Reader Ron Vecchia submitted this photo of the clouds over Winthrop Beach on Wednesday.

By Melissa M. Werthmann Globe Correspondent

A clash between two air masses Wednesday in Massachusetts generated the violent thunderstorms that pounded Eastern Massachusetts and produced a microburst in Arlington. But the storms did not spawn a tornado, a National Weather Service meteorologist said Thursday.

Charlie Foley said the service issued a tornado warning at 2:04 p.m. Wednesday for parts of Essex and Suffolk counties after radar equipment picked up rotation in the clouds. But no tornado touched down, and the warning was called off after 30 minutes.

The service also fielded reports of a funnel cloud over Peabody, but Foley could not confirm that one actually occurred.

“We didn’t have anything on radar to back that up,” he said.

Foley said ominous-looking, black cloud formations, known as “wall clouds” are often confused for funnel clouds.

Meanwhile, in Arlington, a weather service crew met with the fire chief and confirmed that a microburst hit the area, ripping down trees and knocking out power in dozens of homes.

A microburst is a strong rush of wind downward, which spreads out as it reaches the ground, said meteorologist Rebecca Gould.

“It’s like throwing a rock in a pond,” she said. Once the rock touches the pond, water ripples outward. When a microburst touches the ground, strong gusts of winds radiate outward, drastically changing wind direction and speed. Microbursts typically affect an area of 1 to 2½ square miles and last less than five minutes, she said.

The crew was able to confirm a microburst by using radar information, analyzing how trees fell, and checking the size of the damaged area.