Tropical Storm Rina has formed in the western Caribbean Sea, the 17th storm of this active season. Convection has been firing strongly since yesterday afternoon, and the previously exposed center is now tucked under the southeast quadrant of the CDO. The daytime today will be a big test to see whether Rina can sustain this level of convection in the face of very dry air to her northwest which is trying to get entrained into her circulation. However, upper-level conditions are improving, and Rina is now moving over progressively higher levels of ocean heat content, which should help fuel gradual intensification over the next few days. A category 1 hurricane at least is looking more likely now that Rina has put on a good show, though how much she has really strengthened is yet to be determined by the next recon plane. With 3-4 days over water ahead of her, Rina could easily become a strong Cat 1 or weak Cat 2 before interacting with the Yucatan Peninsula.
Rina is stuck in weak steering currents, but some general guiding influences will shape her track. Broad troughing over the southeast U.S. is being replaced by ridging during the next 48 hours, which should curve Rina westward towards the Yucatan. With pressures very high over Central America, the models showing Rina diving WSW into the continent look unrealistic, especially since she is a stronger system than they forecast, which should help keep her north. In 4-5 days, a new trough is forecasted to dig into the southern U.S., which should erode the ridge and allow Rina to resume a northerly motion near the east coast of the Yucatan. This could end up in a nasty swipe for Cancun and surrounding areas. A northeast escape and absorption into the jetstream would then seem likely, with a track near Cuba or southern Florida. However, this is 5 or more days away still, and details are going to be hard to work out until Rina starts to make the turn.
Cuba, Florida, and the Bahamas should watch Rina, as she could be a fairly potent storm coming out of the Caribbean, but conditions will likely deteriorate quickly north of about 22N, as the jetstream will be screaming directly across the Gulf of Mexico, imposing shear on any system trying to leave the Caribbean waters. Thus, weakening is expected after Rina recurves northeastward. There are still a lot of uncertainties in a track this slow and fragile, but the Yucatan from Belize to Cancun should keep a close eye on what could become Hurricane Rina eventually if she survives today and continues to organize.
We shall see what happens!