"Bertha seems to be following an unusual path compared to most tropical systems in the Gulf. What gives?"

Storms don’t always follow climatology since climate doesn’t drive the movement of systems like Bertha.

Tropical systems are often in an enormous game of pinball, being boinked around by bumpers, flippers, lanes and slingshots, being pushed around by whatever other weather systems there are in the box. In this analogy, the main driver was a bumper called a heat dome. You’re probably familiar with heat domes because of the heat wave we saw in the Midwest and Northeast earlier this summer or the record-shattering heat wave that was seen in France and other parts of Europe several weeks ago.

The reason why

These systems – called heat domes, high pressure systems or ridges – feature sinking air and quite literally act like a mountain of air that other systems cannot get through. They act like bumpers.  

These same domes of high pressure bump tropical systems around. 

In the days leading up to Bertha’s formation, a large and strong high pressure system was at home over the western Atlantic and near Bermuda – the Bermuda High. You might be familiar with the Bermuda High, but if not, here’s a refresher from meteorologist Rob Shackelford. 

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Another dome was entrenched across the Southeast before weakening a smidge and moving toward the Southern Plains. This high pressure system has driven up temperatures in Texas, Oklahoma and Louisiana in recent days.  This is the bumper that kept Bertha from moving north or northeast like most tropical systems do. 

These two bumpers helped push Bertha toward the west. And, there are no flippers like a cold front or jet stream, so Bertha has been pretty slow-going ever since its inception. 

Many systems in the Gulf or along the East Coast get flung northeastward by cold fronts or the jet stream when one of those features dips into the eastern U.S. Both of those systems often feature a southwest to northeast flow that works like a slingshot to move tropical systems away from the Gulf. 

All in all, Bertha had no such slingshots, but instead, bounced around with the high pressure bumpers and was forced west instead.