WRAL WeatherCenter Blog

Lightning in our state - when, where and why

Posted January 9, 2012

The National Weather Service office in Raleigh is highlighting some of their research efforts and results this week, and I thought I'd pass along a link to one product that puts together some nice information about lightning strikes in North Carolina, in a compact but information-rich poster format. They've utilized lightning strike data of the type that you see us display on the air in real-time when storms are in the area to develop a climatology of lightning in our state based on the period 2003-2010.

The poster includes a nice series of maps showing strike density (and percent of positive flashes, which tend to be more intense and longer lasting, thus more damaging and deadly) around the state on an annual basis as well as broken down by season, bar graphs illustrating how lightning is distributed through the year (as you might imagine, strikes in the Raleigh area are strongly concentrated with in the May-August time frame) and throughout the day (showing a peak in the Raleigh area around 4-6 PM), and other pieces of interesting information, for example that our part of the state experiences lightning strikes on about 44 days out of the year on average, but Asheville and Wilmington both experience strikes more than 50 days a year (57 and 52, respectively).

They've done a nice job of also providing some bulleted comments to help interpret each set of graphs and tables. If you're interested in thunderstorms and their electrical impacts, be sure to check out the link. Note that it is in pdf format, and you'll probably want to zoom in some to be able to clearly read all the labels and legends.

Of course, right now we're in a part of the year that historically experiences very little lightning, but we will have to keep an aye on a system that will bring showers to the area on Wednesday of this week. Right now, it appears the air may remain a little too stable for thunder and lightning, but it is a close enough call that we couldn't entirely rule it out, especially south and east of the Triangle during the later afternoon and evening.


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  • clif4 Jan 11, 2012

    Thank you for the explanation, as well as taking the time to post it. :)

  • Mike Moss Jan 11, 2012

    Clif4, I haven't found any statistical studies that take a hard look at how well that wives tale verifies, but as with many rules of thumb, the one about thunder and snow within ten days isn't always reliable, but does have a physical basis and so you could say there is some "truth" involved. Thunder in the winter usually requires an upper level pattern with strong northward and southward excursions (something we would refer to as highly "meridional") in order to drive warm, unstable air up into North Carolina. Those same patterns are capable of shifting and introducing deep, very cold air just days later, which can allow follow-on disturbances to produce wintry precipitation.

    Conversely, more "zonal" patterns in which the primary movement of airmasses across the continent are more or less west to east, tend to leave temperatures closer to normal and to produce less in the way of precipitation overall, in the process making both thunder and snow less likely to occur.

  • clif4 Jan 10, 2012

    Has anyone ever done a study on the "urban legend" that, during winter, lightning (thunder) is followed ten days later by a snow fall? I know it doesn't happen every time, but from what I've seen in the fifteen years since I moved here, it happens often enough that it can't just be a coincidence.