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.
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.
12:45 PM. Small Cumulus clouds (humilis) dot sky.
DSC_0379
4:26 PM. Stratocumulus clouds cluster around the Catalinas.
DSC_0386
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.
DSC_0387
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.
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

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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.

2 thoughts on “Storm today, Christmas Eve 2016!”

  1. Art: First of all a Merry Christmas and Happy New Year to you! Second, you really got my attention with that long range forecast. You mentioned January 1969, and that alone gets me excited as that was one cold and snowy month. (at age 10 I was old enough to recall it now instantly) I don’t know if we’ll get something quite that dramatic, but we are overdue for a cold and snowy January to some degree. (It’s often the dullest month of the year ). Looking forward to what will develop!

    1. Hi, Roland,
      I return the good Christmas and New Year’s wished to you, too!
      Seattle-ites still talk about the great snows of January 1969, not that there was any one big one, but that it just kept snowing off and on and wouldn’t warm up. The 21 inches of snowfall that SEA-TAC recorded still stands as the snowiest month since records began there in the late 1940s.

      I sure hope that “cold in the NW; wet in the SW” pattern verifies. We’d both have something to remember about the winter of 16-17!

      a

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