This is a good day for jetstream study in the Western Hemisphere, while again making close reference to images on several other weather maps. We’ll start with a map of the jets, followed by the 500hPa configuration. (If you can do this on the live website it is easier to see how they overlap.) The lineup of the perimeter jets with the mid-red-zone isobar tracks is about perfect, and kind of awesome when you recall that there is a 3-mile altitude difference between the two maps. That means the air pressure configuration must remain pretty much unchanged all the way up. So—would the jetstream winds also be present and have similarly structured powers all the way down? Why not? I don’t have the answer, but the thought does come to mind that the three principal jetstreams, including their least speedy sections, might possibly, and as a regular matter, be filling in vertical passageways that stand in a pose resembling the Great Wall of China, except in this case over three miles high, floating off the ground at the bottom and constantly sliding around. Just a thought.
The middle jetstream pathway, bordering the green zone, shows clear signs of weakness and fragmentation, just like the green zone itself is exhibiting. Don’t miss the little island of green zone off the coast of France that has managed to whip up an active jet of its own. Of some concern, is the main green zone on its way to shriveling down and taking nearly its whole stream down with it, the same thing the blue zone has already done? There are definitely more islands in the making and ready to split off even now. There is one more thing to mention, just as a curiosity, about the red zone jet where it makes a sharp bend just to the north of Idaho. It looks on the map like the jet temporarily splits into two channels as it swings around the bend, resembling what some rivers do on flat lands.
As always, we want to see how the placement of fast-moving jets affects the customary movement of whatever amount of precipitable water has risen to the same altitude. A fairly large percentage of the planet’s total evaporation rises in coherent streams from warm tropical ocean surfaces to a level high enough to be affected this way. The jet winds tend to steer the courses of these streams and thus have quite a bit to say about where they will precipitate, as most of their water content will do before long. This gets plenty of attention from the weather people. The ability of the same precipitable water streams to affect air temperatures at the surface below as a direct result of its greenhouse warming powers is something that gets much less attention, if any. Instead, jetstreams by themselves get much of the credit (or blame) for causing temperatures to change, by moving air masses around. When you look at the next two maps, especially in a broadly-based perspective but also in many of the details, you can see that the placement of every jet has an effect on both the distribution of precipitable water and on temperature anomalies, and that the two are associated, although not always exactly so at first glance. The regular association is a simple reality, true enough to justify more specific investigation from a point of view that shines a clear light on the exclusive power of water vapor.
The reduced amount of precipitable water that reaches the jetstream level but does not precipitate for an extended period of time is of special interest. For one thing it keeps trying to navigate in the general direction of the nearest pole, where airborne water of any kind is always a scarce commodity. For another, water vapor has unsurpassed power as a greenhouse gas, and that power is magnified when significant amounts are injected into any atmosphere that is normally on the dry side. Again, as I see it, under ideal conditions, which are not uncommon, any doubling of existing total overhead vapor content will quickly bring on a temperature increase of 10C for as long as such a situation lasts. Or 20C for a redoubling, which is not at all unusual in the higher latitudes.
Carl