This is what the ‘dirty side’ of a storm really means

. (Photo by GEORGE DESIPRIS from Pexels)

Meteorologists often refer to the right side of a hurricane as the “dirty side” of the storm.

“Personally, I like to channel my inner boxer and call it the storm’s ‘right hook,’” meteorologist Paul Gross said. “That’s because this part of the storm has the most intense weather associated with the entire system.”

Gross went on to explain, saying, here’s why that is: Let’s say that a hurricane is moving due west toward the U.S. east coast at 20 mph, and maximum sustained winds blowing around the eye are at 100 mph. The wind on the RIGHT side of that eye (meaning, for this particular hurricane, on the north side of the eye) is blowing in the same direction as the hurricane itself is moving. Conversely, the wind on the LEFT side of that eye (the south side of this particular eye) is blowing in the opposite direction of the storm’s movement.

So, the wind to the right of the eye essentially has a tail wind, and blows harder (perhaps 110-120 mph) than the wind to the left of the eye, which is blowing against the storm’s movement (perhaps 80-90 mph). That’s why the right side of an approaching hurricane has the strongest wind.

But wind speed isn’t the entire story.

The wind on the right side of that hurricane is blowing directly toward shore, and that pushes a wall of water into the shoreline, and inland. This is called storm surge, and is the most destructive aspect of a hurricane.

On the left side of a hurricane, the wind is blowing offshore, which can obviously cause problems, but is not destructive like the storm surge on the other side.

One final aspect to remember, Gross said: The stronger wind on the right side of the storm, acting in concert with a change in wind direction at the surface due to friction from terrain, buildings, trees, etc., creates an environment conducive to smaller spin-up tornadoes, which are most common in those spiral bands sprawling out away from the center of the storm.

So, those on the right side of a landfalling hurricane get a double whammy -- the strongest wind and storm surge, plus the tornado threat.

Bottom line, Gross said, is that while all parts of a hurricane are bad, the “dirty side” is just worse.

About the Authors:

Local 4 meteorologist Paul Gross was born in Detroit and has spent his entire life and career right here in southeast Michigan. Paul has researched, written and produced eight half-hour documentaries for WDIV, as well as many science, historical and environmental stories.