From drought to floods: 'We never saw it coming'

University Park, Pa. -- It seems like it hasn't quit raining since Bryan Swistock voiced worries in mid-April about an impending groundwater drought in Pennsylvania. After the floods at the end of June that caused millions of dollars worth of damage in the eastern part of the state, he's not sure whether he should be pleased he was wrong.

"We really missed that one, didn't we?" said the Penn State Cooperative Extension water resources specialist with a chuckle. "We went from a drought situation to floods in the span of a week. We never saw that coming."

In reality, April and May brought below-average amounts of precipitation across the state, worsening the drought, before the deluges of June washed in. State officials had declared a drought watch in April after an unusually warm, nearly snowless winter was followed by one of the driest months of March on record. Swistock -- who monitors groundwater levels across the state -- pointed out that streams and groundwater levels in southeastern Pennsylvania were already extremely low.

"I don't like the way this is shaping up for our groundwater supplies," he said then. "A drought is never a good situation to be in, but for us to be this dry, this early in the year, is a very bad thing."

But June changed everything, and state officials lifted the drought watch for the whole state on the last day of the month after a storm wobbled up the East Coast and stalled over eastern Pennsylvania. "It was never called a tropical system, but it looked almost like a hurricane as it spun up the coast -- it was a really interesting system," Swistock said. "It brought a lot of tropical moisture with it."

For the eastern third of the state, according to Swistock, June delivered so much precipitation that most counties recorded 7 to 10 inches above normal for the month. "That means that some counties got 15 inches of rain in one month -- that is pretty extraordinary," he said. "Conversely, counties in the central part of the state received just a few inches more than average for June, and precipitation in most western counties was close to average."

Despite the wet month of June, Swistock notes, there are still spots in Pennsylvania where groundwater levels remain below normal. "Groundwater is always the last thing to respond in the summertime because it is so hard to get water into the ground past the thirsty plants," he said. "But for the most part, groundwater across the state has recovered.

"We almost always come out of droughts because of tropical moisture from the remnants of hurricanes," Swistock added. "That is how we end droughts in Pennsylvania. But what made the storm that came at the end of June unusual is that it arrived in early summer, and not in the fall. It is uncommon to get that much tropical moisture this early in the summer."

Swistock hopes the June storm that caused so much flooding isn't a sign of things to come. "It just continues the trend of what is happening worldwide that we have been having more extreme weather," he said. "It is just getting harder and harder to predict what is going to happen long-term when you go from drought to floods in just days. It was once very unusual here to get a storm that dumps 10 or 12 inches of rain.

"I am personally convinced -- the scientific evidence is irrefutable -- that global warming is happening and that it is behind a lot of the extreme weather events that we have been seeing over the last 10 years or so," Swistock added. "Now whether human activities are causing or worsening the phenomenon, I can't say. But I am sure about this -- even though weather models are improving, these extreme weather systems are throwing everything out of whack. I have gotten less and less confident about long-term weather predictions."

With another extremely active hurricane season predicted, Pennsylvania could be in for another wet fall. "That is about the only prediction anyone is making now," Swistock said. "We hope we don't see more flooding."