Bertha brings more rain to western Virginia
As quickly as Tropical Storm Bertha sorted itself together in the warm water off South Carolina on Wednesday morning, it dissipated into a tropical depression by the afternoon after coming ashore.
Bertha’s status as the second named storm of the Atlantic hurricane season was easy come, easy go.
But all along, the rain associated with it has been of far more concern than the wind.
That soggy low pressure system was due to spread additional rain across already-soaked southwest Virginia by Thursday morning and renew the risk of flooding.
The six-hour tropical storm
Bertha emerged from a mass of rain and storms that plodded up Florida’s Atlantic coastline since the weekend, but odds of a proper tropical storm spinning up still seemed slight as late as Tuesday evening.
But after the low pressure formed a coherent circulation and winds ramped up, the National Hurricane Center christened Tropical Storm Bertha shortly after 8 a.m. Wednesday.
About ninety minutes later, it came ashore near Mount Pleasant, S.C., just east of Charleston.
Bertha’s winds were minimal in both size and strength: peaking at 50 mph within a compact zone stretching just 25 miles from the center.
By 2 p.m., Bertha had weakened to a tropical depression over central South Carolina with sustained winds of 35 mph.
Unwelcome rain for western Virginia
As of Wednesday evening, Bertha’s swirling clouds and rain were on a course to spread 1 to 3 inches of rain into the foothills and mountains of North Carolina and Virginia overnight, along with locally higher amounts up to 5 inches.
For areas already drenched by up to 10 inches of rain last week, it could be the trigger for creeks and rivers to once again rise into homes and roads.
A flash flood watch was posted until Thursday morning for the region surrounding Roanoke, Lynchburg, Danville, Martinsville, Blacksburg, Lexington, Wytheville, Galax and Bluefield.
The National Weather Service in Blacksburg also cautioned that the system’s weaker 20 to 30 mph winds could still bring down trees in the saturated areas.
The eastern fringe of that rain was poised to bring lighter totals into metro Richmond and central Virginia.
Fortunately, it’s moving faster than last week’s stalled wet weather pattern.
That remnant tropical low will be scooting well into Ontario by late Thursday, but the sticky air mass it leaves behind across Virginia will fuel scattered afternoon thunderstorms, and possibly a few severe ones.
Landfalling tropical systems, even the weak ones, usually bring along an extra bit of spin and buoyancy in the atmosphere that can translate to a fleeting risk of tornadoes or strong thunderstorm winds.
But the rain chances continuing into our forecast for Friday and Saturday will be due to a front sweeping in from the west and encountering that sticky air mass from the south.
The extra rain falling in the upper James River basin will keep the river levels higher than usual. By the weekend, Richmond’s Westham gauge might flirt with minor flooding for the third time this month, and the fifth time this year.
Sunnier skies — and a less tropical feel to the air — will return by Sunday.
The 2020 season strikes early ... again
Bertha’s short-fused existence is another interesting and early development in the 2020 season, following Tropical Storm Arthur’s brush with the Outer Banks on May 18.
Only a handful of years have seen two named storms develop before the conventional June 1 start date to the Atlantic hurricane season.
Just in the past decade, 2016 brought Hurricane
Alex in January and Tropical Storm Bonnie in late May, while 2012 saw Alberto and Beryl form in the second half of May.
In recent years, the earliest appearance of the “B” storm was Beryl on May 26, 2012. Historically, the earliest known instance was on May 17, 1887.
According to the National Hurricane Center, the average date for the formation of the second named storm is August 1.
Looking past these early storms, large-scale conditions are still expected to favor above-normal activity in the Atlantic when the season’s peak arrives in late summer and early autumn.