Heavy rains are predicted to drench large areas of the Southeast and Mid-Atlantic, as well as New England.
“Flash and urban flooding, some of which may be significant in the coastal Carolinas and Virginia, is expected through midweek along and near the path of Isaias along the U.S. East Coast,” the National Hurricane Center wrote.
Along the coast, the storm will push ocean water ashore, resulting in flooding. When Isaias makes landfall in the Carolinas, the National Hurricane Center is warning of a “dangerous” storm surge that could result in several feet of inundation.
Areas at particular risk of storm surge flooding include Charleston and Myrtle Beach, S.C., and Wilmington, N.C., and eventually vulnerable areas in coastal Virginia.
Isaias now and its track and intensity forecast
As of 11 p.m., Isaias was centered 50 miles east of Cape Canaveral, Fla., moving north-northwest at 9 mph. The storm’s maximum sustained winds are 70 mph, making it a strong tropical storm. (The threshold for hurricane intensity is sustained winds of 74 mph.)
Although it is passing over warm water, which would ordinarily support strengthening, Isaias has battled dry air and wind shear since Friday, which has not allowed it to become well-organized. Wind shear occurs when winds change in strength and/or direction with height.
Despite hostile influences, the Hurricane Center found Isaias has intensified slightly since Sunday morning, and it could even regain hurricane intensity before landfall in northern South Carolina or in North Carolina on Monday night. Its official forecast calls for small fluctuations in strength and for its peak winds to remain around 70 mph until it comes ashore.
Along Florida’s east coast, the storm’s outer rain bands have produced periodic showers and gusty winds, sometimes reaching tropical-storm-force. However, dry air west of the storm center has cut back on the rainfall, and on Sunday afternoon and evening, shower coverage was rather spotty.
Generally, because Isaias’s center has remained just offshore and its heaviest rain and strongest winds are to the east, Florida has avoided serious storm damage.
Link: Radar loop of storm
The Hurricane Center forecasts Isaias to remain a tropical storm as it surges up the East Coast through Wednesday, with the greatest threat coming from the storm’s heavy rains and coastal surge, and damaging winds confined to coastal areas closest to the storm center.
From the eastern Carolinas into the Northeast, the storm may interact with other weather systems to create periods of heavy rain on Monday into Tuesday. More than half a foot of rain or more could fall somewhere in the corridor from Raleigh, N.C., to Washington to New York, some of which could fall well ahead of the tropical storm itself.
A tropical storm warning extends from Sebastian Inlet, Fla., to Fenwick Island, Del., and is likely to be extended north with time. This warning zone includes Melbourne, Daytona Beach and Jacksonville in Florida; Savannah, Ga., Charleston, S.C., the North Carolina Outer Banks, Virginia Beach, and Ocean City, Md.
A tropical storm watch extends northward from Fenwick Island to Watch Hill, R.I., including the Chesapeake Bay, the Tidal Potomac River, Delaware Bay, Long Island and Long Island Sound.
Since the storm is unlikely to move inland over Florida and push large amounts of ocean water into the coastline, the Hurricane Center discontinued the storm surge watch along Florida’s east coast. Even so, minor storm surge inundation is still possible from Sebastien Inlet north, especially around high tide.
The Hurricane Center issued a new surge warning from Edisto Beach, S.C., to Cape Fear, N.C. This includes Charleston and Myrtle Beach, S.C., near where the storm is more likely to come ashore.
A storm surge watch is in effect from Cape Fear to Duck North Carolina, including Pamlico and Albemarle Sounds.
A mandatory evacuation order was issued for Hatteras Island in North Carolina effective Sunday at 6 a.m.
Before skirting the Florida coast as a tropical storm, Isaias caused damage in Puerto Rico, the Dominican Republic and the Bahamas as a hurricane.
On Friday and Saturday, the storm drenched the southeastern and central Bahamas, buffeting the islands with hurricane-force winds. It was also expected to produce several feet of storm surge inundation. The northwestern Bahamas caught the brunt of Isaias on Saturday as it closed in on Florida, making landfall on northern Andros Island midday Saturday.
Impacts on Florida
Wind gusts could top 60 mph right along the Treasure and Space coasts Sunday night. Farther inland, isolated gusts could reach 45 to 55 mph.
One to three inches of rain are possible before the storm pulls away.
Impacts from Georgia through the Carolinas
Sunday night through early Tuesday morning, Isaias will parallel the coast of the southeastern United States, causing strong winds and squally weather in southeastern Georgia before potentially making landfall near the South Carolina-North Carolina border late Monday or early Tuesday just below hurricane strength.
Heavy rain and flooding, tropical-storm-force winds and coastal flooding are possible in coastal Georgia and the Carolinas.
Just north of wherever the center comes ashore, the Hurricane Center says a “dangerous storm surge” is possible. This is most likely in the zone from Edisto Beach, S.C., to Cape Fear, N.C., “where water rises of 2 to 4 feet above ground level are possible.”
The Weather Service office serving Charleston is advising coastal residents to “[p]lan for life-threatening storm surge flooding of greater than 3 feet above ground” and the possibility of evacuations. Charleston has seen increasing instances of coastal flooding in recent years as sea level rise and land subsidence combine to make the city more vulnerable.
A slightly lesser, but still dangerous, storm surge of one to three feet is project along the North Carolina Outer Banks.
Over a broad area of the Carolinas, including inland locations, the Weather Service predicts three to six inches of rain and isolated amounts to eight inches. One to two inches of rain is favored in southeast Georgia.
Where the heaviest rain falls, flash, river and/or urban flooding could occur.
Virginia to Maine
From Virginia Beach to coastal Maine, tropical storm conditions are possible from Isaias between late Monday and Wednesday from south to north. This may include very heavy rainfall, strong winds, dangerous surf and coastal flooding.
Even areas well inland from the coast, including the Interstate 95 corridor all the way west to the southern and central Appalachians, are forecast to receive two to six inches of rain, with isolated amounts up to six to eight inches.
The extremely humid air transported north by Isaias will also interact with a cold front preceding an approaching dip in the jet stream. That will help to focus the rainfall and will probably cause at least isolated flooding issues, particularly in the Mid-Atlantic and along the Appalachians.
In the Virginia Tidewater and Chesapeake Bay, a storm surge of one to three feet above normally dry land is predicted.
Storm sheltering during a pandemic
The coronavirus pandemic complicates the decisions both of local emergency management officials tasked with ordering evacuations and opening shelters, and residents, who may find themselves forced to use them.
On Thursday, the American Meteorological Society released guidance on sheltering during the pandemic, stressing that “if you evacuate to a shelter, you are responsible for your health.” The document notes, however, that states and municipalities that open shelters will most probably provide for social distancing and mask use, among other precautions.
They recommended that residents procure and bring their own sanitation supplies while also following Centers for Disease Control and Prevention recommendations.
The Federal Emergency Management Agency plans to rely less on deployed field teams in areas where community spread of the coronavirus is occurring, instead processing damage claims remotely. In addition, storm planning documents encourage officials to consider ordering those not vulnerable to storm surge or other flooding impacts to shelter in place.
Getting to “I” in July: Isaias in historical perspective
Isaias became the ninth named Atlantic storm of 2020, which does not usually develop until closer to early October. It’s the earliest “I” storm on record by more than a week, and the latest domino to topple in a season that has also brought the earliest-forming C, E, F and G storms on record in the Atlantic — Cristobal, Edouard, Fay and Gonzalo. Including Isaias, 2020 has produced five named storms in July, tied for the most on record with 2005.
It is the first time on record that the last week of July has produced two hurricanes (Isaias and Hanna) in the Atlantic.
Matthew Cappucci contributed to this article.