Ida weakened to a tropical storm yesterday as it churned toward oil and gas facilities in the Gulf of Mexico and was forecast to hit the US Gulf Coast early today between Louisiana and Florida.
Ida posed the first real storm threat of the 2009 hurricane season to Gulf of Mexico oil and natural gas production, and forced some companies to shut down off-shore platforms and evacuate personnel.
Alabama Governor Bob Riley declared a state of emergency to allow its government to mobilize troops and rescue workers. Louisiana issued a similar declaration on Sunday.
In El Salvador, rivers burst their banks and hillsides collapsed under rains triggered by Ida's passage, cutting off parts of the mountainous interior from the rest of the nation.
At its earlier hurricane strength, Ida triggered floods and mudslides that killed 124 people in El Salvador.
Ida's top sustained winds dropped to 113 kph, and the storm is unlikely to regain hurricane strength before it makes landfall, the National Hurricane Centre said.
Oil rose more than $2 to near $80 a barrel yesterday on fears that Ida would cut the US oil and gas supply.
The Louisiana Offshore Oil Port, the only US terminal capable of handling the largest tankers, stopped unloading ships due to stormy seas. And the Independence Hub, a major offshore natural gas processing facility, also was closed.
A quarter of US oil and 15 per cent of its natural gas are produced from fields in the Gulf, and the coast is home to 40 per cent of the nation's refining capacity.
The Miami-based hurricane centre discontinued hurricane warnings along the US Gulf Coast, and said a tropical storm warning was in effect from Grand Isle, Louisiana, eastward to Aucilla River, Florida, meaning that tropical storm conditions are expected within 24 hours.
The warning area included New Orleans, which is still recovering from the devastation of Hurricane Katrina in 2005.
At 1 p.m. EST (1800 GMT), the storm was about 185 km south-southeast of the mouth of the Mississippi River, the hurricane centre said.
River traffic between New Orleans and the Gulf of Mexico was halted due to rough seas, the US Coast Guard said.
In Mobile, Alabama, on the US Gulf Coast, Governor Bob Riley warned the state's residents to be on their guard, and declared a state of emergency for the state.
"At this point, we don't know how substantial this damage could be," Mr Riley said. "We hope it continues to dissipate."
Local authorities reported flooding from waves and storm surge at the developed west end of Dauphin Island, the barrier island off Mobile, which was heavy damaged by Katrina in 2005.