Why city was hit with unexpected downpour
Tuesday’s deluge dropped more than 5 inches of rain within 2 hours in Baltimore
Baltimore braced for a second round of thunderstorms in as many days Wednesday, expecting a chance for something like the deluge that flooded much of the city Tuesday evening.
Storms did materialize, downing trees and power lines across much of Carroll, Baltimore and Harford counties, the National Weather Service said. Baltimore Gas and Electric Co. reported more than 28,000 power outages, more than 20,000 of which were quickly restored.
David McMillan, the city’s emergency management director, said city officials were bracing for flooding even as crews worked to assess the damage left when more than 5 inches of rain fell in parts of the city within two hours Tuesday. He urged residents to document damage and high-water marks across neighborhoods city,” said Cody Ledbetter, a National But on Tuesday, the atmospheric action in Southeast Baltimore and elsewhere as Weather service meteorologist. “There was more scattered, leaving some areas officials considered setting up a disaster was some instability, so it just kind of with sunny skies and making storms more recovery center to provide assistance. popped off.” isolated.
But unlike on that evening, the flow of That was the first bad turn of fortune. It was not an unusual setup for summer the atmosphere overhead steered storms Then there was the fact that the flow of air in Baltimore, but because the storms were relatively quickly through the region over the region, typically steering storms at so slow and persistent, they dropped an Wednesday. Meteorologists said condiperhaps 30 mph or 50 mph, was nearly unusually large amount of rain in areas tions just happened to align poorly in stagnant. The average flow overhead was prone to urban flooding. Radar estimates Baltimore on Tuesday. about 12 mph, Ledbetter said. suggest as much as 5 inches of rain fell
It might have been a breeze off the Storms developed and then would die within a couple of hours — on par with the Chesapeake Bay, or off another nearby out only for new cells to form right behind deluges that flooded Ellicott City in 2016 storm, that stirred raindrops to begin them, making it appear that a single, and 2018. falling over Baltimore on Tuesday, they massive storm cloud was nearly stationary That was despite what Ledbetter called said. over Baltimore. “pretty average” levels of moisture in the air.Whateveritwas,itcreatedliftthatsent“Theyweremoving,butjustkept the hot, humid air over the region rising forming on the back end (of the storm For the rest of the week and through the into relatively colder levels of the atmossystem) and moving over the same area,” weekend, sunny skies are in the forecast — phere. That triggered a release of instabilLedbetter said. but for only a slight chance of storms ity in the clouds over Baltimore — in the On some days, storm activity is wideFriday, meteorologists said. form of downpours. spread, such as when a large cold front
“It pretty much formed right over the moves across the area.