Ask Greg

The most direct way to find your question is to search for the name you used when you submitted it (first name, last name or both). If you did not include a name, then you can search using keywords from your question. Of course, since many weather-related terms are common to a lot of the questions we receive, this may turn up a number of others in addition to your own.

Thanks again for sending your questions to Ask Greg!

Answer: While not exactly the same in long-term averages, the two cities' weather with respect to the type of events you asked about are close enough that other considerations would probably be more important to you, thanks to something of a balance between Raleigh's more northerly latitude and Charlotte's more westerly longitude. In terms of winter weather, both cities average about 4-5 "snowfall events" and about 4-6 "sleet and freezing rain events" per year, with some overlap between those two sets of numbers due to the tendency for winter storms here to produce multiple and rather variable precipitation types. Raleigh averages a little more snow overall, at 7.6" annually versus 5.8" for Charlotte. Thunderstorm days for the region run about 40-50 per year, with Charlotte averaging about 2-3 more days than Raleigh. Most of this information is summarized in various portions of the State Climate Office web site at www.nc-climate.ncsu.edu.
Nov. 1, 2009 | Tags: cool sites, normals, snow, thunderstorms

Answer: For background on the definition and mechanisms associated with the term "heat burst," see one of our Ask the Meteorologist replies from a few years back at www.wral.com/weather/blogpost/1554550/. The combination of conditions that support them are quite rare and they seem to be climatologically favored over the plains states more so than in our area. While it would be hard to rule out that heat bursts have occurred on some occasions in our state, we were unable in a quick search to turn up any documented cases.
Oct. 18, 2009 | Tags: heat, thunderstorms

Answer: There were clearly thunderstorms in the area on the afternoon and evening of 22 Sep 09, as documented by a series of METAR observations from the Raleigh-Durham airport (see www.wunderground.com/history/airport/KRDU/2009/9/22/DailyHistory.html?req_city=NA&req_state=NA&req_statename=NA for a listing). As far as specific lightning strike data goes, that information is not publicly available and must be requested in the form of a fee-based "lightning forensics" report from one of two private companies. See the following addresses for more information. You may want to request that the insurance company provide a report, or cover your cost to obtain such a report, from one or both of these sources that shows whether lightning was observed by their networks within 5-10 miles of your address. If it was, the combination of lightning data and the diagnoses from your telephone and air conditioning repair personnel would seem to make a strong case that lightning caused the damages in question. See www.uspln.com/forensics.html and www.vaisala.com/weather/products/lightning/dataarchivereports/strikenetfax (click the "FAQ" link at this address for more details).
Oct. 16, 2009 | Tags: cool sites, lightning, past weather, thunderstorms

Answer: You probably noted in the class that most significant tornadoes form on the right rear flank of supercell thunderstorms, relative to the direction of storm movement. If the supercell is a "discrete" storm, out on its own, then most of the rain, thunder and lightning would be over when the tornado moves through or very shortly afterward. However, sometimes the tornadic supercell can be just one part of a larger group or line of thunderstorms, in which case additional areas of rain, lightning and perhaps hail may pass across the same area. In rare cases, there can even be multiple tornadic cells that cross the same or nearly the same location.
Sep. 17, 2009 | Tags: severe weather, thunderstorms, tornadoes

Answer: Lightning can travel between charge centers in separate clouds (cloud-to-cloud, CC), those within a single cloud (in-cloud, IC) and between the cloud and surface (cloud-to-ground, CG). There tend to be many more IC and CC flashes than CG strikes, though the ratio can be highly variable. On average, there are about three IC or CC flashes for every one that strikes the ground. CG flahes are generally more dangerous and destructive, as they may strike people, cause fires, interrupt power or damage electrical devices, while flashes aloft only rarely cause problems, for example by striking aircraft. However, any storm producing flashes aloft should be assumed capable of also producing some ground strikes.
Sep. 4, 2009 | Tags: lightning, thunderstorms

Answer: Clouds that are deep enough to produce heavy rain, lightning and hail contain a tremendous amount of water in the form of cloud droplets, rain drops, ice crystals and hail, all of which can scatter, reflect and absorb light. If you happen to be on the opposite side of such a cloud from the sun, it will appear dark due to the lack of light passing though it, and likewise it will become rather dark underneath the storm. On the other had, if you see the same storm cloud, but you are between the sun and the cloud, it will appear bright white due to the light it reflects and scatters back toward you.
Aug. 27, 2009 | Tags: atmospheric optics, clouds, thunderstorms

Answer: A process called near field coupling can occur in which strong electric fields associated with lightning can induce large voltages and currents in conductive materials, in some cases sufficient to cause damage to sensitive electronics. However, at the small size of cordless phones, cell phones and the like, this doesn't appear to be a major issue and virtually all lightning safety literature supports the use of these items in place of corded phones during a thunderstorm (assuming you are otherwise in a well-protected location, of course).
Aug. 24, 2009 | Tags: lightning, thunderstorms

Answer: It's more likely you're noticing the coincidental influence of some other weather features, namely a marine airmass boundary and/or a weak line of low pressure called the "Piedmont Trough" that are not influenced by the highway, but happen to align themselves in its vicinity with some frequency at certain times of the year. Both of these features are products of North Carolina's topography, its soil types, and the orientation of its coastline relative to the Atlantic Ocean.
Aug. 14, 2009 | Tags: fronts & airmasses, thunderstorms

Answer: It has been observed that some hail and/or tornado-producing clouds have a greenish tint to them, but it has not been established that most do, and one can't assume a greenish cloud means a tornado or large hail is imminent, nor can one assume that those things will be absent from a cloud that is not green. The precise reasons for the green apperance remain in some doubt, but one theory is that sufficiently tall and wide cumulonimbus clouds scatter light in such a way as to take on a bluish cast, and then in some cases reddened or deep-yellow light from a low-angle sun (many green cloud observations occur near sunset) combines with the blue to yield the green appearance.
Aug. 10, 2009 | Tags: atmospheric optics, clouds, thunderstorms

Answer: One of the many driving forces that affect the intensity of thunderstorms is the level of instability in the lower and middle atmosphere, and that instability depends in part on the difference between the temperature near the surface and the temperature higher up. Sometimes lots of cloudiness can mute the intensity of thunderstorms by keeping surface temperatures cooler and therefore leaving the atmosphere more stable. On the other hand, sunshine can heat the ground and the air near the ground, leading to greater instability and more intense storms, by increasing the difference in temperatures near the ground and aloft.
Aug. 5, 2009 | Tags: general meteorology, thunderstorms