Source: Corey Davis, NC CLIMATE OFFICE, 6/8/20


The early onset of hurricane season included two storms visiting North Carolina in May. They helped make it a wet month, as well as a cool one across the state.

The Tropics Storm to Life
The 2020 Atlantic hurricane season didn't officially begin until last Monday, June 1, but the ocean and tropical atmosphere have operated on their own schedule so far this year.

A pair of named storms formed in May, and both affected North Carolina, from the shoreline to the summits in the Mountains and Foothills.

Tropical Storm Arthur developed from a lingering low pressure system over the Bahamas on May 17, and it continued tracking up the southeast coast and paralleled the North Carolina coast before turning eastward.

While the center of Arthur stayed offshore, its outer bands lashed the southern coast with 3 to 5 inches of rain, including 5.08 inches over three days at the Croatan RAWS station in Newport. The storm also produced high surf and, farther up the coast, overwash and beach erosion along the Outer Banks.

Later in the month, Tropical Storm Bertha formed in a similar location with a similar atmospheric setup as Arthur, but its track took it onshore north of Charleston, SC, on May 27.

As the remnants of Bertha moved inland, the center of the low pressure system crossed North Carolina. Rain from the storm totaled 2 to 4 inches across the southern and western Piedmont.

While storms outside the bounds of the traditional June-through-November hurricane season are somewhat unexpected, they haven't been too unusual in recent years. Every year since 2015, at least one named storm has formed before June 1, and 2020 is the ninth year since 1851 with at least two pre-season named storms.

Many of these systems have targeted North Carolina -- including six of the ten pre-season storms since 2012 -- and that's not a coincidence. Through the late spring and even early summer, some of the warmest water in the Atlantic basin is in the Gulf of Mexico and the Gulf Stream off our east coast.

Disturbances such as stalled frontal boundaries in these areas can more easily develop into tropical characteristics, fueled by the warm ocean water beneath them.

A kick northward by the subtropical steering currents can then bring them near or over land, and when that happens in North Carolina, the result can be some abnormally wet weather well before we usually expect such an influx of tropical moisture.

Water, Water Everywhere
As a landing spot for tropical storms and a moisture dumping ground for a slow-moving low pressure system, North Carolina received plenty of rain in May. The National Centers for Environmental Information (NCEI) reports the statewide average precipitation was 7.45 inches, making it our 3rd-wettest May out of the past 126 years.

It may seem hard to believe given how wet we were in the last two weeks of the month, but prior to Arthur's arrival, May began with several dry weeks and limited precipitation, especially in the Foothills and Piedmont.

In the first 15 days of the month, Marion recorded just 0.14 inches of rain while Greensboro had 0.11 inches. In the second half of the month, though, Marion added an additional 8.23 inches while Greensboro picked up an extra 9.34 inches, becoming the 2nd-wettest May on record there after only 1905.

Several Mountain and coastal sites weren't quite so dry early on, so their monthly accumulations were even greater. The Transou station in Ashe County reported 12.79 inches in its wettest May dating back to 1946. In Ocracoke, the 9.18 inches ranked as the 2nd-wettest May out of 35 years with observations.

For the full report, click here.