Back to North America, where the green zone in the configuration is putting on quite a show for us. The first thing you will see is an island of complete separation from the main body:
The island is there because surface air in that spot is in the 10C area, surrounded by air that is at least a little bit warmer. This degree of cold temperature is all it takes to set up the air pressure differential condition that will cause the creation of a regular pathway for high-velocity wind flow. As we see here, it can be set up in total isolation, with no need for freezing temperatures or blue zone in the core. Even the weakest spots of green we see here have a bit of extra wind velocity:
Now for a bigger attraction, which is the regular wind we see circling on a pathway around the main body of the green zone. It provides a stunning example of how the variations of placement, depending on fixed direction of motion and exact geographical positioning, may or may not result in a significant transport of precipitable water (PW) being carried along by the body of wind. In today’s situation when the pathway is angling down across North America, heading toward the south, it is practically empty of PW. The path then makes a full turnaround in the Gulf Coast area and heads almost straight north, taking it all the way to Greenland and beyond. The place where it turns around happens to be a perfect location for collecting vast amounts of PW, in the form of steady streams being freshly evaporated from the Caribbean Sea and other nearby sources, clearly visible on this image:
This interaction is also notable for the immense amount of precipitation it produces, snow as well as rain, all along the Atlantic seaboard, continuing to fall over Baffin Bay and parts of Greenland. Along with the precipitation there are lots of clouds, plus plenty of uncondensed water vapor that is needed for constantly producing an abundance of precipitation over the entire distance. These are the principal components making up the unified airborne complex we define as “precipitable water,” seen here in one of its most extreme distribution-weighted formats.
There is more to the story of the material we call PW. It has a habit of producing powerful greenhouse energy effects wherever it goes. We always see this effect, consistently produced, whether or not any kind or any amount of precipitation is being generated by the same material at the same time. In this event it produces warm anomalies over open ocean water and warmer yet , by as much as 12-14C (call it 23F), in some of the air above Greenland and Baffin Bay, even where snows are falling. That seems like a lot of energy, being generated only by whatever remains of a PW stream that has lost so much substance over such a long distance. Solar energy could not have been a factor except for losses due to albedo reflection that need to be netted out.
