The breakdown in the stratospheric polar vortex is still hanging around, wreaking havoc on the normal structure of the separate but related air pressure configuration in the upper level of the troposphere. This map shows how concentrations that constitute the deep blue zone, representing the lowest levels of 500hPa pressure readings, are now divided into nine distinct sections of roughly comparable size, plus one smaller section. Normally there would only be only one, much larger and more compact blue zone at this time of year. The green zone, representing a higher step in the 500hPa level, that would normally show up only as a narrow fringe surrounding the single compact blue zone, now enjoys a great deal of extra room in which to spread out and show more of itself.
Knowing how jetstream pathways are all established by the contours of the zones in the configuration as they exist at any one time, this gives us a rare opportunity to study what happens to these pathways, and to the jet winds that occupy them, when everything is scrambled in this way. The winds themselves get weakened in many places and often just disappear from the map. When that happens the map still shows us the locations of the isobars that mark out the locations of the pathways. Here they show up as an array of tight circular patterns, one for each of the nine small-sized deep blue zones. There are also several looping isobar patterns matching the interior sections of expansion in the green zone territory. All of these distinct isobar figures could potentially bear stronger winds if they were more conventional in size and placement. A few of them at least manage to earn a weak color display.
With this setup in place we are ready to investigate how high-altitude streams of precipitable water (PW) are being affected. We already know that the overall organization of jetstream wind activity has a powerful influence over the movement and eventual dissolution of the concentrated content of these streams. The influence has plenty of complexity, but there are well-defined patterns of regular behavior that can be picked out by those who are willing to regularly spend some time studying match-ups on the maps. Today’s jetstream wind pattern is holding the movement of PW to an absolute minimum over much of the lower portions of the North American continent, and at the same time is allowing more than normal quantities to advance and spread out over areas farther north, including the Arctic Ocean itself. Studying the large vapor streams emerging from the Caribbean Sea and moving up the Atlantic is one good way to check out the current jetstream influence.
As usual, my interest in PW is focused on its role as the preeminent provider of greenhouse energy effects rather than on its more common focus as sole provider of precipitation. Readers who are familiar with the way PW departures from normal are associated with temperature anomalies at any given location on any given day will see many examples today simply because there are so many extremes on exhibit in the Northern Hemisphere. No other cause of daily anomalies can compete with PW when the outcomes are this extreme. Note the outstanding
cold anomaly today covering nearly a third of the state of Montana, where the reading that is displayed falls within a range of -24 to -28C, equal to at least -43F. Total PW is hovering around the 1kg level. While we have no data for what the average PW value would be for this area on this day, there are nearby areas having small warm anomalies accompanied by PW values of around 7kg, creating a fully consistent relationship between the two locations (based on the rule of +10C per each double of kg value).
Carl