Cloud-maven – Page 15 – About real clouds, weather, cloud seeding and science autobio life stories by WMO consolation prize-winning meteorologist, Art Rangno

Sutherland Heights storm total now 0.71 inches as of 7 AM; soil turning green as moss look alike growth reminding one of Seattle spurts from bare ground!

First, in blogging for dollars, this:

3:55 PM. Rainbow fragment and solar home. Yesterday's visual highlight. Yours for $1995.95. If you call now, we'll throw in a exact same photo FREE! — 3:55 PM. Rainbow fragment and solar home, an extraordinary combination.. It was yesterday’s visual highlight. Yours for $1995.95. And, if you order now, we’ll throw in a second, exact copy of this extraordinary, magical scene FREE!

Here’s a nice one from the day before as the clouds rolled in, starting with Cirrus and Altocumulus, lowering to Stratocumulus later in the afternoon.

5:04 PM, 30 Dec. Sun break amid Stratocumulus. Stratus fractus topping mountains.

Yesterday’s clouds; an extraordinary day with a little drizzle amid light showers

Hope you noticed the true drizzle that occurred yesterday, namely, fine (larger than 200 microns, smaller than 500 microns in diameter), close TOGETHER (critical to the definition of “drizzle”) drops that nearly float in the air. They may make the least impression, or none, when landing in a puddle.

When you see drizzle, you have the opportunity of chatting up your neighbor by educating them informally to what drizzle really is (many, maybe most, TEEVEE weatherfolk do NOT know what “drizzle” is, btw), and 2) by telling your neighbor, if he/she is still listening to you, that the droplets in the clouds overhead must be larger than 30 microns in diameter, or better yet, “larger than the Hocking-Jonas diameter of 38 microns, at which point collisions with coalescence begins to occur” and “drizzle is not produced by ice crystals in the clouds overhead; they’re not enough of them to produce ‘fine, close together drops.'” Your neighbor has likely left the building at this point, but, oh, well, you tried.

Here, in Arizona, shallow clouds, such as we had yesterday, hardly ever can produce the broad droplet spectrum in which clouds have droplets larger than 30 microns in diameter. Its because this far inland from the ocean, where the air is very clean, the air has picked up natural and anthro aerosol particles that can function as “cloud condensation nuclei” (CCN). As a result of ingesting dirt and stuff, clouds have too many droplets here as a rule for the droplets in them to grow to larger sizes. They’re all mostly less than 20-25 microns, sizes in which even if they collide, they can’t coalesce.

In “pristine” areas, if you go to one, such as on a cruise out in the oceans, droplet concentrations in clouds are much lower, and even a little water that might be condensed in a shallow cloud can produce a broad spectrum, one that extends to droplet larger than 30 microns.

So even little or shallow layer clouds can precip over the oceans, produce drizzle or light rain showers (in which the larger drops are bigger than 500 microns in diameter). Of course, here we recall that the (whom some consider “villainous”) geoengineers want to stop drizzle out over the oceans so that clouds have longer lifetimes, are darker on the bottom, and reflect more sunlight back into space.

Those guys can be lumped into the same ilk as those who want to change the color of the sky from blue to whitish or yellowish by adding gigantic amounts of tiny particles in the stratosphere, again for the purpose of cooling the planet! Unbelievable. Please ask before doing this!!!

A Pinatubo sampler for what “geoengineering” would do to our skies, say, sunsets in particular. I took this photo from the University of Washington’s research aircraft in 1992 off the Washington coast in onshore flow. But we saw these same sunsets, sunrises, yellowed by the Pinatubo eruption of June 1991 everywhere we went, including in the Azores in June 1992.

OK, pretty boring, whiney, really, so inserting picture of a nice horse here to make people feel better if you’ve been depressed about what our scientists have been pondering to do about global warming other than controlling emissions:

8:57 AM. Zeus. Led cloistered life for 13 years; likes to bolt now that he's getting out. — 8:57 AM. Zeus. Led cloistered life for 13 years; likes to bolt, now that he’s getting out on the trails.

7:40 AM, yesterday, Dec. 31st. The low hanging Stratocumulus clouds, about 1500 feet above Catalina, and the mountains had a bit of an orange tinge. It was probably due to sunrise color on a separate much higher layer.

Later….drizzling Stratocumulus, same view:

10:30 AM. Stratocumulus praecipitatio, if you want to go "deep" into cloud naming. "Stratiformis", too, covers a lot of the sky. — 10:30 AM. Stratocumulus praecipitatio, if you want to go “deep” into cloud naming. “Stratiformis”, too, covers a lot of the sky. Note misty-like view, lack of shafting.

12:48 PM. More Stratocu P., an example of those clouds in the distance that kept dropping little and light rain showers on Catalina.

1:01 PM. Highlighting amid the RW-- , (weather text for "very light rain showers"). — 1:01 PM. Highlighting amid the RW– , (weather text for “very light rain showers”). Stratcu P., with maybe Stratus fractus or Cumulus fractus below. The shadowed, dark shred clouds in the mddle would be Stratus fractus IMO.

3:55 PM. Zooming in on that pretty rainbow. You know, this is a cloud heaven here. I hope you all appreciate it! Maybe that’s why I get upset over “geoengineering” and changing the sky anywhere.

3:57 PM. Between showers, but new ones erupted upwind. This one have a shaft, implying a higher cloud top than the prior, non-shafting clouds that brought us semi-steady RW--. — 3:57 PM. Between showers, but new ones erupted upwind. This one have a shaft, implying a higher cloud top than the prior, non-shafting clouds that brought us semi-steady RW–.

The second extraordinary thing about yesterday was that the top temperatures of these clouds was around -10° C (14° F), temperatures that ice does not form act as a rule in Arizona. To get ice at temperatures that high, you also need larger cloud droplets, and they have to occur in the -2.5° C to -8° C range. In this range, it was discovered that falling ice crystals, mostly faster falling ones like “graupel” (aka, soft hail) when colliding with larger drops, ice splinters are produced. The cloud droplets must be larger than 23 microns in diameter in THAT particular temperature zone, something that would occur more often in our warm, summer clouds, but would rarely be expected in our winter ones.

Why?

Again, it goes back to clouds in inland regions ingesting lots of natural and anthro aerosols that cut down on droplet sizes in clouds (by raising droplet concentrations in them). Our recent rains have helped cut down on that process on ingesting dirt, for sure, and was a likely player yesterday. Furthermore, our winter clouds are moisture challenged relative to the summer ones with their tropical origins and high cloud base temperatures, a second reason not to expect larger droplets in our winter clouds.

Here is the TUS sounding with some writing on it for yesterday afternoon from IPS MeteoStar. (Satellite imagery was also indicating warmer than usual tops for precipitating clouds yesterday.):

The TUS balloon sounding ("rawinsonde" in techno speak) launched at about 3:30 PM yesterday afternoon. Balloon rises at about 1,000 feet a minute, FYI. Typically they pop up around 100,000-120,000 feet! Instruments are parachuted down. Sometimes they are found and returned to the NWS and re-used! How great is that? — The TUS balloon sounding (“rawinsonde” in techno speak) launched at about 3:30 PM yesterday afternoon. Balloon rises at about 1,000 feet a minute, FYI. Typically they pop up around 100,000-120,000 feet! Instrument package is parachuted down so it doesn’t conk somebody on the head. Sometimes they are found and returned to the NWS and re-used! How great is that?

Here’s the punchline: If clouds are drizzling, then they are ripe, if the tops get to lower temperatures than about -4° C for what we’ve termed “ice multiplication” or “ice enhancement”. A very few natural ice nuclei at temperatures between -4° and -10° C, say, starts the process, those forming “soft hail” which then leads to ice splinters. This is the leading theory of this anomaly of ice in clouds at temperatures only a little below freezing, if you think 23° to 14° F fits that definition.

There are exceptions where this process did not explain the ice that formed at such high temperatures, so standby for further elucidation about how in the HECK ice forms in clouds at some point in the future.

As usual, no time to proof, so good luck in comprehending what’s been written.

The weather just ahead:

The second main rainband is just about here at 9:25 AM. Cloud tops will be deeper and colder than in the prior rains, raising the possibility of some thunder today, and maybe another third of an inch of rain. Watch for an windshift line cloud (“arcus” cloud) might well be seen today. That’s always dramatic and exciting here in Catalina cloud heaven.

The End at last!

And a happy, weatherful year to all!

0.39 inches falls on Sutherland Heights; more rain on way

The End, or is it?

Altostratus opacus virgae transitions to Altocumulus during day! Storms to bring rain!

What a day for cloud maven juniors and me, too, watching the Altostratus opacus (but sometimes “translucidus” cuz you could see where the sun was) become Altocumulus! It happens pretty often and is the result of lowering, and warming of the cloud tops, but I need to generate some excitement on an otherwise somewhat dull day.

What else is happened as tops warmed? Good-bye virgae (“virga”, in plain speak), except in a couple of locations that raised the question, “Was it hers (Mother Nature’s) or ours (aircraft effects)?”

2016122912Z_SKEWT_KTUS — The TUS balloon sounding through all that Altostratus opacus virgae. Launched at about 3:30 AM. The top temperature is so cold (-60° C, -76° F) we don’t even want to know here in Arizona that such temperatures are possible. So, you can imagine all the ice that might form in a moist layer of air. The bottom is even cold at nearly -15° C, there were the temperature jumps out to the right. This is a situation we call “overrunning”, where warmer air is going over a colder air mass. This cloud was about 22,000 feet thick, 7 km at this point.

The slight spread between the two lines illustrates the classic representation of what we measure when the balloon passes through an all ice crystal/snowflake cloud like this version of Altostratus was yesterday morning. The humidity element on the balloon measures the humidity relative to liquid water, not ice, so there will be some spread between the dew point temperature (line on the left) and the temperature (line on the right) when the balloon ascends through an ice cloud. Saturation with respect to ice is indicated here in that deep “overrunning” layer, something also likely to happen tomorrow to the writer’s “company” fubball team tomorrow.

And here's the TUS sounding launched yesterday afternoon when we only had Altocumulus opacus clouds, just as dark as Altostratus opacus, but much thinner. Tops around -10° for the most part, but there may have been some turrets to almost -20° C. The balloon almost certainly passed between clouds, did not go exactly through a Altocumulus cloudlet. — And here’s the TUS sounding launched yesterday afternoon when we only had Altocumulus opacus clouds, just as dark as Altostratus opacus, but much thinner. Tops around -10° for the most part, but there may have been some turrets to around -20° C. The balloon almost certainly passed between clouds, did not go exactly through a Altocumulus cloudlet. Don’t worry if you can’t make out the actual temperatures on the lines sloping up to the right, just take my word for everything I say. You can easily see how much it dried out in the middle and upper cloud regions between the morning sounding and this one.

Yesterday’s clouds and the transition

8:29 AM. Altostratus opacus virgae (has some downward pendants of ice and snowflakes coming out of it). The TUS radar had some sprinkles showing up here and there.

Now let’s look over here:

9:19 AM. Thin spot in the overcast. — 9:19 AM. “Thin spots in overcast”: we used to say that a lot in our human weather reports of ages gone by. Here the thin spot makes this Altostratus translucidus.. While there is an irregular look to this Altostratus due to virga hanging down, there is no indication of liquid water elements, ones that would show up as sharply-outlined darker elements. While this is hours later than that morning TUS sounding, it is likely that in spite of this thin spot, the Altostratus layer was still many kilometers (thousands of feet thick). Ice crystals and snowflakes are far less numerous than droplets in liquid clouds, and, therefore clouds composed of ice are more transparent given equal depths. Compare the visibility in a dense fog with being in a light snowfall.

9:38 AM. Example of a some sharply-outlined liquid clouds embedded in the Altostratus layer have formed. The growth of ice crystals and snowflakes is enhanced in liquid clouds because they represent regions where it is saturated with respect to WATER, and highly supersaturated with respect to ice (the relative humidity with respect to ice is well over 100%). Also, if the droplets in these clouds are large enough (larger than about 15 microns in diameter) they can be collected by the falling ice and snow, adding to their mass of those, causing them to fall faster.

10:29 AM. Had numerous, dramatic outbreaks of mammatus around this time, probably representing the fall back of turrets on top of the Altostratus as this time. We will say no more about mammatus since the author has tended toward the prurient to break up the tedium in past notations about mammatus. — 10:29 AM. Had numerous, dramatic outbreaks of mammatus around this time, probably representing the fall back of turrets on top of the Altostratus as this time. We will say no more about mammatus since the author has tended toward the prurient to break up the tedium in past notations about” mammatus.” This might be viewed as an upside down look at the cloud tops at this point, BEFORE they collapsed and dropped below the main bottom of this layer. At the top (rumpled area), regions of a liquid cloud layer are beginning to appear, a sure sign that tops are receding.

11:55 AM. Moving along,looking upwind across the Oro Valley. Still looks composed mostly of ice, but liquid clouds are on the far horizon. — 11:55 AM. Moving along,looking upwind across the Oro Valley. Still looks composed mostly of ice (Altostratus opacus virgae here), but liquid clouds are on the far horizon.

1:21 PM. Altocumulus opacus rules. The deep icy cloud is all gone by now. No virga. Notice, too, in spite of being less than a kilometer thick, this cloud looks as gray as the Altostratus that was many kilometers thick. The droplet concentrations in a liquid cloud such as this might be 200, 000 per liter, while the ice concentrations in that Altostratus cloud were likely in the 10s per liter. The smaller particles in Altocumulus clouds, average perhaps only 15-20 microns in diameter also are able to reflect far more sunlight back into space, and less sunlight reaches the bottom making it darker. In contrast, the (ice) particles in the Altostratus would be hundreds of microns to millimeters in diameter (i.e., precip-sized).

2:22 PM. Looking around at these cold Altocumulus clouds, generally not showing virga, you begin to wonder if those areas you do see have been the result of an aircraft passage, as here in that little spot of virga.

2:28 PM. Some breaks in the overcast allowed some nice scenes to fall upon our mountains. Here, the Charouleau Gap is highlighted.

The weather just ahead

Here’s the latest projected rain totals from the U of AZ Wildcat Weather Department Weather Calculator:

From the global ingest of data at 11 PM AST last evening. Indicates that green Catalina will be in the half inch to three quarters of an inch between now and New Year's Day afternoon. Comes in two segments, the first overnight tonight, and then another starts New Year's Eve. — From the global ingest of data at 11 PM AST last evening. Indicates that green Catalina will be in the half inch to three quarters of an inch between now and New Year’s Day afternoon. Comes in two segments, the first overnight tonight, and then another starts New Year’s Eve. Seems reasonable. Probably not quite reasonable is the red on the Cat Mountains, indicating 3-4 inches accumulation during this time, probably a bit overdone. Both storms are rather small in size, so the amount of rain depicted in these model runs has varied a lot. But, they seem to be settling on something decent. Seems the least we’ll end up with has to be more than a third of an inch, worst case scenario. See Bob and the NWS for a good look at these incoming events. We’re mostly about clouds here.

Undercutting flow from the tropical Pacific is on schedule. So, a good chance for major rains along the southern portions of the West Coast in a few days, with a pretty good chance they’ll leak into Arizony.

The End

Cold clouds and pretty, wintry scenes as long as they don’t last too long

What a gorgeous day yesterday was with deep blue skies dotted with Cumulus and one or two shallow Cumulonimbus, highlighted by our snow-capped Catalina Mountains. After the brief warm up, more storms ahead for Catalina!

Yesterday’s clouds

10:23 AM. By this time Cumulus were popping up all over, and with the temperature at just 10,000 feet above sea level (7,000 feet above Catalina) cloud mavens everywhere were pretty sure ice would eventually form in lots of Cumulus.

10:24 AM. Shallow Cumulus congestus (left side) converting into an equally shallow Cumulonimbus capillatus (right half of cloud). This scene from a fairly primitive area of Arizona.

10:26 AM. Pretty scene over Saddlebrooke.

10:37 AM. Ice, there it is. Even shallow clouds spewed ice crystals and or small snowflakes (clusters of individual ice crystals.

Explanatory module below

The TUS balloon sounding, launched at about 3:30 AM yesterday morning from the campus of the University of Arizona Wildcats.

10:27 AM. Wintry scene #1, view toward the Charouleau Gap, and why do the French make spelling so hard?

11:04 AM. "Ice, there it is!", to paraphrase a song from "In Living Color." — 11:04 AM. “Ice, there it is!”, to paraphrase a song from “In Living Color.”

11:12 AM. Wintry scene #2. View is toward the Charouleau Gap.

11:12 AM. Icy, but shallow Cumulonimbus cloud heads toward Catalina spewing a light rain shower and soft hail called “graupel.”

12:32 PM. Not an advertisement for the University of Washington Huskies sports powerhouse, but rather a demonstration and graupel did, in fact, fall from our shallow Cumulonimbus clouds yesterday. BTW, the Washington Huskies play the NFL-ready, #1 Alabama Crimson Tide on New Year’s Eve at 1 PM AST in a fubbal playoff game. It would be great if you watched, raising viewer numbers, and possibly therein, the revenue stream flwoing into the University of Washington (from which I emanated). Oh, there appears to be a conical graupel there on the left. Graupel falling through a cloud of droplets often stays oriented with one face down, and that face collects all droplets that are freezing on it making that downward facing side, as you would imagine, bigger than the rear part, and so you get a pyramidal-shaped piece of soft ice. If it mainly tumbled on the way down through the cloud, it would be pretty spherical. That white streak on the right is one that’s falling.

11:45 AM. Another ice producing candidate forms in cloud street aligned with Catalina. — 11:12 AM. Another ice producing candidate forms in cloud street aligned with Catalina. Couple of drops is all that came out of this.

3:18 PM. Very shallow, ice-producing clouds. Few in the area had ice at this point in the afternoon, and a very tedious inspection of these clouds, comparing them with surrounding clouds, suggested that their tops were just a bit higher than the ones around it that did not spew a little ice.

The TUS balloon sounding launched at 3:30 PM AST, also with writing on it.

5:06 PM. Wintry scene #3 Pretty, eh? — 5:06 PM. Wintry scene #4 Pretty, eh?

5:32 PM. Stratocumulus with red liner. Nice.

After the brief warm up ahead, still looks “troughulent” and stormy in the SW as December closes out, continuing into January.

The End

Cold front with a spectacular arcus cloud rolls across Catalina; 0.68 inches logged in Sutherland Heights!

The “entrance” of our major cold front yesterday was spectacular! Hope you were able to stand upright in the wind, gusts to 60 mph, that just preceded it and saw that arcus cloud march across the Tortolita Mountains and into Oro Valley and Saddlebrooke. If you didn’t, its reprised here, of course.

The arrival of the rain and front was PERFECTLY predicted¹ by the U of AZ model night before last; the first drops were supposed to fall between 3 and 4 PM, and by 4 PM, there they were, framed by one of the most spectacular arcus cloud formations I have ever seen. Let’s look now, instead of wading through the whole cloud day leading up to it. Feature a lot of views of the same thing, zoomed differently, it was THAT spectacular:

3:58 PM. And as it passed over Sutherland Heights. Not quite as spectacular appearing as elsewhere.

Here’s what the temperature did yesterday afternoon as this arcus cloud and wind shift line hit:

A temperature record (in Fahrenheit, of course) of our cold front passage yesterday. Got down to 37° F for a few minutes before the recovery started.

The End

——————————–
¹CMP got a little overexcited and had rain in the area prematurely in his own forecast (i. e., rain in the area beginning between 11 AM and 2 PM), trying to go 1 up on the model. Bad idea. And no ice whatsoever was seen in those afternoon Cu that started to develop, as CMP was SURE was going to happen, eyeballs straining for ice. Didn’t see the expected precursor lenticulars, either!

Storm today, Christmas Eve 2016!

First of all, how did it get to be 2016 so fast?

Yep, a dramatic Christmas Eve storm, complete with rain and bluster, maybe even ending with a little snow, in case you’ve been in a cave for the past couple of days and haven’t heard about it. Media folks have been all over this, so am tuning it here just a bit, if, in fact, I can, for Catalina.

The wind today in Sutherland Heights will likely gust to over 40 mph from the southwest in 1-2 second bursts here , similar to the wind in the last big couple of FROPAs, so best to put loose stuff away.

In fact, the U of AZ mod from last evening sees winds of 115 mph above TUS at mid-day at just the 500 millibar level (15,000 feet or so above Catalina), a quite unusual strength of wind at that elevation, to give an idea of how strong the jet stream will be above us today. So, if it looks like the clouds are moving too fast, as in a time lapse movie, they are!

The core of that jet at 500 millibars passes over during the middle of the day, and that pretty much should coincide with the onset of rain as it usually does. So, look for rain to start around between 11 AM and 2 PM AST today based on that passage; the U of AZ mod output from last evening’s global data sees the start time somewhat later, between 3-4 PM. Be ready, though; it will come in a hurry! From IPS MeteoStar, this for 11 AM AST today, a real screamer of a jet is overhead:

Forecast of the flow at 500 millibars valid at 11 AM AST today. Its based on the global data, such as is available, from 11 PM AST last night, the most recent model prediction available.

We’ll have the usual “temperature slam” when the wind shifts to the NW here in Catalina during the FROPA late this afternoon or early evening. Looks like it will be a good 15° F drop, typically occurring within an hour, the first ten degrees in 15 min or so, with the temperature likely ending up in the mid-upper 30s. This is where some snow is possible. Imagine, a little SNOW in parts of Catalina on Christmas Eve is possible.

And with fronts/jets as strong as this, the rain band with the front should lead to at least moderate rain for a couple of hours. “Moderate rain”, probably “immoderate” in intensity for some desert dwellers and snowbirds, is 0.10 to 0.30 inches per hour. So rain will pile up pretty good during those periods of “moderate rain. ” Even a couple of hours of that intensity will lead to a substantial amount for our desert.

AZ mod (see link above) sees half inch to an inch here in the Catalina area to Mt Lemmon! That would give us a December total that’s above average, something we haven’t seen in a few months, an above average monthly total. A shot from hip from this keyboard yesterday to a friend was for a lesser total, 0.40 inches in Sutherland Heights¹. Truly hope it is LOW!

One of the best sights today will be the transition in the clouds from dawn today (if any) until the jet core gets here in the middle of the day. Typically, on the right hand side of the jet (looking downwind), which is also the warmer side of it, the air is stable and its a great environment for lenticular clouds (smooth ones that hold in place, such as downwind of Ms. Mt. Lemmon).

As the jet core arrives at mid-day, which divides that warmer air from much colder air aloft on the left side, looking downwind, the lower clouds deepen up or move in, merge with higher cloud layers, ice forms begins to form like mad, and you start to see virga and precip all around. So, a pretty dramatic sky change should occur in the middle of the day today; have camera battery charged up, and maybe video or time lapse cameras ready to go as well.

Some cloud shots from yesterday’s “in between” day:

12:45 PM. Small Cumulus clouds (humilis) dot sky.

4:26 PM. Stratocumulus clouds cluster around the Catalinas.

5:35 PM. Nice sunset of precursor to storm, Altocumulus perlucidus deck. But what’s that over there, far right corner? Let’s go zooming, take a closer look.

5:35 PM. Right there next to that tree on the right is virga, the only virga in this whole layer! And, though hardly visible, there’s a clearing above this patch of virga, a hole in the cloud deck. This layer was “seeded” at this point, that is, ice was caused to form in what otherwise were clouds composed of supercooled liquid water droplets, by the passage of an aircraft. This demonstrates what happens in any cloud of supercooled droplets when ice is introduced. The droplets evaporate, and the vapor deposits on the ice crystals, causing them to grow and fallout. You may recall that it was Catalina’s own Cloud Maven Person and Hobbs that brought this phenomenon to the attention of the airborne research community way back in ’83, something I wish I could point out everyday! (J. Appl. Meteor.) That’s why even the tiniest blip of virga caused by an aircraft is brought to your attention as often as possible!

The exciting possible weather WAY ahead

We have a penchant here for pointing out quasi-disastrous storms that appear in the models beyond the normal skill period of 7 days or so. Remember last year, when Cloud Maven Person was talking up those gigantic, Big Niño storms that would appear in the models, but not one actually occurred as shown? Typically, as we all do, we look at the NOAA spaghetti factory outputs to see if there is much credibility to those sometimes wild predictions. As in the current weather, the indications of frequent trough passages was well indicated in those crazy plots more than 10 days ago. (How much precip will come with them is very “iffy” but we’re doing well this time!)

Well, there’s another set of “doozies” showing up in the mods now, ones that roar out of the central Pacific and into California, just like we expected with last year’s Big Niño! How odd. Those kinds of trajectories over the warmer waters of the eastern Pacific lead to the heaviest of all rainfalls in California, and heavy amounts here in AZ. Here’s my talking point, this:

Valid in only 312 h from now! Look at that "low rider" trough off southern Cal! This is SO EXCITING to see. Something like this COULD happen. If so, a trough with this trajectory and magnitude would be one of those that can bring 10-20 inches of rain in a DAY to southern California mountains, and, as shown later, continuning on at lower latitudes, bring a few inches in a day to the mountains of AZ! — Valid in only 312 h from now! Look at that “low rider” trough off southern Cal! This is SO EXCITING to see. And something like this COULD happen. If so, a trough with this trajectory and magnitude would be one of those that can bring 10-20 inches of rain in a DAY to southern California mountains, and, as shown later, continuing on at lower latitudes, bring a few inches in a day to the mountains of AZ! These are the kind of model outputs that make life truly worth living. A key ingredient here, too, is that trough that would bring extremely cold air down along the Pacific coast from Canada. That would help energize and deepen the surface low under the big trough offshore of southern Cal as it got closer to the coast. (Kind of reminiscent of what happened in Jan 1969, cold in the Pac NW, super rains in Cal, and maybe reminiscent of the weather configuration during the truly gargantuan Cal flood of late December-Jan of 1861-62 when 35 inches or so fell in 30 days in the Los Angeles area, which, in normal circumstances would have meant 70-100 inches during that time in the higher mountains! The LA Basin was a lake at that time, reports said. Does that much rain sound crazy for southern Cal? Well, the DAILY record Hoegee’s Camp Ivy, is 26.12 inches in ONE DAY, January 1943! More than 25 inches fell in one day in January 1969 before the gauge floated away. So, you COULD have 70 inches in only three days or so! Man, I am filled with historical facts today!

But does “spaghetti” support these exciting model outputs? I don’t know because I haven’t looked yet. But let’s do look at a couple and see if catastrophic, well, heavy anyway, rains are headed to Cal, and maybe AZ, too. The onset of this “break through” pattern begins in about nine days or so (exact timing will vary a bit):

Valid for about nine days out from now, and shows a great beginning to this pattern. This says with pretty good confidence that the jet stream will break into Cal from the Pacific. — Valid for about nine days from now, and shows a great beginning to the pattern discussed above. This says with pretty good confidence (judged by the bunching of the red contour lines) that the jet stream will break into Cal from the Pacific. The red lines bound the southern edge of the jet stream.

Moving ahead into the distant forecast future….(wow, this is getting to be too long again!):

Valid for 14 days from now. Note says it all.

Will look at this in a few days, noting that the ACTUAL model outputs will bounce around this “solution” but SHOULD tend to gravitate back toward it if it does bounce away from it (producing what would be considered an outlier).

Fun times in weather following ahead!

The End

——————————–

¹Feel I have to ride that 0.40 inches rain prediction out since its “out there” and it was in the context of a friendly competition with a friend whose also big faculty member at a famous university in Fort Collins, CO, as well as a Catalina snowbird. In this regard, I have noted that some friends change their forecast with each model run, then in retrospect, select the forecast they made that was closest to the observed amount of the many they made, and then claim that they “really nailed” a rain prediction for Catalina.

Yesterday’s blog was re-written and re-organized some after finding several occasions of not such great writing and org.

Summer-like storm surprises with frequent thunder and a half inch of rain in 18 min

Here are the latest 24 h totals, ending this morning the 23rd at 3 AM AST from your Pima County ALERT gauge network. Our own amount over this period is embedded for comparison purposes:

Gauge         24         Name                        Location
    ID#             hours
    —-     —-       —-        —-       —-         —-       —————–            ———————
Catalina Area
    1010          0.71      Golder Ranch                 Horseshoe Bend Rd in Saddlebrooke
    1020          0.83      Oracle Ranger Station         approximately 0.5 mi SW of Oracle
    1040     0.87      Dodge Tank                   Edwin Rd 1.3 mi E of Lago Del Oro Parkway
    1050     0.59      Cherry Spring                approximately 1.5 mi W of Charouleau Gap
    1060     1.10      Pig Spring                   approximately 1.1 mi NE of Charouleau Gap
    1070            0.79      Cargodera Canyon             NE corner of Catalina State Park
    1080            0.79      CDO @ Rancho Solano          Cañada Del Oro Wash NE of Saddlebrooke
    1100            0.67      CDO @ Golder Rd              Cañada Del Oro Wash at Golder Ranch Rd
xxxx     0.58     Sutherland Heights, Catalina

Santa Catalina Mountains
    1030         1.14      Oracle Ridge                 Oracle Ridge, approximately 1.5 mi N of Rice Peak
    1090         1.34      Mt. Lemmon                   Mount Lemmon
    1110        1.22      CDO @ Coronado Camp          Cañada Del Oro Wash 0.3 mi S of Coronado Camp
    1130         0.87      Samaniego Peak               Samaniego Peak on Samaniego Ridge
    1140         0.79      Dan Saddle                   Dan Saddle on Oracle Ridge
    2150         0.71      White Tail                   Catalina Hwy 0.8 mi W of Palisade Ranger Station
    2280         0.71      Green Mountain               Green Mountain
    2290        0.35      Marshall Gulch               Sabino Creek 0.6 mi SSE of Marshall Gulch

Yesterday, with it many twists and turns, with that significant rain overnight providing a happy, moist beginning. Then, there was a sad middle of the day when two windshifts passed, the second a major, long-lived one one bringing a substantial drop in temperature and fronted by a dramatic arcus cloud, but there was no rain to speak of with either……at first.

Then the surprise, the unlikely resolution of the sad middle of the day just as a dismal clearing advanced from the west: a highly unusual thunderama and cloud burst beginning at 1 PM, one gushing a half an inch of rain in 18 min! This, just when it looked like a total dud was certain from the passage of that front. That “TRW++” (weather text for an extra heavy thunderstorm), provided the happy ending, thus making it a day truly out of Hallmark. The total rain was 0.58 inches, with the three day total at 1.03 inches! Yay, flower help! Rain table at bottom.

Though it was late December and at the winter solstice, the breezy 63° F damp air yesterday morning made it feel like you had awakened from your long vacation flight and found yourself in Hawaii or Miami. It was a truly remarkable, even a joyful feeling.

With that strong upper low WAY off to the southwest of us yesterday morning, and moving right this way, you KNEW that the rain wasn’t over, that thought adding to the joy of yesterday’s early morning. 0.34 inches had fallen mostly during the night before, adding to the humid feel.

Too, yesterday morning’s joy had a withering effect on all those dry weeks that had preceded these past few days with measurable rain, maybe even withering the hard feelings that remain in many of us about those disappointing Big Niño forecasts of a wet Southwest last year. You were finally beginning to feel that you could let go of those hard, grinding, grudge-holding feelings you had against weather forecasters, the ones that misled us so much last year about the Big Winter in the Southwest due to the Big Niño, a record Niño, they told us, indeed, a “Godzilla Niño.” Then, what followed was, “The Big Winter that Didn’t Happen.” And it will be years before we get another Big Niño!

But, let us move on from that tirade to current events; you can see that I am personally completely over the hard feelings of last year’s disappointing forecasts and have moved ahead, as we need to do in life…

Now, finally (!), for yesterday’s clouds, so fantastic in all their presentations and drama, that one really could finally forget the busted Big Niño forecasts of last year²:

Oh, yeah, the cloud diary for yesterday, probably more than you need to know, but, what the heck:

7:56 AM. A shower complex heads north toward Catalina, only to graze the city.

7:57 AM. Stratocumulus clouds topped Sam (Samaniego) Ridge as that shower approached, the lower bases telling you how humid the air was. Dewpoints were in the low 50s!

8:04 AM. Gettin' closer, gettin' pumped for a nice rain blast in tropical air! — 8:04 AM. Gettin’ closer, gettin’ pumped for a nice rain blast in tropical air!

8:22 AM. That complex of rain mostly slud off to the east of us, as so many have this year. However, note the lack of good shafting, just rainy areas that are a little thicker and thinner. This tells you that they're really not Cumulonimbus clouds, but rather shallow ones not having strong updrafts. Earlier, it appeared to be a complex with a Cumulonimbus in it, and in that case, you would see strong shafting. — 8:22 AM. That complex of rain mostly slud off to the east of us, as so many have this year. However, note the lack of good shafting, just rainy areas that are a little thicker and thinner. This tells you that they’re really not Cumulonimbus clouds, but rather shallow ones not having strong updrafts. Earlier, it appeared to be a complex with a Cumulonimbus in it, and in that case, you would see strong shafting. Wonderfully dismal scene, I suppose to those of you with normal sky values; sunny and blue are just fine. Those of you with sky values like that might just as well get the HELL off this page right now! There’s a lot more dismality ahead, except maybe for the next couple of photos…

10:24 AM. Sky breaking out more and more, probably some non-cloud maven people exulting over the clearing. But, it was still moist and humid, and no real windshift had occurred, something that woud presage descending air behind it, and a true clearing. Indeed, true cloud maven folk were exulting over the clearing since with the low aloft approaching, some warming of the ground might lead to real Cumulonimbus clouds while the air aloft was cooling! In this photo are Cumulus humilis and fractus (down low, darkish cloudlets) a riff of Altocumulus castellanus (indicating mid-level instability) and above those, a separate layer of Altocumulus with ripples (“undulatus”), and maybe Cirrocumulus adjacent to the higher Ac clouds. A Cu fattening on calories of sunlight can be seen on the horizon, center. I hope I can be done with this cloud story before dark today….

10:22 AM. Here we go! A line of Cumulus congestus and "soft-serve" Cumulonimbus clouds HAS to be associated with a windshift line. Its got to come through Catalina. This view is looking to the NW. Such a band is likely to extend to the SW from here, and beyond the SW horizon, so you won't see it yet over there. — 10:22 AM. Here we go! A line of Cumulus congestus and “soft-serve” Cumulonimbus clouds HAS to be associated with a windshift line. Its got to come through Catalina. This view is looking to the NW. Such a band is likely to extend to the SW from here, and beyond the SW horizon, so you won’t see it yet over there. Altocumulus perlucidus clouds overlay Catalina at this time along with a few puffs of Cumulus fractus. Its still humid.

11:44 AM. Pretty scene of course, but look carefully on the horizon below the bases of the clouds and you will see arc-shaped clouds curving back toward the NW. THis view is to the SW. Those arc-shaped clouds are that windshift line where air converges to form a line of clouds as was seen in the prior photo. Too many invervening clouds prevent seeing a line here, but as a cloud maven junior or expert, you know there will be a LINE! We hope to have a lot of good testomonials at the next club concerning who saw these arched clouds first. — 11:44 AM. Pretty scene of course, but look carefully on the horizon below the bases of the clouds and you will see arc-shaped clouds curving back toward the NW. This view is to the SW. Those arc-shaped clouds are that windshift line where air converges to form a line of clouds as was seen in the prior photo. Too many intervening clouds prevent seeing a line here, but as a cloud maven junior or expert, you know there will be a LINE! We hope to have a lot of good testimonials at the next club concerning who saw these arched clouds first. Right here, you KNEW something dramatic was about to happen to the sky, and almost certainly something to your rain gauge as well.

12:25 PM. Here it comes! No telling how many inches we might get! (However, the shafting looks weak to me... Not congruent with big "Cumulonims" with good updrafts....so some doubt creeping in.) — 12:25 PM. Here it comes across the OV! No telling how many inches we might get! (However, the shafting looks weak.. Not congruent with big “Cumulonims” with good updrafts in them….so some doubt beginning to creep in.)

12:31 PM. I feel like I am in Louisiana or Alabama awaiting a cold front. THis was SUCH a dramatic scene, I know you were having a hard time constraining yourselves, and not running to tell neighbors about it. — 12:31 PM. I feel like I am in Louisiana or Alabama awaiting a cold front. This was SUCH a dramatic scene, I know, like me, you were having a hard time constraining yourselves; not running to tell neighbors about it.

12:32 PM. Zooming in on a fantastic scene for Arizona! Camera can't fire fast enough! — 12:32 PM. Zooming in on a fantastic scene for Arizona! Camera can’t fire fast enough! I was getting light-headed here.

12:39 PM. The windshift to the NW has passed the house, but those arched clouds above the windshift are getting pretty ragged. And where's the rain? — 12:39 PM. The windshift to the NW has passed the house, the temperature is dropping like mad, but those arched clouds above the windshift are getting pretty ragged. And where’s the rain? Pretty scene, though.

12:45 PM. Within a few minutes, a few hundredths of an inch fell, propelled on gusty NW winds, but then it quit, the low clouds banked up harmlessly against the Catalinas, which still had sun on them! This was looking really bad. No rain was in sight, either. Pretty scene, though. We don’t want to lose sight of beauty when its in front us, even when we’re getting sad about the turn of developments, which in a Hallmark movie would be that point when the owner of the building that a bakery or flower shop is in, says he has to lick them out because he has sold the building. Yep, that’s how bad it looked right at this point.

12:50 PM. The arcus clouds and windshift had moved in from the west, and so this clearing out there HAD to be approaching, the day's rain likely over. I can only imagine how glum you all were out there in seeing this abyssal scene, "sunny skies just ahead", spoken sarcastically. — 12:50 PM. The arcus clouds and wind shift had moved in from the west, and so this clearing out there HAD to be approaching, the day’s rain likely over. I can only imagine how glum you all were out there in seeing this abyssal scene, “sunny skies just ahead”, spoken sarcastically.

12:53 PM. The Stratus clouds now hung even lower, as though wanting you to touch their empty innards, a truly humiliating scene. I have never seen such vacant clouds, so filled with portent only minutes before. This was, indeed the low point of the day. The sun would soon burn them off.

1:02 PM. Just after the most amazing thing, a blast of THUNDER overhead E or SE, And, it was starting to rain! But here you can see lower clouds (Stratus or Cumulus fractus) that are separate from a higher layer (top). So, where the HECK was the Cumulonimbus? — 1:02 PM. Just after the most amazing thing; a blast of THUNDER overhead E or SE, And, it was starting to rain! But here you can see lower clouds (Stratus or Cumulus fractus) that are separate from a higher layer (top). So, where the HECK was the Cumulonimbus?

1:09 PM. Heart of the blast, visibility is less than a quarter mile, thunder, close to overhead it seemed, had become more frequent, once every minute to two, unheard in winter storms. It almost exactly the intensity of our summer ones. Completely out of control here snapping photos of nothing but rain, hoping camera battery doesn't give out. But, then I know I would have had company with all of the CMJ's out there losing your minds over this as well. What a day, Mr. and Mrs. Catalina! — 1:09 PM. Heart of the blast; visibility is less than a quarter mile, thunder, close to overhead it seemed, had become more frequent, once every minute to two, unheard in winter storms. This winter storm, on the solstice, was almost exactly the intensity of our summer ones. Completely out of control here snapping photos of nothing but rain, hoping camera battery doesn’t give out. But, then I know I would have had company with all of the CMJ’s out there losing your minds over this as well. What a day, Mr. and Mrs. Catalina! Is this what “global warming” has ahead for us, as one Arizona scientist mused? Summer-like storms in the heart of winter? Maybe it would be so bad…. Hardest rain I’d seen here in nine winters.

1:18 PM. A few hundred photos, 18 min, and a half an inch of rain later, I ventured out to see what was the result. Here, ponding had occurred in a swale. I wondered whether toads would re-emerge after this warmish rain? — 1:18 PM. A few hundred photos, 18 min, and a half an inch of rain later, I ventured out to see what was the result. Here, ponding had occurred in a swale following the gush. Considering the warmish nature of the rain, would toads now re-emerge along with flying ants?

4:42 PM. One of the rewards of clearing skies, are the quilted-with-sunlight mountains sides of the Catalinas.

4:43 PM. While plump Cumulus clouds and dark skies abounded, these clouds no longer reached the level where ice could form, and were "dry" clouds as far as precip goes. — 4:43 PM. While plump Cumulus clouds and dark skies abounded, these clouds no longer reached the level where ice could form, and were “dry” clouds as far as precip goes.

5:16 PM. More evening color; note rain gauge. Such a pretty scene!

The End

New storm marches toward Catalina! Due in tomorrow afternoon.

¹Meteorologists, outside of Buffalo and Seattle, have inverted values regarding clear and cloudy.

²I hope we get 30 inches THIS water year, dammitall, busting this year’s seasonal forecasts of a dry Southwest.

Wasn’t expecting rain to arrive this soon (overnight Tues into Wed); much more in route

0.11 inches logged in Sutherland Heights. Amazing, considering nothing was expected last night in mods, but rather tonight.

This rain situation from the tropics is looking better all the time, with an inch between tonight and tomorrow night looking very possible. Next, let’s see what the AZ Uber model predicts, from the 11 PM AST run to get some constraint on a shot from hip one:

Total rain expected between about now and 7 PM AST tomorrow evening. Note something like 3 inches is expected atop Ms. Lemmon!

Annotated version below since no one will be able to find Ms. Mt. Lemmon….

Same as above except with arrows and writing on it.

Well, we know these tend to run on the the high side, so look for something between a third and three quarters of an inch here in Sutherland heights, a really nice rain! We need it so bad, too. Desert looks awful dry thanks to the deficient Oct and Nov rains.

The future is hopeful, though, for rain anyway in Catalina. Recall that spaghetti (the “ensembles” told us were we going to be in the area where troughs collect at lower latitudes like ours and Baja. Well now its looking more and more like they’ll have rain in them and not just “temperature fluctuations”! I’m pretty excited here, hope you are, too!

The End

(more later)

First measurable rain in recent memory falls in Catalina! Also, strange and regular undulations observed

“Recent memory” is, of course, only about three weeks, certainly not more than a month….

BTW, FROPA is occurring now (3:55 AM-4:10 AM, marked by the usual wind shift to the NW from the SW, heavy bursts of rain in this case, and a sharp drop in temperature–so far we’re down from 55-56° F to 45° F in about 20 minutes. Likely will hit the upper 30s before the cooling stops. The rain total yesterday morning by 7 AM from the first rain band, mostly fell from mid-level clouds, was but 0.02 inches. Today, the total is going to be over 0.25 inches by 7 AM. Excellent indeed.

(Update: 7 AM rain total here in Sutherland Heights is 0.51 inches, as measured in a NWS style 8-inch diameter gauge! Awesome. The U of AZ model really nailed this event, predicting 0.25 to 0.50 inches here.)

Let us begin the cloud marathon that led to “rain.”

12:52 PM, December 15. Altocumulus (perlucidus translucidus) announces the storm, sans the Altostratus that was actually expected.

4:36 PM. Now we’re getting serious with Cirrostratus on top of Altostratus and scattered Altocumulus clouds. Three separate layers whose appearance tells you that the atmosphere above is in gentle lift, the kind of thing that precedes the actual storm, though not so much in deserty climates like ours where such scenes may only lead to a pretty sunset.

Creeping toward the present….by yesterday morning, things looked serious. I hope you noticed how FAST the clouds were moving, ones just above Ms. Mt. Lemmon:

7:20 AM. Stratocumulus layer with undulations and concave bases zipping along at 50 kts or more from the SW. Did you notice the stationary clearing to the SW horizon? These clouds were forming by the lift provided by the Catalinas and other mountain ranges downwind from the lower SW desert areas. Sometimes steady rain falls for hours with this scene. Yesterday, only sprinkles around mid-day since tops at this time were marginal for ice formation.

Some sounding comments, this nice sounding plot from IPS MeteoStar:

Ann 2016121612Z_SKEWT_KTUS — The TUS sounding launched around 3:30 AM when rain was falling in Catalina, giving us eventually our 0.02 inches of rain. No doubt the clouds in the preceding photo had warmer tops than these did. The top of the lower, and mostly liquid layer was about -16°C, normally plenty cold enough for ice to form. The humidity element on these balloon soundings can measure the humidity with respect to liquid water quite well, and so when the temperature and dewpoint lines are on top of each other in these soundings (are the same temperature) you can bet that the balloon when through a cloud of mostly liquid water. When the lines spread apart, as higher up in the balloon sounding, but are still close, you can be almost sure its an ice cloud that the balloon went through. This doesn’t apply on partly cloudy days or broken layers when the balloon passes between clouds. But when the balloon went up yesterday, we had a solid overcast, likely in two separate layers, one being mostly liquid and the higher one mostly ice. The spacing between the two is so small, if it even existed, that ice likely fell into the lower cloud layer. Sometimes this is called the “seeder-feeder” situation, since the ice crystals have a chance to grow like mad and/or collide with droplets while falling through the lower layer.

Kind of a crummy diagram of a "seeder-feeder" situation. That lower cloud is CRITICAL for enhancing precip! Believe or not, most precip in winter storms is added in the last kilometer at the bottom of the clouds, essentially by what are Stratocumulus clouds below Nimbostratus decks, themselves considered "middle-level" clouds in our cloud nomenclature. — Kind of a crummy diagram of a “seeder-feeder” cross section for the Seattle area. That lower cloud is CRITICAL for enhancing precip! Believe or not, most precip in winter storms is added in the last kilometer at the bottom of the clouds, essentially by what are Stratocumulus clouds below Nimbostratus decks, themselves considered “middle-level” clouds in our cloud nomenclature.

But what about those strange clouds later, undulations and cave-like cloud bottoms? For the person still reading this tedious blog, here are a few shots of those extraordinary scenes, ones you might only see with the ferocious winds aloft yesterday:

8:00 AM. Strange scene, concave cloud bases–personally would call this layer Stratocumulus, but with a base height of about 8,000 feet above ground, so could also be considered an Altocumulus opacus layer.

9:33 AM. Was taking photos every few seconds as sky seemed to change.

9:35 AM. While scary clouds were overhead, you could see that a clearing was going to move in before very long, given the horrific winds aloft from this direction. Note again “undulatus”, waves in the atmosphere showing up in clouds! But, it took hours for a clearing to occur because that was a standing zone of cloud formation to our SW yesterday, something like a gigantic lenticular cloud that stands in place downwind from mountains.

9:36 AM. Having taken three photos in the past minute, each one looks pretty much the same. But, this one has a bird of some kind on the side of that bird feeder at the bottom. Was small, yellowish; maybe a canary. Its important to note that each photo was taken at exactly the same spot, but rather tens of feet from the prior photos. Moving around helps provide perspective in photos….

9:51 AM. More undulatus. Looks like its going to clear up now. Nope, it didn’t as clouds kept being added to the upwind end of these.

9:53 AM. Waves began breaking out over or just downwind of the Catalina Mountains. Would want to be flying in them!

9:54 AM. Zooming in. What is going on here? Fortunately, for the sake of having to explain this to his three blog readers, Cloud Maven Person set up his video camera and starting a film of this phenomenon. Here’s the result: dry waves of air are causing the concave bottoms of these clouds. The air in the cloud layer was moving faster than the dry waves pushing up into them, and so clouds were forming on the right side of those concave bottoms (upwind side), and dissipating on the left side (the downwind side). So those dry waves that pushed up into the cloud layer, were in effect creating cap clouds at their highest point, the kind of cloud that tops a mountain for minutes to hours (not the same as a “lenticular” cloud which is almost always downwind of the peak). Without video, I would not have known this, might have put forward something crazy in the way of hand-waving….maybe.

11:55 AM. As you can see, that clearing is still out there. Here some ice began to form in these Altocumulus opacus clouds (I would call them) and a few drops made it to the ground about this time. Eventually, it did clear up; “the clearing before the storm” as we see so often here in Catalina and Arizona where dense bands of middle and high clouds, this time thick enough to provide us with a little measurable rain overnight (that 0.02 inches), is separate from the thick, lower-topped clouds that produce the actual storm such as this morning’s blast of rain accompanying the cold front.

3:55 PM. The evening closed with “partly cloudy”, producing those nice scenes on the Catalinas. These clouds are Stratocumulus, tending toward lenticulars if that bit smoother. You no longer see any ice or virga from these clouds. Since mid-day, the tops lowered to around -5 to -10° C, a little too warm for ice formation, and the upper atmosphere dried out, so no higher clouds around either, as the main front approached.

The TUS rawinsonde balloon sounding for yesterday afternoon. The arrows denote cloud bases and cloud tops. Yesterday, there were no overshooting tops, so they probably were at -9° C as shown in this sounding. Here, following up on the prior sounding discussion, the balloon passed between clouds since if it had gone in them (droplet clouds) the two lines would have indicated the same temperature (water saturated conditions).

Well, at 6:41 AM, the rain is over, with nothing definite now in sight, though there are close calls since we seem to be in or near the “mean trough” where individual troughs and fronts like to collect and reach their farthest points south. While rain is “iffy” in these passing troughs, fluctuating temperatures from pleasant days to cold days following dry cold fronts passing by is virtually certain.

The End.

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