(CNN)The National Hurricane Center believes Isaias -- the ninth named storm of 2020 -- will form in the Atlantic by the end of the day Wednesday.
"The system is expected to become a tropical storm when it is near the Leeward Islands on Wednesday," says the National Hurricane Center (NHC).
This prompted tropical storm warnings to be issued for Puerto Rico, Leeward Islands and Virgin Islands.
A tropical storm warning was issued for the Dominican Republic, from Cabo Caucedo to the northern border with Haiti.
The storm on Tuesday evening was located 340 miles southeast of the Leeward Islands and was moving to the west-northwest at about 25 mph.
It will impact the Leeward Islands by Wednesday and Puerto Rico by Wednesday night into Thursday.
It is already delivering tropical storm-force winds of 40 mph that extend 230 miles outward from the center of the storm system. The winds are forecast to increase in intensity.
Rainfall amounts of 3 to 6 inches are likely, with locally up to 10 inches expected over the next few days across the Leeward Islands, Virgin Islands and Puerto Rico. The heavy rain could lead to flash flooding and mudslides.
Why it is being called Potential Tropical Cyclone Nine
It is not a tropical storm quite yet. The reason this is being called "Potential Tropical Cyclone Nine" is that the storm does not have a round center of circulation, says CNN meteorologist Chad Myers. Instead, it is very elongated. "When a circular center finally forms, that is when it will be called a tropical storm."
By calling it a potential tropical cyclone, it allows countries to issue warnings.
Once it is given the name Isaias -- pronounced (ees-ah-EE-as) -- it will be the earliest storm to begin with an "I" on record. The previous record was set on August 7, 2005, part of the busiest season to date.
This would continue the record-breaking pace of the 2020 Atlantic hurricane season. Hurricane Hanna smashed the record for the earliest storm with an "H" name by 11 days.
There is uncertainty where and how strong the storm will be when it nears Florida
"Every model that I looked at today develops this area into some form of tropical system and turns it toward or north of Puerto Rico," Myers said.
Even though the storm won't threaten land for a few days, the models are consistent in showing the storm tapping into warm waters and strengthening.
"Rarely do you see the convergence of models like you're seeing with this next storm," Myers said. "There's a consensus with this that the storm is going to do something and that it's going to get into that Bahamas area."
But how it interacts over the Leeward Islands and Hispaniola could impact the intensity of the storm.
Hispaniola, the Bahamas, Cuba and Florida should continue to monitor forecasts as changes to both track and intensity are likely, the NHC says.
"It cannot be stressed enough that since the system is still in the formative stage, greater than average uncertainty exists regarding both the short-term and longer-term track and intensity forecasts," the NHC said.