There is an interesting development in the Antarctic region today that I think should be recorded. It involves a concentrated stream of precipitable water (PW) that looks and behaves exactly like those we see entering the high-altitude wind system, except that it turns out to be not one of them. Here is a picture of the stream, specifically the one that emerges from northeastern Australia in the form of a spike. You can follow its path around New Zealand and over the sea ice, finally ending before it reaches the Antarctic continent, while constantly decaying as it proceeds:
This stream could not possibly have its existence within the upper level wind system because its poleward movement would then be blocked by a strong jetstream wind instead of passing under it. The jet wind is plainly visible in this image:
What got me interested in the first place is that I happened to notice a peculiar break in the sea level air pressure map, something I have been paying more attention to lately, and wondered whether it had any special effects. Well yes, the PW stream appears to be using the gap as a clear and well-defined passageway—probably available within a higher part of the low-level wind system.
This meant opening the low-level Wind Speed map (also not a regular habit) and sure enough, there is a pretty good breeze that can be tracked without interruption along the very same course where we see the PW stream. Here and there the wind gains speed, before finally coming to an abrupt end over an area of sea ice, where it curls around and veers off mainly toward the east:
What is the altitude of this wind? I can’t say for sure, but it has to be high enough to enable a constant outpouring of first rain and then snow over its entire course, as you can see on this next map. The map also provides a clear indication of exactly where it comes to a halt, well short of the continent:
This stream obviously carries a heavy load of PW at all times, as we saw on the first map and again on the most recent one. Everything about it, except for altitude, matches up in many ways with the PW streams we analyze more often as they move through the upper wind system. With nothing in the way to block this one’s movement, I think it could possibly have merged into a low-lying jet wind shortly before coming to such an abrupt halt. That’s only a guess. We don’t need to guess about whether so much concentrated PW had an effect of surface temperatures as it passed overhead—we’ll just see what the anomaly map has to say:
There is evidence of warming over the entire course, except for the stretch that showed heavy snowfall over open water. Of further interest, the strongest anomaly we see, a bit more than +6C in a spot over the ice, is not far from a cold spot that reads minus-18 or less, also over ice and at the same latitude. The first has a PW value of not less than 8kg, the latter no more than 2kg—a difference of better than twice doubled, well in line with the Carl’s theory rule of 10C per double. Temperatures over Antarctica’s sea ice remain generally much colder than they were on average for this time of year thirty years ago, which accounts for today’s average reading of only -3.5C for Antarctica as a whole. That by itself is enough to penalize the full SH number, and even has a possibly significant effect on the average for the globe as a whole!
Carl