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Weather Questions tagged “tornadoes”

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Question: Each time we have to take shelter, we don't know the safest place. We have a walk under crawl space. We also have several interior rooms with no windows and stairway slants. Usually we go to the crawl space but the Internet conversations say no-no because the pillar cement becomes the weakest point and shifts causing the home to fall .....trapping anyone there. What do you recommend? Thanks for being with us in an emergency, we listen exclusively to you guys. — D.M. Adams

Answer: We got a similar question from Gary, and the general idea is that the best place to be is an interior location that puts the most possible walls between yourself and the outdoors, preferably on the lowest floor other than a crawlspace. Tornado safety experts typically recommend against the crawlspace for a couple of reasons. Reaching one often requires going outside first, potentially exposing you to airborne debris. Also, intense winds may shift a house while leaving it partially intact, in which case the floor could pancake onto or tilt into the crawlspace, making it preferable to be above the floor rather than below.
Apr. 4, 2014 | Tags: tornadoes, weather & health

Question: Say you have two completely different storm systems coming towards each other, and both produce a tornado at the same time. One tornado is rotating clockwise, and the other rotating counter clockwise, and they collide, what happens? Do they cancel each other out, or do they make a stronger and bigger tornado? — Crystal

Answer: This is one of those questions that hard to answer in the sense that the physics of the atmosphere is such that it works against the likelihood of the event we're talking about actually happening. For well-organized supercell thunderstorms (the kind that are prone to produce significant tornadoes that can become intense and last a while), the larger scale conditions that spawn them would lead to the cell following parallel paths that wouldn't tend to intersect. If you did manage to have a clockwise-rotating storm and a counterclockwise moving on paths that would merge them, it is very likely that outflow winds would disrupt the circulations that allow the storms to feed on low-level warm, moist inflow, so that before they ever reached one another they would cause a dissipation of the tornadoes involved.

There have been cases where one supercell produces a series of tornadoes and a decaying one still exists while a new one intensifies. On rare occasion, one can orbit the other as a "satellite" tornado before its circulation either dissipates or is disrupted by the flow around the stronger vortex. If they were able to actually merge, then it's likely the weaker circulation would simply disappear into the stronger one, without a noticeable effect on intensity (keep in mind tornadoes aren't "objects" as such, but instead are processes, in the form of organized movements of air).
Mar. 4, 2014 | Tags: general meteorology, severe weather, tornadoes

Question: We live in Louisburg and we were wondering, since we don't get them that much, what are the signs to look for when a tornado is coming? — Rosemari

Answer: Weather systems that produce tornadoes in North Carolina most often tend to result in humid and unseasonably warm weather, usually with a stiff wind from southerly direction, and there are usually other thunderstorms in the area, so there tend to be a lot of clouds and often some periodic rain, thunder and lightning. All of this, of course, can also be the case with routine thunderstorms that never produce tornadoes.

Beyond that, detecting the tornadoes that most often occur in our state can be difficult, because they are often hidden behind rolling terrain, trees or buildings, and in many cases obscured by other clouds or rain shafts, making them hard to see at any distance. Their high winds do produce a roaring sound that has been likened to trains or jet aircraft, so listening for that kind of sustained noise, especially if it seems to be getting steadily louder, can be another sign one is approaching.

Any of these kinds of signs can be easy to miss, so we recommend keeping track of weather forecasts that will usually give some advance notification that severe storms are possible, then on those days paying special attention to forecast updates and any watches or warnings. Finally, it is a good idea to have some kind of alerting service that can let you know a tornadic storm may be approaching. This could be something like the WeatherCall service (type that into a search form on our web site for details), our WRAL Weather Alert apps for iOS and Android, or a NOAA Weather radio programmed to alert for tornado warnings for your county.
Nov. 25, 2013 | Tags: tornadoes, weather & health, weather radio, wral.com

Question: We are approaching the 25 year anniversary of the November 28, 1988 F4 tornado that started in Raleigh. How many EF4 or EF5 tornadoes has North Carolina experienced? — Wade

Answer: That long-track tornado in 1988 took 4 lives and injured 154 in our state, and is one of 12 F4 tornadoes on record since 1950, all of which occurred on 6 dates, with the most recent being May 7, 1998 in Caldwell County. No F5 or EF-5 tornadoes have been confirmed in our state so far in the time since reliable records have been maintained.
Nov. 21, 2013 | Tags: past weather, tornadoes

Question: My 4-year old twins would like to know if tornadoes can occur close to each other at the Same time and even collide. If so, what happens. If not, why not? — Nathan and Samantha Pitchford

Answer: Tornadoes have been observed to occur rather close to one another, including the phenomenon called a satellite tornado, which is a small tornado that forms within the same thunderstorm cell as a larger more intense one and circles around it. There isn't much data on tornadoes colliding, or more appropriately, merging. It is possible on rare occasion for a strong tornado to capture a smaller one, with the smaller circulation being absorbed into the larger one. When thinking about tornadoes approaching one another it is useful to remember that they are not solid objects, but processes in which air is moving in an organized fashion. The stronger circulation would typically disrupt the organization of the weaker one as it reached a sufficiently close distance.
Nov. 14, 2013 | Tags: tornadoes

Question: What causes the air in a tornado to spin? — Hope Beltran

Answer: While it is a complex process with many parts that leads to a tornado, the most basic requirement is wind shear that either starts out with a vertical axis (imagine a pencil standing up with a stronger wind on one side and a weaker wind on the other, so that it is forced to rotate) or starts with a horizontal axis (here the pencil would be sideways, with a stronger wind above and weaker wind below, so that it rolls) and then is tilted upward into a vertical orientation. In either case, the existing shear is then stretched out vertically, usually due to upward motion associated with a thunderstorm or other convective cloud, with the upward motion stronger near the top of the rotating air than at the bottom. This vertical stretching of the initial shear axis and rotating column of air causes it to contract horizontally, a process that leads the speed of the winds to increase through a process called conservation of angular momentum. When conditions are right, this process can lead to the formation of tornadoes (or in other, weaker circumstances, waterspouts and dust devils).
Nov. 11, 2013 | Tags: general meteorology, tornadoes

Question: Can you give information about the tornadoes that struck North Carolina in the last few years? This information is needed to develop a science fair project — Meri

Answer: We can't be sure what aspects of tornado activity you're interested in, but what we can suggest are a coupe of good sources of information with regard to data, reports and maps that cover activity in our state. Three good places to check are the searchable National Climatic Data Center Storm Events Database at www.ncdc.noaa.gov/stormevents/, a series of annual summaries (in pdf format) of severe weather impacts across the country called "Storm Data" reports at www.ncdc.noaa.gov/oa/climate/sd/, and track maps and summaries of most tornado outbreaks affecting our state that you can locate by scanning for the word "tornado" on the Raleigh NWS office "Past Events" listing at www.erh.noaa.gov/rah/events/. Good luck!
Oct. 7, 2013 | Tags: cool sites, past weather, tornadoes

Question: What are Suction Vortices within a Tornado? — Mark Faison

Answer: Some tornadoes have a single rotating column of air in contact with the ground, but in some others, usually larger and more intense, the lower portion of the column breaks into multiple swirls, or subvortices, that rotate around a common vertical axis. These smaller vortices (typically 3-6 or so) are sometimes called suction vortices, and are one reason that damage patterns from some tornadoes can be so complex, since the motion of individual subvortices around the larger tornado circulation results in concentrated areas of much higher and lower wind speeds due to addition and subtraction of the forward speed of the subvortices to their rotational wind speeds.
Oct. 4, 2013 | Tags: general meteorology, tornadoes

Question: In terms of mixing of different air masses in tornado alley, proximity to tropical waves off Africa, etc, would that rank The United States as having the most violent weather on Earth? — T. Sykes

Answer: Because violent weather covers a spectrum of sizes and types, it's difficult to make a blanket statement to that effect without some qualification. The geography of the United States and its location relative to the Atlantic Ocean and Gulf of Mexico do make parts of our country clearly the most prone to intense tornadoes, though you might be surprised that accounting for all tornado intensity levels, the United Kingdom has the greatest number of tornadoes per unit land area of any country. The southeastern United States is also in one of the world's more active land-falling tropical cyclone areas, subject to impacts from storms that may develop in the eastern Atlantic, the Caribbean, the Gulf of Mexico and occasionally off the southeastern coast. However, the most active tropical cyclone basin on the planet is the northwestern Pacific, and one result of that is that China leads the world in land-falling cyclones, averaging almost 9 per year,compared to a little less than 2 per year for the United States.
Sep. 28, 2013 | Tags: hurricanes, severe weather, tornadoes

Question: It occurs to me that there never seem to be any tornadoes down in Latin America--is this true or are there just fewer of them? I ask because I saw a report a day or two ago of a tornado in Europe which made me realize that I hadn't heard of them being anywhere else but here. — Jim Carver

Answer: Tornadoes of one form or another are at least theoretically possible almost anywhere, but conditions that are favorable for more frequent and intense tornado formation are considerably more limited, with the central and southeastern U.S. more prone to them than most anywhere else in the world. That said, there is an area in South America covering east-central Argentina and much of Uruguay that is a known region for tornadoes according to a distribution map produced by the National Climatic Data Center. While the map is becoming a little dated, it does give a good sense of where else on the globe tornadoes are more likely to occur. You can see the map at www.ncdc.noaa.gov/img/climate/research/tornado/globdist.jpg.
Aug. 11, 2013 | Tags: tornadoes

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