Tropical Storm Francine is forecast to shift track eastward Tuesday morning, putting New Orleans uncomfortably close to the storm’s center.

As of 10 a.m. Tuesday, Francine was expected to reach Louisiana by midweek, about 86 miles southwest of New Orleans. Does this mean Crescent City is in the path of the storm’s notorious “dirty” side?

What is the ‘dirty’ side of a storm?

The “right side” of a storm is not always on the east side — it is determined by the direction the storm is moving. If a storm is moving north, the right side is on the east side. If it is moving west, the right side is on the north side.

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According to Rob Frye, a meteorologist with the National Weather Service, Francine is expected to continue moving north-northeast over the next few days, with the bad side generally moving east.

Why is the dirty side more intense?

According to Frye, the right side of a storm is associated with slightly higher wind speeds and more intense storm surges, for a number of reasons.

All storms that form in the Northern Hemisphere spin counterclockwise because of the Coriolis effect, which we don’t need to go into here. As a storm moves forward, that driving force and the counterclockwise motion creates stronger winds on the right side.

“It just adds that little bit of extra spice,” Frye said.

So if a storm with winds of 70 mph is moving at 10 mph, it could have winds of up to 80 mph on its right side and winds of 60 mph on its left. Francine was moving at 9 mph with sustained winds of 65 mph as of 1 p.m. Tuesday, but is expected to hit the Louisiana coast on Wednesday with winds just under 100 mph.

Frye said that because of the storm’s counterclockwise rotation, the left side of the storm attracts winds from land, where houses, trees and other obstructions slow the storm’s winds.

On the right side the wind is picked up from the obstacle-free sea.

“There’s less friction, there’s just water,” Frye said. “That’s another reason why our area specifically is a little more vulnerable on the east side.”

That swirling effect also affects coastal waters, pushing tides higher on land and creating a more intense storm surge on the dirty side of the storm.

Who’s on Francine’s bad side right now?

The National Hurricane Center’s forecast for Francine was for a track toward the east Tuesday morning, with the eye of the storm making landfall just south of Morgan City Wednesday evening.

If that path remains, Frye says, Interstate 55 and everything just east of it will be on Francine’s dirty side, including much of the New Orleans metro.

According to Frye, the effects on the right side are most noticeable closer to the eye, and the farther you are from the center of the storm, the less severe they are.

“If there is another shift further east, we can’t rule out the possibility of a somewhat larger impact,” Frye said.

Don’t get caught up in the exact track

Dan Brown, a hurricane specialist with the National Hurricane Center, agreed that the right side of a storm often brings stronger winds, storm surges and sometimes even more precipitation.

But Brown said residents within Francine’s predicted path shouldn’t get hung up on the exact path, which will likely continue to shift here and there over the next two days. Some model trends show Francine’s path moving even farther east before landfall.

“A hurricane is no big deal,” Brown said, adding that its impact extends far beyond the eye of a storm, no matter which side you’re on. He encouraged people in southern Louisiana to start preparing today.

“It doesn’t take much wind to cause power outages,” he said.