Weekend slider, cloud excitement ahead, more about spaghetti

Check out these forecast maps from IPS Meteostar from last night’s 5 PM AST global data (less data from GOES-15, the satellite that covers the eastern Pacific and western US, which has gone belly up lately):

A ludicrous baseball metaphor for today; after all,  its almost baseball season:

Let’s say your a very tall person with a bat a few hundred miles long standing in the batter’s box somewhere around Hermosillo, MX.  A trough, like a baseball, has been thrown by the Pacific Ocean.  Its coming down the “middle of the plate” (see panel 1) with the trough easing into southern California with a lot of rain).  This one is gonna be jacked (will bring rain to all of Arizona!)   It can’t miss.   If it rains in southern California it can’t miss bringing rain to AZ!

You take a mighty swing (forecast rain), to go back to this silly metaphor.   You didn’t noticed the “red dot”, something batters can see on the spinning ball when a pitcher throws a “slider”, a curving ball that,  from a right handed pitcher to a right handed batter, veers away from the plate.

In this case the “red dot” to stretch this metaphor, is that the north winds on the backside of the southern California trough will be weakening as a new trough from the Gulf of Alaska roars down toward California and begins to catch up to it.  The “ball” (trough) veers suddenly to the outside corner of the “plate”, Arizona, and spins into the dirt over Nevada and Utah.  But you have swung anyway and struck out with the bases loaded (if you had thought rain from southern California was going to get here and water our wildflowers).  The fans are booing now.

Well, enough baseball for today.  The season is too long anyway.

Recall the  AZ “jet rule”; no jet here and to the south of us as troughs go by; no rain no how in this cooler time of the year.  Whilst the jet is south of our latitude on Sunday’s map  (first panel), you can see that by Monday night at 11 Pm AST, the high velocity core has oozed over the NW corner of AZ (brownish regions in the second panel).  The strongest winds are now on the east side of that trough, telling you its going to rocket off to the NE.

 Cloud prognostication:  get yer cameras ready!

The great thing about our “missed” storm is that the skies should be especially fabulous over the next three days (make sure all cameras are charged) because of having marginal moisture in the mid and upper levels of the troposphere as our “miss” goes by.  That should mean interesting and photogenic clouds of all kinds up there:  Cirrus, Cirrocumulus (fine grained clouds), Altocumulus (probably castellanus, lenticulars), and probably a spate or two of Altostratus clouds.  Gee, you’ll have to get a cloud chart to know what I am talking about here!  (Maybe you should get this one;  it seems better than some of the other ones I’ve seen, and I don’t just say that because if you do get it, I will get some money.)  ((Or go here, if you like to shop around)).  Is this crass or WHAT?

The great thing, too, is that the Altocumulus clouds are likely to have nice virga trails, and it that kind of cloud (Altocumulus castellanus virgae) or Altostratus occur at sunrise or sunset, you can get the MOST fabulous photos.  I like’em during the daytime, too, though.  OK, so very excited about the cloud prospects ahead.   Will be scanning skies.

The weather ahead

Another giant cold spell has erupted in the models.  Check this big boy out over Az, valid for Sunday morning, 5 AM AST, nine days from now.  Yep, you got yer low snow levels again, some showers, too.  But the really interesting part is that it gets cut off out of the stream and sticks around for a few days.  Look at the second panel, for FIVE days later!  A remnant of it is still there, producing showers!  In April?  Seems unlikely, but could happen.

How do we check out how likely this cold spell and rain/snow is?

We think about spaghetti.  Now remember, too, with GOES-15 out, there is also the fact that the models are working without as much information as they usually have.  So, right off the bat, you have to downgrade anything “strange”, more than you normally would.OK, here’s some spaghetti for 168 h out, valid for a week from last night.  This map was SHOCKING to me, because its telling you that the set up for our big boy is virtually guaranteed!  I couldn’t believe it, its amazing!

So what am I ranting about?

This plot below says that a gigantic trough in the eastern Pacific between Hawaii and the mainland is virtually guaranteed.  Look at how closely the contour lines are spaced in the eastern Pacific!  This closeness says that the “signal” for this to happen is huge in the global data.  Compare this spacing in the eastern Pacific, with the bowls of rubber  bands, say, in the Atlantic and western Europe.   The models are clueless about what is going to happen there.   Conclusion:   a few days before our forecast trough shows up, it is out there, and at least has the potential to be realized here in AZ two or three days later.  Somebody on the West Coast is going to get whacked, little doubt about that.

But what happens on the days we are concerned about, April 1st and beyond?  See next panel of spaghetti plots (2) for the afternoon of April 1st.  The yellow lines are a couple of the contours in the forecast map for April first above.

The confidence factor has gone to HELL!  Sorry for having to cuss.  In the western Pacific, you can still be pretty confident of where the troughs will be, but look at the MESS now in the central Pacific to Moscow!  Nothing is assured.  All is hazy, fuzzy, out of focus, dimly lit, a drunken spider’s web, DAMMITALL, to cuss that bit more.  While our trough has been foretold as of last night’s data, and it will maintain itself right up until reaching the West Coast (spaghetti 1), after that its anyone’s guess.  Chances are good for a cool spell, but will it be historic with rain and snow, or a slight drop in temperature under sunny, breezy skies?

No one knows, but that first dish of spaghetti (1) has to make you at least hopeful that something strange will happen in early April here.  Go here if you want to see the full animation.

The End.

 

 

Epilogue to historic storm; your broken records

Here, thanks to weather pal and researcher, Mark Albright, at the University of Washington, the low temperature and precip records set during our recent historic storm.

 

 Cloudcast

Unfortunately, the next few weeks, it appears, will be characterized by only chances of clouds, not rain, and mostly high ones at that.   Middle clouds like Altocumulus and Altostratus,  MIGHT appear on the 24th.  (Pitiful.)

Today it looks like a couple of  Cirrus clouds are heading our way from the northwest.  Of course, the temperature will be ratcheting upward now, too.

Sad to see that the poppies were mostly gone around this Catalina neighborhood yesterday.

 

Glumly, The End.

Whence graupel?

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

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

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

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

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

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

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

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

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

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

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

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

The End I think.


Re-living the Last Glacial Maximum–well for a day, anyway

After yesterday’s re-acquaintance with winter, a brief period of snow falling here in Catalina for a few minutes, and a whopping 0.67 inches of rain, we have another deep winter day ahead.

Here’s the National Weather Service’s forecast for Catalina, at least elevations of about 3200 feet.

“Today: Snow showers likely before 2pm, then rain and snow showers likely. Partly sunny, with a high near 46. West southwest wind between 8 and 16 mph. Chance of precipitation is 60%. Total daytime snow accumulation of 2 to 4 inches possible.”

A glimpse of a Catalina paleoclimate

A day like this, with snow expected and daytime temperatures reaching only the mid-forties let’s us experience what Arizona was like in the springtime 15,000 years ago or so during the Last Glacial Maximum (sometimes called the Wisconsin Maximum, referring to the area around the Great Lakes where ice was really piled up–no wonder we get visitors from Wisconsin; they remember.)

But, let us not overlook the other areas of the country during that Last Glacial Maximum.  Ice was piled up more than a kilometer deep in Seattle!  I am not kidding.  Here is a shot of what the Space Needle might have looked like in those days of the Last Glacial Maximum when snow and ice were building up.  Its pretty impressive since the Space Needle is a few hundred feet high.  Hard to imagine, but there REALLY was ice deemed to have been 1 km deep in Seattle 15,000 years ago!

A huge amount of global warming took place, of course, after the Last Glacial Maximum, people started going back to Wisconsin and other northern climes.   The warm era that followed the end of the Last Glacial Maximum, and the one we are now in is called the “Holocene”, BTW.

However, our current era also has a rather dark moniker,  also being termed an “Interglacial” period, as were all those periods between ice ages in the Pleistocene when it was nice and comfy.  “Interglacial” sounds kind of temporary, and they were back then, only about 10, 000 to 20,000 years long, and we are about 12,000 years into the “Holocene.”  However the duration of interglacials is not pinned down real well and “orbital” forcing of ice ages (Milankovitch cycles, Wiki) puts the next one around 50,000 years from now.

Maybe it would be good to go look at some petroglyphs today and think about what the weather was like back then for those folks who made them.

Oops/Correction:  Actually, in researching “petroglyphs” they seem to have appeared AFTER the Last Glacial Maximum, about 7,000-9,000 years ago.   Hmmmph.  That petroglyphs would appear then is understandable.  People were happy it was warmer and took their happiness out on the rocks which were no longer so cold, thus explaining the world-wide burst of rock work.  I work hard to provide you with information like this, information you can’t get elsewhere.

Today’s clouds

Its so cold up top today!  Its -11 C at just around the top of Mt. Sara Lemmon.  Since the tops of the clouds over us, even shallow ones,  will be -15 c, and the deeper ones to -30 C today, lots of snow will form in them, and that means virga and rain/snow showers, graupel (soft hail likely).  The upper level trigger for most of this will begin affecting us this morning, and with a LITTLE heating, cumuliform clouds should begin enhancing the Stratocumulus deck we now have.

Lower clouds with lots of ice in them look like yesterday afternoon’s clouds, shown in the photo below.  That smooth texture on the left side of the photo is due to ice falling out, but the snowflakes and ice crystals are too small to reach the ground, except only the very largest.  The shaft in the distance is due to a much deeper cloud in which the snowflakes and graupel (soft hail) were able to grow far larger than in the other cloud regions nearby. That’s because it had much higher cloud top, forced by stronger updrafts.  The stronger the shafts, the the higher  topabove it is a pretty good rule.

Gee, starting to “graupel” right now at 6:31 AM AST!  Exciting.

So, look for a lot of smooth looking clouds today like those in this photo.

 

 

 

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.

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!