James Eberwine / Derecho’s winds likely topped 100 mph

Residents and businesses are being asked to report storm damage as Atlantic County officials seek to appeal the federal government's refusal for aid to South Jersey homeowners.


The highest wind gust measured in the early morning hours of June 30 was 81 mph in Tuckerton. The highest measured gusts in Atlantic County were 74 mph at the Atlantic City International Airport and also in Absecon. However, the true wind speeds can be inferred by the damage sustained by the type of trees that were snapped or uprooted using a new enhanced wind scale.

The tornado F-Scale that we have all become accustomed to was developed in 1971 by professor Theodore Fujita and has been used by National Weather Service personnel to conduct on-site post-storm assessments. The scale was developed to determine the extent of damage and assign wind speeds associated with tornadoes. However, the scale has also been used to determine the wind speeds in cases of nontornadic straight-line wind events - in this case, a derecho. These events are determined by the debris path, which is pushed along in a particular direction. Such was the case June 30.

An enhanced version of the scale (the EF-Scale) was adopted in 2007 in order to utilize the knowledge of both meteorologists and engineers to arrive at a more comprehensible and realistic evaluation of wind speed.

After viewing the "meteorological crime scene" throughout Atlantic County and applying the EF-Scale, it is easy to come to the conclusion that winds easily gusted over 100 mph, judging by the number and type of trees snapped or uprooted. Thousands of trees came down on homes and power lines, and according to Dave Parker, owner of Tree Works in Egg Harbor Township, it included "every type of species, shape, size and condition." This included not only old or decaying trees, but also many that were very large and healthy.

The EF-Scale addresses damage to two types of trees - softwoods such as pines, spruce, fir, hemlock, cedar, cypress and redwood, and hardwoods such as oak, maple, birch and ash.

The scale suggests the wind necessary to uproot softwood trees would have an expected speed of 87 mph, as low as 73 mph or as high as 113 mph. Softwood trees snapped at the trunk would have experienced a wind speed of 104 mph, as low as 88 mph or as high as 128 mph.

The EF-Scale suggests that the winds necessary to uproot hardwood trees would have an expected speed of 91 mph, as low as 73 mph or as high as 118 mph. Hardwood trees that were snapped at the trunk would have experienced a wind speed of 110 mph, as low as 93 mph but as high as 134 mph.

The derecho that blew through the region had a history of strong winds from Indiana through the Washington, D.C., area and strengthened significantly once it entered several counties of southern New Jersey. Four people lost their lives in the storm, but the toll could have been far worse had the storm not hit in the early morning.

James Eberwine, of Absecon, is a retired National Weather Service meteorologist and the emergency management coordinator in Absecon. To learn more about the EF-Scale, go to www.spc.noaa.gov/fc/tornado/ef-scale.html.