Storm Nate kills at least 22 in Central America before heading towards US

A state of emergency has been declared in central America after tropical storm Nate left at least 22 dead in Coast Rica, Nicaragua and Honduras as it heading north towards the US.

Nate, which is now forecast to become a hurricane by the time it reaches the northern Gulf of Mexico, caused violent rains, landslides and floods which led to blocked roads, destroyed bridges and damaged houses leading to the disappearance of further 20 people.

Meteorologists then predicted that the storm will make a landfall on Mexico's Yucatan Peninsula late on Friday, ahead of gaining strength and turning into a category one hurricane and prior to hitting either Florida or Mississippi in the United States on Sunday.

The US National Hurricane Center said warnings had been issued for portions of the Louisiana, Mississippi and Alabama coastlines.

New Orleans Mayor Mitch Landrieu declared a state of emergency overnight and advised residents to stay put over the weekend.

"There is no need to panic. Be ready and prepare. Get a plan. Prepare to protect your personal property," Landrieu tweeted.

While oil companies operating in the Gulf of Mexico said they were evacuating staff from platforms lying along the predicted path of the storm.

A Friday forecast from the NHC showed a wide predictive route for Nate but the central forecast is that it will head towards Florida or Mississippi.

"Reports from Air Force Reserve and NOAA Hurricane Hunter aircraft indicate that maximum sustained winds are now near 50 mph (85 km/h) with higher gusts," the report said.

"Additional strengthening is forecast during the next couple of days, and Nate is expected to become a hurricane by the time it reaches the northern Gulf of Mexico."