The weather ahead

Old “Joe Trough”; cool temperatures move into Catalina later today

Mr. Cloud Maven person tried to trick you by titling his “piece” (“piece”, hah!) using a popular but not quite proper weatherspeak phrase, “cool temperatures”; something he ranted about a few days ago. Properly, and we try to be quite proper here, but probably aren’t, its cool “air” that’s moving toward Catalina.

As a demonstration of this assertion about cooler air moving thisaway, here, from our friends at Intellicast Inc., ones who hate Accuweather I’ve heard, is today’s 24 h temperature change chart (like to throw in some gossip from time to time, helps build ratings):

That blob of blue is associated with the encroachment of a cold front, where cooler air is replacing warmer air. Its the cold front that came ashore with Joe Trough (that trough that was so well predicted in its path across the Pacific Ocean for more than a week in advance) and his big low pressure center that brought hurricane force winds to some portions of the Oregon coast yesterday.

Unfortunately, both the warm side of the cold front (east of the cold front’s windshift line) and the incoming Pacifc air are both too dry for precip here. However, there should be a few small Cumulus later in the day as that cooler and more moist air arrives here in Catland. Also with a bit of moisture at mid and high levels, we could also see an Ac or Cc lenticular–keep an eye toward the NE and downstream from Mt. Sara L. Expecting a nice gold-lined small Cu sunset.

201204010900_500mb — "Joe Trough", the one we've been following, goes from Vancouver Island to San Diego here.

201204010900 — Joe Low, or just J-Lo, is trying to reform around Tonopah, but the main center is way over there in eastern Montana.

Where Joe T is this morning, brought to you by the U. of WA, is shown in the next panel, and the third one shows that Joe’s Low, or “J-Lo” for short, is all the way into eastern Montana! However, a second low is attempting to form around Tonopah, of course.

As Joe Trough ages, moving SLOWLY across the Southwest today (passes over Catalina at 8 PM AST), it will cast off by the main jet stream and will eventually become an isolated, enfeeble-ized meandering cut off low with a weak circulation over Texas, finally ending up, like so many old things, in Florida six days from now.

Not a great way to go, but with more moisture rising up from the Gulf of Mexico, this moisture being something of an age enhancer for “Joe”, huge amounts of precip will fall in the southern Plains food basket of the US. You don’t need so much strength as a weather system to generate huge clouds when you have Gulf air to play with. Think of our summers. No lows required, just that high dewpoint air and a blazing early sun for a good downpour here and there.

Note the new header today, along with an AZ Cat color scheme implemented by my web page person, Jenny Rink. She’s great! Go Wildcats! Huskies, too, though.

Speaking of summer and humid air….

Longer range models have something akin to a summer rain regime breaking out on April 10th, blazing hot with lots of tropical clouds streaming up from Mexico. Rains in SE AZ for three days, ended by a sharp trough and cold front on the 13th. Something to keep an eye on, dream about.

Will have some April precip climo tomorrow.

Joe the Transformer

“Where’s Joe?”, a new game for kids and adults. I’m talkin’ “Joe Trough” here, that little big boy we talked about a coupla days ago that’s going to bash the West Coast now in a little over 48 h. Try to find “Joe” here.

Did you find him in the satellite clouds on these weather map? He’s entering the scene, “stage left” as a hint. If this was a silent film, there would very a dramatic and dark organ accompaniment at this time: “Joe” is a villain, about to transform into a monster. Yes, that’s right, “Joe” is a “Transformer”, to recall movies that we’ve all enjoyed where things turn into bigger things (I am so kidding here). But, “Joe” WILL destroy some stuff in a couple of days.

For us little older weather-centric folk, it was obvious where “Joe” is. Of course, I know you, too, are weather-centric, hungering for more information, thinking about quitting your current job to become a weatherman, “why did I chose my current profession in the first place?”, the kinds of things that TRULY weather-centric folk ruminate about all day.

So, I will tell you. “Joe” is that comma-shaped cloud in the north Pacific almost due north of the Hawaiian Islands at this time (5 AM AST, 12 GMT today), and oddly, separate from and to the north of the long bank of clouds that stretch from Duckville (sometimes called “Oregon”, sorry Beavs) and northern California into the central Pacific and then on to Okinawa I think.

So, how do we know “Joe” will become a monster? Our computer models are so good these days, they just never miss a situation like “Joe” is presenting to us. All the ingredients are there, sharp air mass contrasts, STRONG upper level trigger (“Joe Trough”) on top and approaching the long frontal band mentioned above, and starting to make it expand and swell up. The most incredible thing to us weather folk, is that now, “Joe” doesn’t even have an eyeball (no low center) on these maps above and in the latest one below for 5 AM AST today! I will show you that latest map with a “no eyeball Joe” below, it’s just a bend in the isobars (yellow lines of equal pressure); his power comes from above. Soon, JT will cause the air to start wrapping around itself and a hurricane like eye-center will form out of what was just a long, almost straight band of clouds.

But look below at what the models say will happen in but 48 h! The transformation is into practically a cold season hurricane striking Oregon. Certainly hurricane force winds and pounding rains of several inches will strike northern California and the Oregon coasts in but two days. There are so many isobars I can’t count them all, and, as you know, the more tightly packed a lot of isobars are, the stronger the winds.

Two things are exceptional about this storm, the time of year, and that its so far south with this kind of intensity. Very rare to see such an intense low strike the West Coast south of Seattle at any time, but in late March? Wow.

Look for some damage reports in the Pac NW and Cal beginning on Saturday.

Here?

Just some friendly, non-threatening Cirrus clouds (ooops, and maybe a lenticular or two since I just saw one–something we meteorologists call, “retrospective forecasting”–really helps your accuracy ratings…and here at 8:03 AM, seeing Ac cas with long virga trails. Better predict those, too, now).

Not much else for the next few days in the skies, but we’ll get a part of the remnant of “Joe Hurricane” on Sunday. Expect a lotta wind and dust in the air, and then a SHARP drop in temperatures after the dry (boo-hoo) cold front goes by. Also, go here to experience more excitement at the Tucson NWS when it gets a bit closer.

The End.

The case of the spaghetti plots; an update

In our last episode, it was foreseen that a confidently predicted, “Joe Trough” , was going to bash the West Coast on the last day of this month with a strong storm, little doubt about it. He had been tracked nicely by the computer. Looked the same, “buff”, potent, day after day 4-5, ten days away as he crossed the Pacific Ocean. But after entering the USA at the end of March, “Joe” lost control of himself, it was unpredictable about what he would do next. At that time, displayed here on this blog, one computer guess was that he was going to break up into pieces, one piece over Arizona for days, sitting around, dawdling really, producing scattered showers in the first week of April thoughout Arizona. It was an unusual pattern, but there it was on the model outputs.

Sadly, from the spaghetti factory at our NOAA Super Weather Computer weather center, and the wild fluctuations it showed, indicated “Joe T” might do a lot of different things after he entered the USA. We could see that this rainy Arizona forecast was just one of many possibilities for “JT”, he was “unreliable” after approaching the West Coast no matter how badly we wanted that forecast that came out to come true; we just couldn’t count on it.

Now “JT” is only a few days away from crashing into the West Coast, still well predicted. But how about after he enters the West Coast? What will happen now? Will Joe break up into pieces and dawdle over AZ? Will there be rain? Or will we have just a dust storm and a dry cold front?

Let’s look in on the spaghetti factory and see what happens to Joe on the way in now, only few days from possibly affecting our weather.

From last evening’s spaghetti plots (“ensembles” in weather higher ordered weatherspeak) this 96 h forecast showing “Joe Trough” as it is about to hit the West Coast. As you can PLAINLY see, the entire earth’s weather north of the equator is well predicted as far out as 96 h, valid the evening of March 30th, 5 PM AST. In case you’ve forgotten, when all of the lines run almost on top of each other, things are well predicted, little chance of a busted forecast. The southward bulge in the turquoise and red lines just off the West Coast is our incoming “Joe Trough.”

The next panel, for later, valid for 5 PM AST, March 31st, shows that “Joe” is now in the Great Basin doing his thing, and the southern part of “Joe” is over us! Yay! Or not.

Remember the Red Zone, not in fubball, but in these plots? The red lines represent pretty much the southern edge of the jet stream at this level, 500 millibars pressure, around 18,000 feet above sea level. The turquoise lines represent pretty much the northern side of the jet stream at this level.

So, what’s wrong with this pretty picture (2nd panel)? Joe’s Jet (sounds like a singer I’ve heard of), doesn’t pass south of us by all reasonable expectations. Those little “perturbations” they put into the model at the beginning of the run to see how they might change the prediction, and thus get a handle on its reliability in case of errors, missing data, chaos in general, have the Red Zone (where the red lines are grouped) north of us. Jet north of us, as these red lines indicate, means no precip no where ’round here.

Well, unless you count dust as precip, and it certainly will pile up some.

“Joe” is strong and cold, but passes too far to the north. But as he does, a huge, intense low forms in the Great Basin, drawing dusty southwest winds across southern Arizona before the dry cold front goes through with quite a chill.

Now, for a little humor to end this blurb, a real laugher spaghetti plot, that for 15 days from now. You’ll go into conniptions, burst out laughing, like I did I am quite sure with your knowledge of spaghetti plots when you see this one and what virtually “unforecastable” weather looks like in a spaghetti plot. They should put these in the newspaper as kind of weather cartoon.

Actually, after 15 days, they mostly look like this.

Ending on humor, The End.

Arriving in local skies today: clouds, high and middle ones

Now that your camera battery is fully charged, you will be ready for the panoply of high and some mid-level clouds that will be arriving overhead today. Should make for some great sunrise and sunset shots, but also daytime shots due to the interesting twists and turns in the Cirrus (ice) clouds that will float by. Maybe later today, Cirrocumulus and Altocumulus clouds will show up adding that extra dimension to sunset color. Typically, in these situations, the first clouds on the scene are Cirrus at the highest levels (30,000 to 500,000 thousand feet above ground level (hahaha-just checking to see if you are reading this)–OK, 30,000 to FORTY,000 feet above the ground here on a warm day in Catalina-Tucson like today.

Next, with the moisture layer thickening downward from those high CIrrus levels as the day goes by, there might well be some Cirrocumulus (Cc) cloud patches, ones between about 15,000 and 25,000 feet above ground level. Some times they evolve to Cirrus clouds within minutes after they form when they’re colder than -30 C (-22 F). Cirrocumulus are short-lived clouds usually in thin, isolated patches. They can have no shading by definition and they can display the most delicate granulations imaginable.

But those patterns change in seconds to a few minutes, and you have to have your camera by your side to get the best shots of that sort of thing, like other nature photographers who shoot birds and stuff like that. Did you realize that by shooting clouds that you were becoming a “nature photographer”? Often these patches can be higher level lenticular clouds (thin sliver clouds) that have smooth portions on the upwind side and then break into tiny elements downstream.

Finally, as the day comes to a close, some Altocumulus clouds might arrive on the scene; if not today, then by tomorrow at daybreak. They may also be in the form of sliver clouds, lenticulars that hover downwind of mountains–look to the northeast of Mt. Sara Lemmon today. But, given the high temperatures aloft, indicating that the Altocumulus clouds will have more water in them than on a cold day, look for some sprouts and little turrets. That extra warmth, say at 15,000 feet, results in an enhance updraft when clouds form at those levels because condensation releases a small amount heat to the atmosphere inside the clouds. That bit of extra heat is likely to lead to those itty bitty turrets (castellanus species of Ac)

Here is an example of the delicate Cirrocumulus (Cc) clouds we may see today and tomorrow.

No rain seen in models for two weeks now, but remember the wild chaos of the predictions beyond six days now, as indicated in “spaghetti plots.” That means rain for southern AZ may well show up again soon, along with that horrific early April cold spell.

The End.

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.

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.

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.

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.

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¹Sassen (1986, Science)