After a rain-filled weekend, 2018 is now the wettest year on record for the State College area.
The most recent count from AccuWeather on Monday evening has the annual precipitation at 59.86 inches, surpassing the previous record of 59.30, set in 1996, with a month left to go.
The rain never seemed to stop this year, starting in February, which saw 6 inches of rain, compared to the average 2.5 inches, according to AccuWeather senior meteorologist Paul Pastelok, took a break in March, then went on almost continuously through November.
“It kind of seemed that no matter what the pattern was specifically at any given time, it just always was going to rain here,” said Steve Seman, Penn State assistant teaching professor of Meteorology and Atmospheric Science. “We’ve had five months this year that were in the top 10 wettest.”
Why was there so much rain in 2018?
The reasons for the seemingly endless rain vary.
In February, Pastelok said there was a big high-pressure system that built up over the southeast coast and pushed off over the Atlantic during the months of March and April and May — the sort of high-pressure system not typically seen until the summer, commonly called a Bermuda High. As fronts came from the west, they kept running onto that block, which made for a cool and wet late winter and early spring.
Summer typically brings drier weather, but that was not the case this year, as 10.15 inches of rain dropped from July 21 to Aug. 3, a period which typically sees 1.62 inches, according to Pastelok, helping to make that summer the wettest on record for this area.
“What was happening in the western U.S. was that a bigger high developed in the northwest and western Canada, and it kept sending down stronger systems into the east. Usually the pattern starts to flatten out a little bit in the summer — you don’t get as many systems, the jet steam’s way north — but this time the jet stream was taking a bigger slip into the east and our stormtrack got pretty active,” he said.
Fall typically brings more rainfall, as Pennsylvania gets hit with the remnants of tropical storms. But one thing that makes this record stand out is that it was done without the significant contribution from a tropical storm.
“We had over 4 inches of rain in September, the remnants of Tropical Storm Gordon, which was a contributor,” Seman said. “Then we got a little bit more rain from the remnants of Hurricane Florence. So we did have some direct tropical contributions, but in general, the wettest part of our year was the later part of summer or early fall.”
In 1996, Seman said it was a blizzard and January with a quick warmup and consequential flooding that helped boost the precipitation totals. This time, it was a series of constant storms, rather than a few major events, which lead to the high precipitation.
“Normally we get a break,” Pastelok said. “Usually we get a drier period, whether it’s in the late spring or the middle of the summer, and we just never got a break this year.”
In November, Pastelok said there were only seven days without rain in some sort of capacity.
“It was just kind of a progressive pattern. We had systems coming in every couple days and persistent south-to-southeast flow from Gulf of Mexico and southwest Atlantic in the fall that all contributed to the tropical moisture that we saw and the heavy moisture,” he said. “We had warm waters. The waters off the Atlantic were running pretty warm here in the fall season, and when you got a fetch wind coming out of that direction off that water and systems coming in from west, you can get a pretty good rainfall.”
It was that lack of a dry period, he said, that contributed to the dismal fall foliage this fall as the leaves never got the chance to dry out and just went right from green to brown and yellow.
Will the rain ever stop?
As we turn the corner into the final stretch of the year, Pastelok said State College area residents can expect a little bit of a break. He said there’s a little bit of rain coming, and a storm meteorologists are watching that might dive to the south and miss central Pennsylvania, but aside from a few snow showers and light precipitation here and there, December should be pretty dry.
That is not expected to last, however, as things are expected to pick up again by the middle of January and into February.
“In February, we could have some pretty big systems coming up out of the south — snow, mixed precipitation events,” he said. “I looked out into the spring and summer, and I can’t make exact predictions, but it doesn’t look like a dry pattern. I’ll just leave it at that.”
Although he doesn’t think 2019 will be another record-breaking year, he does expect it to continue to be wet, as he doesn’t see another dry pattern until about summertime.
Seman said that while it’s hard to predict whether the high precipitation will continue into future years, as weather is highly variable, the pattern does favor wetness — and those future years stand to be wetter than those before them.
“When a pattern does favor wetness, we are more prone to extreme wetness,” he said. “After going 100-plus years of regularness and never having more than 50 inches, then having five of them in like a 23-year period, is pretty notable.”
The 1996 record shattered the previous record of 48.25, set in 1994, by more than 10 inches. After that, 2003, 2004, 2011 and now 2018 have all eclipsed 50 inches, according to National Weather Service records.
That pattern of rainfall can be expected to continue, Pastelock said, as long as the waters off the Atlantic and in the Pacific Ocean remain warm.
“If you look up toward Alaska right now, the waters are running way above normal, and sometimes that contributes to big highs. What happens is, when you have upper-level highs, it’s drier there, the stormtrack goes way up north then comes racing back south into the eastern part of America and you end up getting bigger, deeper, stronger systems,” he said. “As long as that water continues to stay warm, we may get a very active pattern.”