Tropical Depression 13 has formed in the northern Gulf of Mexico from a tropical wave that has been sitting over the area for the last day or two. The National Hurricane Center anticipates TD13 to become Tropical Storm Lee tonight or tomorrow, and very slowly make its way towards the Louisiana Coast.
In anticipation of TD 13 strengthening into Lee, the NWS has issued a Tropical Storm Warning from the Texas/Louisiana border eastward to Pascagoula, MS. Showers and thunderstorms have been impacting the northern Gulf Coast all day (I'm near Mobile and got soaked on my way to class earlier), and this squally weather is expected to increase as TD 13 moves closer to the coast.
TD 13 is expected to strengthen to a Tropical Storm by tonight or tomorrow, and slowly strengthen as it makes its way towards the coast. The NHC predicts that it'll have about 60 MPH winds by landfall on Saturday, but that's not set in stone as intensity forecasts tend to have a large margin of error.
Here's the track forecast from the NHC. The areas shaded in blue are Tropical Storm Warnings. Keep in mind that these warnings extend a county or two inland as well. Click to enlarge in new tab/window.
Here's the latest satellite image of TD 13.
Here's are some radar images showing the squally weather associated with TD 13.
This one is from Mobile AL:
This one from Slidell LA:
Meanwhile in the Atlantic, Katia has temporarily weakened to a Tropical Storm but is expected to turn into a Major Hurricane by the end of the weekend. It still looks ominous to the United States on the 5-day forecast, but I doubt that it's going to hit the US. It'll be more of a threat to Bermuda, Atlantic Canada and shipping lanes. Keep an eye on it, though.
5:31 PM PT: I should amend my Katia remarks to say that places like the Outer Banks and Cape Cod might feel some of Katia as it starts to recurve out to sea, but it's unlikely to make a US landfall.
5:48 PM PT: Here's the rainfall forecast from the HPC. The potential exists for 10+ inches, yes inches of rain from about Mobile AL over to the middle of the Louisiana Coast. Areas near New Orleans could get 15-20 inches of rain from this system.