Bryan's look at the Weather: The Return of the Bermuda High

Ok, if you are reading this from the southern states you may be thinking, heat... we have dealt with heat for weeks now. But lets turn some attention to the famous Bermuda High.

What is the Bermuda High you might ask, as you will be hearing about it likely over the next few weeks of summer. The Bermuda High is a permanent weather feature that is situated over the Atlantic Ocean and is usually centered near the island of Bermuda, hence the name.

Lately the weather pattern has shunted this feature off to the south and east, but as the upper level winds relax and become more zonal (meaning a smooth west to east flow) the Bermuda High can set up, as forecast beginning later this weekend.

The Bermuda High is set up all across the Atlantic in this forecast model for July 13, 2011

Wind flows clockwise around the Bermuda high and the Bermuda high is infamous for several things including:

East Coast Heat
Drought
Hurricane Tracks
"Ring of Fire" Thunderstorms

Under an area of high pressure, air is sinking. So in the atmosphere it is like scouring out an area of weather. During the summer, this area can expand over much of the ocean and encroach inland to the Gulf of Mexico and to the mid West US.

Lets look at the 4 topics pointed out:

East Coast Heat
Under the western side of a high pressure system, the air is typically warm and more humid. Just looking at the weather map provided above, you can get the sense that a parcel air is traveling from the tropical areas over the warm Gulf of Mexico to pick up more moisture and humidity up the Ohio Valley and into New England to make us warm and humid.

Heat Wave on August 2, 2006 with an intense Bermuda High (See radar from same day below)

Drought
Under the high, air is sinking, and with that sinking air, clouds have a hard time forming. The air is very stable and thunderstorms especially cannot form as easily. A persistent Bermuda high can make areas very dry underneath them. As on the map below, look at areas of the Southeast US. You want to imagine the Bermuda High as a bubble umbrella over these areas protecting it from any rain.

The high will act as a dome over the area and scour out any rain or clouds for that matter, increasing the likelihood of droughts.

Hurricane Tracks
With the Bermuda high in place, a hurricane will follow the periphery of high pressure and it can be easy to forecast where a hurricane may go. Take a look at the typical tracks of hurricanes in the picture and you can see the outline of the Bermuda high. if the Bermuda high is strong the hurricane will track westward into say Texas, or if it is weak may go up to East Coast or even out to sea.

Hurricane tracks with various extents of the Bermuda High. Gilbert in 1988 went into Mexico, Bob in 1991 came up the east coast into New England as did Bertha in 1996. All going around the Bermuda High. Please note: I am not forecasting any hurricanes, just to show you examples of what happens.

"Ring of Fire" Thunderstorms
On the outer periphery of the Bermuda High the air mass clashes with other air at boundaries and can produce thunderstorms that stretch in a ring from Texas to the Great Lakes.