At 5 a.m., the center of TD #4 was about 1435 miles east of the Lesser Antilles.
Hurricane prediction experts at Colorado State University have increased their estimates on the number of tropical storms they expect in the Atlantic this summer.
However, forecasting intensity has been more hard because it depends on the interactions between the ocean and thunderstorms at the core of a tropical storm, and those interactions happen in an area just tens of miles (kilometers) wide and are hard to observe even with advanced dropsondes, drones and satellites, Franklin said. Four is expected to become post-tropical by Sunday.
Warm water temperatures in the tropical and subtropical Atlantic Ocean along with the dwindling chance of El Niño's development later this summer, are contributing factors to CSU's updated forecast predicting more storms. Conditions ahead of it, toward the Caribbean, aren't as conducive to tropical systems at this point, Cangialosi said.
The probability for at least one major hurricane - Category 3, 4 or 5 - making landfall along the entire US coastline is 62% compared with the 52% average over the last century, researchers said.
Forecasters are keeping an eye on a tropical disturbance in the Atlantic that has a high chance of becoming a full-fledged tropical storm within the coming days.
2017 has so far seen three named storms: Tropical storms Arlene, Bret, and Cindy.
The first, Tropical Storm Arlene, was noteworthy because it formed over the open Atlantic in April, which doesn't happen often. Hurricane Matthew, which scraped the coast in 2016 as a minimal hurricane, did more than $100 million in damage. According to forecasters, a named storm forms in June once every other year.