Punctuation: its hard. Not sure about that in the title. Oh, well. Kind of sad that English is my first language, too.
Yesterday was definitely more Stratocumulus-ee (clouds flatter than expected) than anticipated, which hurt since it was foretold here that it would be Cumulus-ee day. And there was but the slightest evidence of any ice around, something that was also expected. So the record of almost always being right on weather and clouds (i.e., >50% of the time) took a hit, which hurt, to repeat something about personal feelings.
Too, with noticeable breezes at times, the sky almost completely overcast at mid-day as well, and the temperature well below 80 °F, it seemed darn COLD for late April.
Today, looking ahead, the air cools over us again as it did two days ago as a puddle of cold air slams down the interior of the West Coast and into AZ, and we should see some nice, photogenic Cumulus/shallow Cumulonimbus this afternoon, and, since the coldest tops will be well below -10 °C, there should be some virga and light showers around. So, another chance today for a little measurable rain here in Catalinaland before April closes out. The jet stream at mid-levels remains south of us, too, a critical aspect for cool season rain in the Great SW.
With more instability today than yesterday, there should be some more sun around compared to yesterday since holes due to downward moving air around the upward moving air in cumuliform clouds will be out there. Looking forward to today!
Still looking for the good rains next week as extra jumbo-for-May trough crashes into Cal from the Pac.
Yesterday’s clouds
In reverse order, today. They imported that way, and am too lazy to move them all.
6:49 PM. Looking toward Romero Canyon. Very nice lighting and shadows on our beautiful Catalina Mountains. Hard to believe that enough folks voted to cut off views like this when Oracle was widened and sound walls were put up in front of their homes to save, oh, 2-3 decibels is all, AZDOT said.6:49 PM. Nice lighting on Samaniego Ridge as the sun went down.4:23 PM. Nice “muffin-like” Cumulus over Ms. Mt. Lemmon producing a huge shadow. (hahah; its the cloud overhead left that’s causing the shadow. Kind of a dramatic shot I thought.3:15 PM. Lots of cloud coverage by those flattened tops (Stratocumulus cumulogenitus) with small to moderate Cumulus clouds below.3:12 PM. Thought I saw just that slight veil of ice (center), but maybe “grasping for a seed and swallowing a camel” here.1:06 PM. Looking NNW at Cumulus cloud with flattening tops due to an inversion lurking north of Saddlebrooke village.1:06 PM. A mix of Stratocumulus with small Cumulus clouds below lurk over and west of the Catalinas.7:35 AM. “Regular” Altocumulus with underlying Stratocumulus lurk to the north.7:29 AM. Altocumulus lenticulars lurk behind the Catalinas.
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:5 AM yesterday. Jet at this level races across central AZ. 11 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.
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. 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
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.
Partly its because I can’t think of anything else, brain pretty empty, but check this out:
Valid for May 9th. Shows the kind of “split flow” we expected from the Big Niño, storms dividing in the central Pac or so, parts going northeast, often just grazing the Pac NW, so that area ends up drier than normal, whilst a southern branch from the CenPac carries storms to lower latitudes of the West Coast, drenching southern Cal and the Great American Southwest that we live in. Was that too long for one sentence? Well, moving ahead, you can see this pattern in how the non-political red lines diverge in the eastern Pacific from the non-political blue ones to the north, which there is quite a bit of in politics today as well. Well, anyway, it was kind of interesting of me to point this classic “Niño” pattern out to you, even though it is seen in a computer output form that is largely incomprehensible to most. What does it mean for AZ and Sutherland Heights? The red lines down thisaway on most of these maps to this point mean that there will be chances for rain, AND lower than normal temperatures for the first 10 days of May. Nice! The resultant headline is below:
Measurable rain to fall in the Sutherland Heights, Catalina, in May 2016!
OK, got that “scoop” out…. Here’s the link to NOAA from whence the above map came.
BTW, here’s what a split flow storm looks like as it comes into southern Cal. Man, if it was January or Feb, this would be a real gully washer, a “get the sandbags out” kind of storm. I love this map so much!
Valid just ahead, really, for May 4th 11 PM AST. This is the best example output lately and its from yesterday, but who cares. We should see something resembling this come out of the lower latitudes of the Pac. From IPS MeteoStar.
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Now a little more on these kinds of crazy ensemble maps (“Lorenz”, as named here, or more known more generally as “spaghetti” plots)
This kind of map was telling us we had rain threats at this time in April and at the end of the month some 10-15 days in advance, so far in advance that media weather folk would likely consider it unprofessional to make such a prediction so far in advance. Since we’re not worried about being unprofessional here, we have leapt into the void! Just go ahead and say things! Get the story out now!
Today a strong upper level trough with precip in the mountains of central and northern AZ will indeed be occurring today and tomorrow as was indicated by those crazy maps so long ago. The hoped for rain here will not occur.
However, the storm near the end of the month, also indicated way back then, looks even stronger than the present one, and it will reach farther south than today’s, and so will not only bring some rain and very cool air to the central and northern AZ mountains, but likely around us, too!
I was really happy for everyone out there when the skies were dotted with so many perfect examples of Cumulus humilis. It was like a numismatist finding a perfect Indian head penny. If you were like me, and I suspect you are, you were just going CRAZY taking pictures of those flat little pancake clouds. Those clouds were pretty much limited to about 1,000 feet (300 m) thick at most
Not cold enough for ice in them, of course, since the temperatures at Cumulus cloud tops were only around -3 ° to -5 °C (28 ° to 23 ° F, respectively). Around here, ice USUALLY does not appear in clouds until the temperature is lower than -10 °C at cloud top.
Yesterday began with some light snow falling on Mt Lemmon…well, it was falling downward TOWARD Ms Lemmon, actually. Fell out of some thick Altocumulus clouds up there around where the cloud top temperature is… what? OK, silly question for you, probably lower than -15 °C (5 ° F).
Let’s check the sounding to be sure, remembering that the launch site (University of AZ) was downwind of air flowing from the NW yesterday that went over the Catalinas, so a sounding at the U of AZ might suggest higher temperatures than this cloud was actually at since the air was probably descending before it got there.
Indeed, as just seen by me, the TUS sounding indicates that layer, up around 14 kft above sea level, 11 kft or so above Catalina, not a city, but rather a Census Designated Place or CDP, was “only”at -10 ° C.
I reject that as the temperature of the virga-ing cloud over Ms. Lemmon! Its a little too warm IMO.
8:41 AM. That white haze under the Altocumulus clouds is composed of ice crystals, concentrations probably a couple or less per liter of air. Likely stellar or plate crystals, ones that form at temperatures less than -10 ° C. Almost certainly no aggregates of crystals; concentrations too low to form “snowflakes” which are aggregates of single crystals. Snowflakes form when higher concentrations of crystals collide and get locked together, as in stellars, and their cousins, dendrites, that grow in a similar temperature regime. Dendritic crystals are usually seen in deeper clouds than these because those crystals have time to grow extensions in various directions, are not just “planar” ones. If the cloud is thin like this one, not much growth can take place in the droplet cloud and simpler crystals like hexagonal plates and stellars (Christmas card crystals) fall out. There is a lot of hand-waving here….10:20 AM. A horse named “Zeus” looks to see if any Cumulus clouds are forming over the Mogollon Rim to the NE, or, maybe he’s fixated on the horses in that corral below…
By afternoon, the skies over Catalinaland were spotted and dotted with spectacular Cumulis humilis examples. (The littlest shred clouds are Cumulus “fractus.”)
I’ve left the time of the photos off today. After all, there was only one true time yesterday, “perfect humilis time!” or as we like to say, “PHT.” Immerse yourself.
All I can say about this plot is, “wow” here and then once more in the caption:
Valid at 5 PM AST, April 28th. Wow. The periodic storm threats will continue for AZ for the foreseeable future, which is about two weeks. Temperatures should be moderate, too, for April. Patterns like this also lead to tremendous storms in the Plains States. It might be time to get out there.
“BN”, sometimes referred to in the media as the, “Godzilla Niño” of 15-16.
Before, one year ago, the drought status as presented by the National Drought Monitor folks there in Cornhuskerland, Lincoln, NE:
First, a legend, no, not a story, though we could write one, “The Legend of the Ghost Niño of 2015-16“, but rather a guide to the colorful drought intensities on the maps below:
One year ago
Western drought status as of April 7th, 2015.
Now let us look closely below–you’ll have to–to see what the Big Niño has done to ameliorate drought so far THIS water year (since Oct 1):
Western drought status as of April 5th, 2016!
Of course, the giant low centers spinning around in the central Pacific sent a stream of large waves over and over again that blasted the Cal coast. That was expected, and verified. But not much else did. Drought should have increased in the Pac NW–recall it was forecast to be drier and warmer due to Niño conditions. Instead, the Pac NW had record amounts of winter rain!
Cal, especially, central and southern were to be slammed. Southern Cal residents were advised to consider purchasing sandbags in one media story last fall. And, of course, we here in AZ are profoundly disappointed; conditions have only improved some in the north part of the State.
Well, of course, there’s not one dry meteorological eye in the house after a bust of this magnitude. And when our best models predicted giant West Coast storms that looked like the kind we were expecting due to the Niño, even though they were 10-15 days out, they seemed sure to happen. CMP, bloated with confirmation bias, was sucked in several times this past winter.
Sure, we knew that Niño correlations with weather are not 1.00, that is, perfect, still, the “signal”, the size of the Niño, was so huge we figured it had to come through with those mighty storms striking the lower West Coast as happened in 1982-83 and 1997-98. Those correlations, as strong as they were, of course, were limited in number since these large events are rare. Those correlations will, let us say in place of cuss words, “degrade.”
Oh, me, what will we say when the next Big Niño appears?
The weather ahead
You’re probably pretty excited about the wind and very cold air just ahead. CMP is. And, with the jet stream at 500 mb (18, 000 feet or so–5.5 km above sea level) eventually circumscribing us with its charateristic moist lower region of air, we should just enough moisture for some isolated very light showers, probably just in the Catalinas, during the period of low freezing levels that hits late Friday and continues through Sunday. Low freezing levels mean even moderate Cumulus clouds could form ice, leading to virga.
Amounts could, at the most, only be a few hundredths here, and most likely we will be missed; precip just limited to snow flurries on Ms. Mt. Lemmon and thereabouts. The U of AZ mod sees the cold blast arriving late Friday after dark.
On the other hand, Saturday and maybe Sunday as well, will be good days for you to practice your ice in clouds detection skills in smallish Cumulus clouds.
The weather way ahead
Still looking to see at least two more troughs and chances of rain during the last two weeks of the month. NOAA ensembles suggest so. Best chances, 23rd-25th, and again around the 28th or so.
Some cloud shots from our little 0.01 inch rain day on Tuesday:
6:02 AM, Tuesday. A summer-like scene, complete with thunder frames the post dawn hours.10:35 AM. After the morning excitement cleared off, a pretty Cumulus congestus erupted north of Saddlebrooke town. There’s a hawk in the photo.12:12 PM. That Cumulus congestus and its sisters, were able to reach the level of glaciation, and wind shear, send a plume of ice downstream toward the east, and rain below that overshooting turret.2:36 PM. Pretty much the perfect cloud for ice in cloud studies. As the air warmed aloft and capped the Cumulus clouds, this one just poked up high enough to form some ice. It would have been a great sample to determine the temperatures and cloud conditions at which ice onset in clouds on Tuesday.4:16 PM, Tuesday. Those shadow and sun highlights that make our mountains so darned pretty. I just never will be tired of these views!
Since the forecast given HERE for large Cumulus clouds becoming Cumulonimbi did not happen last evening, it seemed appropriate to show some wildflowers as a distraction. First, a light, purple one of some kind; second, what we here call an “Arizona rose”, those fabulous blooms that form on prickly pear cacti. The photos below were, in fact, taken late yesterday afternoon as the forecast of the development of those larger Cumulus was failing to materialize.
Wouldn’t it be great if we could GM these to have long stems?!
Now that you’ve forgotten the erroneous forecast of large cumuliform clouds made here yesterday, I would like to point out that the cooler air up top has finally arrived in the pre-dawn hours today, and we do have Cumulonimbi in the area; even some LTG over there by Mt. Graham around 4 AM as this is being written.
However, bases are pretty high, 7,000 feet above the ground, and so only the central cores of the rain shafts are producing much rain to the ground right now. However#2, these are the kinds of situations that incredible photos of long virga trails during sunrise can be gotten. Be ready! The whole situation is moving east pretty rapidly.
Yesterday’s clouds
10:22 AM. Cumulus fractus and humilis topped by Cirrus spissatus enhance a blue sky.10:28 AM. Wow, a Cumulonimbus capillatus top can be seen just beyond Mt. Sara Lemmon! And it only mid-morning! This is a test. A patch of Cirrus has aligned itself above some small Cumulus clouds topping the Lemmon. We’re you fooled for a moment? I hope not.5:13 PM. More Kelvin-Helmholtz billow clouds at Cirrus level. Pretty rare sight, actually. Shows waves in the atmosphere. Don’t want to fly in them. This was about the greatest cloud excitement of the whole late afternoon and evening.6:06 PM. “Slab lifting” by our incoming upper level thingy has led to the formation of a couple levels of flat clouds, Altocumulus lenticularis, some Altocumulus perlucidus (honeycomb look), and some Cirrus perlucidus way up top. Some small to moderate Cu can be seen on the horizon. Was still thinking they might “pop” as cooler air moved over us. You might be able to see that some of the little cloudlets at Cirrus-levels started out as droplet clouds before transforming to ice. Ma Nature likes water so much it almost always develops first before ice even at temperatures below -30 °C. Pretty amazing, really.
Thunder just now! Wow. 5:20 AM. Sorry for the delay, had to go outside and check things out. Really will be a fabulous sunrise!
6:16 PM. Still thinking it might pop. Didn’t even see ice as that Cumulus turret declined.
Though the clouds faded as the sun went down, there were still some highlights on the Catalinas that made it a near perfect day.
6:17 PM. What’s to say? We’re so lucky to be able to see scenes like this in Arizona.
The weather ahead
Turbulent, changeable, unsettled through the remainder of April. More chances to add to our 0.73 inch total so far for this month. Stay tuned to your favorite media weather folk!
It doesn’t get better than this for April in old Arizony. We’ll make up a lot of lost precip ground this month. In this series, you’ll see MANY days with the maximum winds curling around us, good for precip here as one trough after another barges into the Great SW from the Pacific. !Fantastico! !Commensar la lluvia del Niño! !Ya lo creo!1Getting pretty excited here.
With this series, April rainfall in the Sutherland heights should be twice or more above normal (that is, at least an inch). ‘Bout time.
The End.
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Oh, yeah, the title. I slipped off the keyboard some in the dark and got some inadvertent gibberish. But gibberish sells. Lot of people will now drop by, their curiosity peaked and piqued, “What the hell izzat about?”, focusing on the key word, “storm.” People in deserts like storms. Gibberish is one of the innovations that’s been developed here, btw. You don’t see it too often, except maybe in political campaigns.
1Oh, yeah the title; “has bi-lingual content” We’re desperate for readers here, and this is clearly a cheap ploy (is that redundant, “cheap ploy”?) since I know only a few sentences in Spanish, though my second wife was Hispanic2; that should count for something. Also, I do know that the first exclamation mark should be upside down, but can’t do it.
2Being as nosy as you are, you probably want to see her, maybe you don’t believe me, too, I just said that to get more readers….
Yesterday was a great day both for airborne researchers studying the onset of ice in clouds, and for my followers to test their “ice” Q detecting abilities, to come up with a clever play on words there.
What was so great about yesterday’s clouds?
Well, they were real cold, bases up around 9,000 feet above Catalina (about 12,500 feet above sea level) at -7° C (19° F). Excellent. Nice data point.
Cloud tops?
This is what was pretty great for you and me; they didn’t overshoot much, the clouds were pretty flat, not very deep, not a lot of flight time needed climbing to cloud top to see what it was around here. That means that if you are flying around up there sampling clouds for ice content, that the tops you smashed with your aircraft were pretty much the ones at the temperature that the ice crystals you ran into later formed at. Remember, when cloud tops first rise up, they usually have little detectable ice (the ice crystals are too small for your instruments, or, they haven’t formed yet, takes a little time.
When there are big overshooting tops, an inexperienced, well, crummy researcher in an aircraft finding the ice, as it is usually found, lower down in the cloud, might put the origin of the ice at the temperature of the collapsed top, not at the lower temperature where it formed and the original top reached up to.
So, the lack of much overshooting made it a great day to assign the ice you found to the right cloud top temperatures.
What else was great?
It was a marginal day for ice formation here in the Catalina area, so you get a good data point on when ice starts to form in clouds given that base temperature. As the cloud deepens upward, more ice would be expected with the lower temperatures.
And, as noted by Ludlum way back in the 1950s, and by Prof. Battan right here at the University of Arizona which I did not attend, btw, that level at which ice and precip onsets changes from day to day (largely related to how warm (crazy isn’t it?) the cloud base temperature is. On days with warmer cloud bases, the ice onset temperature is also higher. For example, in summer here, its not unusual to have ice onset between temperatures of -5° and -10° C (23° and 14° F) when bases are warmer than about 10° C.
Anybody still out there?
So, yesterday, with the deepest Cumulus clouds around 2,000 to three thousand feet thick right in our area (they were deeper elsewhere), tops were running around -15° C, this temperature, as you know, leads to the formation of plate-like crystals, hexagonal plates, stellars (Christmas card crystals), maybe some spatial dendrites (stick out in different directions) if the latter crystals were in the Cumulus cloud long enough. If the concentrations of ice get high enough, you’ll get “snowflakes”, interlocking dendritic crystals. A single, good-sized snowflake might have 20-50 individual dendritic crystals.
Is anybody still out there?
Below some shots from yesterday afternoon when there were traces of ice spewing out of local clouds. Did you see those regions and note them in your cloud diaries, that’s the important question.
3:23 PM. A nice view of the overall scene around here with our small Cumulus clouds (Cumulus humilis and mediocris). You see a house in the distance off this dirt road. Pretty say when you think that in America some people still live on dirt roads.3:49 PM. Oh, there’s a nice little Cumulus toward the Charoleau Gap. Doesn’t seem to have any ice…. Let us look closer, and, of course, we look for ice to appear at the downwind edge where cloudy air has been in the cloud the longest, see if anything is falling out.3:49 PM zoomed view. Oops there it is, a little ice, single crystals, concentrations likely lower than 1 per liter of air. You wouldn’t expect to find any “aggregates” here, since they require higher concentrations of ice to bump into each other and lock together. Wow, this is an incredible amount information based on a little hazy spot in a photograph!4:13 PM. Lets look over here toward the south. OK, there’s an obvious ice haze beyond the Catalinas, but what about the cloud in the middle? See anything coming out the downwind (right) side?4:13 PM zoomed view of the fall of ice crystals out of this cloud. This patch of ice haze is so obvious it would have been pretty embarrassing for you not to have noticed it, made a note about it. Of course, we care so much about ice because that’s where nearly all of our rain here in Arizony comes from, as you know, recalling the work of Wegner, Bergeron, and Findeisen, where it was shown that an ice particle in a water cloud will grow at the expense of the droplets around it. For a time, it was thought that all precip of consequence was due to that process, but not so. Ask Hawaiians. Or powder snow lovers about storms consisting only of little dry ice crystals, no water drops in those clouds.
Stormy weather still ahead as noted here I don’t know how long ago. April looking more and more to be a generous month of rain here in Catalina. But will those showers be too late for May flowers?
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.
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.
Why?
“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. 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.
Finally, at the extreme end of the medium range forecasting frontier, this:
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
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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.
5 AM yesterday. Jet at this level races across central AZ.
11 AM yesterday. Maximum winds getting closer! Tiny Cumulus clouds begin to appear over the Catalinas and on the west to north horizon.
