This is a perfect day to do a jetstream exercise, especially for those who have not done this before, and also because it includes a new discovery. The main purpose is to provide a graphic demonstration of the location of various jetstream pathways with reference to air pressure configuration in the upper part of the troposphere. You will need to open up the Climate Reanalyzer website, https://climatereanalyzer.org/wx/DailySummary/#gph500, containing Today’s Weather Maps, where you will get this image when you scroll down:
Then go back to the top part and click on the Jetstream Wind Speed link to get this next image. Set the magnification so you can easily toggle back and forth between the two links and still see the full chart at the bottom with no more scrolling needed. You could be toggling fifty times or more when you see how well this works!
From here on it is simply a matter of visually locating each of the intermittent, intensified bursts of jetstream wind on one of the pathways I will next define. (There are a few exceptions, to be described later.) There are three of these streams in each hemisphere that normally stand out, but one of them is virtually out of business in the NH, mainly due to seasonal weakness, so we will just focus on the south. The south, moreover, has many more of those strong “jets” to look at and some additional and interesting structural variation as well.
The three main pathways, when healthy, will all form complete circles which are fairly regular and concentric to either pole. Their locations can all be identified in an unexpected way by viewing the air pressure map, where they exist unmarked except for the fact that their courses are perfectly described by the different color shadings on the map. I am not sure whether the creators of the map had this in mind, but that is how it all turned out, and there are logical reasons to be noted behind the coincidence. The color shades all represent ordinary breaks in the pattern of air pressure configuration, where certain pressures are found to have an unusual degree of vertical separation compared to these nearby. This creates the a condition that favors speedier wind development along the break, not unlike the workings of the wind and air-pressure system at the surface, where the total configuration otherwise has many notable differences.
The innermost major pathway formed by such a break tracks along the thin light blue line surrounding the large area of deep blue shading—this being the basic zone and pathway now temporarily missing in the north. Where you see pronounced bends in the pathway there is always a weakening of wind speed, and the light blue line tends to back this up with a bleeding of its color at the point of the bend. The middle jetstream pathway is similarly marked off, this time by a thin yellowish line that creates a fringe on the edge of the dark green zone. It too can be seen to weaken and bleed wherever the pathway makes a bend.
The outer pathway is basically located along a track that is formed where you see the sharpest distinctions between darker and lighter shadings within the red zone and not far from its outer edge. It is also a bleeder, sometimes in ways that may make it seem a little erratic. The discovery I mentioned above suggests that the full red zone may even be hiding the makings of a fourth pathway, a piece of which seems quite visible on this map. It is located in an area of intermediate shading inside the red zone which has become stretched out in width. A lengthy burst of wind speed can be seen to have formed in this area, moving across the center of South America and to either side, appearing for over some distance as literally the marking of a fourth concentric pathway. This is the same object that led to some confusion in a vapor stream analysis made here last week.
One more point to emphasize is that whenever any two of the pathways move into positions that are relatively close together there is almost always a mutual acceleration of their wind speeds and often a rather wide and complete combination of the streams. With a little practice these can be predicted just by looking at the air pressure map and nothing else. Today’s maps are good ones to practice on for all purposes because there are so many curves and twists to be followed. They offer plenty of evidence of regularity with respect to how the system is governed. You might also give the NH a try, which works just as well when you can pick out the faint markings of the wind jets. For me it helps to view these jets on the screen by looking downward at it from quite an angle above, making it quite a bit lighter. Isobar lines are also best brought to life in the same way.
Carl