The Atlantic remains active Sunday with several areas to watch in the long-range. In the short-term the sixth named storm of the Atlantic season, Fiona, hangs on over the open Atlantic. As of 11 AM EDT max sustained winds are at 40 mph and it moves west-northwest at a brisk 16 mph. The small tropical storm battles dry air and wind shear. Strong westerly shear exposed its center early Sunday. Some showers and storms fill back in late Sunday morning but the storm is still very disorganized. If Fiona can survive this hostile environment wind shear relaxes some early work week as it heads west-northwest. The 11 AM forecast calls for Fiona to dissipate by early Tuesday but the remnants may bring some rain/squalls near Bermuda if any convection remains. Regardless, Fiona is no threat to the U.S..
On the heels of Fiona is Invest 99L between the Lesser Antilles and the Cape Verde Islands. There is still high uncertainty on the future of Invest 99L. On Sunday morning it is nothing more than a tropical wave with some scattered convection. While wind shear is favorable for development plenty of dry African air will keep this process slow, if at all. The NHC bumps the odds of development down to 20% over the next 2 days and 50% over the next 5 days. Squalls will approach the Leeward Islands mid-week.
Until a low-level center forms, if at all, there is error in the computer model forecast for Invest 99L. More models early Sunday trend towards a weak system/open wave through mid-week with a track near the Lesser Antilles Wednesday and Puerto Rico/Hispaniola Thursday. By late week and over the upcoming weekend Invest 99L may tap into some enhanced energy over the warm waters near or east of the Bahamas. The 06Z GFS (which has been all over the place with track and intensity) bites on this solution. Meanwhile the Euro is luke warm on any development at all. The next named storm is Gaston.
It looks like Invest 90L will beat Invest 99L to the punch and become our next named first (the next two names are Gaston and Hermine). The vigorous tropical wave is south of the most extensive dry African air in the Atlantic. There is a bit of moderate wind shear in the vicinity but upper levels are generally conducive for organization. A tropical depression is likely over the next few days as Invest 99L moves westward. The good news is while development appears likely models show a track out to sea (similar to Fiona).
While the long-range forecast calls for a track west-northwest out to sea many intensity models suggest a hurricane is likely over the next 5-7 days. The 12Z suite of models shows anywhere from a tropical storm to a category two hurricane is possible by next Sunday (7 days from now). The future intensity of Invest 90L may play a role is the future intensity of Invest 99L. If Invest 90L becomes a full-blown hurricane Invest 90L is less likely to become a nearby strong tropical system. Stay tuned. There is plenty of time to watch both of these features here in the U.S..