Over the past several days, most of the model guidance has begun to latch onto the idea of a tropical cyclone developing over the western Caribbean Sea by Central America. There is a lot uncertainty with this forecast, however. Where this storm will track, if it is a tropical cyclone (and how strong it will be), and how may it impact the United States are all questions that surround this storm. What we do know is that the National Hurricane Center is also keeping close tabs on this area of disturbed weather, designating it as Invest 90L.
A Central American Gyre has developed, and this may allow for a more organized low pressure to form later on in the week. According to the American Meteorological Society, a Central American Gyre is a “large, closed, cyclonic circulation that occurs during the rainy season (May–November), which can yield exceptional rainfall leading to catastrophic flooding and large societal impacts.” Sometimes these gyres can help form a more discrete area of low pressure, which can eventually develop into a tropical cyclone. We’ve already seen this several times during the 2017 Atlantic hurricane season.
All model guidance predicts the development of a surface low pressure around the middle of this week. Whether a low pressure forms or not (which can eventually organize into a tropical cyclone tropical depression, tropical storm, or hurricane), this area of disturbed weather and enhanced convection (thunderstorms) will drift to the north. It will likely head toward the eastern Gulf of Mexico and Florida, a state that has been getting drenched by heavy rain this week. These heavy rains will move in as early as Memorial Day Weekend, and some model guidance suggests numerous inches of rainfall.
If a tropical cyclone were to form, it will either occur over the western Caribbean Sea or the central Gulf of Mexico, where water is warm, air is moist, and wind shear is on the lower end of the spectrum. Environmental conditions are expected to become non-conducive over the northern Gulf of Mexico due to strong winds aided by the jet stream and another upper-level low. This wind shear would make it very difficult for thunderstorms to organize around the surface low.
The key takeaways at this time is to monitor the forecast and expect more heavy rain through the foreseeable future, especially in Florida.