Tropical Storm Katia
Katia has slowly gotten better organized and appears to be on the verge of becoming a hurricane. The storm looks very healthy on satellite imagery this afternoon with nice curved convective bands. Katia continues to move slightly north of west way out in the far eastern Atlantic.
Not a lot has changed from in the forecast philosophy for Katia. Katia will continue on a west-northwest track and all model guidance has it going north of the Islands. The 12z data has came in and supports this as well. So it looks like the Islands will not have to worry about Katia.
Most of the model guidance continues to re-curve Katia thanks to a parade of troughs through the Great Lakes and northeast US and also possibly due to an enhanced trough caused by the interaction of a shortwave and potentially Lee in the Gulf of Mexico. The 12z GFS shows this but this is far from a certainty.
Although the details of how it will all play out are still sketchy, qualitatively it seems like Katia will get too far north and there will be too many s/w troughs for Katia to not re-curve off the eastern US. Bermuda though could be in the path. This is not set in stone; several GFS and ECMWF ensemble members look more threatening so that scenario is still out there. The 12z ECMWF brings Katia much further west but still re-curves it off the eastern US although Bermuda is threatened.
Right now odds favor Katia not threatening the US, but I would be foolish to write it off this soon with the models still oscillating and it still being 8-10 days off.
Gulf of Mexico
The NHC has raised the area in the Gulf of Mexico to a 30% code orange area. The area is not well organized at the moment as it appears some shear is in the area. This will probably be an area that takes some time to develop. Both the 12z GFS and Euro have a 1007mb low in the northwestern Gulf by Friday morning. They both allow the system to sit in the Gulf and intensify although the GFS is further east near southeast Louisiana and the ECMWF is off the La/Texas border by Labor Day morning.
The GFS then absorbs the storm into a trough in the eastern US as Lee would make landfall in the Florida panhandle. However, it is significantly different than the rest of it’s ensemble members which are further west with Lee in the western Gulf of Mexico as the trough to its northeast bypasses it. This lines up also with the new 12z ECMWF. The euro then strengthens Lee into a category 2 hurricane and moves it to the WSW into southern Texas by next Wednesday. Many of the 12z GFS Ensemble members show the same thing and few show what the operational model shows.
The bottom line is that the global models are showing the development of significant tropical cyclone in the Gulf this weekend and over Labor Day. There is still uncertainty with this as it may get picked up by a trough and threaten the central or eastern Gulf next week, or be missed by this trough and threaten the western Gulf. I would say the odds right no favor the latter scenario.