The system, which had maximum sustained winds of 40 miles per hour as of 11 p.m. Saturday, is slowly gathering strength and is anticipated to continue to organize as it moves to the northeast, parallel to the Florida and Georgia coast. Breezy conditions and rip currents are likely for the east coast of Florida and coastal Georgia, while the Carolinas may see more significant impacts.
However, there is a risk that the shoreline of the Delmarva Peninsula could be in line for tropical storm force winds, a coastal flooding threat and perhaps a drenching rainfall, depending on how the system evolves and how it interacts with another weather system spinning south from the Midwest.
Approaching upper-air systems lead to forecast uncertainty
In addition to the intensification of the storm, forecast uncertainty is unusually high with Arthur since a broad area of circulation in the upper atmosphere, known as an upper level low, is set to dive south from the Midwest, to a position over the Appalachians early in the workweek. That pinwheeling low pressure system could affect Arthur in a variety of ways, ranging from shoving it out to sea to yanking it inland.
Forecasting the evolution of these slow-moving weather features, which can be cast away from the jet stream’s steering currents, left to drift aimlessly for days, can be difficult.
To make matters even more complicated, another upper level low is dropping south over the Pacific Northwest, heightening uncertainty further.
If the upper-level low — accompanied by a dip in the jet steam — is quick to arrive, it may slingshot Arthur to the northeast, passing over the open Atlantic but bringing an increased rip current risk from the Outer Banks of the Carolinas to southern New England.
But if the trough of low pressure is delayed in its arrival, there would be a window of opportunity for Arthur to be captured and drawn westward by it — with moisture, if not the storm’s actual circulation, moving over land somewhere between the Outer Banks and New Jersey.
The National Hurricane Center has issued a tropical storm watch in North Carolina from New River Inlet to Duck, including Pamlico and Albemarle sounds. Such watches are issued when tropical storm force winds (sustained winds greater than 39 miles per hour) are anticipated within the next 48 hours.
Inclement weather, including the potential for heavy rainfall, is likely to occur in the Mid-Atlantic next week anyway, related to the upper level low. But if Arthur’s moisture is added to the mix, there’s a potential for some torrential downpours and flooding in some areas.
Regardless of what scenario plays out, Arthur is not likely to be a particularly intense storm, limited by a lack of moisture in the air mass surrounding it, according to Hurricane Center forecasters.
Preseason tropical and subtropical cyclones used to be rather rare. After all, hurricane season doesn’t “officially” start until June 1. But they are becoming increasingly common, which some studies show may be a result of warming ocean waters from human-caused climate change.