Every month we need to take a fresh look at upper-level air pressure configurations in each hemisphere in order to make ongoing comparisons as the seasons change. We’ll start with the southern view, which is slightly disheveled because of the summer warmup, but I see nothing remarkable here to report:
In the north the one thing that stands out is how well the blue zone has become reestablished with a neat compact shape and some deep blue coloring. Remember how last summer at times we could see only a few small bits of faded blue, and no blue-zone jetstream capability of any kind worth mentioning? Today the light blue border is intact and can maintain a steady pathway over a complete circle. Wind speeds on that pathway are basically fairly mild, but that quickly changes whenever the path attains close proximity with a healthy pathway on the outer fringe of the green zone, allowing mutual acceleration via the combination. On this image we can see that the green zone border is indeed healthy in places, and snuggled tightly up against the blue zone, but at least half of the border is terribly frazzled and misshapen, which will surely leave its normal jetstream pathway in a similar condition and poorly situated in those places:
So let’s see how this all turned out for jetstream development in the north. The first thing to notice is in the far upper left of the image, where you see a long leg of high-speed jet wind. It corresponds perfectly with the blue and green pathways proximity we can see in the above image. Then everything changes, starting with the sharp northward bend in the middle of the Pacific. The two pathways remain almost as tight but the bend forces an abrupt deceleration, followed by only a partial recovery during the upswing. After that comes the massive deformation of the green zone fringe and its jet wind pathway and nothing but confusion for blue/green pathway pairing. Another moderately strong jet wind that we see starting in south Texas and heading north is the result of a pairing of a healthy red-zone pathway and the weak green fringe. It has served to carry a huge load of fresh vapor from the Gulf and Caribbean Sea northward, mostly raining or snowing out along the way, until finally it’s all interrupted by a breakdown of the pathway connection next to northern Greenland.
We should take a quick look at the sheer amount of precipitation involved in this jet over a distance of nearly 4000 miles. There may still have been some vapor left over and able to spread greenhouse effects into the polar zone, but probably not very much. Also note the similar but shorter occurrence of heavy rainfall in the Pacific after the jet wind first mentioned had turned northward:
I need to show one more map because of the unusual warm temperature anomaly it reveals. This anomaly is the one that is heaviest in the center of Canada, coming to a point further south in the center of the US. The high-level water vapor that produced the anomaly can be traced back to the central Pacific, transported all the way by the same jetstream wind we opened with. After this jet turned south again near Alaska it abruptly stopped and split apart, as shown above, and I think it must have dumped a lot of remaining vapor into the interior of the diluted part of the green zone. From there the vapor appears to have moved southward as a broad “warm front,” carried by light winds. So much greenhouse energy moving straight down from north to south over such a long distance is not too common.
Carl