Tropical Storm Barry: Why rainfall is his biggest threat


A storm system hovered over the northern Gulf of Mexico that had already dropped more than eight inches of rain on New Orleans. Tropical storm Barry.

The flash flood that ravaged some New Orleans districts on Wednesday served as a warning to residents along the Gulf coast of what would happen if the slow-moving storm on Saturday reached its expected supply, possibly like a hurricane: rain, and many of them.

New Orleans is located on the eastern edge of the storm path prediction models, showing that the center could land almost anywhere along the Louisiana coast. The model of the National Hurricane Center also shows the potential for major flooding as far inland as Baton Rouge and the southwestern parts of Mississippi.

In the video below, the specialists at the center explain the "cone" prediction and its limitations.

"The cone represents the likely trace of exactly the center of the storm," says one of the specialists, John Cangialosi. "The center of the storm stays within the cone for about two of the three predictions."

The specialists added that hazards associated with a storm usually extend beyond the edge of the cone, and the cone should not be used as an indicator of whether or not to evacuate.

It is predicted that about 10 to 15 inches of rain will fall from the end of Thursday evening to Sunday. "The rain will be there because it is a very slow moving storm," said Freddie Zeigler, a lead predictor in the New Orleans / Baton Rouge office at the National Weather Service. "Some areas that do not normally overflow can overflow."

The Mississippi River, already swollen by spring rains, is expected to arrive in New Orleans at nearly 20 feet this weekend. The dikes along the river are between 20 and 25 feet high, according to Ricky Boyett, the spokesman for the Army Corps of Engineers in the New Orleans District.

"We'll go to the top of some of our lower dikes if the forecast is right," he said, pointing out that it was too early to include a forecast.

Boyett said the corps was trying to identify and reinforce weak areas. "We are not concerned with the integrity of the dikes," he said, only with how high the water rises.

The wind reached tropical storm temperatures of at least 39 miles per hour on Thursday morning. The storm can become a hurricane at the end of Friday, meaning that the wind is at least 74 m.p.

National predictors of the Hurricane Center also predicted storm tides of three to six feet along the coastal areas. For comparison: the the storm surge from Hurricane Katrina in 2005 was at least 25 feet along the Gulf Coast.

Mr. Zeigler said the meteorological service and the national hurricane center were in Miami updating their forecast every few hours and urging residents of Louisiana, Mississippi and Texas to keep checking, as the path of the storm can change.

The Atlantic hurricane season this year officially runs from June 1 to November 30. It is unusual to have such a large storm system so early in the season, the records show. Hurricanes only hit Louisiana in July three times in 168 years. All have taken place in the last 40 years.

Experts say that this trend can be partly attributed to climate change that is warming the waters of the Gulf of Mexico. A study by recent hurricanes showed that climate change increased rainfall by no less than 9 percent.

[Read "As climate change, hurricanes become wetter"]

New Orleans has always been a place where heavy rainfall fell, but recent floods and expectations for this storm are in line with the effects of climate change: warmer air contains more moisture, which then comes down as extremely heavy rainfall.

In Plaquemines Parish, along the Mississippi River from New Orleans and the southernmost city of the state, nearly 10,000 residents have a mandatory evacuation order. The entire east bank of the city, which lies on the Gulf of Mexico, will be evacuated, as well as a part of its west bank.

Residents gather at designated places and are taken by bus to a registration point and then travel with another bus to a reception center.

In New Orleans, Mayor LaToya Cantrell asked the residents to hide again, recording her decision to the Army Corps of Engineers' belief that the dikes would hold back most of the water. Like water