Spring time in Pennsylvania usually brings its ups and downs. Chilly nights, warm days, even snow, but something we haven’t seen much of this spring…thunderstorms.
There are many ways we can visualize how quiet it’s been. One way is to show the number of severe thunderstorm and tornado warnings issue so far. We’ve only had one issued by our weather service office in state college, and that was a tornado warning up in elk county a few weeks ago. This is lowest number of warnings year to date since we’ve starting keeping track around 1990.
Local storm reports are another way to show this. We’ve had five total this year in central pa, tied-lowest to date in this category since we started keeping track in 2006. In fact, with the exception of the Philadelphia area, much of the northeast and great lakes have seen an absence of severe storms.
So what’s causing such a quiet spring? It has to do with the mid atmospheric weather pattern over the northeast. Typically, for severe storms, we like to see a ridge of high pressure centered just east of New England. In the more active years of 2011, 2017, and 2019, we had this pattern, which pulled in moisture and kept the strongest dynamics nearby. This year, the opposite has occurred. A trough or ‘dip in the jet’ has been centered over the same location, keeping us dry and stable. This pattern has not just kept storms at bay, but we are running drier than normal across much of the viewing area. As of Tuesday, our rainfall departure from normal is around 2” in Harrisburg, and across much of the northeast, rainfall is anywhere between three and six inches below normal. Peak thunderstorm season is upon us, and we’ll begin to see some storms next week, but given how dry this year has started, we have ways to go if we’re going to recover back to near normal rainfall.
-Meteorologist Adis Juklo