Tropical Storm Isaac has strengthened into a hurricane, the National Hurricane Center has just announced this afternoon (Aug. 28).
Hurricane Isaac is the fourth hurricane of the 2012 Atlantic season, and is set on a collision course with the Gulf Coast.
Isaac lingered at tropical storm strength for days, with atmospheric conditions hampering its growth into a hurricane. It finally achieved hurricane strength this afternoon and currently has winds of 75 mph (120 kph), just over the hurricane threshold.
Hurricane hunters with the Air Force Reserve made the report that Isaac's winds were finally sustained at hurricane strength.
The storm is 75 miles (115 km) south-southeast of the mouth of the Mississippi River and 160 miles (250 km) southeast of New Orleans. Isaac's path is projected to take it to a landfall Tuesday afternoon or evening along the southeast Louisiana coast.
A hurricane warning is currently in effect from east of Morgan City, La., to the Mississippi-Alabama border, an area that includes New Orleans. The storm is bearing down on New Orleans seven years to the day after Hurricane Katrina devastated the city.
Hurricane watches and tropical storm warnings and watches have been issued for other areas of the Gulf Coast. The NHC has warned that the impacts from Isaac's storm surge are likely to be significant and that the storm could bring large amounts of rain, as well as the possibility of tornadoes in some places.
Storm surge and rain are likely to cause significant flooding in coastal areas, the NHC has warned.