Almost always, tourists will consider the big “H” letters on weather maps a friend. It stands for “High.”

But there’s no judgment about temperature involved in this. The high air pressure, centered where the letter is placed, can mean hot, warm, cool or freezing cold conditions. For tourism, a clear sky is usually the most desirable condition, and that’s what we get when the air pressure is high.

A “haystack” of air is the term I recommend as a memory aid. Because it’s stacked high in the atmosphere, the air settles down under its own weight, and thereby suppresses tendencies for rain.

Once again, North Georgia is going through a serious drought period, and the highs are no longer a friend. There are plenty of rainstorms, even frontal systems, in the states farther west. But here, sunshine every day at breakfast time is more reminiscent of Los Angeles than Gainesville.

The culprit here is high pressure over the Atlantic Ocean. A few days ago, the weather charts showed two huge highs, with the remnants of Tropical Storm Nicole wedged between them. The one on the European side of the Atlantic is named Azores High, because that’s its average location over the course of the year.  The one close to the U.S. East Coast is known as the Bermuda High.

Those two systems can get very large and quite strong. For all of this fall season they have acted as giant roadblocks, preventing frontal systems from reaching us, and in general discouraging the atmosphere from dropping rain on North Georgia.

Most of the time when we have a drought, it’s caused by the Bermuda High, or a bigger version of it when it extends into the Gulf of Mexico. You can imagine the behavior of highs and lows like the workings in a pinball machine. The ball represents the rain-carrying low. It moves around, going to wherever the forces will bounce it.

The mushroom-shaped bumpers in the machine kick the ball away, and sometimes it’s tough to make it pass between two of them. Tropical Storm Nicole got a similar bounce from her spot between the Bermuda and the Azores highs. But she was already moving away from our continent.  

In Georgia, we can only wait and hope that the high pressure loses some strength, so that we can get much-needed rain again.

Rudi Kiefer, Ph.D., is a professor of physical science and director of sustainability at Brenau University. His column appears Sundays and at gainesvilletimes.com.