“Will it ever stop raining?”
A toddler growing up in Lexington, Ky., or Louisville, or in Beckley, W.Va., has lived through those cities’ wettest and driest Septembers, based on weather records going back more than a century.
The bluegrass is turning brown in Kentucky. Lexington had just a trace of rainfall in September and Louisville just .04 inch, the driest Septembers at both cities in weather records dating to the early 1870s. This arid September comes a year after the soggiest September on record with over 10.42 inches at Lexington and 10.91 inches at Louisville.
Beckley’s rainfall plunged exponentially, from almost 10 to a tenth, between the Septembers — 9.98 inches in September 2018 to 0.10 inches in September 2019 — the wettest and driest in records that go back to 1894.
The last two Septembers in Washington and Baltimore reflect a similar theme, just not quite as extreme.
Washington followed its fifth-wettest September in 2018, with 9.73 inches, with its fourth-driest September in 2019, measuring only a quarter-inch of rain — most of it, 0.14 inch, on Monday, the final day of the month. Baltimore moved from its sixth-wettest September in 2018 at 9.19 inches to its second-driest in 2019 with 0.16 inch. Both locations have weather records dating to 1871.
Other locations with more than 100 years of records that just had a top-10 driest September after a top-10 wettest September the year before include:
- Elkins, W.Va., second-wettest (8.16) to second-driest (0.48), data begins 1899;
- Charleston, W.Va., wettest (11.62) to third-driest (0.54), data begins 1892;
- Danville, Va., fifth-wettest (9.64) to driest (0.04), data begins 1916;
- Knoxville, Tenn., seventh-wettest (7.40) to driest (0.03), data begins 1871;
- Nashville, seventh-wettest (6.90) to driest (0.02), data begins 1871;
- Charlotte, fifth-wettest (9.48) to tied for fourth-driest (0.19), data begins 1879;
- Cincinnati, sixth-wettest (6.76) to ninth-driest (0.61), data begins 1871;
- Greensboro, N.C., second-wettest (9.17) to 10th-driest (0.56), data begins 1903; and
- Columbus, Ohio, fourth-wettest (6.57) to 10th-driest (0.85), data begins 1878.
Seasonal patterns in and around September have something of a bias toward drought or deluge, historically, over much of the eastern United States.
For example, a quarter of Washington's 12 wettest months going back to 1871 are Septembers, including the record wettest month with 17.45 inches in September 1934, while four others are Augusts. On the flip side, a quarter of Washington's 20 driest months are also Septembers, with six others being Octobers.
Weather patterns across the Mid-Atlantic, Ohio Valley and Southeast in and around September are often focused either on large high-pressure systems lingering from summer, trapping hot, relatively dry air across the region, or slow-moving troughs of low pressure infused with abundant Gulf of Mexico and/or Atlantic moisture, often including hurricane and tropical storm remnants.
Faster jet stream flow for more progressive patterns that would lead to more moderate amounts of rainfall often remains too far north so early in the opening stages of the transition between summer and fall.
This September is the former example, with strong high pressure at the surface and aloft dominating much of the month over the eastern two-thirds of the country, leading to many record-high temperatures, deflecting cold fronts and inland low-pressure systems to the northwest, and bouncing most tropical systems out to sea.
Last September was more of the latter example, with rounds of gulf and Atlantic moisture scooped across the eastern half of the nation, augmented by the landfall of Hurricane Florence along the North Carolina coast and the slog inland of its remnants northward through the Mid-Atlantic.
Hurricane Dorian’s scrape just off the Southeast coast last month, with eventual landfall on the Outer Banks of North Carolina, kept many locations closer to the coast out of the drought that has developed farther inland.
While no single drought — especially one as short in duration as this one is so far — can be blamed solely on global climate change, studies have pointed toward a tendency for both wet periods and droughts to be more intense as the climate warms, with the implication that some locations could alternately fall under each extreme.
“In a warming climate, there will be more evaporation from surfaces, which include soils … not just oceans, rivers, and lakes,” said Sean Sublette, a meteorologist at Climate Central, in an email. “As a result, the heaviest rain will be a bit heavier, and the drier periods will be drier.”
Sublette cautions that this signal seems to be stronger for arid climates in the West rather than humid climates in the East, although recent extremely hot conditions in the southeast quadrant of the nation appear to have triggered a rapid-onset “flash drought."
September's wetness in 2018 was part of a soggy year that set many records for annual rainfall up and down the East.
That overflow rainfall caused plenty of problems, but it has proved to be a blessing in one way.
“Unquestionably, the wet 2018 (and into early 2019) is having an significant ameliorating effect on the impacts of this developing drought,” said Peter Corrigan, the hydrologist at the National Weather Service office in Blacksburg, Va., via email.
Recent dryness has managed to bring previously high streamflow and groundwater levels back to normal range, Corrigan noted, and most reservoirs are down only slightly from previous full-pond statuses.
“Bottom line: Droughts take time,” Corrigan said. “We are in the early stages of what could become a more significant drought, but the fall-winter precipitation regime will tell how bad it gets.”
Kevin Myatt is an editor at the Roanoke Times and pens a weekly weather column.
