Storm Damage near Cecil, OH (Picture courtesy of Rick McCoy, Van Wert EMA)
By: Josh Steiner
On May 18th, 2017, a few scattered thunderstorms impacted Paulding County, bringing sporadic straight-line wind damage to parts of the county. The two main areas impacted were near Haviland and Cecil. In Haviland, some power poles and tree limbs were snapped from the first storm. The second storm caused more significant damage to a barn at the intersection of 114 and 87. The damage from both was determined to be due to straight line winds in the 80-85 mph range according to the National Weather Service. In Cecil, a barn sustained significant damage around 4:29 p.m. EDT (according to the NWS) from the first series of storms. The NWS says that there is evidence of weak rotation and so they are still investigating the possibility that the damage was tornado. The information and data cited here comes from this webpage from the National Weather Service: https://www.weather.gov/iwx/SevereWx_20170518
In terms of the technical aspects of the event, and why it was so surprising, is that these storm cells were spawned by weak convergence along a drifting cold front in far northern Indiana. May 18th was a surprisingly warm and slightly humid day across the area, with many areas hitting their first 90 degree day (officially at Fort Wayne International Airport), but only isolated storms were expected by the nighttime. Based on previous forecasts, the atmosphere was expected to become unstable by early afternoon, with CAPE values, or Convective Available Potential Energy (a measure of how volatile the atmosphere is in terms of convection) reaching 1500-2250 J/kg along and south of U.S. 24. Values above 1000 J/kg are generally considered to be enough for decent thunderstorm development when the conditions are right. However, severe weather wasn’t really anticipated because the wind shear throughout the atmospheric column was relatively weak and disorganized. Generally, thunderstorms that form in an environment where the wind strongly changes its speed and direction with height will be more organized and longer-lasting than storms that form in an environment where the wind does not change with height. Even though the “environmental shear” on Thursday was relatively weak, a few thunderstorms became severe because the mid-levels of the atmosphere were relatively dry. The dry air creates a greater potential for evaporation of cloud water. As cloud water is evaporated, the air begins to cool, making it heavier. This enhances the downdraft in a thunderstorm. Every thunderstorm has a downdraft, but in the thunderstorms where evaporation enhances the cooler, heavier air aloft, the downdraft may become more powerful leading to something called a microburst. Microbursts are localized zones where the downdraft accelerates towards the surface, causing localized wind damage in isolated regions. This is exactly what we saw in Haviland and Cecil this past Thursday. In fact, when the storm came through Antwerp, I was watching the storm from my front porch and noticed the wind becoming rapidly stronger in a very small amount of time. Even though the wind wasn’t severe in the town of Antwerp, it was from the same storm that later caused the storm damage in Cecil.
One of the things that we can learn from this event is that severe weather doesn’t alway occur on a widespread, regional level. Localized, isolated severe weather poses some of the biggest challenges to the local forecasters as it is often difficult to pinpoint locations that are more likely to see severe weather on a given day when the probability of severe weather is unlikely. For the most part, this is due to the lack of a more detailed observational network in rural areas, which is especially the case for northern Indiana and northwest Ohio. As long as these challenges are still present to the forecaster, it is even more important that everyone becomes more aware of the weather and the challenges it may pose to you and your community on a daily basis.
