Florence becomes hurricane and threatens the Southeast and the Middle Atlantic

It is even less likely that the storm will turn into the sea and spare the coastal and inland areas from devastating, devastating winds, rains and floods. It is to be feared that the storm will slow down or stagnate on the Mid-Atlantic from Friday to next weekend and produce disastrous amounts of rain, although it is too early to know where.

"There is a growing risk of two deadly impacts of Florence: a storm surge on the coast and freshwater floods caused by a prolonged rainy episode inland," wrote Sunday the National Hurricane Center. Storm surge is the rise of ocean waters over normally dry lands off the coast, which can flood homes, roads and businesses.

South Carolina, North Carolina and Virginia have declared the state of emergency to place money and resources for the storm.

The Hurricane Center's official forecast brings the storm in southeastern North Carolina Thursday night near the intensity of category 4, although this placement is in a large cone of uncertainty. Given the possible deviations from the exact trajectory of the storm, Florida residents in southern New England should follow its progress.

At 1100, Florence was centered 1,500 miles southeast of Wilmington, NS, and crawled westward at 6 mph. Its winds have reached a maximum of 75 mph, making it a Category 1 hurricane. Over the next few days, its advance movement is expected to increase as it turns westward. the northwest, and its intensity is expected to increase rapidly. But the storm is expected to slow down as a likely landing approaches.

The environment before the storm for the next four days at least a category 3 hurricane on the southeast coast at the end of the week. The storm will pass over warmer than normal ocean waters, which will provide fuel. And there will be little wind shear to disrupt the development of the storm at its base. It is not excluded that Florence will become a category 5 hurricane at some point.

The Hurricane Center expects to reach Category 4 intensity by Tuesday, with maximum winds of 140 mph.

Coastal residents of Georgia, South Carolina and North Carolina should continue to prepare for the arrival of a major hurricane and have a plan if they are to be evacuated.

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In these coastal areas, waves and high water levels arrive on Wednesday morning and precipitation could start on Thursday morning.

Tropical storm winds could reach the coast as early as Wednesday night, by which time all outdoor preparations should be completed. Extremely violent winds of hurricane force could hit the coast Thursday to Friday. Hurricane winds due to tropical storms could extend inland depending on the exact course of the storm.

We are particularly concerned about the pluviometric potential of the Atlantic. Models agreed that a turn north before reaching the United States is unlikely and that a high pressure area north of the storm will slow down or stagnate once on the coast or soon after.

Florence could sit for several days on a portion of the Mid-Atlantic, just like Harvey did last year in East Texas. It is possible to dump unimaginable amounts of rain over a large area of ​​the central Atlantic coast and perhaps the northeast. Precipitation could start on Friday or Saturday and continue the following week. Where exactly the heaviest rain zone is, there is a lot of uncertainty. It could reasonably occur anywhere between the mountains and the coast.

On Sunday morning, the American model shows a nine-day rain, with many areas reaching one to two feet and even larger amounts in eastern North Carolina. Of course, this is a unique simulation of a single model, so do not take it literally, but the message is that historic and catastrophic rainfall is possible in the Atlantic.

This region will be particularly vulnerable to floods due to much higher than normal rainfall in the region since May. In addition, since the soil is probably saturated, the trees will be vulnerable to strong winds.

Parts of the Mid-Atlantic, particularly from Virginia to Pennsylvania, have recorded 150 to 300 percent of their normal rainfall since May.

Further north, in Delmarva, New Jersey, Pennsylvania and New York, coastal and inland areas are also expected to prepare for significant storm effects.

When the storm affects the coast, the strongest winds and the greatest rise in coastal waters can occur, but high winds and extreme precipitation could occur at great distances from the landing site. Keeping this in mind, here is the probability of landing at different locations depending on our evaluation of the model data:

• 60 percent in the Carolinas.
• 15% between Virginia and southern New England.
• 15% offshore.
• 10% between North Florida and Georgia.

Even in the unlikely event that the center of the storm remains just offshore, it is almost certain that it will be close enough to cause dangerous winds and floods in the coastal areas. Interior areas may be somewhat spared in this scenario.

If a major hurricane (category 3 or higher) touches the southeast coast, the rarity of such an event is relevant. Since 1851, only 10 major hurricanes have done so and the most recent, Fran, in 1996, 22 years ago. In 1989, Hugo was the precedent and was a category 4 on the ground. No hurricane landed as Category 5 in this region.

There are probably many people in the Southeast and Middle-Atlantic who have not experienced a storm of potential magnitude from Florence.

Elsewhere in the tropics

We are also watching tropical storm Helene south of the Cape Verde Islands and tropical storm Isaac west of Helena.

Helene is almost a hurricane, and warnings of tropical storms and hurricanes cover the islands of southern Cape Verde. It is expected to intensify, likely becoming a category 2 hurricane by Tuesday, then turn north into the open central Atlantic, where it will quickly find itself over the Cold water.

Isaac, on the other hand, looks like a problem. He is expected to remain in the deep tropics and reach the Lesser Antilles on Thursday as a category 1 or 2 hurricane. Currently 1,500 miles away, he could cross the same islands devastated by the Hurricane Maria Category 5 last year on September 19th.

After crossing the Lesser Antilles, Isaac is expected to continue westward through the Caribbean Sea but weaken gradually in the face of strong wind shear. We have time to look at this one, but the immediate concern is in the Lesser Antilles.