'Do not drop your guard': Tropical Storm Barry threatens heavy rain after landfall

• New Orleans residents told to seek shelter as 50,000 lose power
• NHC director details 'amazing amount of moisture'

Carrying "off the chart" amounts of moisture, Barry crawled ashore on Saturday in Louisiana at hurricane strength. It quickly weakened back to a tropical storm but it promised heavy rains that could last for days, testing flood-prevention systems built after Hurricane Katrina.

Officials warned that the storm could still cause disastrous flooding across a wide stretch of the Gulf coast.