WILMINGTON — Even though the official start of autumn was Sept. 23, the month felt more like mid-July across southwest Ohio, and the National Weather Service in Wilmington confirmed it was also drier than normal with much of the area still in a borderline drought condition.
Brian Coniglio is a staff meteorologist at the weather bureau office in Wilmington. He told The Times-Gazette it was a trio of factors that set up the September heat wave.
“There was a persistent pattern of high pressure in the upper atmosphere that was more typical of a hot period in the middle of summer,” he said. “That ‘dog days’ pattern allowed the sun to bake the ground and the lower atmosphere, and combined with that was a southerly wind flow that allowed those temperatures to reach 90 degrees often during the month.”
He said Dayton recorded 90 degree or above temperatures for eight days, while Cincinnati reached the milestone nine days through the end of the month, with the Queen City recording a 95 degree high which he said broke the record for the single day highest temperature in the city for September.
“The ground drying out as much as it did just perpetuated the problem,” he said. “If the ground is wet, some of the moisture is evaporated and that uses heat, but with no moisture to evaporate that adds a few degrees to your high temperature right there.”
While September brought with it a scarcity of rainfall, the period that began in January and ran through Labor Day was ironically the wettest period ever recorded, National Oceanic and Atmospheric Administration (NOAA) authorities said, with the contiguous U.S. having its wettest year to date at nearly 28 inches of rainfall.
The above to much-above-average precipitation stretched from coast to coast, with record rainfall recorded across South Dakota and into Michigan, and even though locally it seemed as if Mother Nature turned off the faucet after Labor Day, NOAA reported wetter-than-normal conditions extending from the west coast to the northern plains and Great Lakes, with North Dakota experiencing the wettest September on record.
Other highlights from NOAA’s latest monthly U.S. Climate Report included:
• The average U.S. temperature for the year to date (January through September) was 55.8 degrees F., 0.8 degrees above the 20th-century average, which ranked in the warmest third of the record.
• The average temperature for September across the contiguous U.S. was 68.5 degrees F. (3.7 degrees above the 20th-century average), which ties 2015 as the second warmest September on record.
• The average precipitation for September in the contiguous U.S. was 2.42 inches (.07 inch below average), which puts the month in the middle third of the 125-year record.
• Record dry conditions were present across Mississippi, Alabama, Georgia, Florida, Kentucky and West Virginia.
• The long-term wet streak continues, with average precipitation across the lower 48 states for the 12-month period October 2018 through September 2019 at 36.45 inches, 6.51 inches above average, which ranks as the wettest 12-month period, and the fifth wettest among all 12-month periods on record.
• An early winter snow storm impacted the northern Rockies from Sept. 28–30, with between one and four feet of snow falling across parts of Idaho, Montana and Wyoming, shattering September records across the region.
As for the outlook through Halloween, Coniglio said the weather service’s long-range predictions are calling for temperatures to be slightly above average, and a milder forecast through the end of the year.
“It’s calling for a pretty good chance for above normal temperatures into November through January,” he said. “It’s also calling for above normal precipitation, and then some colder air blowing in from the northwest later in the winter, say around late January and into February, but still a prediction for above normal temperatures.”
Reach Tim Colliver at 937-402-2571.