On this very first day of the Atlantic hurricane season, a brand new disturbance, tagged as Invest 91L, has formed in the Bay of Campeche. It has been given a moderate chance, 60%, to develop over the next 5 days as it slowly progresses westward and then northwestward towards the Mexican coastline.
As of now, the system is still quite broad and embedded within a large monsoonal gyre across southern Mexico. Scatterometer passes were unable to find a closed and tight circulation with the disturbance, but it is gradually organizing. The system is situated underneath an upper level anticyclone, which is allowing for low shear, removing all dry air from the surroundings, and instigating upper divergence. All of these factors are favorable for the development of 91L. The only inhibitor at this time is its proximity to the Mexican coastline, as it is possible that an interaction with a separate, weaker disturbance near the Yucatan Peninsula may force it closer to the shoreline. Over time, the plentiful convection should allow for gradual organization, and a tropical cyclone could form over the next few days while it slowly meanders in this same general region.
91L is moving slowly westward under the influence of a mid-level ridge centered over the central Gulf of Mexico. This ridge should slowly strengthen and align from east-to-west to northwest-to-southeast as a cutoff low approaches in from California and northern Mexico by early next week. This interaction will cause 91L, which could be a tropical cyclone by this time, to gain some latitude. The question will be how close it is to the Mexican coastline during this northward turn. If it’s too far inland, it will dissipate, but remnant moisture would stream northward into Texas and western Louisiana. If the system stays just offshore or barely onshore, however, then it may be able to retain some of its energy as it progresses northward and eventually northeastward as the cutoff forces the ridge to weaken and orient from northeast-to-southwest over the Gulf. Either way, the system will likely not be particularly strong given high proximity to land and the northward acceleration, which could shear the storm and could kill it off, if it had not already dissipated due to land interaction. Eventually, whatever is left of the system would move into the upper Texas coast or western Louisiana in this scenario by Thursday.
Regardless of development or landfall, heavy rains will be coming to the western Gulf Coast of Mexico and portions of Texas over the next several days. The EURO is forecasting the possibility for over a foot of rain over the Mexican state of Tamaulipas as 91L moves briefly onshore. Wind impacts from this system will likely be minimal, as none of the reliable models forecast nothing stronger than a minimal tropical storm at this time. An aircraft reconnaissance plane is scheduled to investigate the disturbance tomorrow, if necessary. Further articles will be published if 91L becomes a tropical cyclone or if there is a notable shift in the forecast.