A long-lasting coastal storm will soon hit the East Coast
A long-lasting coastal storm will plague the East Coast with numerous hazards into early next week. Storm alerts for coastal flood and wind cover nearly the entire near-coast region from the Florida Keys to southern Maine.
In addition to scattered flooding downpours from Florida to New England, large swaths of the Southeast and Mid-Atlantic are at risk for major coastal flooding over several tidal cycles. Large, battering waves are also triggering dangerous rip currents at beaches and unsafe boating conditions for mariners up and down the East Coast.
Widespread rainfall totals of greater than 2 inches are on tap from the Southeast shores to much of southern New England, with upward of 3 to 6 inches in some locations, the heaviest probably ending up near the coast.
While the storm is imminent, interactions between dueling low pressure centers at the surface and the jet stream aloft are keeping the situation more fluid than is often the case.
Areas most affected
Zones of heavy rain will cause scattered flooding from Florida northward with the heaviest probably near the shore in the Southeast and perhaps New England. Long durations of nor’easter conditions – onshore winds from the north and east – are anticipated.
The most widespread concern is coastal flooding and the damaging high surf that will impact much of the East Coast. Coastal flood alerts stretch from around Miami to the Boston area and could expand farther northward.
On Friday, coastal flood warnings covered most beaches from near Port St. Lucie, Florida, to the North Carolina and South Carolina border. The Cooper River at Charleston Harbor, South Carolina, topped major flood levels in Friday’s high tide and on Saturday.
“Expect travel delays near the coast, as some low-lying coastal roads will flood, and possibly become impassible,” the National Weather Service in Charleston wrote.
Flooding is forecast to envelop the Virginia Capes on Sunday with locations near Virginia Beach likely to witness major flooding.
On Monday, major flooding is expected at least as far north as central New Jersey.
The general rise in water levels – known as storm surge – will be overtopped by large and damaging surf. Waves of 10 feet or higher are possible in Florida, the North Carolina Outer Banks and perhaps Delaware northward to southeast Massachusetts.
Waves as high as 20 or 25 feet are possible in nearby offshore waters.
High waves and storm surge are driven by the storm’s unceasing winds. An advisory in effect Friday for areas around Jacksonville, Florida, calls for wind gusts up to 50 mph. That threat will shift north, as well.
“Damaging winds are possible across eastern portions of NYC, and Long Island Sunday into Sunday night,” the Weather Service office serving the region warned.
Outside these details, there is still enough uncertainty that it’s worth highlighting what we think we know and what we are less sure we know.
Increasingly certain forecast details
The storm is still coming together, so shifts can be expected. Complex interactions between two upper-level jet stream swirls driving it are causing some late forecast headaches.
Among the things we’re watching, some are more probable than others.
• Rain will be heavy at times, focused near coasts from Florida to the Carolinas through Saturday. Rainfall rates of 1-plus inches per hour were ongoing in eastern Florida, where Orlando and Daytona Beach areas have seen 2 to 4 inches of rain.
• There will be major coastal flooding over multiple cycles and days. At least three dozen water gauges are forecast to see moderate to major flooding from South Carolina to New York thanks to long-duration onshore wind which may peak in intensity for areas near New Jersey to Long Island.
• Portions of southern New England will probably also see a soaking. Any slower initial storm development is less critical to rainfall in New England than the Mid-Atlantic because it juts farther east.
Impacts with bigger question marks
A number of weather models over recent days printed out significant rainfall as far west as the D.C. area – with no consistency, a red flag. Recent consensus is for much less in that area.
A big reason is that the storm is slower to develop because the two upper-level waves feeding it remain separate rather than “phasing,” or combining their power, into a rapidly developing nor’easter.
• Mid-Atlantic rain is less certain than the New England rain despite being closer in the forecast. If a storm is slower to develop, it swings the heaviest rain east after the Carolinas, then north toward New England.
• Heavier rain dropping west and south behind the low Monday is far from a sure thing. While many weather model runs have shown this from New Jersey to Maryland, it is relatively uncommon as a way to get significant precipitation in a storm’s wake.
• Track loops or backtracking of the storm are infrequent. This is a direct response to the convoluted weather model set up aloft and is easing on weather models as the storm closes in.
When will
it be over?
With a blocked-up pattern and plenty of evolution questions ahead, it is hard to be sure on end time. With that in mind, it should be moving east by Tuesday as a strengthening storm gyre over the North Atlantic scoops it up.
A trailing dip in the jet stream on its heels may spark another storm in the Gulf of Maine and eastward, with showers possible across New England again Thursday and a reinforcement of chilly air across the region.