Nice day, OK clouds

Here they are, left column:

7:09 AM. Altocumulus, trending toward perlucidus. Height? Aout 13,000 feet above the ground, from reading the TUS sounding. Temperature? -10 C (14 F). No ice trails visible.
12:13 PM. Nice, high-based small Cumulus (or Altocumulus castellanus) with snow virga moved over the SE part of the sky in the early afternoon. Bases were around 11, 000 feet above the ground at -5 C (23 F). Sprinkles (very light rain showers-its not drizzle) reached the ground in a few isolated areas.
2:02 PM. A somewhat rare example of Cirrocumulus and Altocumulus probably at the same level in proximation with one another. Cirrocumulus (Cc) is defined by a very fine granulation and no shading. The fine granulation gives the impression here that its much higher than it really is. Altocumulus clouds are defined as having much larger elements, shading allowed. Well, even if the Cc was at a slightly higher level, this is a good example of the difference between the two.  Tell your friends.
5:10 PM. Mind drifted toward road runners for some reason…. This is Cirrus uncinus with long trails of ice crystals streaming back from the little cloudlet that originally formed, like an hour or two prior to the photo. The trails survive because its a bit moist up there below where the cloudlet formed.

The weather ahead

A huge buckle in the jet stream is forecast to form right off the West Coast in about a week, and its a pretty spectacular interruption in the pattern of a jet stream whizzing by far to the north of us that we have had now for sometime. Below is an example of ‘now” in the jet stream winds, and below that, a forecast panel (from IPS Meteostar) showing this striking change a week from now.  There’s a big (“high amplitude”) trough in the eastern Pacific, a high amplitude ridge (hump in the jet stream toward the Pole) in the West and another big trough in the East.

Patterns like this are usually associated with extremes in temperatures;  warmth in the West; cold in the East. It is certain when this pattern materializes in about a week, some high temperature records will fall somewhere in the West and some low temperature records will fall in the East.  In the West,  warm air is drawn far northward, aided by low pressure centers spinning around in the eastern Pacific, while in the East, cold air zooms down with high pressure centers from northern Canada.

Why bother talking about a forecast a week in advance?

Because it has a lot of “credibility” in our ensemble (spaghetti) plots.  Here is last night’s “ensembles of spaghetti” plot produced by NOAA for one week in advance.  Look below at these “ensemble members” the different blue lines, ones that are loaded with slight errors at the beginning of the model run, to see how strong the forecast a week ahead is.

Those bunched blue lines in the eastern Pacific (see arrow) inspired this whole spiel about the coming change because its a nice example of when the plots show something reliable in the way of a longer term forecast, and in this case, a forecast that also shows a big change in the weather patterns over thousands and thousands of miles, from eastern Pacific to the western Atlantic.

If you’re looking around this whole plot, you’ll see the lines are also very bunched in the extreme western Pacific and westward across Asia.  Those blue lines are always bunched over there because there is little variance in the flow in that region; its locked into a pattern by the geography, unlike in the central and eastern Pacific and into the US where the jet stream is MUCH more variable.  A simile:  imagine a fire hose turned on at the hydrant, the part of the hose at the hydrant stays in place while the end of the hose flops wildly around. Its something like that; western Pacific to eastern Pacific.

Our weather?

Well, after all that gibberish, not much change will occur here; its everywhere but here! Seems we’re doomed to another dry seven to 10 days ahead with occasional periods of high clouds and great sunsets as weak disturbances from the sub-tropics pass by, ones that can only produce Cirrus clouds.