Into the cold

Today, as everyone knows, will be the last pleasant day for quite awhile, so we’d better get out and enjoy it if you can, maybe call in sick.  Likely to be a couple of AZ low temperature records set over the next week.

The skies will be great today, as they always are with some clouds present, and for a few days afterwards in the cold air with those deep blue skies along with passing Cumulus clouds, that at times and even though they are shallow, will send some virga down as the colder parts of the troughs go by.   Should provide for some nice late afternoon and evening photo ops in the days ahead.

Today the satelllite imagery plus looking out the window, shows lots of Cirrus clouds today, probably devolving into dense, shady Altostratus at times.  And a scenic,  Altocumulus lenticularis cloud1 downstream from the Cat Mountains is pretty much a lock.

Also, in the progression of clouds today, we will probably see that clear slot that so often separates the middle and high clouds from the low, frontal clouds go by.  If the timing of that clear slot is right, could be an extra special sunset.

Some Cirrus from yesterday, another one of those rarer days with virtually no contrails in the Cirrus, followed by a nice Catalina sunset:

2:36 PM.  Cirrus fibratus (pretty straight fibers) looking NW.  Note lack of contrails.
2:36 PM. Cirrus fibratus (pretty straight fibers) looking NW. Note lack of contrails.
5:45 PM.  Cirrostratus with embedded Cirrus of some kind (upper right).
5:45 PM. Cirrostratus fibratus (has streaks) with what looks to be  a lower Cirrus uncinus (upper right and in the distance).

Rain, from the U of AZ mod run at 11 PM AST,  has the rain beginning tonight after 10 PM AST and lasting but a couple of hours.   Amounts here in Catalina, between 0.10 and about 0.40 inches, average of 0.25 inches, virtually no change from what was predicted 24 h ago.

Just about everything mentioned yesterday is the same today in the model, marginal cloud top temperatures for precip at the TUS site for most of the time the front goes by (in the model), but  cloud tops will be colder over us and more likely to precip.

Seems temperatures will  be marginal for ice-in-rain drops at the ground here since the much colder air will not arrive with the front’s very narrow rain band but encroach as it departs.

Also of some interest, the jet core at 500 mb is shown to become bifurcated with one branch overhead S as the rain moves in (another branch over NW AZ).  This would be compatible with a rule of thumb about the rain and the jet at 500 mb.  Rain, with extremely rare exceptions (<5% of the time), does not fall here on the southeast side of a jet stream racing to towards the NE, as we will have over us today.  Will be curious to see if this “rule” holds up this time.

Tomorrow will be one of those cold days with spectacular small Cumulus clouds contrasted against the deep, dark blue of the winter sky.  Should be some great scenes of light and shadows on the Catalina Mountains.

Snow ahead?

Snow falls here later in this cold, almost week-long episode, as a series of troughs plunge southward along the West Coast to AZ.  Most likely day for some snowfall in Catalina, is now on the 14th2.  Here’s the map for that, valid for 11 AM AST, Monday, from IPS MeteoStar:

Monday the 14th 2013011000_CON_GFS_SFC_SLP_THK_PRECIP_WINDS_114
Green areas denote those regions where the model has foreseen precip in the previous 6 h.

 

The weather way ahead–Dr. Jeckyl or Mr. Hyde?

Check out these bowl of rubber bands from “flapping butterfly wings” (slight perturbations put into the initial data ingested into  the WRF-GFS model after which its re-run a number of times to see what slight differences do). The first one below is for the evening of January 20th, a real laugher considering its only 10-11 days away now and the mods are still clueless.

Note the yellow lines, a “control” run from last night’s 5 PM global data, and see how they BULGE toward the north over the western half of the US.  Then look at the hard-to-see gray lines representing a “control” run from just 12 h earlier, that from yesterday’s 5 AM AST global data.  They BULGE southward, the opposite way the yellow lines do.

The yellow lines indicate a huge ridge over the West, with little precip and seasonal temperatures in the SW US.  On the other hand, the 5 AM control run shows a continuation of our present storm pattern and continued injections of cold air down the West Coast.  Check out that gray line over northern Cal, for example.

So, from one model run to the next lately, our weather toward the end of the month in Catalina has gone from “yawn” to “yikes” (the latter  blurted out yesterday when I saw that 5 AM output and all the storms it had).  But blurted out a “yawn” when viewing the output from last evening.  No precip after the cold week.

However, in deciding which of those two outcomes is most likely you have to dwell on the predominance of those blue lines that also bulge northward and are mainly located in southern Canada.  Those strongly indicate that the “highs” , the  bulges to the north over the western US, will prevail on the 20th, not the storms and cold weather with them.

annotated Evening of Jan 20th spag_f264_nhbg
Arrow points in the general direction of Arizona.

But how about after the 20th, at the very end of last night’s model run 15 days out?  Now you see BOTH the yellow and the gray lines are bulging to the south (creating a trough bowl), AND, more importantly, those blue lines are not constrained to southern Canada, but are all over the West as well.  Remembering that the atmosphere remembers suggests that the models are remembering, too, trying to regenerate the kind of flow pattern we’ve already been experiencing after a significant, quite pleasant, really, break from the cold week.

tated_spag_f360_nhbg

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

While this last panel  is also a real laugher in many ways, due to all that uncertainty that’s indicated, the wildness in all those lines, you might want to hop off the fence in a longer term forecast toward the end of the month by thinking that what we’ve been having will return, a sort of “Back to the Future.”

Re-inforcing this view is how the red lines (570 dm height contours), usually on the periphery of the jet stream, become more compacted in the LATER, second plot compared with the first!  This is a little remarkable since that would suggest the models have a better handle on the circulation pattern at 15 days over 11 days.  Odd.  Note, too, that those lines at 15 days are FAR to the south of AZ, supporting the idea of a cold trough in the SW.

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1These are the almond shaped clouds composed of droplets with smooth, sharp edges that hover over the same spot, expanding and shrinking, sometimes for hours at a time, as the grade of moisture changes in the air being lifted behind the mountains.

2Personal aside:  Have friend, former WA State Climatologist who also worked at the U of WA as I did, arriving here with his wife on the 12th for a vacation from the dark days of wintertime Seattle.  They will be here for the whole cold week and possible snow as it turns out, and then go back.  Having looked at the progs,  he now wants to take a “vacation from his vacation”, maybe head off to Costa Rica after arriving in AZ!