There are many stories in the news about a major heatwave settling in across southwestern parts of the US, where temperatures are soaring to new records in some places. Much less is being said about a much larger and stronger heatwave that is more fully established in eastern Canada and all of Baffin Bay, extending well into the Arctic Circle in the north. The temperatures are not as high as the US wave in absolute terms but the deviation from normal, around 10C in places, is truly in a higher class. Anomaly size is of course what counts most when assessing the overall progress of the global warming trend. Here is a map comparing these two:
As you may have guessed, I am interested in finding the sources of heat causing both of these regions to be so warm, which means going straight to the Precipitable Water map, so let’s have a look:
I can see three different sources of high-altitude water vapor that have combined to feed the Canadian anomaly. They are supplying enough to bring the total vapor supply up to 30kg in the center, as much as 25kg in the more northern part, and a solid 20kg where the stream is seen rolling around and heading south as it proceeds on a downward course through Baffin Bay. Those are adequately large numbers from the standpoint of generating sizeable temperature anomalies in the Arctic part of the world. As for the southwestern US, where the main vapor stream is entering from high over the Pacific, 20-30kg is meaningful but not nearly strong enough to produce anomalies like those observed in Canadian north country.
With respect to the way the Canadian vapor stream in the above image has made a sharp bend at the top and turned south, we need to look for the cause behind such a strange movement. High-altitude air pressure is probably involved along with the jetstream winds that are under its control, so those are the next two maps we need to pull. The tightly-looping shape of the green zone is exactly what we could have expected, because its border would perfectly serve as the home of jet winds strong enough to hold back further progress of the incoming vapor stream. In this case the winds have actually picked up the stream and carried it intact over a considerable distance as they both proceeded along a regular counter-clockwise moving pathway. The vapor stream was at no time able to find an opening that would take it deeper into the green zone territory.
In this final map we can see how jet winds are indeed active around that loop. Maybe not so much on the west side, but jets are very active at the top and then along the edge of Greenland heading south. Also, don’t miss that nice little circle of jet wind sitting in the middle of the Arctic Ocean. Do you suppose it may be connected in some way to the air pressure pattern in that area? While you are at it, see if you can find any more corresponding matches between visible jet winds and the curving borders of the green and/or darkish red air pressure zones wherever they may be situated on the maps.
Carl