Indiana in path of Hurricane Isaac

One of the ways of assessing the likelihood of getting the effects of Isaac is looking at a "spaghetti plot."
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Hurricane Isaac is striking the Gulf Coast, but it could bring severe and dangerous weather to Indiana's Labor Day weekend. People are being warned to start planning now to keep themselves safe.

As Isaac bears down on Louisiana and other Gulf Coast states 800 miles away, its path and power are raising concerns among National Weather Service forecasters in Indianapolis. The storm's so-called "leftovers" could bring up to six inches of rain, flash floods and severe and damaging winds.

Latest updates on Isaac

"We could see not only thunderstorms, but we could see rotating storms that could produce tornadoes," said NWS Chief Meteorologist Dan McCarthy.

The powerful tornadoes would be different from those that typically strike Indiana.

"Quick-acting, quick-striking type storms. They don't get on the ground and last for miles and miles and miles," McCarthy said. "They are very quick and they are whip-like tornadoes," McCarthy said.

As the hurricane moves north, it will create a storm of dangerous weather almost a thousand miles wide, stretching from western Kansas to western Ohio. After Isaac is through with the Gulf states, it is predicted to move up the Mississippi Valley to Indiana. Four years ago, another Hurricane took a similar route.

Ike, a much more powerful hurricane, caused the worst disaster in Indiana history. Storms struck Indianapolis during the Speedway's Moto GP race, tossing tents aside, toppling trees and making a mess of neighborhoods. Flash floods swept across northern Indiana, forcing 5,000 Munster residents to flee their homes. Tornadoes raked through southeastern Indiana, 350,000 people were without power. Damages totaled nearly $2 billion. Seven people died in those storms.

Indiana's emergency management center is monitoring the hurricane, taking calls from states asking for help, but not making any commitments.

Arvin Copeland, director of response and recovery for the Indiana Department of Homeland Security explains, "For the most part, we are keeping out staff in Indiana for potential weather that may come in this weekend."

The worst of the weather is expected to hit Saturday and Sunday. The National Weather Service is warning people to start planning now. Where are you going? What are you doing for the holiday weekend? What will you change and how will you stay safe if there is severe weather?

And most importantly, keep track of the changing forecasts.

Hurricane Isaac forecast

At 12:20 this afternoon, the National Hurricane Center upgraded Isaac from a Tropical Storm to a Category 1 Hurricane with maximum sustained winds of 75 mph. The storm is likely to remain at Category 1 strength as it pushes toward an overnight landfall on the Louisiana coast.

Moderate to heavy rain will develop across the Gulf Coast on Wednesday as Isaac moves onshore. After moving over land, Isaac is expected to reduce to a tropical storm on Wednesday as it moves over southern Louisiana and the mouth of the Mississippi River.

Counter-clockwise flow around this system will continue pushing abundant moisture onshore, producing heavy rains and strong winds from eastern Texas through Mississippi and Alabama. This system is capable of producing 4 to 6 inches of rain over most areas, with up to 10 inches possible in southeastern Louisiana on Wednesday.

This will create flooding problems for the next few days. Expect winds to range from 39 to 73 mph in the vicinity of the storm.

One of the ways of assessing the likelihood of getting the effects of Isaac is looking at a "spaghetti plot." Each line (which looks like a strand of spaghetti) corresponds to a computer model. When you compare multiple computer models, if most of them follow the same path, the confidence in that track becomes high. If the models have paths that don't agree, that leads to lower confidence. Since most of the paths head through Indiana this weekend, my confidence at this point in heavy rain threat for Indiana is becoming increasingly high.

So what does this mean for Hoosiers? Plan on rain this weekend. How much could still change, but based on the information Tuesday, we could get between two to six inches of rain along with sustained winds of 15 mph and gusts of 20-30 mph.

Because of the circulation of Isaac, we might also have severe storms with the possibility of isolated tornadoes. Timing looks like Friday for our first impacts (some computer models bring us rain by Friday morning, others wait until Saturday). My forecast for rain Friday: 30%, Saturday and Sunday: 60%, Monday 30% in the morning.

If we get the high end of the possible rain this weekend (around 6″), then that could nearly erase our precipitation deficit. That could make a huge dent in the drought. We'll have to wait and see.

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