An interesting warm anomaly of considerable size has emerged in eastern Asia, depicted below. It may have the potential to develop into a major heatwave so we will need to keep a close eye on it. The anomaly stretches from Turkey all the way to the shores of the Arctic Ocean in one large block. More than half of its area is unclouded, mostly the part showing maximum temperature strength.
Warm anomalies of this size are normally generated by a major influx of high-altitude precipitable water carried within a stream, so that is the first thing we look for. No problem, as we see next, except there is one curiosity. Most of these big streams arise from warm tropical ocean waters, but not this one. By all appearances, from looking at this map, the main source of these vapors is nothing other than the Mediterranean Sea, with a possible boost from the Black Sea and even the Caspian:
Next question, is the Mediterranean, without major assistance, actually big enough and warm enough to produce the amount of vapor we see moving in the stream? The standard I always look for is a minimum surface temperature of around 25C for generating such a high volume of vapor and also the heat energy needed to loft the vapor stream more than three miles high in the atmosphere. That qualification has been met, although not by much of a margin, with both the Black and Caspian Seas being similar. The warmer waters farther south could also be weakly connected to the stream and some vapor coming from a stream off the Atlantic may also be contributing.
If this anomaly is going to turn into a classic heatwave it will have to pass two more tests. The first will be to keep the existing vapor stream flowing for many more days without significant depletion of the current sources of energy. That could be a challenge because so many of them look marginal. The other test is met when the anomaly throws off enough warm air to have a pronounced effect on the configuration of high-altitude air pressure directly above. Just holding the pattern in place will keep its associated jetstream winds from moving into new positions that could block the course of the main water vapor stream. The current setup suggests that the vapor stream is in control with expanding influence and should have staying power, creating the potential for development of positive feedback effects that could lead to a durable and still greater temperature anomaly. We’ll soon see.
This is from a recent study: “Heatwave trends accelerate worldwide” (ARC Centre of Excellence for Climate Extremes). “The first comprehensive worldwide assessment of heatwaves down to regional levels has revealed that in nearly every part of the world heatwaves have been increasing in frequency and duration since the 1950s…..Climate scientists have long forecast that a clear sign of global warming would be seen with a change in heatwaves…..The dramatic region-by-region change in heatwaves we have witnessed over the past 70 years and the rapid increase in the number of these events, are unequivocal indicators that global warming is now with us and accelerating.” https://phys.org/news/2020-07-heatwave-trends-worldwide.html
Carl