Tropical Storm Isaias strengthened into a hurricane early Friday as it pulled away from the Dominican Republic and headed towards the Bahamas. Meanwhile, the threat to the East Coast is starting to increase.
As of early Friday morning, Isaias was centered about 45 miles southeast of Great Inagua Island in the southeastern Bahamas, and was moving toward the northwest at 18 mph. Maximum sustained winds have increased to 80 mph based on recent data from reconnaissance aircraft. A Hurricane Warning is in effect for the northwestern, central, and southeastern Bahamas.Tropical Storm Warnings remain in effect for the entire Dominican Republic, the north coast of Haiti and the Turks and Caicos Islands. A Tropical Storm Watch is in effect for the east coast of Florida from Ocean Reef to Sebastian Inlet.
The short-term forecast for Isaias is rather simple. It will continue to move toward the northwest across the Bahamas while gradually slowing down. Waters remain very warm in this area (29-31C), and wind shear shouldn’t be that strong, which will allow Isaias to strengthen a bit more over the next day or two.
Once Isaias gets into the northwestern Bahamas, things get a bit trickier. A large high pressure area in the western Atlantic, and a trough of low pressure moving into the eastern United States will help to steer Isaias more towards the north-northwest, and then north, and eventually northeast. Exactly when those turns occur is critical to the forecast.
The current forecast calls for Isaias to make the northward turn east of Florida, sparing the Sunshine State from the worst of the storm. It may be close enough to bring some gusty winds and heavy rain to east-coastal Florida over the weekend, which is why the Tropical Storm Watch has been issued. That watch will likely be extended farther north on Friday. After that, it will head towards the Carolina coastline late Sunday into Monday. This is where the uncertainty is magnified.
If the Western Atlantic high is stronger than currently expected, or if the trough moving into the East is sharper than the models are currently showing, then Isaias will continue northward, likely moving across eastern North Carolina. A weaker high or flatter trough, would allow for a more northeastward movement, which could allow Isaias to only graze the Outer Banks or possibly even miss them completely.
Once the storm is beyond the Carolinas, there is more uncertainty with its track. Again, a more northeastward motion would bring the storm out to sea with little additional impact to any land areas. A motion that is more toward the north-northeast or even north would increase the threat to parts of the Northeast, including New England, for late Monday or Tuesday. As this point, coastal residents from Florida to New England should all keep tabs on the storm’s progress, as it could impact a large stretch of coastline this weekend and early next week.
If Isaias does make its way to New England as a hurricane, it would be extraordinarily early in the season for an impact up here. The earliest that a hurricane has ever made landfall in New York or New England was when Hurricane Belle slammed into Long Island with 90 mph winds on August 9, 1976. Hurricane Arthur passed just offshore of Nantucket on July 4, 2014. While it did not make landfall, it made for a rather wet and cool holiday, especially across Cape Cod and southeastern Massachusetts. Statistically, the most likely time for a hurricane to hit New England is between the middle of August and late September. Of the 18 hurricanes that made landfall in New England or Long Island since 1851, 16 of them have done so between August 19 and September 27. Since 1951, 36 storms have made landfall in New York or New England as tropical storms or hurricanes, but only 5 have done so before August 5.
- An Unnamed Tropical Storm crossed Long Island on May 30, 2008 with winds of 45 mph.
- An Unnamed Tropical Storm made landfall new Newport, RI on July 21, 1916 with winds of 70 mph.
- Tropical Storm Cindy made landfall near Falmouth, MA on July 11, 1959 with winds of 60 mph.
- Tropical Storm Agnes made landfall near New York City on June 22, 1972 with winds of 65 mph.
- Tropical Storm Beryl crossed Nantucket with winds of 50 mph on July 21, 2006.
If it seems like we’ve been talking about this storm for a while, it’s because we have. Isaias was well-advertised by the models for almost a week before it finally developed over the eastern Caribbean on Wednesday. We even mentioned it in our Weekly Outlook early Monday morning. It has produced wind gusts of up to 60 mph and heavy rain that produce flooding across parts of the Virgin Islands, Puerto Rico, and the Dominican Republic. Wind gusts as high as 54 mph were also reported in the Turks and Caicos Islands Thursday evening.