On Friday, an intense line of thunderstorms moved across the Midwest and Mid-Atlantic, producing very strong winds and widespread damage to trees, power lines, and homes. The storms developed in the Chicago area and tracked rapidly east-southeastward along a weak stationary front, moving across northern Indiana, much of Ohio, West Virginia, and then into Washington, DC. The stationary front separated very hot, humid air to the south from (slightly) less hot, drier air over the Great Lakes. The first image is storm reports from Friday, clearly showing the path of this storm. Wind gusts between 70 and 95 mph were common along this path; several people were killed (mostly in car-related accidents with trees) and millions were without power. Long-lived thunderstorm complexes producing straight line winds are called derechos. These systems are not uncommon in the summer months, usually over the northern United States or southern Canada. This one was particularly notable though for its track through heavily populated areas, and that it cut power to millions during an intense heat wave.
The second picture is a series of radar images as the derecho moved across Indiana and Ohio. Note how over time, the line of storms expands and takes on a arc-like shape. The strongest winds are usually found near the center, or apex, of the bow. Some weather and media sources have started referring to this system as a 'land hurricane', because wind gusts were equivalent to minimal hurricane strength. Really though, the term 'land hurricane' is inappropriate for this system. This name only serves to confuse the general public and implies that Friday's event was a new phenomenon that has not occurred before. Hurricanes are large, slow moving systems that feed off warm ocean waters. Hurricanes do not form, and are not associated with, frontal boundaries. The derecho that occurred on Friday was extremely fast (moving at 75+ mph) and developed along a stationary front, the interface between two dissimilar air masses. Clearly, the comparison is bad at best.
On Friday, an intense line of thunderstorms moved across the Midwest and Mid-Atlantic, producing very strong winds and widespread damage to trees, power lines, and homes. The storms developed in the Chicago area and tracked rapidly east-southeastward along a weak stationary front, moving across northern Indiana, much of Ohio, West Virginia, and then into Washington, DC. The stationary front separated very hot, humid air to the south from (slightly) less hot, drier air over the Great Lakes. The first image is storm reports from Friday, clearly showing the path of this storm. Wind gusts between 70 and 95 mph were common along this path; several people were killed (mostly in car-related accidents with trees) and millions were without power. Long-lived thunderstorm complexes producing straight line winds are called derechos. These systems are not uncommon in the summer months, usually over the northern United States or southern Canada. This one was particularly notable though for its track through heavily populated areas, and that it cut power to millions during an intense heat wave.
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