US weather: Freak ‘homegrown’ tropical storm puts millions of Americans on flood alert

It threatens “significant and alarming” rainfall, “spin-off” tornadoes and a possible coastal storm surge.

AccuWeather meteorologist Jon Porter said: “This type of homegrown development is much more common in the late spring to early summer.

“Most tropical systems that form during the heart of the hurricane season develop thousands of miles to the south over the central Atlantic.

“The threat of life-threatening flash flooding will expand across the Carolinas as tropical rainstorm pushes inland, and there is also a risk of spin-up tornadoes in eastern parts of North Carolina and South Carolina.”

The storm has been classified as a “coastal low” dubbed “Potential Tropical Cyclone Eight”.

It comes as the true Atlantic hurricane season kicks into gear, with Tropical Storm Gordon this week following Francine, Ernesto, Debby, Chris, Beryl and Alberto.

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Up to a foot of rain could hit North Carolina sparking rapid and deadly floods, experts warn.

Porter said: “These are impressive and alarming rainfall totals. Rainfall rates of three to six inches per hour can quickly trigger life-threatening flooding.”

The US National Hurricane Centre NOAA has put parts of the east coast under coastal flood advisories and flood watch alerts.

Most at risk are the Carolinas, Virginia, Washington DC, Maryland, New Jersey, Delaware, and Pennsylvania.

Violent thunderstorms will whip up strong winds while spewing out showers of giant hail, government experts warn.

As the east coast braces from Tropical Cyclone Eight, a separate storm is brewing on the other side of the country.

A NOAA spokesman said: “A coastal low, previously labelled Potential Tropical Cyclone Eight, will continue to slowly move north across the Carolinas towards the

Mid-Atlantic.

“Coastal flooding will be a concern with a prolonged period of onshore winds along the Mid-Atlantic coast, and by Thursday, this system will begin to shift offshore

into the Atlantic.

“Another low-pressure system will move south along the West Coast Wednesday

and Thursday, which will bring another round of unsettled weather.”

North Carolina also faces a potential three-feet storm surge with the risk of tornadoes.

A spokesman for The Weather Channel said: “Gusty winds will impact the eastern Carolinas and the southern mid-Atlantic and some coastal flooding is possible as well at times of high tide.

“A storm surge is expected to be one to three feet above ground level from northeast South Carolina to southeast North Carolina if the peak surge arrives at high tide.

“An isolated tornado threat could also develop in eastern North Carolina.”

Jim Dale, US weather correspondent for British Weather Services and co-author of ‘Surviving Extreme Weather’, said: “With the risk of flooding will be a threat of potential tornadoes.

“It is going to be a very mixed bag in this part of the states through the week.”