On June 29, 2012, a massive severe storm impacted millions of people from Iowa to the east coast of Virginia. This storm, which was later classified as a derecho, took place in under 24 hours moving at an average pace of 60 mph. The SPC noted that the derecho travelled approximately 700 miles in under 12 hours!
General thunderstorms had began to form over eastern Iowa where a “modest band of moist, southwesterly low-level winds (known as the “nocturnal low level jet”) intersected a weak stationary front.” The fronts extension into Pennsylvania provided the derecho’s path for the remainder of the day. An elevated mixed layer deepened the storms severity despite not having a jet stream disturbance. The storms in Iowa produced severe hail and damaging winds. When the storms entered Indiana, they began to “bow” as seen from the image above. In bow-echoes, the main threat is damaging winds because the storm is drawing winds from behind and pushing it forward making the storm “bow.”
As the parent storm over northern Indiana strengthened, new storms to the south began to contribute as surface heating destabilized the region. The two systems joined forces and rapidly intensified as they moved into Ohio. A wind gust of 91 mph was recorded at Fort Wayne which was the strongest wind gust ever recorded in June and July in the last 61 years of recording. The Storm Prediction Center noted that the derecho reached its peak intensity over the southern half of Ohio where numerous trees were downed, roofs were damaged, people were injured and deaths were reported. As the derecho tore through West Virginia, the storm slightly weakened as it crossed over the Appalachian Mountains. Even with slightly weakening, the system still produced very high winds. After crossing the mountains, the system regained some strength producing wind gusts between 65-75 mph in Washington, D.C. The 9-1-1 service was interrupted due to power outages. Cellphone service was halted due to towers and telephone poles being down. As the storm continued east, the winds weakened to approximately 60-70 mph as it entered the Tidewater and Delaware. Numerous trees had fallen and two deaths were reported in New Jersey when a tree fell on their tent.
This derecho was not the first in this area, however, it was the first to gain headlines. The SPC noted that this system was “not-well forecasted,” however, this event will serve as a tool to use for the next event. To read the SPC’s full report, and for more graphics, click here!
For more on weather history, click here!
ⓒ 2017 Meteorologist Brandie Cantrell