Tropical Storm Dorian formed Saturday afternoon about 725 miles east-southeast of Barbados, according to the National Hurricane Center. It has sustained winds of 40 mph and is expected to strengthen. According to the Hurricane Center, Dorian “could be near hurricane strength when it approaches the Lesser Antilles Tuesday.”

The storm is moving west at about 12 mph and is forecast to turn more to the west-northwest on Sunday while gradually intensifying.

The intensity forecast for Dorian is particularly uncertain, but anyone from the Windward Islands through the Caribbean should be watching this system closely. Puerto Rico, which is still recovering from 2017′s Hurricane Maria, is in the possible path of this storm in about four to five days.

The National Hurricane Center predicts it will strengthen to a Category 1 hurricane by Wednesday, but because it is a compact storm, the intensity forecast is particularly challenging. Such small systems can rapidly intensity or fall apart, and computer models have a hard time projecting their strength.

In the case of Dorian, some models project it to become a hurricane while others suggest it could dissipate entirely once it arrives in the Caribbean.

Storms that form as far east as Dorian frequently escape into the hurricane graveyard of the North Atlantic, deflected by weather systems to their west. However, that isn’t likely in Dorian’s case, given the presence of a sprawling area of high pressure to its north and west.

Dorian isn’t the only tropical disturbance that forecasters are watching. A system developing just off the east coast of Florida also has the NHC’s attention.

Florida disturbance could become Tropical Storm Erin

The National Hurricane Center gives the system near Florida a 70 percent chance of developing into a tropical depression or tropical storm over the next 48 hours and a 90 percent chance over the next five days.

In its Saturday-morning discussion, the Hurricane Center wrote that the disturbance is unlikely to strengthen Saturday, given its proximity to land. But that’s not the end of it.

“Environmental conditions appear conducive for gradual development once the low moves off the east-central coast of Florida over the western Atlantic by Sunday,” it wrote.

The main risks from the disturbance at present are rainfall-related. Parts of South Florida could see downpours today and into Sunday. Some isolated flooding could result, although the most widespread torrential rain seems likely to stay offshore.

Computer models insist that whatever forms from this disturbance will not strike the United States. But because it is likely to parallel the coast between the United States and Bermuda, high waves, rip currents and even some coastal flooding are possible along much of the Eastern Seaboard early next week.

The start of a more active stretch in the tropics

Even with no powerful hurricanes to track, the current flare-up in tropical weather systems is a significant increase in activity, and there are signs it will continue.

Before now, the tropics were unusually quiet. As the Capital Weather Gang’s Matthew Cappucci wrote Friday about storms, “activity has been barely a fifth of what is typically observed by this time of year.” The causes are many, but chief among them has been a layer of dry air and dust blown west from the Sahara, which inhibits storm development, and less instability than usual, which stifles thunderstorm development.

This sudden increase in tropical activity closely aligns with what is often a busy time leading up to the mid-September peak of the hurricane season. Although the Atlantic hurricane season has thus far been relatively quiet, there is plenty of time left until it ends Nov. 30.