A swatch of Altocumulus perlucidus translucidus (sorry, that’s the way we talk around here) passed over Catalina early yesterday afternoon, each “unit” nearly perfectly evenly spaced with its fellow cloud element creating a brief period of cloud awe for those Catalinans (or is it, “Catalina-ites”? “Catalinians”? Who knows, who cares?). Here it is, in case you work indoors and missed it. It was truly a fabulous sighting!
The afternoon was marked by a melange1 of middle clouds:
The weather just ahead
The local TEEVEE met men are, of course, pounding out the good news rain is just ahead for Catalina. Looks like, oh, 100% chance to CMP (Cloud Maven Person) starting after midnight Tuesday to Wednesday. How much?
This is a potent, but fast moving trough. Maybe will have only 2-4 h of rain with the passage of the cold front and its rainband. But, coming from the sub-tropics, should have a appreciable rain band with it.
I would expect rainrates to reach “moderate” as the heart of the band goes by for a coupla hours, anyway. Moderate rain is defined by the NWS as 0.1 to 0.3 inches per hour. So, only two hours of moderate rain should be at LEAST 0.2 inches, and most likely more.
We’re thinking here that there’s a 90% chance of more than 0.15 inches, and a 90% chance of less than 0.70 inches. So, averaging those two leads to a best estimate in CMP’s opinion of 0.425 inches! Wow. Nice.
Now, I will look at the U of AZ nested model and see what it thinks. Kind of game we play here, seeing how a seat of the pants forecast, made over a coupla minutes, measures up to a computer model with billions if not trillions of calculations:
The weather way ahead
After the nice rain just ahead, we have to get through the week-long dry spell before we move into a new stormy regime. First, a spaghetti depiction of the ridge after our nice storm:
Here’s what’s been exciting for a few days now, and below, from last evening’s global model output:
Let’s see what the actual and very latest model run from IPS Meteostar has for us:
How much these coming rains can benefit our spring wildflower bloom and spring grasses I don’t know, but I sure hope they can resuscitate what otherwise will be a dismal spring.
Expecting a snow event during the “new regime” that takes over after mid-month, too. Be ready!
Yep, unless you were outside yesterday morning, you probably missed the few drops that fell. But fall they did, giving us officially a trace of rain for January! In case you don’t believe me, here is a shot of the incoming shafts of rain. OK, “veils” of rain.
Now, a historical forecasting criteria note after that paragraphical blog title, a criterion that still holds true:
In the 1950s and 1960s, the Los Angeles forecast office used the 564 decameter height on 500 mb weather maps (those made for about 18,000 feet above sea level) to delineate where the rain line was for incoming troughs. North of that, rain fell; south, no rain.
It was remarkable how well that worked.
Don’t know it that height criteria holds here in AZ, probably not, but the 500 wind max seems to be a good discriminator for TUS for rain; under or north of that max seems to be a necessary (though not sufficient) criteria in wintertime. (That wind max does not hold in Cal; rain often falls south of the 500 jet max; only east of the Sierras and coastal ranges does it hold.)
Lately, as winter gets colder, the NOAA spaghetti factory has recently lowered the red line heights to 564 dm in their 500 mb spaghetti plots, you can see that in 5 days from last night’s 00Z run, rain is virtually assured in southern Cal using that criterion, and we hope that rain gets here, too.
Check out where red lines are in the plot below. I’ve helped you to find red lines on this plot by annotating them with an arrow:
But after that trough whooshes by like a Nike logo, in ten days (2nd plot), we’re doomed again to be in the midst of a long warm, dry spell:
But what about after that next warm, dry spell? The weather way ahead
In a less professional comment than the usual ones posted here, reaching beyond the 10 day forecast limit, that domain of the models where things that are forecast beyond ten days often go to hell with just the next model run, these spaghetti plots foretell a collapse of that big fat, storm blockin’ ridge after our next warm, dry spell! It collapses into a muddle down, oh, I dunno, way down in subtropics somewhere. Yay! I can feel your happiness as I write this for you!
That ridge collapse means, first of all, that strong storms will blast Cal with needed flooding (well, big rains, anyway), and its likely that those Cal blastin’ storms will reach into all of Arizona providing a much needed hiatus in our drought, that is, will bring appreciable rains right here into Catalina as well. You can see if I have made this up by looking at the whole sequence here, keeping an eye on where those red lines are foretold to be.
So, that’s it, that’s my take on the longer term weather pattern:
“A Change Gonna Come,” as so eloquently sung by the master, Sam Cooke, when that 500 mb criterion was being used in LA, and apropos here because a change is gonna come, not that long from now. (Warning: The historical video scenes with Sam’s heartfelt tune will bring tears I just learned… Everyone should see it. Yep, we’ve been through a lot since he sang that song….)
Will keep you up to date every so often if it looks like my take, cribbed from the spaghetti plots is going to be correct in that drought bustin’ part I’ve described beyond ten days. In the event this “take” goes bad, it will, of course, not mentioned again. May have to fall back on writing about aircraft ice production in supercooled clouds to distract you.
That’s why you come here, to answer important questions like that. After all, those precipitating clouds could have been Nimbostratus, Stratocumulus opacus praecipitatio, Cumulonimbus capillatus incus flammagenitus, or even just “plain” Cumulonimbus capillatus (no anvil), and possibly, Stratus opacus nebulosos praecipitatio.
Of course, with no large fires around, we can at once rule out Cumulonimbus capillatus incus flammagenitus….(the new name for clouds on top of fires, formerly referred to by the more accessible terms, “pyrocumulus” or “pyrocumulonimbus.”
For the curious, and since I broke my camera and don’t have the dozens upon dozens of photos to regale or bore you with, I will reach into the archives for a shot of “flammagenitus” and show you one from the pyromaniacs’ paradise, Brazil!:
Now, on to more recently viewed clouds, like yesterday’s:
Later these scenes were overtaken by a slab of Nimbostratus and steady light rain for a few hours.
A note on the recent southern Cal rain blast
As you know, up ten inches fell in some mountain locations in southern California as a monster low pressure system smashed into the coast near San Francisco1. You might recall, too, that the shift of the jet stream (and thus storm track) into the southern portions of California was well predicted two weeks in advance in those crazy spaghetti plots. You can’t always get much out of those plots except maybe the degree of uncertainty in weather patterns a couple of weeks out, but that was a rare case in which the signal far upstream for something strong barging into southern Cal also strong. And, of course, we are experiencing the residual of that storm, also as was indicated in those plots (“…the weather change around the 18th.”
Presently, a another sequence of extremely heavy rain is in the pipeline for central and northern California starting today, which will take a few days for it to come to an end.
Following a break, what was intriguing in the model outputs, and a little scary was that it appeared that yet another scoop of tropical air was going to jet across the Pacific under another blocking high in the Arctic and Gulf of Alaska into California. Take a look at this prog:
Here’s where spaghetti can shed some real light:
So while it is still possible that some model runs will indicate a blast from the sub-tropics affecting Cal, they can be pretty much waived off as outliers (not impossible “solutions” but rather unlikely ones. Breath easier Califs! At least after the current onslaught ends.
BTW, can you see what kind of weather is indicated in this plot for the SW and old Arizony?
Cold; temperatures below normal, precip likely at times.
——————————– 1The low pressure center that passed over San Francisco yesterday was not as deep (988 millibars) as the notorious “Frankenstormmaggedon” of 2010 which barged into Frisco with a 979 millibar center. You may recall, too, that spaghetti had strongly suggested a “Frankenstormaggedon”, as it was later called, also more than ten days in advance. Recall, too, if you can recall, that 2009-10 was an El Niño winter with this kind of thing pretty much anticipated.
For history buffs, I reprise that January 2010 storm as seen on our national weather map. You may recall that, if there’s anything left in that noggin up there, that Catalina experience no less than THREE inches of rain as this system went by, taking a couple of days:
Well, it will be pretty obvious, ludicrously so to spaghetti lovers, the sequence shown below. It goes from “warm in the West (again); cold in the East pattern to another undercutting flow from the Pacific, the kind we’re having right now under the “soft underbelly” of a big blocking high, except that the tropical flow from the Pac this time is a little too far to the north to give us anything.
But, it will be another floody situation for northern Cal in the coming days. Some places, mainly north of “Frisco”, have already picked up 4-6 inches in the first blast which hit yesterday. Ten to 20 inches more is likely over the next week at favored locations. Having quite the water year there, really a lot of water year.
You may recall that the current situation, alluded to in the “break on through to the other side” refrain used here about ten times, was well predicted about two weeks in advance! That’s what spaghetti can do for you!
OK, enough jabbering, let us move on to the current exciting examples that popped out from last night’s global data ( there are outputs after adding little errors at the start of the model run, to see how the flow is changed with them in it. Sounds crazy, I suppose, but is considered a huge advance in forecasting, a stupendous tool, that is, to make errors in models at the beginning of the run). Heck, they even do that in climate models that simulate 30-50 years from now, and you’d be amazed at how the tiniest fraction of a degree change the beginning makes (see Deser et al 2012).
Well, the first one’s not so exciting since we’re dry and hot for this time of the year, and its a common one that can get stuck for weeks at a time, so you REALLY hate to see models project a bulging ridge poking north along the West Coast. It could mean a rainless February here, if it persisted.
Here’s the exciting follow up, though, pretty unexpected given the above, showing a sudden collapse of the West Coast ridge regime, and strongly suggesting that wet spell has begun in Arizona, including regions of Catalina and Saddlebrooke:
So, you’ll want to get outdoor work done before this.
Historical note of interest, added value content, etc.
Some of you may remember that the 564 decameter contour (those red lines) at this level (500 millibars or around 18,000 feet above sea level on average) was used in the early years of forecasting before computer models (50s and early 60s) by southern California forecasters to demarcate where rain would fall in California–at and north of where that 564 decameter contour intersected the coast when upper troughs came in. The Old Forecaster remembers, though not much else…
So those red lines barging into southern Cal after a LONG fetch from the subtropical Pacific in the plot above mean central and southern Califs better watch out for some major rains a little before we ourselves get a dousing around the 18th of Feb.
Isn’t it great what spaghetti can do, that is, constrain our future weather to fairly certain outcomes two weeks in advance!
There was a sunset yesterday, btw:
Upper level snow flurry passes south of Tucson! Trying to generate some excitement here….
In case you don’t believe me that over an inch fell, this digital record from Sutherland Heights with writing on it:
Probably a little more to come, too. Got some blow damage, I’m sure. Will be looking for roof shingles around the yard today.
And, as everyone knows from their favorite TEEVEE weatherperson, “New Storm to Pound SE Arizonans!” Begins Monday night, Tuesday AM. May have snow in it as it ends.
Your know, its no fun telling people what they already know, so lets look ahead beyond the normal forecast period of great accuracy, beyond not seven days, not eight, but beyond TEN days!
First, we set the stage with a ten day look ahead (from last evening) in a NOAA spaghetti factory plot:
This plot indicates that the pattern of a towering, storm-blocking ridge is certain along the West Coast by ten days–will be developing for a day or three before this, That ridge represents an extrusion of warm air aloft over the entire West Coast extending all the way into Alaska. The couple of red lines in and south of AZ are due to the change of a minor, likely dry, cutoff low in our area about this time (plus or minus a day).
In other words, this plot suggests a warmer, dry period develops over AZ, and storms are shunted from the Pacific Ocean, located west of the West Coast, all the way to Anchorage and vicinity, They will be welcoming a warm up in weather up thataway at some point in this pattern.
Is that it, then, for the AZ winter precip? It could happen. Just one more storm after the current one fades away today?
Hint: Sometimes anticyclone ridges like the one in the plot above get too big for their britches, and fall away, or, break off like a balloon from a tether, and a warm blob of air aloft sits at higher latitudes, often floating off to the northwest.
The exciting ramification of this latter scenario is that in the “soft underbelly” of the “blocking anticyclone” (as in American football), the jet stream throws something of a screen pass, goes underneath the belly of the blocking high, and races in toward the West Coast at lower latitudes. Having done so, such a break through pattern (“Break on through to the Other Side”) results in heavy rains in Cal and the Southwest.
Izzat what’s going to happen?
Let us look farther ahead, unprofessionally, really, and see if there is evidence in spaghetti for such a development and you already know that there must be because it would explain why I am writing so much here. Below, the EXCITING spaghetti plot strongly indicating break through flow breaking on through to the other side, i.e., the West Coast, from the lower latitudes of the Pacific:
Well, we’ll see in a coupla weeks if CMP knows what he is talking about.. I think this is going to happen, resembles what’s happening now, and weather patterns like to repeat, more so within the same winter. However, how much precip comes with this pattern will be determined by how much flow breaks on through to the other side….
Let us begin our look at yesterday’s clouds by looking back three days ago before the Big Storm. We had a nice sunrise. Here it is in case you missed it:
Moving forward to only two days ago, the day preceding the nighttime blast: a cold, windy day with low overcast skies all day, shallow, drizzle-producing clouds, something we don’t see a lot of here in Arizona.
By the end of the day, the clouds had lowered again, and we were about to have a very interesting night!
———————- 1Remember how great we hippie relics thought that first Doors album was? Later, the Doors, and that era were to be made fun of by 80s punk and humor group, The Dead Milkman in “Bitchin’ Comaro.” (Its worth a listen.)
For fans of NOAA spaghetti, this plot generated from last evening’s global data. Really, the uncertainty is overwhelming:
Every so often one of these goofy ones comes out, a real knee-slapper. The real situation is that we have a series of storms on the doorstep, the stronger ones barging in on the 20th or so, as the bonafide spaghetti outputs were indicating. These will be cold ones; yes, cold ones on tap, with a good chance of snow in “Catalina-by-the-Mountains”, which might also be a good new name for our little CDP.
Wasn’t going to blather about clouds and weather for a few days since there wasn’t any, just sit around and wait for those end of November storms to get here, then regale you with cloudy pictures.
But when I went to the NOAA spaghetti factory just now, I was blown away, beside myself, when I saw those outputs. Being one of the meteorological sophisticates, I suspect you’ve already trampled these maps. But, at the risk of being redundant again and again, here are a couple of jaw droppers from last night’s global data with errors input into the computer model at the beginning of the run to see how much the upper level forecasts change. There are always errors in measurements, they’re not perfect, and so by deliberately putting errors in models, we can see that range of differences in the outcomes. At first, there are virtually no differences because the errors are tiny. But over time their effect grows.
In these plots below, when the two colors of crazy lines cluster (red, representing the warmer side of the jet stream, and blue, the colder side) , it means the errors had little effect, and the forecast of a general pattern on the jet stream is one you can have great confidence in.
Below, a forecast via the “errorful ensembles” to be alliterative there for a second, in which the confidence can be quite high showing that a gigantic cold trough will sit atop most of the western US in the coming 9-12 days. Really, these are incredible:
So, how will it play out?
Well, we already have rather quickly passing cold troughs with their cold fronts ahead in late November, one that passes late on the 27th likely to boost our Sutherland Heights precip totals to our average value or above.
Then, the cold pattern gets amplified by this gargantuan trough that sets up a few days after those first couple of cold shots, setting the stage for cold and colder blasts. So the beginning of our cold weather and snowbirds muttering that they came to Arizona too soon, is just a few days ahead (followed by a “sucker hole” of brief temperature recovery and a few sunny days. (Well, I might be complaining, too, since cloud maven person, the writer, moved to Arizona from Seattle to be warm all day, every day. haha, sort of.)
On the other hand, there’ll be some great cloud shots in spite of the cold, and you and I, the rest of the cloud people, will both manage, warmed by the euphoria of being alive with such gorgeous scenes and exciting, changeable weather.
BTW, will close this shot-from-the-hip blog with a forecast of snow in Catalinaland in early December. That’s right, CMP is expecting measurable snow right here in Catalina.
Remember our slogan, “Right or wrong, you heard it here first!”
Note that within this swath, Catalina is predicted to get over an inch of rain! Note that the swath is not very wide. A wide swath of heavy rain would be one as wide as the State. So, we have to figure that this is a lucky hit at this time, and count on something less as a virtual certainty since the swath above will move around as new model runs look at it. Typically, they shift a little east over time in those future model runs. Hope not.
Have cameras ready for a pretty sunrise. Lots of high ice clouds up there.
The weather WAY ahead
Spaghetti suggests more rain chances after a several day dry spell following the Monday rains. Check out the “pretty strong” indications that we are in the trough bowl as the month comes to an end, meaning troughs should be populating Arizona during the last days of November. In turn, good November rains, and one seems to be in the high confidence pipeline for SE Arizona as a whole, means the spring wildflowers will be given a boost. I will go on record here as now forecasting, if that’s what this is, a wetter than normal November rain total1. Our November average since 1977 is 0.96 inches.
1This sentence will be deleted in the event of a drier than average November and will, therefore, not be on record.
Well, I think so, anyway, and those rain chances seem to carry right into the first week of November. I think you can see that in these graphics from NOAA based on last night’s global data. As in “Where’s Waldo”, can you find the State of Arizona? The US?
You got yer ridgy flow on the top (“top” meaning, “Canada”, around where that yellow line humps toward the north) and yer broadly cyclonic flow on the bottom (“bottom” meaning, “Baja Cal and Mexico”) that is, across the whole western part of North America. This indicates that we will have a configuration that suggests a “split flow” where part of the jet stream and a trough is forced into the Southwest. Models are showing a big trough and cutoff that brings substantial rains to Arizona!
Of course, model forecasts are pretty dicey at this range, more than 10 days, and so that’s why I am reporting it fully here with great excitement! That’s what we do here, go over the edge, not just up to it.
And, for that slight amount of additional credibility, the “WRF-GFS” has been spitting out big storms for Arizona over the past several runs during this late October period. See Arizona rain below from this rendering from IPS MeteoStar:
Since I ran out of anything more to say, I will post a second version of this same map as a public service for international readers who are clueless about states in the USA:
Below, the upper level configuration that goes with the pattern above:
So, there are some questions about the magnitude of this event, will it be a spring wildflower energizer with a major rain, or a just a breezy spell with a dry cold front going by? I’m on the side that a good soaking rain will fall sometime in those last few days of October.