Showers and thunderstorms have become slightly better organized with Invest 90L, currently located over the northeastern Yucatan Peninsula. Strong wind shear and land interaction are expected to limit organization for the next couple of days, but some development is likely by Saturday when it emerges into the central or eastern Gulf of Mexico. The National Hurricane Center (NHC) now gives 90L a near zero percent chance of formation within 48 hours, but a 60 percent chance within five days. The main threat with 90L is heavy rainfall.

As of 18:00 UTC Wednesday, Invest 90L was centered near 19.5°N 88.5°W, and was moving slowly north-northwestward. Maximum sustained winds were 25 knots (30 mph), with an estimated minimum pressure of 1009 mb. Although 90L remains elongated with no well defined center of circulation, 90L is slightly better organized than yesterday, with disorganized shower activity to the east of the center over the Northwestern Caribbean Sea. Land interaction with the Yucatan Peninsula, as well as strong wind shear of about 30 kt (35 mph) is expected to limit organization for the next two days. However, by Saturday, 90L is expected to emerge into the central or eastern Gulf of Mexico. Conditions in the Gulf of Mexico are expected to be marginal at most for development, with sea surface temperatures about 27°C (80.6°F), and wind shear remaining moderate to strong. Nonetheless, conditions may be favorable enough for a weak, sheared tropical or perhaps subtropical cyclone to form. Due to the marginal environment, chances of 90L becoming a hurricane are extremely low.

Global models are becoming more confident that 90L will develop into a tropical or subtropical cyclone, but remain unsure about where 90L will eventually track. Of the 12z Wednesday models, the ECMWF, UKMET and CMC models all predicted 90L would develop into a tropical cyclone. The GFS model, interestingly, develops 90L into a weak tropical cyclone inland Florida. The GFS model continues to have issues with convective feedback, and remains somewhat of an eastern outlier. The ECMWF model is farther west, developing a tropical storm over the central Gulf of Mexico and turning it westward towards Louisiana. It is possible steering currents may become weak when 90L approaches the Gulf Coast, and this could lead to significant flooding to the east of 90L’s center. The GEFS ensembles were bullish on development than the operational GFS, and showed a similar westward turn to the ECMWF (albeit with a farther east landfall over the western Florida Panhandle). The CMC was in agreement with the GEFS, while the UKMET model is slightly farther east. Residents from Louisiana to Florida, as well as the southeastern United States as a whole, should continue to monitor the development of 90L.

The primary threat of 90L remains heavy rain, not strong winds, regardless of whether 90L is classified as a tropical/subtropical cyclone or not. The window for heavy rain will be between Saturday and Monday, making for a messy Memorial Day weekend. As is typical with early-season sheared systems, most of the heaviest rainfall occurs to the east of the center. Isolated tornadoes are also possible in the right-front quadrant, if development occurs. The heaviest rains will likely occur throughout the eastern Gulf Coast (including the western Florida peninsula coast), but the Southeastern United States is likely to receive substantial rainfall as well.

I will be back with another post on 90L tomorrow. The first name on the Atlantic naming list is Alberto.