A heat dome is a high-pressure system that, because physics, traps heat and keeps it there. That pressure system’s atmospheric energy is hard to bust up: The high pressure above is met with the rising heat below, which makes the system especially stubborn and slow-moving.
Right now, that pressure system is trapped over land, but that mass is also heating the water in the Gulf of Mexico — it’s making it hotter. Gulf waters have heated to about the same temperatures as last year. When the air from the Gulf blows to the shore, it compounds that trapped heat, saturating the air and creating the conditions under the dome.
Read more from Andrew Weber with Texas Standard here.