Category Archives: The weather ahead

“Peru’s Niño”

I thought you’d like to read this (Peru’s Niño), forwarded to me by Niño expert, Nate M.   Pretty incredible to read about what is happening down there in the wake of the Big Niño of 2015-16,  which really turned out to be more of a couch potato in terms of weather production in the Great SW.

But, all this winter,  along the Equator near the coast of South America, there has been something we used to call an “El Niño”,  but is downplayed or ignored these days because of a new definition that seemed to explain more weather when it occurred, “Region 3.4” a large zone along the Equator WAY out in the Pacific rather than something near the South American coast (that zone now called, “Regions 1 and 2”),  as nicely illustrated by NOAA here.

But what has been the effect of what we might call the “Classic Niño”, a warm strip of water along the South American coast, one that doesn’t extend too far into the Pacific?  “Read all about it”, as they used to say.   Its pretty remarkable.

And here’s what the SST field looks like.  Its boiling down there off South America!  (Speaking figuratively, of course):

Sea surface temperature anomalies as of yesterday from the Navy!
Sea surface temperature anomalies as of yesterday from the Navy!  Wow.  That hot water is fueling giang Cumulonimbus clouds, ones that spew out huge anvils that can affect the weather in the mid-latitudes, disrupt the normal winter patterns of where highs and lows like to go.  Could such a warm anomaly, limited to the near coastal region of South America, have created this astounding winter in the West?

Peru’s Niño can be thought of as a “classic Niño”, the ones written about in the decades before about 1990 or so when the definition of what constituted a  NIño (or Niña) was expanded and delineated more sharply among several definitions that were floating around. We ended up focusing on a region WAY out in the Pacific Ocean called, “Region 3.4” that SEEMED to explain more over the prior years.

What’s so interesting about this is that the “Classic Niño” has been underway pretty much all this winter, and we’ve had, especially in California, a classic Niño response; that is,  abnormally heavy precip farther down the West Coast that no one anticipated.


Well, the correlations with Cal precip and “classic Niño” occurrences will take a huge jump upward after THIS winter!

End of Statement (hand-waving)  on Niñoes.


Local weather statement:  for immediate release

Cooler, fluctuating weather foretold here for that latter part of March, I don’t know how many weeks ago, is on the doorstep after the long, anomalously hot dry spell.  Poor wildflowers have been suffering, too, fading, looking a little stunted after a great beginning, one rivaling the great displays of 2010.

All of the local weatherfolk are on top of this now, and so no point recasting that stuff.  HECK, you can go to Weather Underground1
and get as “good as can be” forecast for Catalina (Sutherland Heights) out to ten days!  And, there’s nothing worse for a weather forecaster with forecasting in his blood, than to be excited about an “incoming” and when you mention it to a neighbor he replies, “Yeah, I heard about that already.  Supposed to get a quarter of an inch.”  There is no air whatsoever in the “balloon” after that.  So, if you have a weather-centric friend who says something about the upcoming weather, pretend that you haven’t heard about it yet, “DON’T say something as hurtful, as “Yeah, I heard about that already.”

So, here, we go the long route because most weatherfolk are afraid to go too far into the future because its often WRONG.  Our models tend to lie a lot after about even a week, so only the brave go out even ten days!

However, here, we go out as much as two weeks and more because its not a truly professional site but rather want to get something out there earlier than other people, sometimes called a “scoop” in the news and weather business.  That’s why our motto here is, “Right or wrong, you heard it here first!”  Furthermore, if a longer range forecast posted here is WRONG, you won’t hear about it anymore!

Cloud maven person will say this about the first incoming of several fronts:  comes in early Thursday morning, its strong!    Rainfall potential:  10% chance of less than 0.12 inches, 10% chance of more than 0.75 inches.  Best of those is the average, or about 0.4350 inches in this one.  It has great POTENTIAL to be a soaker, but mods have been all over the place; hence, the large range of potential amounts.  At least some measurable rain seems to be in the bag, a paper one please, because plastic is insidious.  Note, CMP’s forecast is more generous than that found in WU’s latest forecast for Catalinaland.

The weather WAY ahead, unprofessionally so

Let us look beyond the professional forecasting limits to April:

We know we got several storms/fronts zipping across AZ as March goes out like a lion, but what about April?

Looks like that pattern will continue into April with temperatures below normal for the first part.  The end of the unprofessional forecasting portion of this blog, though we do have our NOAA spaghetti to hang our umbrella on….  Check it out for about two weeks ahead.

Some clouds recent clouds, including a couple from yesterday

2:33 PM.  Yesterday afternoon saw a few globs of lenticular forming on top of mini_Cumulus clouds, ones that made you think the summer rain season could be at hand, given the 90+ heat of yesterday around these parts.
12:52 PM.
12:52 PM.  A high  (above 30 kft above the ground) and cold (less than -40°C patch of Cirrocumulus cloud that is going to transition to CIrrus over the next 10-20 minutes.
1:12 PM:  Later that same patch as those cloudlets spread out and merge into just an ordinary Cirrus after being that delicate-looking patch of Cirrocumulus. Most Cirrocumulus clouds are not this cold, but rather evaporate or fatten into larger elements of “Altocumulus” clouds, rather than transition to Cirrus.
Had a nice sunset a couple days ago (15th), some liquid Altocumulus cloud slivers with higher Cirrus.

The End

1Although “Weather Underground” might sound like an org has a radical origin, maybe something left over from the late 1960s, this particular one was NOT formed by 60s “weatherman” terrorists like Bill Ayers and Bernadine Dohrn (the link is for those of you who may have set trash cans on fire, as happened at San Jose State to protest the Vietnam War, to look back at those days in horror or nostalgia; take your pick) , but rather by genuine weather geeks (haha, I count myself among them, those that can’t get enough of weather, there can never be too much, like the guys mentioned in this “Cloud City” article.)

Measurable rain to fall in Catalina at last!

The chance of measurable between this afternoon and Saturday morning isn’t 10%, or even 50%, but 100% as seen from THIS keyboard.  If you want a better forecast than that, go to the NWS, Tucson, or see Bob’s expert take.  I like Bob.   But we go for it here; don’t mess around.  The last measurable rain, only 0.10 inches,  fell WAY back on November 27th.  I wonder if you remember it?  Probably not.  I don’t.

Rain hits after midnight tonight after a day of heavy middle cloud overcast (that would mostly be Altostratus opacus, probably with virga later, maybe some Altocumulus embedded or at the bottom or below that As layer, with mild temperatures.  Don’t expect sunset color tonight since the cloud deck is likely to extend too far to the west for that.

These middle and upper clouds, whose bases will lower as the day goes on and during the night when the rain hits, are associated with a surge of moist air from the tropical Pacific.  This chapter of rain will followed by an extremely sharp cold front passage (“FROPA” in weather speak) late Friday night or early Saturday morning with another round of light rain.

AZCat model output foresees quarter to half inch here in Catalina.

Wind will be a problem.

This situation will be accompanied by a really intense low developing to the north of us and the wind by tomorrow mid-day through early Saturday morning will be ferocious.  We’re likely to see gusts here in Sutherland Heights to well over 50 mph from the SW as the wind bunches up against the Catalina Mountains, helping to increase speeds here in The Heights.  CMP suggests putting loose stuff in the yard away somewhere.  He might even do that himself instead of trying to find where all his baseball caps, left outside on the front porch,  went the next day.  Some composition shingles likely to come off, too.

The Weather WAY ahead

The good news here, if you like below normal temperatures and chances of rain or snow, is that the forecast models are indicating we’re in the mean trough position.  Periodic fronts and troughs will affect the SW over the next two weeks, bringing with them at least a CHANCE of rain, while cooler than normal spells are virtually certain.

Check out the spaghetti:

From last night's computers, valid two weeks from now, Dec 30th at 5 PM AST.
From last night’s computers, valid two weeks from now, Dec 29th at 5 PM AST.

Notice the broad dip to the south in those red lines beginning in the eastern Pacific Ocean then down to Baja and then back toward the east-northeast into the southern Plains States.  The 5700 meter height contour (red lines) is pretty much on the edge of the jet stream, and a dip like this would be considered a weakness, a vulnerability for troughs in these plots.  Remember these are initial starting conditions in last evening’s global data with DELIBERATE slight errors put into those data to see how slight errors affect the outcomes.   There are almost no differences at the beginning, the errors are so slight.

And there are ALWAYS slight errors in our measurements, of course, so spaghetti helps pin down what those errors might do to embarrass us forecasters.   When those red (or blue lines) cluster somewhere into a band, it means that the errors introduced have little effect on the position of the troughs at this level (500 mb).

For example, over there off SE Asia, the cold continent and the warm ocean constrain the jet stream into a tight bundle of contours.  Errors don’t have too much influence on where that jet stream will be off Asia;  its pretty much locked into place.

Down stream, things are more of a mess, but you can still see, in this case, where there is kind of a bunching to the south in the red lines in our SW domain.  So, there would be, oh, moderate confidence of passing upper level troughs during these latter days of December. At least that’s what I see from this from here.

Worried about wildflowers now, due to the paucity of fall rains….so really hope December can come through with some major rains!

The End

Rain, inches of it, still foretold for Catalina Mountains; and, an inch or more for Catalina itself!

In case you don’t believe me, here’s the model crunch from our very own Banner University of Arizona Weather Department (aka, Hydromet and Atmos Sci Dept).  You can watch the storm play out hour by hour here.

The large totals of rainfall expected by mid-day this Monday, November 21st. This output based on the global data from 5 PM AST last evening.
The large totals of rainfall expected by mid-day this Monday, November 21st. This output based on the global data from 5 PM AST last evening.  As you can see, I hope, Ms. Lemmon is supposed to get over 3 inches!  Wow.  How great would that be? I put some writing on this image to help you understand where you are.

However, as you can see, to throw cold water on such a great prediction, we are in the HEART of a rather narrow band of heavy precip, which raises the uncertaintly level a lot on just how much rain will actually fall.    Somewhere, these days, there is a Gaussian like distribution of the rainfall at point locations so you can see just what the model spread is in the rain predictions, but I haven’t located it and am too lazy to look right now.  If I come up with that, will post it.

So, just as good as that, I will say that measurable rain will fall in Catalina between Sunday evening and mid-day Monday that the least likely amount is 0.15 inches (10% chance of less), which would be a real poop, and the most, 1.00 inches (10% chance of more, a luxuriant rain, washing so much dust off stuff).

The average of those extremes is usually is closer to the actual total, which in this case would be 0.625 (correction! 0.575!  Egad, dividing by 2 is still pretty hard for me) inches at my house.  The idea here is that we meteorologists often know what’s NOT going to happen better than what is,  in the domain of precip forecasts,  and so by starting with extrema, to be erudite there for a second, we can narrow our predictions down, not get too carried away as often happens here.

BTW, if you want really great, professional level forecasting besides that by the TUS NWS , see Bob’s discussions!  He’s always got great stuff.

The first high clouds ought to be arriving later this afternoon.  Have cameras ready.  Should be a nice sunset to go with them since there shouldn’t be a total overcast to the west.

Really looking forward to this rain!

The End

May in November to end; rain dead ahead

Rain?  Cumulative totals predicted here from the University of Arizona Hydro and Weather Dept.  Starts overnight Sunday.  For those too lazy to review the information at the link above, here is a map of the rainfall totals ending at 11 PM, November 21st:

Cum precip through 11-21-2016 11 PM AST

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.

The ensemble or spaghetti plot from the NOAA spaghetti factory from last evening's global data.
The ensemble or spaghetti plot from the NOAA spaghetti factory from last evening’s global data.

The End.


1This sentence will be deleted in the event of a drier than average November and will, therefore, not be on record.

Colorful evening ends day with a colorful morning; a note on the great Cal rains of October 2016

Not much else to talk about, no rain of course;  what is that?

But with so many colorful scenes yesterday, we can be partially sated by the  lives we lead here sans rain here.  October ended with a puny 0.01 inches in Sutherland Heights.

Now, because I grew up in California and remain a little Cal-centric, this brief diversion from AZ:

But droughty Cal got nailed though, from about San Luis Obispo, so we can be happy about that I guess.  One station, Gasquet RS,  near the Duck border,  got just under 28 inches in October; stations in the Santa Cruz Mountains, way down by Monterrey, got between 14-17 inches!  From the California-Nevada River Forecast Center, this nice map of October rainfall anomalies in that domain.  Red is real dry, and that’s the color we would be in if it was the California-Nevada-Arizona River Forecast Center:

Many departures are far over the map color-coding limit of 350%, but are over 1000% of average!
Many departures are far over the map color-coding limit of 350%, but are over 1000% of average!  Note red below normal swath.  This tells you that the mean area of low pressure at the surface and aloft was just off the West Coast.  Pac NW set maximum October rainfall records, too.

But let us not dwell any more of generous rains that others got, but celebrate the color and clouds of Arizona.   Here are yesterday’s glorious scenes, beginning with a spectacular Altocumulus lenticularis under some Cirrus at dawn:

6:37 AM.
6:47 AM. Ac len stack.
10:51 AM. Tiny patch of Cirrocumulus tried to hide in front of some Cirrus. Hope you weren’t fooled and logged this sighting in your cloud diary. Cloud maven person almost missed it himself.
12:50 PM. There were lenticulars aplenty yesterday. Here’s another one in a location a little different from normal, beyond the Catalinas. Upwind edge is the smoothest one at right. No ice streamers coming out the downwind end, so must have been pretty “warm”. Lenticulars, due to their tiny droplets and those droplets having short life times, have been known to resist ice formation to temperatures well below -30°C -22° F). Pretty amazing.
2:42 PM. Kind of clouded up in the afternoon, and with breezes, made it seem like something was up. It was, but far to the NW of us. We have been under a streamer of high to middle clouds originating deep in the Tropics for a couple of days. Here some lower level moisture has crept in on cat’s feet, to be poetic for a second, and has resulted in small Cumulus and Stratocumulus clouds underneath the Cirrus and lenticulars standing around. All in all, though the temperature here reached 87° F, a very pleasant day.

Now, just some nice lighting and color:

5:32 PM. The almost flourescent plant in the foreground is what is known as a “cholla.” The end elements fall off quite easily and attach to things like your pant leg if you brush by them on a horse, or if back into them while walking and correcting your horse for something when he’s acting a little “wild.”  I can report that when seven or eight of them are stuck to the back of your shirt, its really hard to get that shirt off.  In fact, it just about won’t come off without a major scream.
5:35 PM. The higher Cirrus are shaded by clouds to the west, but the lower remnants of Stratocumulus/Cumulus and a few Altocumulus are highlighted as though they were meant to be for this photo. So pretty.  Notice, too, how there seems to be more than one layer of Cirrus.
5:44 PM. Cirrus and Altocumulus, the latter with some turreting making those the species, “castellanus”, if you care.
5:47 PM. A nice flame-out of Cirrus occurred as those pesky clouds blocking the fading sunlight from striking them opened up below the horizon. A few Altocumulus castellanus can be seen, too, but relegated to shadow status.

In a further celebration of dryness here, let us examine the rainfall cumulative rainfall predictions calculated by the University of Arizona’s Dept Hydro and Atmos Sci computer the period ending at Midnight on November 5th.  Says the coming rain in the State misses us here in SE AZ while falling just about everywhere else, of course.  Dang.  Let’s hope it one of the worst model predictions ever!

This really poor forecast is based on the global data from last evening at 5 PM AST.
This really poor forecast is based on the global data from last evening at 5 PM AST.


The End.

Rainbows and sunsets; also, fall weather coming in October!

Should be some good rain today in Catalina, FINALLY!  Thinking maybe half an inch or so over the next 24 h, something decent,  as tropical air drains o northward and over us out of tropical storm remnant, Roslyn (“Rozzi”).

Clouds and weather interruption:

Due to the name of our weather-affecting tropical storm, Roslyn, I am now reminded of a profound, life-altering “Hallmarky” chapter of life when I was in HS, involving another Roslyn  (aka, “Rozzi”).    In an another attempt to increase blog readers, those really not interested in clouds and weather anyway,  I have inserted this story about a 15-year old, shy boy and his incapacitating crush on a Rozzi R as a junior in HS I suspect it is a fairly common one in some ways, although this one leads to the formation of other people with a different classmate.    The Story of Rozzi R

This story was passed to Rozzi, who had no idea who I was,  only in 2009, btw.  She seemed to like it, and told me about her life, family and three kids.  I think its OK to share it.


Back to weather, at 7:11 AM, one pulse of rain is within a half an hour or so.  (Later, we only got sprinkles out of that first pulse).

Yesterday’s clouds

Nice rainbow last evening; nice sunset, too:

6:26 PM. Altocumulus and
6:26 PM. Altocumulus and patches of a higher mostly ice cloud (Cirrus spissatus or Alstratus?) provided quite a nice sunset yesterday evening.  Back the other way, were rainbows galore.
6:11 PM. Rainbow under a more or less stratiform remnant of a Cumulonimbus cloud.
6:11 PM. Rainbow under a more or less stratiform remnant of a Cumulonimbus cloud.
6:17 PM.

The Prodigal Storm yesterday afternoon

Yesterday afternoon had quite the dump and something of a little ‘boob from the outflow winds, so much rain came down initially around Oro Valley/Marana, west Tucson, south of Pusch Ridge.  Was heading this way, too, with nice big, black, solid-looking base.  Started a video of it, thinking about the gush was to strike Sutherland Heights/Catalina.

Here it is, in all of its glory and subsequent dissipation:

3:09 PM. Outflow from TUS storm builds ledge of Cumulus base S-SW of Pusch Ridge.
3:09 PM. Outflow from TUS storm builds ledge of Cumulus base S-SW of Pusch Ridge.
3:20 PM. Only 11 minutes later that new base has unloaded its load on Oro Valley. ).59 inches at the CDO and Ina Road intersection yesterday, but likely an inch fell out of this in the peak rain area. Note how the winds are pushing rain and dust west and northwest.
3:25 PM. She'll be comin' around the mountain when she comes. This was looking so good for us. Why? Look at that great SOLID base coming at us ahead of the rain!
3:25 PM. She’ll be comin’ around the mountain when she comes. This was looking so good for us. Why? Look at that great SOLID base coming at us ahead of the rain!  The lower scruffs of cloud are called “pannus” and in this case they are created by the nose of the outlfowing winds from this storm.  What you want is for those outlfowing winds to keep generating new, fresh Cumulus bases, ones that explode upward into Cumulonimbus clouds.  Without the new, good base and the updraft that goes with it, all of the rain can fallout in less than half an hour from the ones already raining.  Its a supply thing, you have to keep it going.  What if there were no new people born?  Well, after awhile the supply of people would run out.
3:31 PM. By this time, you're getting worried about this incoming system. Look what's happening to the formerly solid base. Its beginning to get "lumpy" looking with dark and lighter spots telling you the updraft is getting broken up, fallling apart, maybe due to the blockage presented by Pusch Ridge.
3:31 PM. By this time, you’re getting worried about this incoming system. Look what’s happening to the formerly solid base. Its beginning to get “lumpy” looking with dark and lighter spots telling you the updraft is getting broken up, fallling apart, maybe due to the blockage presented by Pusch Ridge.  But there’s still hope, the updraft MIGHT reassemble itself….and there are still a couple of pretty good base “hot spots” where the updraft is still good.
3:37 PM. "Its is finished."
3:37 PM. “Its is finished.”  What;s heading toward Catalina is that transparent veil of rain on the left of the shaft.  We now have no chance for a major dump.  Maybe it will measure though, a few hundredths…
3:44 PM. Need more be said? Sprinkles occurred here, did not measure. Warning: A sprinkle isn't drizzle, a continuing theme here.
3:44 PM. Need more be said? Sprinkles occurred here, it did not measure. Warning: A sprinkle isn’t drizzle, a continuing theme here.  Look at the “crapulent” bases now!  Oh, me.  I wanted to go in the house and never come out again, it was SO DEPRESSING to see this happen.  Lots of storms make it past Pusch Ridge, too, but not this faker.
3:44 PM. As usual, major shafting occurred AROUND Catalina, and not on it, pretty much like this whole summer has been.
3:44 PM. As usual, major shafting occurred AROUND Catalina, and not on it, pretty much like this whole summer has been.  This is looking north toward Bio2
5:16 PM. Nice interplay of rain and sun.

Models, with spaghetti support, show a strong, but dry,  cold front coming through next week, and fall will be in the air as nighttime lows drop into the 40s in our colder, lower spots, like at the bottom of Catalina State Park, in the CDO wash, etc.

The End.

Rain follows the jet

0.02 inches of it, anyway, as the core of the jet stream at 18,000 feet or so passed by Catalina yesterday afternoon.  Keep your eye on the orange and reddish streak in these progs from IPS MeteoStar yesterday morning beginning at 5 AM AST and how it slides over us as the clouds began to ice up:2016042812_CON_GFS_500_HGT_WINDS_0005 AM yesterday.  Jet at this level races across central AZ.
2016042812_CON_GFS_500_HGT_WINDS_00611 AM yesterday.  Maximum winds getting closer!  Tiny Cumulus clouds begin to appear over the Catalinas and on the west to north horizon.

11:40 AM.
11:40 AM.

The jet separates deep cold air on the left side, looking downwind, and deep warm air on the south side.  The deep warm air prevents Cumulus clouds from getting very deep due to inversions and stable layers where the temperature does not change much with increasing height, or even rises.  The temperature at 500 millibars or 18,000 feet above sea level dropped from -17.7 °C to -21.1° C over TUS yesterday between 5 AM and 5 PM, while the temperature about which ice begins to form in our clouds dropped about 400 meters during that time.  With the temperatures at the ground rising into the mid-70s as the colder air moved over us, Cumulus clouds deepened, reaching the ice-forming level between 1 and 2 PM.

Also with patterns like this, the cyclonic rotation (vorticity) in the air above us is increasing like mad, and that leads to a gentle upglide motion in the atmosphere, one that also helps cool the air aloft and usually produces sheets of clouds like Cirrus, Altostratus, Altocumulus and NImbostratus.  But yesterday the air was too dry for sheet clouds to form.

First ice was noted just after 1 PM.  Can you find it?

1:11 PM. Looking N toward the Charouleau Gap.
1:11 PM. Looking N toward the Charouleau Gap.  Tiny puff of ice ejects from a Cumulus humilis cloud based at about 8 thousand feet above ground level.  Bases were running about -5 °C

Keep you eye on the brown and yellow streak.

2:31 PM. Cumulus and Stratocumulus clouds launched off Pusch Ridge and the Tucson Mountains stream toward Catalina. The sky begins to fill in rapidly.
3:44 PM.
3:49 PM.
3:57 PM. A horse eating as it clouds up.
4:33 PM.
5:09 PM. Light rain falls in Catalina/Sutherland Heights.
6:04 PM. RW- (light rain showers) continue in Oro Valley.

5 PM yesterday.  Just passed!  B y this time, Sutherland Heights had 0.02 inches as  the tops of Cumulus and Stratocumulus complexes continued to cool and ascend.   The sounding from TUS at 5 PM AST (launched about 3:30 PM AST) indicated the coldest tops had reached -20 °C or so, plenty cold enough for ice, virga, and light rain showers.  Too bad the bases were so high since we could have had some real rain if they had been lower.

But, we were “lucky” to get that.  Even the great U of AZ model had no rain anywhere near us late yesterday afternoon when it fell!  THAT does not happen very often.

Looking ahead….today:

Nice Cu, ice, too.

Farther out:

Substantial rains, maybe half an inch or so,  still on tap between May 6th-8th as previously foretold here.  Yay!  May averages 0.38 inches here in Catalina.  More rain likely after that episode, too.  So an above normal May in rain is pretty much in the bag now.   Could be an especially great May, too.

The End.

April to have measurable rain in Catalina!

In the meantime, step aside;  a cold front is upon us, a dry one, unfortunately.  Should arrive by noon, bringing some small Cu here and there, some Stratocu piling up against the Catalinas, and maybe some lingering Altocumulus lenticular clouds which we got right now (4 AM) downwind of the Catalinas.

From Intellicast, this nice map:

As of 4 AM AST, the 24 h temperature change. The blue blob shows the encroaching cold air.
As of 4 AM AST, the 24 h temperature change. The blue blob shows the encroaching cold air.

Barometer will rise, too, as the cooler, denser air piles on top of it.  There’ll likely be a brief windshift to the NW, followed by backing to the SW again.

Over the next couple of days, the deep cold air in the  interior of a lingering, massive trough will settle over us, dry up top, but enough moisture in the lower layers below to produce eventually deeper Cumulus, though not today, ones likely to reach up to the “glaciation” level, which will be close to -12° C to -15° C in this situation beginning later tomorrow through the April 1st.   The bases of the clouds will be near the freezing level.

Glaciation means that ice will form in those Cumulus clouds, and some (snow) virga will drop out the bottom.  So, some snow showers or just light rain showers are likely on the Catalinas, maybe a trace or hundredth here, too,  beginning later tomorrow  through April 1st.

Should be some really pretty deep blue skies, too, cloud shadows producing quilt-like patterns on the mountains, that sort of thing we are so lucky to enjoy here.

As you know, this end of month March “lion” (at least in wind, anyway) was long foretold in the NOAA spaghetti.  Remember how we could laugh at model outputs that didn’t have a big trough here at the end of the month?

But now we wait and see if we can drain a cloud or two of a hundredth.  Overall rain chances not looking so “strong” now out of this whole several day situation.  Dang.

Clouds will be around today, especially after the cold front goes by, but its unlikely they’ll have anything drop out the bottom.


“2warm4ice”,  to be that bit textual.

Model says today’s cloud tops won’t reach -10° Ç, our magic temperature where we can usually start to thinking about ice forming in AZ clouds, those with our usual cool  bottoms.

Of course, if you’re really sophisticated, you know that the temperature at which onsets in “continental” Cumulus clouds like we have here in old Arizony,  is related to cloud base temperature:

The warmer the cloud bottom, the higher the onset temperature for ice1, “strangely believe it”, as we like to say here after Jimmy Hatlo the cartooonist thought of it first when he was making fun of RIpley’s “Believe It Or Not.”

Now onto the forecasting frontier, forecasting weather patterns way ahead, to far in advance and too specific to be truly professional

Let’s start with something easy.  Its gonna warm up real good after this big trough goes by– see spaghetti below, where a big ridge moves over us for a couple of days.  It won’t last.

Valid at 5 PM AST, April 3rd.
Valid at 5 PM AST, April 3rd.  Notice, too, that unlike most of the spaghetti pe degree of chaos introduced by the deliberate errors input at the start, have little effect (as usual).  The  blue and red contours are bunched really well.  So the positions of the ridges and troughs are normally well predicted out to this time.

Then,  uh-oh, as Robert Ellis Orrall used to sing, in 192 h, predictability begins to fall apart, but not real bad, and it shows a trough is moving in over us.

Valid at 5 PM AST, April 5th. Red contours are bunched enough so that a nice sized trough in the SW is pretty guaranteed.
Valid at 5 PM AST, April 5th. Red contours are bunched enough so that a nice sized trough in the SW is pretty guaranteed.

Finally, at the extreme end of the medium range forecasting frontier, this:

Valid at 5 PM AST, April 12th. Stormfest Southwest!
Valid at 5 PM AST, April 12th. Stormfest Southwest!


Hence, the conclusion that we share that April, will in fact, have measurable rain.  Of course, we only average about half an inch in April, as the overall climatology begins a serious a battle against rain heading into the ovenly days of May and June.

The End


1The old English cloud scientist, Frank Ludlow (1952, Quart J. Roy. (haha, “Royal”, oh my) Meteor. Soc.) noticed this first, then that great Soviet Communist cloud scientist, A. M. Borovikov and his companions did (1961, Israeli Translations).  Finally, Rangno and Hobbs woke up and noticed this tendency in 1988, (Atmos. Res.) and then again in 1995 (J. Appl. Meteor.–you’ll have to go quite a ways to find the relevant diagram)  in their cloud studies and in comparisons with other ice onset reports.




Measurable rain to fall in March 2016

…in case you were wondering at this point.

Looks like it will be on March 7th.  Pretty sure thing at this point, maybe 75%-99% chance of rain here in Catalina, combining “spaghetti1” with other forms of forecasting.

7 AM AST Addendum:  Hell, why not go for some amounts due to extra confidence:

Min in The Heights: 0.20 inches (10% chance of less); max, 1.00 inches (10% chance of more). The average of these “mental ensemble2” extrema, 0.60 inches, which is usually closer to the actual value.

This best guess estimate for the total between midnight March 7th and the evening of the 8th, or over about a 42 h period.  Weather gaming is fun.

What’s your prediction?

—————-T. I. P.————————————

Remember, too, as a “truth in packaging” disclosure statement, that this forecast is being made by the SAME person who forecast about 12 days ago or so,  rain here in the last week of February which didn’t happen, along with large Cal and AZ blasting storms in early March.

In fact, here and in southern Cal, we had “anti-rain” in the last week of February!  This in the form of high temperatures, dry air,  and that combination resulting in unusually high  evapotranspiration rates with those high temperatures (anti-rain, since whatever surface water, soil moisture, plant moisture is disappearing into the air).  In other words, that forecast could hardly have been more incorrect.

Hell, to cuss some more, almost as bad as those forecasts for a drier than normal winter (DJF) for the Pac NW by big forecasting authorities like the Oregon State Climatologist among many others.

In fact, when they were making those forecasts, they were staring at record wetness in the Pac NW!  Incredible!  Both SEA and PDX have set DJF records for the amount of rain this winter!  Wow.  It doesn’t get much worse than that, except maybe here sometimes.

People are mad, too, in southern Cal where they were advised to buy sandbags due to the excessive flooding and rains foretold for their winter.   Well, we’ll see if March can bring back some of the lost credibility, though, frankly, its hard to do.

Think of all those global warming forecasts of a steady rise in global temps made back in the early part of this century which didn’t happen.  Wow.   Lost some credibility there, and those forecasters had to move to a new expression, “climate change” to cover up the bad forecast.

Temps on  the rise now, so watch out!  “Global warming” rising from the ashes more and more now, too.

Changing the subject quickly, the Washington Huskies softball team had a pretty great weekend at the Mary Nutter Classic Tournament in Cathedral City, CA, where it was real hot (90 F), too.  The University of Washington was the writer’s former employer.

Whistling here:  where are you Niño?  Com’ere!  Hmmmph,   nice name for a dog I think, which is what it has been so far for the Southwest.

The End


1 Formally, called “Lorenz plots” by yours truly, and should be by others.

Valid on March 7th. All the red lines are WAY down there in Baja California central. Means a pretty sure thing the jet stream will be south of us when this incoming trough goes by and as you know well by now, when the jet at THIS level is south of us, you almost always get rain. Some 95% of the rain that falls in Tucson falls with the jet at this circumscribing us.
Valid at 5 PM AST on March 7th. All the red lines are WAY down there in Baja California central. Means a pretty sure thing that the jet stream will be south of us when this incoming trough goes by and as you know well by now, when the jet at THIS level is south of us, you almost always get rain. Some 95% of the Nov-Apr rain that falls in Tucson falls with the jet at this level to the south of us.


2No way is this from some big computer somewhere!

Tired of winter

Winter began, meteorological speaking, yesterday with mid-afternoon temperatures in the upper 50s to low 60s with the wind driving the wind chill down to, I don’t know what, something really low .  In other words,  winter  began here in Catalina about 18 h ago.

Enough already!  Retired to AZ for warm air and low house prices. Pretty bad, too, out there this morning, with the temp at 44° F right now here in Sutherland Heights; colder yet in low spots of course.  Only 36° F now in Black Horse Ranch.

More worse cold expected in about nine-ten days.  Precip somewhat doubtful in that a more better cold slam that hits around the 20th1.   Pretty strong support in the Lorenz plots (aka, “spaghetti plots”), too, for that cold slam, so get ready.  Those crazy plots help us to discern whether a predicted pattern in the model output is an outlier or likely to occur.

In the meantime, going out of chronological order here, THIS coming week end’s lesser cold slam  is DRY in Catalina in USA WRF-GFS model run from last evening’s run.

The Canadian GEM, however, based on the SAME global data as the US model,  has rain a plenty here in Catalina and all of AZ, Sunday and Monday!  The Canadians see a lot of tropical air feeding in from the sub-tropics over much of AZ ahead of the cold front that hits us later Monday, and that’s the reason for all the rain in that model.  The US model doesn’t see the moist sub-tropical stream getting much out of Mexico.

Note the large separation between rain in Cal and rain in AZ in the panel below.

Valid Sunday afternoon, 5 PM AST.  Lower right hand panel has rain amounts that have accrued over the prior 12 h in the model.  As you can see, quite a bit is predicted over SE AZ.  Yay!
Valid Sunday afternoon, 5 PM AST. Lower right hand panel has rain amounts that have accrued over the prior 12 h in the model. As you can see, quite a bit is predicted over SE AZ associated with the system coming out of the sub-tropics ahead of the cold front going across Cal.

So, what’s a weather forecaster to do?

Lean on the Canadians! Their model was ahead of the game on our half-incher rains early in the month compared with the US mod, so they deserve that bit more credibility here, too, I think.

BTW, the two models were identical in not predicting  rain in the  passage of the cold front yesterday.

The End.

PS:  Would post photos of yesterday’s gray, non-precipitating Stratocumulus, lacking ice in it2, of course,  for you to review, but in transitioning to a new OS in the past two days, some things have gotten wrecked, don’t work anymore.   SOS, as they say.


1Let’s see if any english teachers are reading this blog….

2Cloud lesson/pop quiz  for cloud maven juniors:  What cloud top temperature range would you guess for those non-preciping Stratocu.  Recall it was a cold day, so you know they were at below freezing temperatures…..

Answer:  Guess that tops must have been warmer than -10° C (14° F, in plain speak)!

In fact, the TUS afternoon sounding suggests they were about – 5 ° C (or only 23 ° F),  way to warm for natural ice to form, hereabouts, anyway3.

3In really clean conditions, ice does form in clouds with tops as warm as -5° C4.

4These would really be a great factoids to pass along to your neighbors, ones that would enhance your weather esteem in their eyes.  Memorization is recommended.