The Hagerstown Almanack Monthly Weather Column
October: Crisp, Fall Ahead?
Wasn’t September a nice change of pace with temperatures?? Now, will we see the first widespread killing frost of the season in October, or do we have to wait until after Halloween?
The biggest pattern driver for our cool temperatures was a weak polar vortex that contributed to a strong high pressure block in Greenland. What does this mean? We saw fewer days with a warm, downsloping southwest wind and more days with a cooler east to northeast wind.
The polar vortex always develops in late August to early September. In its development this year, winds around the vortex have been much weaker than normal. This has allowed the jet stream to become wavier and bring western Maryland and the Potomac Highlands a cooler month overall.
The winds around the vortex will remain weaker than average through most of October. Combined with a likely positive phase of the Pacific North American and East Pacific Oscillation, this will allow periodic cooler spells to push into western Maryland and the Potomac Highlands, particularly during the second half of October.
October 20 is the average date when the first killing frost of the season occurs in Allegany County, but the growing season usually ends by late September in Garrett County. Even with the cold fronts that come through in October, we expect a later than average killing frost in Garrett County. It will occur on October 18. In Allegany County, the first killing frost of the season will occur later in the month, likely within 3 days of Halloween.
Will we finally see rain to fill the reservoirs? Fortunately, a couple of fronts will drive rain into the region, but we will still fall shy of average, which ranges from 2.82 inches in Allegany County to 3.61 inches in Garrett County. Our region is 4 to 6 inches behind average in rainfall since the start of summer, so the drought will continue unabated. The good news is we won’t dig deeper into the upper end of the drought scale (extreme to exceptional levels).
That being said, we will see utilizations in the barometric pressure ahead and behind cold fronts that will foster a dry wind when it’s not raining. The increased dry breeze at times combined with the antecedent drought will elevate the fire risk more so this October than previous years.
The drought will get chipped away in the Tennessee Valley early in October, but it will likely expand back into that region closer to Halloween. A favored western ridge will trigger sustainable hot, dry days that will allow the moderate to extreme drought to expand in coverage and worsen from the central Plains to the northern Rockies in October.
More than 200 brush fires are burning in the central and western U.S. as of late September. A dry, warm pattern will likely instigate more wildfires west of the Mississippi River. At least once in October, western Maryland and the Potomac Highlands will see smokey skies when the upper-level wind flow aligns to bring the smoke across the country.
Now to a bit of risk-taking...we predict the warmest afternoon temperature in our region will be October 9th.
We will see two more named storms in the Atlantic basin in October thanks to cooler air aloft combined with warmer than average Atlantic Ocean temperatures near the Intertropical Convergence Zone. This recipe will help generate clusters of thunderstorms that will be capable of growing into organized tropical systems. Historically, tropical storms and hurricane moisture stays east of Route 220 with October storms though. We believe tropical systems will contribute to 30% or less of our total October rainfall.
The good news for folks in the region is that October will bring episodes of cooler weather that will limitexcessive evaporation and enough rain to keep us out of the danger zone for top 10 driest and warmest Octobers on record. On the contrary, the hot, windy and dry weather in October is the perfect recipe for the drought severity to increase even more from where we stand now (moderate to severe drought).
With the Autumn Glory Festival on the horizon, keep in mind, the drought is contributing to a muted fall foliage season, so not as much color will be found this year with many trees dropping most of their leaves by the time the festivities begin.
Chad Merrill is a Cumberland native and meteorologist who not only serves as the Hagerstown Town and Country Almanack weather prognosticator but has previously been meteorologist with WDVM (formerly known as NBC25) in Hagerstown and at WJAC-TV in Johnstown, Pennsylvania, and most recently, was named chief meteorologist at WOAY-TV in Oak Hill, West Virginia. After a rigourous evaluation, Merrill was awarded the National Weather Association (NWA) Seal of Approval. According to the association, only 1,045 meteorologists currently hold the NWA Seal of Approval. In April, 2023, Merrill, was inducted into the prestigious Marquis Who's Who Biographical Registry! Feel free to contact him at cmweather24@gmail.com or 240-285-8476.
