An Explanation of This Heatwave

As you may well know, we have recently had intense heat around the region. This has been fostered by high temperatures, combined with high dewpoints. And it has been horrible walking outside into it.

It has mostly been like walking into a sauna, or walking outside into an atmosphere in which the air just sticks to your skin. It has been horrible, and borderline dangerous. But why has it been this hot? Well, there are a few reasons, and the main one being the establishment of this ridge that we have mentioned daily for the past several days.

This is essentially a large scale high pressure system in the mid levels of the atmosphere. Within this ridge, the atmosphere is essentially expanded because the 500 mb pressure level is measured by meteorologists in terms of geopotential meters above the surface. Because it is measured like this, we are given a much better representation of what happens when a ridge or trough moves through the atmosphere.

A ridge is essentially the expanding and warming of the atmosphere underneath it, and is associated with subsidence. A trough is the “shrinking” of the atmosphere, and is associated with atmospheric ascent. In particular to what I am discussing today, the subsidence associated with the ridge leads to a surface high pressure system. This is forced by converging air in the mid levels, that then sinks and forces surface divergence.

As air sinks at the mid levels, it diverges at the surface, and forces the surface high. The sinking of air also allows heats the surface up, and leads to temperatures being as high as they are. It doesn’t help that the atmosphere is as filled with moisture as it is, because this just increases the heat index!

There you have it! Our heat wave will hopefully not last much longer, as the models have tended to paint the picture of the ridge shrinking and establishing out west.