Tornadoes caught experts by surprise
Meteorologists were expecting some gusty winds and brief heavy rain as a line of storms approached Maryland on Friday. Not multiple tornadoes.
“Plenty of clouds around much of the morning into early this afternoon has reduced the instability that could aid in the intensity of the thunderstorms,” National Weather Service forecasters wrote Friday afternoon.
But instead, storms intensified quickly and produced Maryland’s first tornadoes of 2018, one killing two people at an Amazon warehouse near Dundalk and another damaging roofs at a gas station and shopping center in Mount Airy. There had not been a tornado death reported in the state since 2002.
“It was definitely a very dynamic storm system, and the line of storms strengthened pretty quickly — a lot quicker and a lot stronger than some of the forecast models were predicting,” said Brandon Fling, a weather service meteorologist.
Larger weather patterns did not suggest that severe weather was imminent, as is sometimes more apparent during spring tornado outbreaks or muggy summer weather. The weather service had not issued any tornado or thunderstorm watches Friday, as the agency’s Storm Prediction Center said the region wasat a “marginal” risk of severe storms.
But that label still allowed “an isolated risk for tornadoes,” Fling said.
The weather service issued severe thunderstorm warnings as the weather system moved eastward across Maryland. But it didn’t declare any tornado warnings, as forecasters sometimes do when radar images suggest a funnel cloud has formed.
Tornadoes are notoriously difficult to confirm while they’re happening, unless someone has spotted one or it is readily apparent on radar, according to meteorological research. Forecasters have failed to successfully recognize tornadoes and issue tornado warnings as much as 40 percent of the time in recent years, according to weather service data.
Unless a tornado is sighted, the weather service typically does not confirm a touchdown until it assesses damage after the fact.
And tornadoes are relatively unexpected at this time of year, when cooling temperatures generally reduce atmospheric instability.
“In November, in the evening hours, you don’t typically see tornadoes in bigger cities,” said Alan Reppert, a senior meteorologist with AccuWeather.com.
In this case, temperatures had surged into the lower 70s both Thursday and Friday, setting up a clash between warm, moist air and cold, dry air as a front approached Friday night.
Similar warmth is expected to create a risk of severe storms across the Mid-Atlantic and Southeast on Tuesday — Election Day. Storms are possible in the morning or early afternoon, Fling said.
The Baltimore tornado was classified as an EF-1, second-lowest on the Enhanced Fujita scale, above EF-0. Though that technically made it “a weak tornado,” it was no less deadly. The roof damage and wall collapse at the Amazon warehouse fit a set of damage criteria used to estimate a tornado’s power and determine where it fits on the scale.
Reppert said though EF-1 tornadoes don’t typically cause the mass casualties that are possible in more intense ones, they are always capable of killing. Even a storm with strong wind gusts or lightning should always be considered potentially deadly, he said.
“When you have such a large structure like that fail, and the concrete panels collapse, that definitely creates a hazard that could result in injuries and fatalities,” Fling said.