The wall of water threatening America's great cities

A woman photographs waves from the Atlantic Ocean in Ocean City, Maryland. Photo: Reuters

I'm overlooking Ground Zero, the site of the greatest disaster ever to hit the United States. It was a man made tragedy.

Now at the World Trade Centre site, they are preparing for another potential disaster, this time a natural one.

Below the 90 floors now rebuilt, they are tying down all the building materials, securing as much as they can - awaiting not planes coming in from the Atlantic but a hurricane, a storm system predicted to punch New York as hard as a natural disaster has ever hit it.

Workers place sandbags at Exchange Place in New Jersey. Credit: Reuters

All across Lower Manhattan, buildings are being boarded up and sandbagged. More than half a million people have been ordered to evacuate coastal areas within an easy drive of New York City.

All low lying areas are at risk of some of the worst flooding this coast will ever see.

What is expected is nothing less than a mini-Tsunami. A full moon and a series of high tides will link up with a hurricane 1,000 miles across, its winds averaging 85 miles an hour, to push a high wall of water inland.

The waves have already been recorded at sea. They are 35 feet high.

The surge is expected to be up to 12 feet. Put all that together and you can see why New York has closed down its underground train system. It might be closed for some time. They're afraid the whole system might be flooded by the sea surge.

Everything in the city is closing or closed - schools, the United Nations, Wall Street (though trading will continue online).

Inspectors have arrived at nuclear power stations across the East Coast.

Remember how Hurricane Katrina devastated New Orleans seven years ago.

And stained George Bush's Presidency forever after his lamentable performance (and that of the whole Disaster Management team).

Remember how an earthquake in Japan triggered a nuclear meltdown.

Remember, and realise how this hurricane could morph into something way beyond a storm.

It could be the defining political moment for President Obama. Handle it well and he'll win re-election. Handle it badly and he's out.

President Obama at a FEMA briefing on Sunday. Credit: Twitter: @fema

If the authorities handle it well, millions will be safe. Handle it badly and hundreds may die.

New York below me is braced. A disaster is looming. The men who are fighting for the White House are watching nervously.

Millions are looking out towards the coast, wondering what a wall of water looks like.