Category Archives: Spaghetti plots

Rainy days and Saturdays

Nice sunset yesterday….as some Stratocumulus spread over the sky underneath a pesky Cirrus cloud cover, clouds that announced the beginning of our next rain spell, now underway.

Light rain is falling this morning at 4:07 AM, and has been for hours, amounting to 0.01 inches.  However, some places in Pima Land have gotten much nicer rains, around a third of an inch in the Cat Mountains overnight, for example; check here.

Progress of the real monsoon, since June 1st, can be checked back there at the beginning of this sentence.  The coastal state of Karnataka has an average rainfall of about 70 inches since June 1st, a below normal amount, believe it or not.  However, being a statewide average, that 70 inches doesn’t reflect the hill stations in the western Ghats, surely to have about twice that amount.

Now, as a further aside, Karnataka, Kerala, two Indian west coastal states  would be a great place to go for a vacation now!  There you could REALLY absorb a REAL monsoon, where passing rains, heavy, pounding, thick with drops, visibility down to less than a mile, go on hour after hour with brief interruptions.  Its really pretty amazing and worth experiencing, at least once.

But, not much lightning there, like we have, because the rain develops mainly through a process not requiring ice, much like the rains in Hawaii where lightning is also rare.  The rain develops largely through the collisions of drops, ones that stick together after they collide, and get bigger on the way down through the cloud, sometimes called the “warm rain process” because ice is not involved, and that causes most of the rain in that Indian coastal region.  Cloud bases are right on the deck, and are typically 20-25 deg C, very, very warm.

In contrast, to continue a pedantic stream, “warm rain” is rare here in Arizony because cloud bases are relatively cool (less than 10 deg C in the summer as a rule), and droplet concentration are moderate to high (hundreds per cc).  Higher cloud droplet concentrations make it harder to grow cloud droplets big enough to collide and stick together inside our clouds.

But, we do get that kind of rain, “warm rain” here once in a great while in Arizona as part of the rain that forms in our Cumulonimbus clouds when their bottoms are especially warm, higher than 10 deg C.  Seems to happen about once or twice a summer in my experience so far.

What’s ahead?

Now that afternoon and evening rains around the area are back for the foreseeable future (5 days), what’s way ahead, beyond the foreseeable future?

There, as you know, when we start thinking about beyond the foreseeable future we start thinking about spaghetti! What do those crazy northern hemisphere-wide plots produced by NOAA with their dizzying numbers of lines mean for us here in Arizona?

First, I present a map of the 500 millibar contours as produced in the Haight-Asbury hippie district by San Francisco State–I mention this because the lines on this 500 mb map look a little nervous and maybe it has something to do with that map origin, being from a cultural area whose norms are “anomalous.”  I have pointed out  on this map, “Our Big Fat Anticyclone”, one whose position is critical for decent summer rains here.  In this map, as you can see, its not really OUR “BFA”, but rather belongs to Amarillo, TX, as of last evening.

Nevertheless, it is well positioned to fan humid air from the southeast into Arizona, as is happening now.  Remember, the circulation around a big fat anticyclone is clockwise.  When it sits on top of us, things are not so good; upper level temperatures are high, humidities are low up there, stifling convection and preventing tall Cumulus clouds.

But when the high is away on holiday, temperatures are lower above us, its more humid up there, and those factors allow for deep convection; huge Cumulonimbus clouds.  It only takes a few degrees difference to go from those dry days we just had with their Cumulus pancakus, to the kinds of days ahead for us now, where clouds stand tall!

Continuing, finally, Here’s is today’s plot for 15 days from now, the afternoon of August 11th, based on global data taken at 5 PM AST yesterday.  What do you see?  You see an arrow pointing to something of a void in all the “spaghetti.”  That void represents the most likely position of our BFA some two weeks from now, and that position is pretty darn good for summer rains here.  And it is in that region, to the north of us, almost the whole time from now!

So, based on this “most likely” position, one would venture that the rich summer rain season we have had thus far, will continue to be active.  Of course, this doesn’t mean rain everyday, but that breaks will likely be short through almost the first two weeks of August.

Can you imagine how tall those desert grasses and weeds will be by then if this is the case?

The last couple of photos document our fabulous re-greening now in progress.  If you haven’t been out in the desert, you should get out there and experience this wonderful event.  Doesn’t happen every year, as we know!

The greening of July

Update at 7:17 AM:  while mods had a dry day today (e.g., U of A yesterday), NWS has a much higher chance at 30% for our area today, and it sure looks like a higher chance.  (U of A Beowulf Cluster mod not available this morning for hi res check.)

While trying to get through the next couple of predicted days with lesser chance of rain though it doesn’t feel like it right now at 7:17 AM, and after a disappointing  0.02 inches yesterday afternoon, I wanted to check the Arizona rain futures in two models, the N-viro Can U-ro (as we would write it today) and the USA WRF-“Goofus”, both spoken with affection, to see how much “green” they have for us.  “Green1” has been the chosen color for rain by meteorologists, a particularly colorful people, who as children had an extra wide assortment of Crayolas and colored pencils.

Both models have a LOT of green in Arizona during the next 6-15 days except, as noted, for today and tomorrow where rain is marginal.

Below, as example from the Environ Can mod result for the evening of July 22nd.  Note green splotches in AZ, lower right hand corner (blue is very light rain; yellows and reds are heavier rains).

Along with the positions of rain here, in the upper left hand corner, is the forecast for where “our” big fat summer anticyclone is going to be on that day: centered way over the state where Dorothy used to live.  The air circulating around that high, clockwise, is circulating moist air into Arizona (while baking Dorothy and a lot of other people in the nation’s mid-section).  I love these maps and what they portend for AZ over the next week!

Below a sample chart for even farther out into the future from a rendering of WRF_GFS from IPS Meteostar for the evening of August 1st.   There is still “green” in Arizona, this time around Yuma, and there has been green in Arizona every day!  With our great start, it could mean that we will experience one of the wettest July’s ever in SE AZ!  The droughty weather pendulum may have swung back to make things up to us.

How do we know such medium range forecasts are have a better chance than usual of verifying?

Of course, if you are a regular part of this blogpire, you will know the answer.

It comes from the NOAA Spaghetti factory.  We meteorologists, not satisfied with one model run, like to mess them up at the start, and then look at the various “perturbed” model runs fro the 500 millibar level, and see if there is one “answer” that remains “strong”, still visible in the output amongst all the many contours of the wrecked ones. The middle of the troposphere, that domain where all weather occurs, is at about 500 millibars of pressure; sea level pressure averages around 1000 millibars (1013.6 millibars is the bottom of the “standard” atmosphere.  We like to see what the pressure patterns are like in the middle because things clarify up there, that’s where you can find jet streams, those steering currents for storms at the ground.

OK, now the punch line, don’t laugh too hard.

Below is the (humorous) plot from NOAA based on last evening’s global data for the 500 mb level due to combining:

1) the model run using the actual measurements made around the world at 5 PM AST,

2) and along with that one run, many model runs due to inputing slightly erroneous data at the beginning of the run.

Many of you will see this as a “knee-slapper”, and it really is because its a faulty production with too many contours.

But, in spite of a faulty NOAA run, there is still some information about our “big fat anticyclone” and where the most likely position will be on the evening of August 1st, some two weeks from now.  Believe or not, it is a powerful tool.

That likeliest of positions of our big fat anticyclone is that little dark spot over the Four Corners area mostly devoid of lines in this humorous output.  On this map, the Four Corners area is straight above the yellow legend line segment. At left,  a close-up of that Four Corners area with the fewest lines.

In the summer, Arizonans “need” to have a high in the middle of the troposphere to the north or east.  And that’s where the signal is strongest, represented by a center of that high situated over the Four Corners area even when the model has been degraded by bad measurements.

So, in sum, look for lots of rain in Arizona overall during the rest of July.  How nice, except when telephone poles are blown over, as happened on Sunday.


PS:  I took a lot of great cloud scenes yesterday afternoon and evening, but you need to have an SD card installed in your camera before a photograph is recorded. So no photos.  I hope this is a useful hint for photographers out there.


1“Green” in the meteorological color scheme of things, means rain, an area where the models think it will have rained is colored green as a rule.  Green has been the choice of meteorologists for liquid precip ever since weather began, back in the early 20th Century at the Bergen School of Meteorology in Norway.  Why did those Norwegian meteorologists with names like Bjerknes, Palmén, Holmboe, Godske, Petterssen, Rossby, Bergeron, choose green for rain?  Just because.


Gone but still there

As expected, the odd pattern of just 24 h ago disappeared on the later model runs.

Is it really gone?

Nope.  Might pop back up on a subsequent run.

While our usual June inferno continues for a few more days (here’s the NWS forecast for Catalina), a cool trough of air is destined to come here 6 days from now and linger for a few.  Here’s the totality of evidence for that assertion, this plot valid 8 days from now, Friday afternoon, June 17th.  In case you have forgotten where Arizona is, I have repeated the map below this one with an arrow to help you out.

What do you see in the western US?

A lot of blue lines!  Ones that outline where a cool-cold trough of upper air will be.  Notice where the red lines are, those ones that outline where the southern periphery of the jet stream will be located, those being the outer boundary of the cool air trough.   They’re ALL WAY down in Baja, California!  This VIRTUALLY guarantees an a trough of cool-cold air along the West Coast in 8-10 days!  Along with that, the possibility that tropical air will move up from the south and get into Arizona.

Yesterday, the model believed a hurricane would form and move northward, its remnant dribbling into Cal and AZ.  The model (at 00 Z last night) saw tropical storms forming, but they remain far to the south of even Baja!

Well, that prediction I showed yesterday was SO STRANGE it certainly wasn’t going to happen nine days out into the future.  It was an outlier.

But, what is guaranteed from an inspection of the maps above, is a trough along the West Coast, and with that, comes the possibility of a rain here, not from the cool air part of the trough, that won’t happen, but rather from tropical air being whooshed up around the outer, warm boundary of the jet, marked by those red lines.  Right now, if you’re in the mountains of New Mexico, eastern plains of NM, and west Texas, you are just about guaranteed to get that tropical air and with it, showers and thunderstorms.

A climate note:  it has not rained in Catalina between June 9th and 19th here in Catalina for 35 years; NO measurable rain on those  days yet.  I’ve reprised the June daily rain frequency for our 35 years here:

What should you take from that?

There are likely climatological factors, one’s having to do with the march of the seasons, that work against even the presence of clouds!  Chances are it is what we would call in climate, a “singularity”, something akin to the January thaw in the northeast US.   Here its a June transition season from the time a cold trough can bring us a bit of rain, and the onset of the tropical air regime with its Cumulus and showers, jet streams not involved then.  (I’ve assumed that 35 years is enough to suggest a real feature, not a statistical fluke.)

So, with this big trough foretold to occur during our normal dry spell-transition period, you’d have to go against the chances of precip in a knee-jerk fashion.  We’d most likely end up BETWEEN where there are showers in cold Pacific air inside the trough, and dry regime outward from that zone, to a plume of tropical air just to the east of us over NM and TX.  Doesn’t mean rain can’t happen, but don’t bet on rain during this period through June 19th.

As a final comment, note the dark area in the central Pacific on these maps. That dark area repersents and extrusion of cold air well toward the tropics out there, also an unsual occurrence, and it is vital for us.  Note that even the blue lines, noting the core of the jet, has extruded southward out there.  That extrusion (my favorite word I think), in essence, creates a “bounce” in the latitude of the jet downstream, a southward extrusion along the West Coast.  The dark hole out there indicates that even 8-10 days out, the computer predictions are extremely confident that there will be that extrusion of cold air toward the equator out there, and that, in turn, strengthens the likelyhood of a  unusually strong  “bounce” trough along the West Coast 8-10 days out.

It will be fun watching this develop, since we’ll like get a much cooler day or two about that time.   But, it would be even better if the hurricane shows up again, and is steered thisaway as it was yesterday!

OK, enough, gotta go ride a horse

Dusty cool snap at hand

In MINUTES, the temperature will head downward as our long foretold (remember the spaghetti plots?) , “dusty cool snap” finally arrives.  This time, from Intellicast,  you can see below the blob coming, that blob of much lower temperatures with an epicenter at Las Vegas. Unfortunately, there are few clouds with this system, oh, maybe enough for a scruff over the Catalina’s a little later this morning and in the afternoon, Cumulis humilis, that sort of thing,  and THEN we’ll get some nice cloud shadows on the mountains for awhile.

If you have a barometer, though, you will get to enjoy the “pressure check”, that sudden, sharp rise in pressure as the air over the barometer gets cooler and denser, mashes down on it more as the cold front goes by!  You could be informing your neighbors about it.  (Actually, “on further review”, with the temperature in descent now (5:18 AM), and barometer on the rise,  I think the cold front has gone by already. )

BTW, while its windy here in Catalina right now, down in Tucson, they’re only reporting 7 knots, no gusts.  This is kind of usual for this situation for us to get the brunt of the winds funneling up the Oro Valley while TUS is protected for the time being.

Still enough wind/pressure gradients around for dust today, but those gusty winds should really be gone by tonight and tomorrow in Catalina as that deep low, still in the Great Basin fades.  See below for a neat looking weather map from where else, the University of Washington.  In case you want to see more maps, go here.

Feels great to be in the circulation of a big low, that one centered in Utah right now (5 AM AST.  People all around the country are probably talking about us and all the weather we’re having hereabouts, at least the ones watching The Weather Channel.

Not much ahead to talk about, just a few very pleasant clear days and rising temperatures.

HOWEVER, updating here at 6:11 AM, and having just checked the NOAA spaghetti factory, it does appear, but with moderate confidence, that another dusty cool snap is ahead for 11-12 days from now in a pattern remarkably like the current one with a “Big Trough” along the West Coast again.  That event would center around June 7th plus or minus a day or so.  It will be fun to keep an eye on this every coupla days.

The End.

Bad trough! No precip, just a dusty cool snap ahead

Making its entrance today into the Pac NW is the first stage of that MASSIVE trough, foretold long ago by your NOAA spaghetti factory to begin happening about now, and peak out between May 25th-26th.

Now you’ll understand why, if you want to get a handle on the exceptional things that might be in the weather pipeline, you have to have some spaghetti every day.  (Note:  right now, 5:10 AM, the “factory” is down, has a bug in the sofware that REALLY makes it look like “spaghetti” because too many lines are shown.  Its kind of a hoot.  I will have to inform NOAA again, as I did a few days ago, or maybe you can, that something is wrong.  Their answer to me back then was that they had not yet noticed the problem; made me think I was the ONLY one looking at them, also funny!)  It is a powerful tool, one that also foretold the excessive heat we are experiencing today–recall the “June in May” writeup based completely on spaghetti.

OK, onward…

That second pulse of cold air aloft, the one shown below in the forecast map for the afternoon of May 25th (upper left panel) over Reno, NV, is REMARKABLY strong for this time of year, and will bring exceptionally low snow levels to northern and central California for later May.

And look at how much the surface map (upper right hand panel) is in a dither with the circulation around the low pressure at the surface extending all the way from Illinois to California!  Its HUGE!

But what about us?  What does all this atmo commotion mean for you and me?

Briefly, just Dust in the Wind, to allude to an old, sweet song by that heavy metal, huge hair group, Kansas, that hit the scene in the 1970s and were quite something I thought.   Yep, the dryness in this HUGE trough makes me as sad as their song does about being only a spec of dirt.

Look at the lower left hand panel in the forecast chart below to see what the moisture expected at 700 millibars, about 10 k above sea level, or a little above the top of Mt. Sara Lemmon, for the afternoon of May 25th.  It’s grim.

As you can see there are two but regions in the SW and West that have moisture at 10 K; that in central and northern California extending northward and expanding eastward, and a TINY stream from the tropics hundreds of miles to the east of us in western Texas.

Thus, there is no HOPE whatsoever of rain in southern Arizona with this huge system, because,  like almost all of our cold winter systems, the core of the jet stream at 500 millibars, that band of wind that circumscribes the Pacific moisture over northern Califonia below, NEVER gets here, dammitall!

And those powerful winds around the outside of the trough core, really representing trajectories of subsided air from the cold Pacific, just race around it, preventing an intrusion of tropical air.  The normal tendency for upward motion on the EAST side of all troughs trough is totally inadequate to produce clouds and precip with such dry air.  About the only thing you could expect to see is a few filaments of rapidly moving CIrrus, maybe a lenticular or two on the 25th-26th, and, after the cool air moves in on the 26th, a couple of Cumulus humilis.  And maybe the same kinds of cloud fragments off and on before that.  Otherwise, the only “precipitation” will be “lithometeors”, dust particles.  I suppose they might add up to an eighth of an inch over several days.  Hahahaha.

Sure looks like the Catalina area will be raked with winds above 40 mph in gusts with this system before its over.

Check the excitement at the NWS here in Tucson here.

The End.

Cooler hot air riding in from the West later today

Should arrive by later this afternoon as foretold in models, unfortunately, in view of fires, with a lot of wind before and after a dry cold front gets here, too.  Check the NWS forecast for Catalina here.

The Cirrus clouds this morning?  The only trace of clouds we’ll see with this trough and “cold front” today, if you can call it “cold”,  with temperatures still in the 90s.  Those clouds will be gone by mid-day.Tomorrow morning we’ll notice a temperature difference!

The weather ahead, as you likely know, fiercely hot early next week, after our little cold front goes by today, followed by another dry, windy,  “cool” front around May 25th.

Of course, if you’ve had your NOAA spaghetti plot this morning, you probably already know about that weather change eight days from now.   Here’s a chart from last night’s spaghetti run.

What do you see in the map below?


Except here at this blog, you have NEVER seen a weather map like this before!  Imagine your TEEVEE weather presenter showing you something like this!  Heck, where’s the land?  Well, you can see Florida and Communist Cuba in the lower right hand corner.  Just remember that Arizona is somewhere to the west of Florida.  The outer dotted line is the Equator, where the date changes.  (Just kidding, want to see if you are paying attention.  Eyebrows should be raised on a couple of counts because TWO things are wrong in that ONE sentence.)  OK, on to the map and no silliness….

First, those yellow lines are where the actual weather map contours of 576 and 552 “decameters” at 500 millibars pressure are predicted to be in last night’s run, on the afternoon of May 25th.   When those yellow lines bulge southward, as they do in our domain in the West, a trough was foretold in that run.   All the other red and turqoise lines help determine how reliable where those two yellow lines will be.

Look at all the red lines pushed down toward the Equator in our sector!  There is nowhere in the northern hemisphere where so many red lines (576 decameter contour) extrude so far toward to the south!  These red lines are from the same model, but run with slight changes in “initial conditions” (you might think of it as with a couple “bad balloon” readings) to see how robust the “signal”, the predicted features in the model are.

So, when all the lines, as wobbly as they are, do the same thing (extrude to the south, or bulge toward the north as they do northeast of the Hawaiian Islands) then the “signal” is quite strong, and the foretold feature more reliable.  So eight days from now, a pretty long time in model predictions, we can be pretty darn confident there’ll be a MAJOR trough in the West that will affect Arizona.   See how the turqoise lines also dip southward for the most part.

And what does that mean as far as Catalina weather?   Dust, wind, and cooler weather for awhile; “dusty cool snap.”

No rain is indicated at this time, though the summer thunderstorms will be close prior to the dusty cool snap.

OK, I think I have confused things enough.


The End.




Rain and cold foretold for Catalina on Saturday as big, long-foretold storm bops Cal then moves on to AZ

Things are falling into place.  Remember the spaghetti from a week or more ago, in which it was clear, or at least at attempt was made to explain to both readers of this blog,  that a large trough was almost certainly going to be along the Cal coast?  We intuited that from the lack of spread in some contours in that “spaghetti” plot along the West Coast some week or more in advance.

Well, that trough is truly turing out to be a behemoth, a gigantosaurus for April.  The people of California are going to be very excited today and tomorrow about cold, showery weather, mountains of snowfall in the mountains, maybe a funnel cloud or two in the Sac or San Joaquin Valleys.  Here is that trough as shown on today’s 5 AM AST 500 millibar map from the U of WA weather department, the one prophesized with high confidence so long ago:

However, for many days after that, the models did not think the rain in Cal was going to get here.  Of course, still being in the cool season, our rain is nearly all dependent on whether the jet stream in the middle levels (500 millibars or about 18,000 feet above sea level) is able to be over or especially,  south of us here in Catalina.

But lately, in the forecasts, been shifting the jet southward and rain has started to show up in two or more recent model runs, always a good thing.  You may also remember that in our spaghetti plots back a week ago, it was not clear in the models where the Cal trough was going to go after it bashed the West Coast.  Hence, while things were clear for Cal (actually, they were going to be cloudy and rainy), they weren’t so clear for here until lately.

From the U of WA, this for Saturday morning (colored splotches denote where the model thinks precip has fallen in the prior 3 h); below, the jet stream at 500 mb from IPS Meteostar for the same time.

Yesterday’s clouds

In case you missed them….   Cumulus and Stratocumulus, punctuated with a splash of Cirrus fibratus undulatus (Cirrus with rolls, showing something akin to swells in the ocean in the atmosphere).  The wind at Cirrus level in that shot is blowing from left to right.   No ice falling out in Cu and Sc; too warm at cloud top.  Only about -5 C (23 F) or warmer.

The End.

Big storm to strike California on April 12th; maybe it’ll bring some rain here though I doubt it

If you have had your spaghetti this morning, you would be able to write headlines like this.  Here’s the plot, no, not  like in a detective story, but an actual plot from the Spaghetti Factory at NOAA, valid for 192 hours from last evening, or in plain speak, next Thursday afternoon at 5 PM, April 12th, AST:

SInce you’ve had lessons in spaghetti, you should be shrieking when you see this one, “My gosh, look at that potent, powerful storm about to strike California! I can’t believe one that big would strike in the middle of April. Quite unusual.”

OK, calm down that bit, but still stay excited.  Yes, the Dark Void radiating from approximately where Santa Claus lives in this plot shows you where there can great confidence that a big trough is going to be present where the Dark Void ends.  Notice the dark tube extending from Nome-Anchorage, AK, all the way SSE to off northern California.  And another one in eastern Canada, etc.   That, as you know, is where a trough will be at 00Z on Friday, April 13th (in ordinary time, 5 PM AST on the 12th, and with that, a strong low center is coiled and ready to strike.  Exciting.

Let’s go to the next chapter of this plot, one but a day later, valid for 5 PM Friday the 14th and see if the Darkness is able to extrude (I really like that word because its fun to stretch it out and make it sound like what it is describing–“ex-TRUDE”, you can feel it oozing along, its an onomatopoeia, like “thunder”).  Now where was I?

Oh, yeah, the plot, revealing the plot (story-line goes), for the next day is below.

Sorry you you have to see this.  After explaining the above plot, and with the background on spaghetti plots I have provided you in ealier blogs, I don’t have to tell you how disappointing the one below is.  Only a slight chance of rain here exists, and there is not much confidence in configuration of the trough and jet stream around it after it rockets up to the Cal coast on the 12th.






















There is another chance of rain indicated from last night’s run, that on April 19th, a day in which it has not rained in 35 years here in Catalina.  Odd.   Are we due?  Or are there climatological factors at work to minimize rain around the middle of April?  I really don’t know the answer.  However, it is not a very reliable prediction at this point.  It will likely come and go in the model runs in the days ahead.

In the meantime, today’s clouds

Here are a couple of shots of the Cirrus/Cirrostratus-with-contrails1 mesh we have overhead this morning, ice clouds, as you now, with a hint of lenticulars off to the distant west.  Should have nice Cirrus-ee clouds all day, and again, a chance of Cirrocumulus or very high Altocumulus lenticulars.  Not much chance of anything below about 15,000 feet above the ground today.








1I HATE contrails except when I am flying to some fun place I want to get to in a hurry!

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.





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.