Gone but still there

As expected, the odd pattern of just 24 h ago disappeared on the later model runs.

Is it really gone?

Nope.  Might pop back up on a subsequent run.

While our usual June inferno continues for a few more days (here’s the NWS forecast for Catalina), a cool trough of air is destined to come here 6 days from now and linger for a few.  Here’s the totality of evidence for that assertion, this plot valid 8 days from now, Friday afternoon, June 17th.  In case you have forgotten where Arizona is, I have repeated the map below this one with an arrow to help you out.

What do you see in the western US?

A lot of blue lines!  Ones that outline where a cool-cold trough of upper air will be.  Notice where the red lines are, those ones that outline where the southern periphery of the jet stream will be located, those being the outer boundary of the cool air trough.   They’re ALL WAY down in Baja, California!  This VIRTUALLY guarantees an a trough of cool-cold air along the West Coast in 8-10 days!  Along with that, the possibility that tropical air will move up from the south and get into Arizona.

Yesterday, the model believed a hurricane would form and move northward, its remnant dribbling into Cal and AZ.  The model (at 00 Z last night) saw tropical storms forming, but they remain far to the south of even Baja!

Well, that prediction I showed yesterday was SO STRANGE it certainly wasn’t going to happen nine days out into the future.  It was an outlier.

But, what is guaranteed from an inspection of the maps above, is a trough along the West Coast, and with that, comes the possibility of a rain here, not from the cool air part of the trough, that won’t happen, but rather from tropical air being whooshed up around the outer, warm boundary of the jet, marked by those red lines.  Right now, if you’re in the mountains of New Mexico, eastern plains of NM, and west Texas, you are just about guaranteed to get that tropical air and with it, showers and thunderstorms.

A climate note:  it has not rained in Catalina between June 9th and 19th here in Catalina for 35 years; NO measurable rain on those  days yet.  I’ve reprised the June daily rain frequency for our 35 years here:

What should you take from that?

There are likely climatological factors, one’s having to do with the march of the seasons, that work against even the presence of clouds!  Chances are it is what we would call in climate, a “singularity”, something akin to the January thaw in the northeast US.   Here its a June transition season from the time a cold trough can bring us a bit of rain, and the onset of the tropical air regime with its Cumulus and showers, jet streams not involved then.  (I’ve assumed that 35 years is enough to suggest a real feature, not a statistical fluke.)

So, with this big trough foretold to occur during our normal dry spell-transition period, you’d have to go against the chances of precip in a knee-jerk fashion.  We’d most likely end up BETWEEN where there are showers in cold Pacific air inside the trough, and dry regime outward from that zone, to a plume of tropical air just to the east of us over NM and TX.  Doesn’t mean rain can’t happen, but don’t bet on rain during this period through June 19th.

As a final comment, note the dark area in the central Pacific on these maps. That dark area repersents and extrusion of cold air well toward the tropics out there, also an unsual occurrence, and it is vital for us.  Note that even the blue lines, noting the core of the jet, has extruded southward out there.  That extrusion (my favorite word I think), in essence, creates a “bounce” in the latitude of the jet downstream, a southward extrusion along the West Coast.  The dark hole out there indicates that even 8-10 days out, the computer predictions are extremely confident that there will be that extrusion of cold air toward the equator out there, and that, in turn, strengthens the likelyhood of a  unusually strong  “bounce” trough along the West Coast 8-10 days out.

It will be fun watching this develop, since we’ll like get a much cooler day or two about that time.   But, it would be even better if the hurricane shows up again, and is steered thisaway as it was yesterday!

OK, enough, gotta go ride a horse

By Art Rangno

Retiree from a group specializing in airborne measurements of clouds and aerosols at the University of Washington (Cloud and Aerosol Research Group). The projects in which I participated were in many countries; from the Arctic to Brazil, from the Marshall Islands to South Africa.