Definitions – Page 63

Diabatics and snow

Its not about L. Ron Hubbard…..but we will try to be “clear” about what happened yesterday morning.

The short of it: when its snowing hard above you, the snow level drops. So, when yesterday’s well-predicted-by-all (models, humans, etc.) frontal band turned out to produce heavy snow above us, the snow level dropped to levels that were lower than expected (below 3500 feet elevation). Those big flakes take longer to melt, chilling the air to the freezing point as they fall and melt. So, down goes the freezing level for a short time during the heaviest precip. When the heavy precip ends, the freezing level moves up again.

We call this lowering of the snow level in heavy precip a “diabatic” effect, maybe get into the effects of enthalpy of fusion, too, because when we miss a forecast, we want use some jargon to make it sound like a very complicated process occurred, one that only Einstein could have anticipated.

Anyway, the diabatic effect yesterday involved heat transfer from the air to the melting snow; melting sucks the life out of the temperature because work is involved in melting snow . Often a little isothermal layer (temperature is steady with height) is present in the atmosphere when light, steady snow is falling in the layer where the snow melts into rain before reaching the ground due to this same effect.

BTW, there was a U of WA IMA Department of Weather softball team called the “Diabatics”. I insert this as a smile-producing distraction to get you off the thought of error.

I’m guessing the media weathercasters were all over “diabatic” effects as well yestserday.¹

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The precip

Got 0.26 inches, 1 inch max depth of snow here at the house, missed “middle ground” prediction of 0.23 inches by only a slight amount. However, there was 0.36 inches, 1.5 inches of snow at a Sutherland Heights gage.

It was so great to see snow just sitting there, melting away slowly on ground in the desert yesterday and on those new grasses and weeds trying to spurt skyward in our droughty winter (so far). For a wider look at the precip totals, go to the U of AZ rainlog site here and input February 8th because even though the precip fell on the morning of the 9th, by convention for the U of AZ, its assigned to the prior day, which is the 8th in this case. If you do go there, you will see that for the TUS region, those areas north of Pusch Ridge got a quarter to a third of an inch while south of Pusch Ridge, totals were far lower. Lucky us.

The most I saw in 24 h in the Pima County ALERT gages as of 5 AM morning was 0.39 inches at CDO wash, northeast of Saddlebrooke.

Might not have been so great for the free range cattle, several of which were gumping down cholla buds as I drove along Equestrian Trail Rd! Ouch! Apparently that snow cover was just enough to prevent them from eating the dry grass out there.

Here are a couple of belated snow shots for your files:

9:01 AM. The Catalinas from Equestrian Trail Road. Trail Road? Hmmmm. — 9:01 AM. The Catalinas from Equestrian Trail Road.
Trail Road? Hmmmm.

SONY DSC — 9:01. Arizona “Christmas tree.” Cows like’em. Kind of fun to have one of these in the house in a pot, put a LOT of artificial snow on it, and then ask out-of-towners who’ve never seen one of these cacti if they wouldn’t mind helping out by putting some decorations that you’ve just bought on it.

Yesterday’s clouds and precip

They were again tremendous, when combined with the Catalinas, Tortolitas, and our deep blue skies! Took too many photos again, more than 200! Hard drive filling up fast!

After the slow dissipation of the stratiform deck in the morning, lifted and thinned, as was happening in the first photo, the Stratocumulus underneath that higher layer gradually dispersed into Cumulus clusters, and with the freezing level so low, ice readily formed in them.² Scattered showers developed by mid-day, and most, in the early going, produced graupel, tiny snowballs, soft hail or snow grains (really tiny ones).

The best CMJ’s out there no doubt rushed out before those little snowballs melted and were treated to the sight of “conical” graupel, cone-shaped little snowballs. Conical graupel, which is kind of comical-looking because it looks like a little, pointy clown hats, forms when an ice particle, say a plate-like crystal in a cloud consisting mainly of supercooled droplets, falls face down. The one side facing down the whole way, with the cloud droplets hitting on that one side, freezing as they do leading to that space shuttle entry vehicle shape. Kind of fun to see them and think of that ice crystal falling face down like a clown, and then it ends up looking like a clown’s hat! Quite funny. Hence, the nickname, “comical” graupel. Here’s one that fell on Catalina yesterday for your edification:

12:38 PM. "Comical graupel. You'd look so funny wearing a great big hat like this, maybe with a clown face! — 12:38 PM. A great example of “Comical “graupel. You’d look so funny wearing a great big hat like this, maybe, too, with a clown face!

Some cloud shots:

10:37 AM. Stratocumulus clouds hug the tops of snowy Samaniego Ridge.

11:15 AM. Snow showers first begin to form in modest Stratocumulus clouds NE of Saddlebrooke (precip can be on the horizon seen just above white roofed house in foreground.

11:53 AM. Let the graupel begin upwind of Catalina.

3:55 PM. Much of the best shots have not to do with storms but with the lighting on our fabulous Catalina Mountains associated with passing clouds on days like yesterday.

6:06 AM. Virga and the lowest cloud bases of a line of Stratocumulus clouds hovering over Oro Valley just after sunset. — 6:06 AM. Like a wind blowing on embers in a fire, virga and the lowest cloud bases of a line of Stratocumulus clouds hovering over Oro Valley are reddened just after sunset, producing another breath-taking Arizona sunset.

I could go on and on with more photos I liked from yesterday, but must close. Haven’t looked at a single prog yet!

The weather ahead

Looks like tomorrow will be a lot like yesterday afternoon (no rain/snow band likely), cold cumuliform clouds with afternoon virga and showers here and there, graupel, soft hail occurrence is a certainty from some of those clouds, followed by a nice recovery in the temperatures for a five day or more spell before the next winter onslaught of storms in the 10-15 day range from now (20th to 25th of February) hits. Hope they do. Those storms are “moderately” supported in the NOAA spaghetti plots.

Let me titillate your rain bucket with this forecasted behemoth on Monday, February 25th:

Arrow points to Arizona. From IPS MeteoStar's rendition of the WRF-GOOFUS model. — Arrow points to Arizona. From IPS MeteoStar’s rendition of the WRF-GOOFUS model.

The End!

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¹It is also interesting that CMP, writing that the temperature would fall “15-20 F” in an hour after the front passed and rain started, did not realize that “15-20 F” minus the temperature of say, 50 F, at the start of the rain, leads to snow falling, fer Pete’s Sake! Kind of an arithmetic oversight.

²Not sure why the Beowulf Cluster at the U of AZ did not have scattered showers in the afternoon around Catalina in that 11 PM AST run I looked at–would have to be a problem in the model microphysics or the forecast cloud depth being too shallow.

Jet stream band of clouds delivers a sunset to remember; its snowing now…

at 6:30 AM…

The sunset? This one:

4:18 PM. Near stationary band of high and middle clouds, clearing to west. — 4:18 PM. Near stationary band of Cirrus, Cirrocumulus and Altocumulus emanating from beyond Kitt Peak, with a “pre-storm clearing” to west sets the stage.

6:06 PM. More overhead and zoomed view of the phenomenal ribbed structure in those clouds. Had never seen this before, waves in the flow spaced like this ("undulatus" as we would term it). — 6:06 PM. More overhead and zoomed view of the phenomenal ribbed structure in those clouds. Had never seen this before, waves in the flow spaced like this (“undulatus” as we would term it).

Raining pretty good now, 5:01 AM, thank heavens. Now, to get that bottom prediction of 0.08 inches… Always worry when foretellling rain amounts. Over is good, under is awful. Can’t look at radar, either, which would tell me what’s just ahead. Just listening to it on the roof, sort of “enjoying” the suspense in the morning darkness.

Back to the clouds at sunset… Would tell you how high they were, except that they were misssed by the TUS rawinsonde balloon. It appears it went up outside and ahead of this little moist plume up there, but indications and my own estimate, and even though these clouds were termed “Altocumulus” in the first photo, they were almost certainly above 22,000 feet above the ground (25,000 feet above mean sea level, or above 350 “millybars.”) ((That may seem exceptionally high for Ac clouds, but it happens^{1, excessive footnote, detracts from the main discussion and that’s why you put stuff like this in as a footnote because it doesn’t look so bad as just a little, itty bitty number. There’s a period just below this in case you lost trackl}.

5:23 AM: Oh, my gosh, temp down to 35 F now! Wow.

On to some an illustrative figure of what was going on last evening, this from the Weather Department at the University of Washington, a 300 mb map. There’s a tremendous number of arrows and amount of writing on it, I hope that’s OK. It is kind of pretty, though, with all the colors on it.

300 millibar (30,000 foot level in the atmosphere) for 5 PM AST yesterday, the 8th.

Back to stream of conscientiousness: 6:11 AM. Quiet now, no rain. Only 0.06 inches so far, need two more. What the HECK is happening? Went out with flash light and its SNOWING! Oh me, Mr. CMP wasn’t thinking snow at 3200 feet today! Dang. But, like the map above, it could be quite pretty, likely precip will get over 0.08 inches now, too. Just won’t go in gauge and tip bucket until later when it melts. Temp now 33.5 F in light snow. Was 47 F before front and rain began to hit, so its down almost 14 degrees now. No wind, either.

Rest of today; now looking at data:

Looks like precip, snow melting on contact mostly, maybe a skiff to an inch at most, will continue for the next 3-5 hours before the clouds lift into a higher layer of Stratocumulus toward mid-morning (this from the Hollerith technique illustrated a couple of days ago). Probably will be some gorgeous Stratus fractus along the snow-covered Catalinas, too. Later the sky should devolve into scattered to broken coverage in Cumulus and shallow Cbs with virga and passing light showers, probably will barely measure. Now, lets look at the U of AZ model and see if this has ANY credibility…. Seems to be about the same, rain/snow precip ends by 9 AM here in Catalina. However, no passing showers are indicated in this model after that.

Should be a memorable day with the Catalinas in some snow again, and passing clouds and shadows on them.

The End.

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¹During our (Cloud and Aerosol Group’s study of aircraft-produced ice holes and canals in Ac in the early 1980s when Reagan was President and just after he fired all of the air traffic controllers, we were able to talk to guys at the Air Traffic Control Center in Auburn, Washington, working the jets coming into SEA-TAC! We were able to get from them real time heights of Altocumulus cloud layers in which holes or canals due to ice formation occurred due to an aircraft. While Mr. Cloud Maven person has won cokes off pilots who questioned his estimates of how high clouds were, who then, following a bet, took off and measured them, even HE was surprised at how high some Altocumulus cloud layers were. Some were well over 20,000 feet above ground level! In the days before heights were measured by machines, now up to 12,000 feet above ground level, it was almost routine for human ground observers at weather stations, when seeing Altocumulus clouds, to put down “12,000 feet” or “15,000 feet” above ground level for the estimated height of those clouds in aviation weather reports. Older pilots will know this, having heard the sequence in verbal “transcribed” aviation reports, something like, “Five thousand scattered, estimated one-two thousand broken, two-five thousand overcast….” Oh, yeah, that’s how it was so long ago.

Our next winter this winter

Overview

It seems we’re heading into another “trough bowl”, a persistent collection area for cold air in the upper levels over us during the next couple of weeks. In the meantime, something about today’s great weather, if you like a little drama.

Underview

The wind starts blowing pretty hard later on this morning or certainly by mid-afternoon. As it gets gusty and dramatic, its only natural for our heads to start swiveling around, looking skyward, knowing something ominous is happening; something’s changing drastically, like the barometer. That gut reaction comes not from the gut, as popular lore would have it, but from the deep responses to fear located in the amygdala, that ancient piece of brain that knows scary things¹. And it would be right.

Here is the scary stuff that going to happen, first from the NWS, as told in their latest (as of 4:30 AM) very “Special Weather Statement“, FYI. Have goose bumps now!

Also shown at that link is a “Special Statement” from the Albuquerque office of the NWS, one in that I particularly liked because of their use in their own Special Statement of the word, “potent” to describe this incoming storm. Its a great word to employ, and apt in this case; and its a word that conveys power. A “potent” this or that is something tremendous! “Po-tent”; fun word to say, too. Think, too, of the devastation when just two little letters are prefixed to that word.

Today is the precursor day for our “potent” storm, a day with potent winds, likely reaching 40 mph in momentary “puff gusts” (lasting just a second or two) here in Catalina, especially in the hills overlooking our little berg. The air gets squeezed against the Catalinas today as it races northward into a large Great Basin low center. Should be gusty here right up to when the potent cold front hits tomorrow morning. When that front hits, we should see light to moderate rain for a couple of hours, along with our usual temperature drop of about 15-20 degrees in an hour, too. And, as it always does, the wind will drop off dramatically, turning to the northwest for awhile before returning from the southwest.

BTW, since we haven’t had strong winds in so long a time, there will likely be more dust raised today and tonight than would normally be the case. Also, you tend to see more branches break off trees after a long non-windy period such as we have had.

All the mod outputs I’ve seen from overnight (3, USA, Canadian, and the downscaled U of AZ one) have rain here tomorrow morning followed by the chance of a passing, brief shower in the afternoon. Those passing shower clouds would be Cumulus congestus converting to small Cumulonimbus clouds. Very pretty to see in the winter.

The chance of measurable rain here in Catalina tomorrow?

Oh, 100%. We don’t mess around here; but then we don’t have any particular responsibility to anyone either.

Amounts?

U of AZ mod has us on the edge of the 0.25 inches region, slightly less than was forecast yesterday at this time. SOP from this keyboard: minimum 0.08 inches, maximum 0.38 inches, middle ground, 0.23 inches, same forecast as yesterday. However, as a person who suffers from a desert version of precipophilia, I love it when its MORE than I think it could possibly be. (Didn’t really have this syndrome in Seattle…)

Rain chance here HAS to be near 100% due to our position near the Catalinas, and how those frontal band clouds will be fattening up as they approach them, especially to the point tops are fattened up to BEGIN raining in the trailing part of the frontal band (requires the formation of ice up there, as you know). The trailing parts of storm bands is where we in Catalina Census Designated Place pick up an additional amount of rain over outlying areas in fronts like the one coming tomorrow.

So, in sum, tomorrow will be a fun day and a dramatic one with rain pounding down in the early morning, and, with the snow level plummeting to below 3500 feet during the rainy part of the storm, and a scenic one when the leftover, non-raining Stratocumulus clouds begin to break open, build into scattered Cumulus and small Cumulonimbus clouds. Those snow covered mountains will come fully into view. So, a VERY photogenic day ahead tomorrow, particularly in the afternoon. Charging camera batteries now.

Today’s clouds

First, as we saw at sunset yesterday, Cirrus clouds, lots of different varieties/species today, probably including the patchy thick versions with shading called Cirrus spissatus. Most likely these clouds will thicken enough in coverage to be termed, Altostratus, widespread gray looking ice clouds. Below those, maybe a brief Cirrocumulus or maybe an Altocumulus lenticularis–again, look to the northeast of the Catalinas for that. These latter clouds can have the best, really delicate patterns embedded in them on days like this. But, they may only last minutes if they form.

Our high cloud spawning grounds have been doing their work overnight, as you will see in this infrared satellite loop from the University of Arizona. You will see that high clouds have spawned from clear air in the lee of both the mountains of southern California and those in northern Baja California. Those cloud spawning zones have quit for the most part now as the air dries out aloft over them, but the shield of clouds they launched now extends over the middle of Arizona, some are over us now, too, so a good chance of some sun rise color. That nice plume of ice clouds launched by those mountains is wrapping around our coming upper level low center as it marches down the California coast.

As you know, those high clouds are “decorations” in a sense because they will have nothing to do with the surge of lower clouds and rain that blasts into Catalina tomorrow morning. But they do present us with the chance of great sunrise and sunset color. Just now I saw that the U of A model foretells drying at Cirrus levels over us near sunset today, meaning that the huge clear slot that (oddly) precedes storms so many times, may arrive just as those Cirrus/Altostratus clouds depart around sunset. Hope so.

The weather ahead and far ahead (beyond 10 days)

This is great news and not so great news (if you’re snowbirding in Arizona); the coming rejuvenation of winter. The mod output from last night’s 5 PM AST global data crunch (can be seen here) has a series of troughs of cold air dropping southward from the Pac NW into the Southwest US, meaning multiple chances for rain, but even if no precip, lower than normal temperatures. In other words, it appears that we are entering another spell where we are in a trough bowl, a nesting place of sorts for cold air aloft and the storms that come with them.

Below, from our TUS NWS, is an example of what it means to be a thermometer going in and out of “trough bowls”, that region where one or more upper level troughs find us for a couple of days or more, this graph for January. You can see that if you were a thermometer, it would be like being in the ocean with big swells driving you up and down, up and down. That’s what’s ahead now, that same temperature roller coaster we saw in January appears to be ahead for us through the remainder of February.

Temperature roller coaster due to sporadic positioning of "trough bowls" in the SW US. — Temperature roller coaster due to sporadic positioning of “trough bowls” in the SW US.

But, with troughs come chances to joyfully fill our February rain gauges and see our desert vegetation spring to life. So, really, snowbirds aside, its all good.

Would refer you to our venerable error-filled NOAA ensembles of spaghetti plots to support or weaken these longer term conclusions, but I haven’t been able to get in, seems site must be down.

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¹May be some kind of “first” here, seeing the word amygdala in a weather briefing. Tell your friends.

Knock, knock…. Who’s there?

Cold slam!

But first, continuing from yesterday: “…and a few small to moderate sized Cumulus (humilis and mediocris) clouds as well to go with the high and middle clouds.”

Sorry I took so long to finish that up, but it was worth the effort because it was pretty darn accurate.

The storm on the doorstep

Here is your very excellent Catalina forecast as of now (4:50 AM) from the computers at the NWS. There is a statement on the exciting New Mexico weather, posted by the Tucson NWS here. You can feel the excitement in NM in this message they consider quite special, labeling it a “Special Statement.” Hope our Arizona guys and gals get on board with the NWS in ABQ and issue something special soon! Being weathercentric, of course, I am at one with the ABQ office even now.

Here’s a depiction of the incoming storm from our best model, that at the U of AZ, one that downsizes the “WRF-GFS” model to smaller scales so we can see what happens in our local mountains and valleys as it barges across California and then into Arizona on Saturday. Precip is shown to begin on the Catalinas before dawn on Saturday, but probably won’t reach here for a few hours after that. The model onset time here in Catalina is 8 AM AST on Saturday. However, this model tends to run a bit fast in these situations, so it may be mid-morning before those cold, cold raindrops start falling. But, 8 AM vs maybe 11 AM AST? Amazingly close no matter how you put it. It just shows how good our modeling systems have gotten over the years.

The amounts? Seems measurable rain is certain here in Catalina–the flow pattern jetting against this side of the Catalina Mountains favors us here. The finest scale model at the U of AZ, the first place to look, is showing a range of values between 0.25 and 0.50 inches, oddly corresponding with a ludicrous guess made too far in advance here a few days ago. Hmmm. The Catalinas are shown to get more than an inch and that calls for a celebration.

Here is the scoop from the 11 PM AST U of AZ model run for total precip (snow on the Catalinas again, the best kind of precip because it just sits there and soaks in when melting):

Valid at 10 PM Saturday the 10th. — Valid at 2 AM AST Sunday the 10th, the storm is long gone from Catalina at this time but still adding some in the mountains up to about here.

Out of character a bit, but also since we’re on the edge of the predicted range of amounts, I think the bottom is closer to 0.08 and the top likely amount is 0.38 inches, with a “median”, most likely amount of about 0.23 inches, to be a little silly here.

Clouds today?

Probably (and this time I will examine the TUS sounding more carefully than yesterday), just a few isolated Cumulus clouds again, likely dissipating during the afternoon, and a couple of Cirrus clouds.

The clouds tomorrow (more interesting)

One of the interesting cloud formation zones for Arizona is over and downwind of the mountains in northern Baja (Sierra de Baja California). Gigantic plumes of Cirrus/Altostratus ice clouds often form in these situations as moisture at high levels from the Pacific Ocean (located west of Baja, California) travels over those mountains. Those clouds would be something akin to standing wave clouds, lenticulars, but because the air is pretty moist (“ice saturated”) wrapping around this powerful low, they don’t evaporate downstream once having formed but end up as a huge, icy plume across central and southern Arizona. I think we’ll can see that start to happen today, first in the lee of the Sierras of California, as the jet stream works it way down the West Coast toward us.

Eventually, the higher level moisture dries out over those Baja mountains, as it will later tomorrow, and the icy plumage source ends, and many times we see the end of that plume from those Baja mountains (Cirrus/Altostratus clouds) as a huge clearing that, oddly, preceeds the real storm; the surge of lower level clouds that carry the precip. And with that clearing as well, the passage of the core of the jet stream (in the middle levels) above us.

I know many of you have seen this sequence over and over again, the clearing of a high dense layer of clouds from the actual storm that’s on its heels.

Such a separation in those two clouds systems, the high and the low, can lead to spectacular Catalina sunsets. Tomorrow, out on a limb here, is the kind of day where that could happen–the sun sets in the distant clearing to the west as the shield of icy plumage overhead passes.

Yesterday’s clouds

Yesterday was another one of those especially gorgeous days here in the wintertime. Delicate patterns in Cirrus, as well as the dense patches. Then, a few lower Altocumulus clouds above scattered small to medium Cumulus clouds against a vivid blue sky and limitless horizontal visibility. Here are some examples:

7:47 AM. Old Cirrus (foggy stuff above palm tree) below newly formed Cirrus (flocculent, specks). — 7:47 AM. Old Cirrus (foggy stuff above palm tree) below in altitude newly formed Cirrus (flocculent specks to left and right).

10:34 AM. — 10:31 AM. Only the exceptional cloud maven junior would have noticed this rogue Altocumulus castellanus masquerading as a Cumulus. Its betrayed by those specks of Ac floccus around it. Also, if there was a true Cu fractus nearby, you would have noticed a tremendous difference in the relative movement of the much higher Ac cloud and the real Cu.

12:02 PM. Last of the high clouds (Cirrus spissatus) approach Catalina with Cumulus fractus and humilis starting to form.

2:36 PM. One of the best shots of the day; small Cumulus with a trace of Altocumulus perlucidus above.

5:51 PM. Though it was clear to the west, we still had our sunset color on the Catalinas, and an orange reflection on the bases of the last clouds hanging on above them.

Kind of rushing around today, hope this is intelligible….

The End.

Sunset color today?

First, yesterday’s interesting clouds:

Earlier Today

You will soon notice a nice sunrise with a sky full of clouds, Cirrus-ee ones, Altostratus, some Altocumulus tending toward lenticulars (red denotes cloud forms added after the sun came up and I saw them.)

I am late today, not because I overslept some, but also because I wanted to post a great sunrise photo for you.

You know, its all about YOU again, isn’t it? Maybe you should step back and think about that for a second…ask yourself just where your life is going? Thanks in advance for doing that!

Here is this morning’s nice sunrise, Altostratus clouds with virga:

When you see this morning’s clouds, and the great sunrise, no doubt you will be thinking along the lines of a great sunset today as well.

But you’d be so WRONG!

Using a technique developed here, you can foretell where the back side of today’s band of high and, later, middle clouds will be quite accurately. You won’t need the Titan supercomputer to do it, though it would be nice if you had one. Will reprise that methodology for you:

1. First go to, say, a web site having infrared image loops, such as here in purple and gold Huskyland up there in the wet Pac NW

2. Select a loop that you like that shows the clouds to the west of us, such as the one I have selected for you.

3. Stop the loop at a time period not less than 4 h from the current time (probably best not to exceed 12 h).

4. Get out a Hollerith card (computer punch card), and carefully mark the position of the backside of the cloud band of interest that is upwind of your location, pressing the card hard against your computer montior.

5. Proceed in stepwise fashion to the current time in that satellite loop and mark on the same punch card, the location of the backside of the cloud band. You will now have two “tick” marks denoting the movement of the backside of the clouds over the time period you chose.

6. Now, move the first “tick” mark to the current backside, carefully moving the card along the direction of movement of the band, and pressing it against the computer monitor.

7. The second tick mark you made will now be ahead of the band at a future position and time, based on the time increment you have used.

8. Determine from that future position whether local sunset will occur to the west of the backside while it is still OVERHEAD. If the answer is “yes”, then a tremendous, memorable sunset is likely.

Illustrative example, using an 11 h time increment to enhance difficulty:

Satellite image 1

6 PM yesterday. Cloud band backside is over central California.

Satellite image 2

6 AM this morning. Backside approaching Colo River Valley. But is it moving slow enough to be overhead at 5-6 PM? — 6 AM this morning. Backside approaching Colo River Valley. But is it moving slow enough to be overhead at 5-6 PM with the big clearing to the west?

Preparation of the Hollerith card; no “hanging chads” here–some people disperse incense now:

Results

The back edge of our cloud band is too far east for a good sunset tonight. New clouds would have to form on the backside for a good sunset. Yes, that COULD happen, and it sometimes does in certain situations, but it probably won’t today. Be thankful for a nice sunrise.

The weather ahead? The cold slam?

Well, every weather presenter is on top of that big time, and so why blather about it here? Of course, tomorrow….”tomorrow is another day” to quote a quote. And after I see how this mostly clear sky sunset prediction turns out.

While waiting for rain, some useful information…

Let’s look at February’s climo for Catalina, now that the month is practically half over (hahahah, sort of):

2012-2013 updated water year rainfall — Oh, my, such a sad chart so far….

What the experts at NOAA's Climate Prediction Center are thinking--a smudge of higher precipitation for Arizona! — What the experts at NOAA’s Climate Prediction Center are thinking–a smudge of higher precipitation for Arizona, thought the chances, they feel, aren’t great, 30-40 % is all. Still, its something. This would be a pattern of precip that goes with our upcoming storm, one that will be much more of a dumpster in the northern half of the State than here. With the spaghetti plots having already indicated a high probability of a big trough in the SW US a week ago, this forecast may be based only on that one pretty sure thing which would give a monthly prediction of above normal in the Four Corners area and northern Arizona a leg up, so to speak. I mean, you wouldn’t want to forecast below normal precip in a region for a whole month if you knew there was going to be a flood in the first two days of that month! Hope this forecast is due to more than our Cold Slam, coming up!

BTW, yesterday I discovered at first sunlight that a trace of rain HAD fallen the previous night by finding raindrop images in the dust on my “trace detector” instrument (a car parked outside under the open sky). Hope you found drop images somewhere, too, and properly reported or at least, logged, your trace of rain.

Here’s a radar depiction of those areas of sprinkles from WSI Intellicast, amounts ending at 5 AM AST yesterday. If you are in one of the faintly blue areas shown below, and DID NOT report a trace, we will have to consider confiscating your Cloud Maven Junior tee….and you should consider whether being a CMJ is really for you. Its OK if its too much…

Here the rain forecast from the WRF-GFS model, our best, as rendered by IPS MeteoStar:

Valid for 11 AM February 10th. This is the first WRF-GFS run with rain here in it. Only the Canadian model had rain here before this one.

The End.

Cold slam3, the sequel; arrives in air around theatres February 9th

CS3 preview: its got rain in it, likely also our first real good windy day in awhile. In sum, a real action packed, thriller of a day coming. Don’t miss it!

1. We didn’t get the odd cloud bases yesterday. That lower undercutting layer of…..Altocumulus clouds (of course, you knew what they were) below the icy Altostratus clouds was too thin, not embedded in much wind shear, so the hoped for weird cloud bottoms didn’t materialize though there were hints of those concave bases off to the north late in the afternoon.

2. Since I was disappointed that really weird cloud bases didn’t show up yesterday afternoon, instead of showing the clouds that did show up right away, I thought I would annoy you first with a public service message:

“Arizona reminds drivers that when you see a sign informing you that you are on a DIRT road, that the speed limit is often no more than 15 mph.”

Yesterday’s clouds

Here are the clouds that did show up yesterday, pretty much as the U of AZ model predicted:

12:50 PM. Your mid-day Altostratus opacus virgae with virga. — 12:50 PM. Your heavy mid-day Altostratus opacus virgae with virga.

3:13 PM. Undercutting layer of Altocumulus overspread sky rapidly from the west. Starting looking for strange cloud bases here. — 3:13 PM. An undercutting layer of Altocumulus clouds overspread sky rapidly from the west. Starting looking for strange cloud bases here.

4:24 PM. Altocumulus undulatus. Actually there are two layers of Ac, and a full sky description would add the word "duplicatus", used when more than one layer is present, I am not kidding. — 4:24 PM. Altocumulus undulatus. Actually there are two layers of Ac, and a full sky description would add the word “duplicatus”, used when more than one layer is present. I am not kidding.

Ocean swells coming ashore near Monterrey, CA. — Ocean swells coming ashore near Monterrey, CA, in case you have never seen the ocean, breaking waves and swells. These are unusually large and were due to a giant low center off the Ca coast. Cirrostratus and Altostratus clouds, with flakes of Altocumulus droplet clouds, are present.

6:09 PM. With the Altostratus now gone, a hole in the clouds allowed this brief rosy "bloom" in the remaining Altocumulus clouds. The higher layer sported some virga, and some remnant virga can be seen in the center of the photo. — 6:09 PM. With the Altostratus now gone, a hole in the clouds allowed this brief rosy “bloom” in the remaining Altocumulus clouds. The higher layer sported some virga, and some remnant virga can be seen in the center of the photo.

Since there were sprinkles around Catalina last night, you’ll want to check your “trace detector”–a car parked outside overnight with a coating of dust on it–for drop images in that dust. I hope you didn’t forget to keep your car outside last night, as good CMJs do in possible sprinkle situations that you might otherwise miss. Happy to report a sprinkle here last night.

Today’s clouds?

Residual Cumulus and Altostratus, some Altocumulus (now that I can see them) patchy Cirrus, clearing out later in the day.

Cold slam3, the sequel

Sat 9 Feb 2013 00_054_G1_north@america@zoomout_I_4PAN_CLASSIC@012_132 — Valid for February 9th, 5 am AST. Precip is shown in the lower right panel by green coloration, and its over us, which you can see if you take out your microscope.

Saturday, February 9th. Precip looks substantial, likely MORE than half an inch here in Catalina should Canadian GEM model, shown below, verify.

Rather unsettling is that the USA! WRF-GFS, our best model, has virtually NO precip with this cold blast. When two numerical model outputs are so different the term thrown around is, “model divergence”. However, since “wetter is better”, a kind of non-viable theme here, I am now going on record as foretelling at LEAST 0.15 inches, top amount 0.60 inches, beginning on February 9th. This is the sports-like part of weather forecasting, riding the models, seeing how they change in the days ahead, and whether you get the amount you foresee, around a third of an inch median amount.

What is ASSURED for us here in Catalina is the cold blast, with or without liquid refreshments. Check this NOAA plot below out:

Valid for Saturday, February 9th. A cold spell is ASSURED! Check out that HUGE cold bowl over the Southwest US. No confusion here!

The End, unless I think of a correction or addendum, which seems to happen every day!

Arizona, center of northern hemisphere uncertainty; weird clouds today?

Here’s a nice little example of how the weather computing models start to go awry fast when a little flummoxed when little DELIBERATE errors are input into them as they start their northern hemisphere data crunch (below, from the global data ingested at 5 PM AST yesterday). Us folks here in Arizona and those in the Southwest US comprise one of two “centers” of the greatest uncertainty in all of the Northern Hemisphere, as shown below in the red and blue lines (selected height contours at 500 mb).

Model outputs and what they are predicting will go to HELL faster due to our “zone of uncertainty”. Chaos in action. Wiggle something here, and it falls apart over there and all over. This example is the contour forecasts for 5 PM tomorrow.

Valid for 5 PM AST Monday, February 4th.

Does this epicenter of uncertainty hereabouts mean we have a chance to get some real rain in the next 36 h?

No, but its great that you know about this uncertaity and how it plays out in the NOAA “ensembles of spaghetti”; useless-in-some-ways-knowledge, absorbed just for the sake of knowledge.

The uncertainty illustrated above is associated with a upper level wiggle in the winds and exactly how that will play out as that wiggle moves toward us from the NW today. Its a little baby trough in the upper air flow that the model is uncertain about but it is too weak to have much affect on the big cloud mass that will be drifting over us today, that cloud mass originally from a location about halfway between the Galapagos and Hawaiian Islands. These are real tropical clouds over us today, and they’ll be piled in layers (Altostratus, Altocumulus, Cirrus, Cirrostratus) over us to more than 350,000 feet!

Below, you can see the moist air piled to 350,000 feet as depicted here in the U of AZ model run from 11 PM AST last evening. But hardly a drop falls on us from all these clouds. (A deliberate numerical error of some magnitude has been put in here to see if you’re paying attention.)

Range of amounts here in Catalina: ZERO on the bottom to 0.10 inches, tops.

Below is an example (full set here) of what the Beowulf Cluster from the U of AZ sees in the moisture overhead at 3 PM local time (in other words, during the 84th hour of the Superbowl pre-game show). I realize that many of you will not be able to go outside and look at the sky at any time today due to this historical sports emergency, and so I will tell you something now about what you likely would have seen had you gone outside, perhaps even missing an equally historic commercial break of some kind:

Forecast sounding for 3 PM AST today, an hour before Superbowl kick-off.

What does this mean?

Weird clouds, most likely. Scoop clouds, concave (downward) looking cloud bottoms. Some areas of the sky might look like ocean waves upside down, “undulatus” clouds (we had a short-lived Ac undulatus yesterday to the NW of Catalina). Clouds with waves on the bottom. The bases of our tropical clouds are likely going to be in a “stable layer”, one where the temperature remains the same as you go up. It would be located just above the top of Ms. Mt. Lemon. Along with that stable layer, and is always a part of them, is wind shear; the wind turning in direction and speed as you go upward from just below this stable layer to above it.

Stable layers and wind shear produce waves, not ones always seen since the air is often too dry for clouds, but in this case, they should be visible. Could make for some interesting cloud shots this afternoon and evening. Here’s a risky example of what I think is likely, though with too much virga falling from above, they won’t happen, hence, the risk in a cloud detailed forecast:

An educated guess about how this afternoon's cloud bases will look. There's likely to be much more cloud cover, however, than is shown here. — An educated guess about how this afternoon’s cloud bases will look. There’s likely to be much more cloud cover, however, than is shown here.

Yesterday’s clouds

Lots of contrails overhead yesterday, an unusual number. Really, we are SO LUCKY not to have many days like this, kind of a sky pollution, though at present, an unavoidable one. Just be glad we don’t live right under a main, well-traveled airway (though, with predictions of a doubling of air traffic by 2020, we are likely doomed to more days like yesterday when Cirriform clouds are present).

2:16 PM. Signs of the modern world in the sky.

Sky on fire; chance of rain still ahead for southern Arizona (but not much)

Chance of early Feb rain still ahead, and I can prove it. This panel below is from last night’s 5 PM AST global data ingest into the WRF-GFS model, our best, as rendered here by IPS MeteoStar. As you can see, there are quite a few acres of rain showing up in southern Arizona on the 5th at 11 AM AST. I’ve added an arrow to help you find it.

What’s gone wrong with the possibilities of a good rain?

A low center is positioning itself off Baja as we speak, in almost exactly the same spot as the one that gave us our drenching rains of a couple of weeks ago. But, like a raggedy-looking hitchhiker that no one picks up, there’s no interaction with this developing low center down there by a trough zipping by in the westerlies to the north of it, one that dips down to the south just that bit and scoots our promising low and all its water to Arizona. Before that happens, that low wanders around and dies a quiet death down there.

When low centers are as far south as this one that is developing off Baja and over the warm waters out there, it’s cool center gradually warms up due to all the Cumulonimbus clouds it spawns, that warm air shooting up into its center and around it, and the circulation around it dies; it gradually just goes away. This is because there is no longer any temperature contrast between the center and regions outside of it, that which drives the circulation: no temperature contrast, no circulation.

Valid at 11 AM AST, February 3rd. This is looking very good indeed at this point. — Valid at 11 AM AST, February 3rd. This is looking very good, indeed, at this point.

You can see what happens to that low center in the panel above when no trough ejects it right away toward Arizona and it has to survive on its own in the next forecast map below.

Valid for 11 AST, Tuesday, February 5th. I thought I was going to cry when I saw what happened to our promising low and storm. That remnant passing south of Arizona means dense middle and high clouds with a lot of virga, sprinkles, and that’s what the models are seeing in that small area of rain in the first panel. Could be some great sunsets, like yesterday.

Yesterday’s cloud sequence, a classic one we see over and over again

First the thin Cirrus or Cirrostratus. Then, as though a real storm was coming, the sky lowers and thickens up in Altotratus. It non-desert locations, this sequence to Altostratus leads to rain about 70% of the time, that number from ancient cloud observation studies conducted before satellites and models. Finally, the back of the “storm”, well, at 25,000 feet you would’ve have thought is was a “storm” with all the snow that fell on you. Here is the start, middle and end, the latter of our fabulous sunset:

1:39 PM. Too thick, too much shading to be defined as Cirrus; its now Altostratus. CIrrus typically, from cloud radar studies, thickens downward to become Altostratus. — 1:39 PM. Too thick, too much shading to be defined as Cirrus; its now Altostratus. CIrrus typically, from vertically-pointed cloud radar studies, thickens downward to become Altostratus, with cloud tops staying at the same height.

6:01 PM. The backside, the last of the Altostratus clouds, allows the sun to illuminate their undersides, and the light snow that falls from these clouds, only to evaporate here in Arizona.

A look back at our end of January rainstorm

Radar-derived total precipitation for the week ending January 31st, 2013. The Tucson radar was down several times and so our local heavy rains are not shown. But look at what the mountains got SE of Flagstaff! So great in this droughtful winter. — Radar-derived total precipitation from WSI Intellicast for the week ending January 31st, 2013. The Tucson radar was down several times and so our local heavy rains are not shown. But look at what the mountains got SE of Flagstaff, 4-8 inches! So great in this droughtful winter.

The End.

Randoming around

A friend sent a link to this image of the day with a discussion from NASA. I thought it was a stunning statement. NK will likely not be a big player in anthropogenic climate perturbations¹.

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Computing stuff

In the most recent issue of Science mag (Jan 18th) that I received, I was alerted to a new fact:

the Japanese Fujitsu super computer “something or other” that I mentioned yesterday as the fastest, has been superseded in performance by the Oak RIdge National Laboratory’s Titan super computer at Oak Ridge, TN, USA! Oh, yeah, baby! Does 17.6 “petaflops” a second.

You can read about these developments here (or here: Exascale Science-2013-Service-264-6) as “exascale” computing is considered as the next major step in super computing, a step required for progress in several fields, including materials science.

Exascale supercomputers will run 57 times faster than the current best. Also, if such a computer that can do “exaflops”, was to be constructed using today’s technology, it would require FOUR HUNDRED FORTY-SIX MEGAWATTS of electricity to run it! That’s enough electricity to power half a million homes, this article pointed out!

But such a incredible super computer is needed for better weather and climate forecasting so I think we should go ahead and get one.

Cost?

Oh, maybe 100-200 million…IF they can make one.

But, “has the world has gone mad?”, you might ask.

Just think of how many hundreds and hundreds of these “ExecuTower” computers you could buy with that same 100-200 million, and all the computing they could do. They come with a 1-year warranty, too:

486 at 386 prices_001 — From Byte magazine, 1990.

Our clouds for awhile?

Cirrus, patchy enough for nice sunrises and sunsets.

Not mentioning model outputs….why dwell on dryness and negativity? Life is too short.

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¹Sans nuclear catastrophes.