Franklin was centered about 380 miles (610 kilometers) east-southeast of Chetumal, Mexico, late Sunday.
Far out in the Atlantic Ocean, a separate tropical system has a 20% chance of developing into a named storm over the next five days, the hurricane center said. It will continue to spread heavy rain and gusty winds across Mexico's Yucatan Peninsula through Tuesday before emerging over the Bay of Campeche.
By late Wednesday, forecasters in Brownsville say there will be a 30 percent chance of rain increasing to 50 percent on Thursday and then falling to 40 percent on Friday.
Tropical Storm Franklin is showing signs of strengthening as it nears the Yucatan Monday night. Global forecast models are now generally unanimous on this system failing to develop while turning northwest then north by the weekend a little east of Florida - as an "open" tropical wave. However, Cayman Islands forecasters still expected some locally heavy rains overnight with wind gusts between 12 and 18 miles per hour. Franklin could be near hurricane strength by the time it makes landfall on the eastern Yucatan. If it does become a hurricane it will be the 1st hurricane of 2017 in the Atlantic Basin. Storms of course could be strong, and will produce tremendous tropical downpours that could lead to very localized areas of flash flooding.
Landfall probabilities forecast by the Colorado State team remain above average, suggesting a greater threat that a hurricane could strike the USA coastline than in recent years. We have time to track the wave of low pressure as it moves across the Atlantic, but it will need to watched closely next weekend and beyond as it approaches the USA coastline.