At 1500 UK time on Tuesday 28 August, Tropical Storm Isaac was located about 150 km southeast of the Louisiana coast and heading northwest at about 15 km per hour. Mean wind speeds of 70 mph at the surface have been observed by the United States National Hurricane Center aircraft. These mean wind speeds maintain Isaac as a tropical storm, just below hurricane strength which requires mean wind speeds of over 74 mph.
Although Isaac is expected to make landfall within the next 12 to 18 hours, there is still time for Isaac to intensify and become a hurricane. The official United States National Hurricane Center (NHC) forecast track predicts an intensification of this system into a category 1 hurricane as it continues its track northwestwards over the very warm Gulf of Mexico with winds increasing to around 80 mph when Isaac makes landfall at around 0600 UK time on Wednesday morning.
The latest forecast from the NHC suggests that Isaac will pass just to the west of New Orleans, though there is still some uncertainty over the exact track and intensity of the storm and the impact of Isaac will be felt quite widely along the Gulf coast region.
Although hurricane Isaac is not expected to be as intense as hurricane Katrina which caused massive damage to New Orleans 7 years ago, there is still a risk of extreme rainfall with up to 500 mm in 48 hours resulting in flash flooding and storm surge along the coast, in addition to the damaging winds. As Isaac moves inland it will weaken, but is still likely to result in torrential rain, perhaps with tornados or very squally winds. There is a risk of flooding over the lower Mississippi valley region for the next few days.
You can find out more about Tropical Cyclones on our website or read our case study on Hurricane Katrina on the Met Office Education website.