in southern Nevada is ahead.  The NWS, Tucson is quite excited about all the things that might happen, as you will see here!

Enjoy and interesting day!

 

The End