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Hurricane Isaac remnant less likely to spawn tropical storm

Updated at 10:50 a.m. ET -- The chance that a remnant of Hurricane Isaac will give birth to a tropical storm in the Gulf of Mexico was greatly reduced overnight by the National Hurricane Center. It's now at 20 percent, down from 40 percent Thursday afternoon.

"Conditions are expected to become less favorable for development," it said in a Friday morning advisory.

Already producing rain, the system is southeast of the mouth of the Mississippi River. 

A hurricane that deteriorates only to have a remnant redevelop into a tropical storm is not unheard of -- Ivan in 2004 was one case -- but it is unusual, Weather Channel meteorologist Jon Erdman reported Thursday.

"A funny thing happened to this remnant," he wrote in describing what's brewing. "Basically, the polar jet stream was never able to catch up" and whisk it away northward along with the rest of Isaac.

If a tropical storm does form it will not keep the name Isaac and instead would be Nadine, the next name on the official list.

Hurricane Michael became the first major Atlantic storm of 2012, while Hurricane Leslie continued to slowly move northward Thursday morning. Michael was not expected to make landfall, but Leslie was already creating waves in Bermuda. NBC's Brian Williams reports.

That's because the remnant in the gulf is only a small piece of the former hurricane. When a weakened Ivan regenerated into a tropical storm the name was kept because most of Ivan was still intact.

Isaac's daughter would be only the second time on record where a system regenerated along with a new name.

"This is the only example that we can find in the modern era where the partial remains of a system went on to regenerate and, so, get a different designation," National Hurricane Center meteorologist Todd Kimberlain told the Associated Press. 

The only other time? In 2005, a remnant from a tropical depression that dissipated near Puerto Rico eventually became part of a new depression -- which became the catastrophic Hurricane Katrina. 

This time, however, any new storm's impact will likely be minimal, Erdman stated.

Most of the rain could stay over the Gulf of Mexico "until it's kicked east or northeastward ... this weekend," he wrote. "Good news for those recovering from Isaac's surge and rainfall flooding in Louisiana and Mississippi."

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