The rare string of tornadoes and severe thunderstorms that ripped through Maryland communities Wednesday night — toppling trees and power lines and injuring five people in Montgomery County — could be the opening act for a busy summer storm season ahead.
The Atlantic hurricane season began June 1 and forecasters believe it could be “extraordinary” this year, said Rick Spinrad, administrator of the National Oceanic and Atmospheric Administration, during a briefing in May.
NOAA’s Climate Prediction Center, based in College Park, also is predicting good odds for above-normal temperature and precipitation this summer in the Northeast, including Maryland.
“If you read between the lines, above-normal precipitation in the summer usually correlates to more rain, more thunderstorms,” said Connor Belak, a meteorologist at the National Weather Service office in Sterling, Virginia.
It’s far too early to predict those storms, or to say whether they could be severe, causing the level of widespread damage observed Wednesday, Belak said. The Weather Service dispatched teams Thursday to assess damage in parts of Frederick, Montgomery, Howard, Carroll and Baltimore counties and Baltimore City, and look for evidence of tornadoes reported by spotters and emergency responders.
But generally speaking, warmer and wetter conditions are key ingredients for summer storms, said Dan Collins, the meteorologist at the Climate Prediction Center who produced the three-month summer outlook.
“These are the elements that we need for thunderstorm activity — increased moisture and increased heat,” Collins said. “There’s some general sense that we may see more storms as a result of the outlook. But we’re unable … to predict severe weather on this kind of time scale of a three-month outlook.”
The Climate Prediction Center’s prediction for Baltimore includes a 44% probability of above-normal precipitation this summer, compared with a 33% chance of normal conditions and a 23% chance of a below-average rain tally.
In general, tornadoes are formed by severe thunderstorms as hot, humid air rises and colder air falls, causing air currents to spin within the cloud. If those spinning currents reach the ground it’s considered a tornado. Tornadoes range in strength, based on wind speed, from EF-0 to EF-5. An EF-0 or EF-1, with winds up to 110 mph, can cause mild to moderate damage much like a minor hurricane or tropical storm, snapping limbs and knocking down trees. More powerful tornadoes can cause extensive damage, lifting cars and ripping homes apart.
Tornadoes are uncommon, but not unheard of in Maryland. Each year, the state experiences as few as a handful to as many as about a couple of dozen. That’s what makes Wednesday’s outbreak with multiple reports of tornadoes in different places so eye-opening.
It is difficult to predict future tornado activity, because they depend on the specific conditions in an area at any given time, said Daniel Gilford, climate scientist at the nonprofit Climate Central, based in Princeton, New Jersey. But, climate change and warming conditions could be contributing to instability in the atmosphere, a precursor for tornadoes.
Each May, NOAA releases a prediction for the Atlantic hurricane season, and this year’s featured the highest-ever number of storms.
NOAA expects there could be 17 to 25 named storms, with winds 39 mph or higher. Not all of those storms would become hurricanes, but many would — and four to seven of those storms could be major hurricanes, with maximum sustained winds of 111 mph or higher.
Warm ocean temperatures in the Atlantic Ocean could be driving the predicted high activity.
“Hurricanes are like giant heat engines. They need some sort of fuel source to spin,” Gilford said.
With the hurricane season underway, the climate pattern in the Pacific Ocean is also likely to quickly transition from a particularly strong “El Niño” to a “La Niña.” The latter pattern is known to be more favorable for hurricanes, because it lessens wind shear in the tropics, making it easier for hurricanes to form.
“It’s kind of a confluence of the worst of both worlds,” Gilford said.
Often, these storms do not travel all the way up to strike Maryland. Their landfall is far more common along the Gulf Coast and the Southeast. But a warming climate could shift hurricanes’ range northward, Gilford said.
“We certainly know that the conditions are ripe for there to be strong storms out there, that they are on average trending further north,” Gilford said, “and that sort of brings Maryland and surrounding states more into focus than they would have been historically.”
