Bertha is forecast to take a curved path near the islands in the northeastern Caribbean, just east of the Bahamas and then northeastward off the East coast of the United States.
Bertha became a tropical storm Thursday night and is the second named tropical system in the 2014 Atlantic Hurricane Season.
While Bertha is expected to remain a relatively weak tropical system, the strength of Bertha will fluctuate. Regardless of intensity, locally heavy rain and gusty winds will occur over part of the Caribbean this weekend.
The system is not likely to become a hurricane and could slip below tropical storm status at any time over the next five days. A tropical storm has sustained winds of 39 mph or greater. A hurricane has sustained winds of 74 mph or greater.
Schedule for Bertha's Impacts
Disruptions from the system will tend to be brief over the Caribbean islands.
While the rainfall from Bertha will bring a risk of flash flooding and mudslides to the islands, it will also bring needed rainfall. Many of the islands in the path of Bertha, especially those from the British Virgin Islands to Hispaniola, are experiencing significant drought.
A general 1 to 2 inches of rain is forecast in the vicinity of Bertha, but local amounts of 2 to 4 inches are possible, especially just to the north and east of the center and in mountainous terrain.
According to AccuWeather Hurricane Expert Dan Kottlowski, "The Windwards and southern Leewards will experience episodes of drenching rain and gusty thunderstorms into Friday night."
The rather swift-moving storm will impact the U.S. and British Virgin Islands during Saturday.
"During Saturday afternoon and night, Bertha will affect Puerto Rico and the Dominican Republic with drenching rainfall and locally gusty thunderstorms," Kottlowski said.
Minimal impact is forecast farther west on Hispaniola for Haiti and on the eastern tip of Cuba, but there can be a couple of locally heavy thunderstorms.
No impact is forecast farther west in the Caribbean, such as Jamaica and central Cuba.
Bertha is forecast to be in the vicinity of the Turks and Caicos on Sunday.
"Bertha or its remnants could still pass close enough to the Bahamas to bring tropical storm-force wind gusts and an inch or two of rain during Sunday and Sunday night," Kottlowski said.
Beyond the Bahamas, Bertha is forecast to curve more to the north then to the northeast. This projected path will keep direct impacts offshore of the U.S. Only a shift farther west than expected would bring the system right along the East coast.
The surf can become rough from northeastern Florida to North Carolina for a time early next week. The greatest risk to bathers will be an uptick in the strength and number of rip currents.
As Bertha interacts with a front pushing off the East Coast of the U.S. during the middle of next week, some rain could reach Bermuda.
Low Hurricane Count for June, July Not Uncommon
The relatively quiet Atlantic tropical season so far in 2014 is not that uncommon. Although the season officially begins on June 1, the most active period does not really get going until mid-August. It is during August and early September, when the waters across the Atlantic are the warmest, and typically, the dry air and wind shear taper off.
Stef Davis and Senior Meteorologist Bernie Rayno explain the ebb and flow of the hurricane season in the video below:
AccuWeather is forecasting a slightly below-average number of tropical storms and hurricanes this season in the Atlantic.
What is Affecting Bertha?
"The system is being steered by the Bermuda-Azores high pressure area," Kottlowski said.
Wind shear was already affecting Bertha on Friday and was preventing thunderstorms from wrapping uniformly around the center of circulation. Wind shear is a zone of strong winds at mid-levels of the atmosphere blowing from the southwest, west or northwest that can prevent a tropical system from forming or limit the intensity of a formed tropical system.
According to AccuWeather Meteorologist Rob Miller, "In addition to problems with wind shear along the projected path, the mountainous terrain of Puerto Rico and Hispaniola will disrupt the wind flow of the storm as it approaches."
It is possible the system struggles to recover from the frictional effects of these large islands early next week as it turns northward. However, if Bertha was to slip in between the two large islands, it could emerge as a stronger system farther north.
The system battled wind shear, cool water and dry air much of this week over the southern Atlantic.