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Question: Early the morning of April 24th (6:00 a.m. ish) there was what sounded like an explosion and it continued for what seemed like a minute. There was no other thunder or any lightening before this or after. It was just once and was the strangest thunder(?) I have ever heard. I was speaking with my mom who lives about 10 miles away and she said they heard the same thing at the same time. How is this possible and was this indeed thunder? — Patricia Vaughn
Answer: We weren't sure of your exact location based on the wording of your question, but did take a look at radar data for that time frame, which was available for visualization at gis.ncdc.noaa.gov/maps/ncei/radar. We found that there were showers and possible thunderstorms in the general region, spreading in from the south. Your description of the thunder you heard did sound unusual, but it does appear at least possible there could have been a lone strike in your vicinity. If you had a strike nearby, but from a lightning flash that happened along a lengthy path that ran from close to your location to a significant distance away, you could have heard thunder for a considerable time, as the sound from successively more distant parts of the path would arrive in sequence, stretching the duration of the resulting thunder. If you happened to be in an area where rain was not currently falling, that can make the thunder seem especially loud, and there is also at least the chance you heard a positive strike, which transfers positive (rather than the more common negative) charge to the surface. If so, these strikes tend to be more powerful and to have a bit longer duration than typical negative strikes. Of course, this is all somewhat speculative, and we can't entirely rule out that there was some other, non-meteorological source of the sound you heard.
May. 27, 2017 | Tags: cool sites, lightning, past weather
Question: Since the broadcast area of WRAL covers an area that could produce a wide range of weather, particularly north to south but also west to east, what specific area are you predicting on your online forecast? — Rick
Answer: When you come to our default main weather page, the forecast shown there applies to the Raleigh-Durham area. Of course, in some situations there can be a range of conditions across even that small region, and if that's the case we attempt to highlight that in the written description of the forecast. For purposes of the 7-day forecast image, we have to choose a single temperature value as a forecast high or low, and a single icon to capture as best we can the prevailing expected weather condition. Because the expected conditions can vary even more widely, as you noted, across our entire viewing area, our web site is set up with a box above the 7-day forecast that allows you to enter a town name or a zip code and click "change." This will replace our local forecast with one that is specific to the location in question. Registered users of our web site who are signed in will see that location on future visits unless they change it to someplace else. Those forecasts for other locations are based on gridded forecast data that accounts for expected differences in temperature, precipitation chance, cloud cover and so on, and under the appropriate circumstances may be very different from our local Raleigh-Durham area forecast.
May. 26, 2017 | Tags: maps & codes, wral.com
Question: Just an interesting note. My Dad is a 1959 or 1960 Gradute of Elon College. One of his professors told the class that if we don't stop paving the earth, flooding will become an increasing problem. I think he hit the nail on the head. — Dina Grinstead
Answer: Replacing permeable, natural areas with more urbanized development featuring significant impervious surfaces and drainage systems has long been recognized as contributing to increased flooding problems. Water that may have soaked into the ground and either recharged groundwater or slowly traveled to creeks and streams instead rapidly runs off or is carried to streams it wouldn't otherwise run into, and in a much shorter time. This has been observed to cause rapid increases in water levels for streams in and near urban areas, while similar rainfall amounts produce slower rises and lower peak levels in rural streams subject to similar rainfall rates. There is a good U.S. Geological Survey fact sheet on the effects of urbanization on flooding, including some ways for developers and municipal planners to mitigate these effects somewhat, at pubs.usgs.gov/fs/fs07603/.
May. 25, 2017 | Tags: climate change, cool sites, flooding
Question: Dear Greg....I am a fellow Pennsylvanian, been here since 1981. Do you remember the tornado event from 1985? — Jane Newberry
Answer: Yes, indeed - you're referring to an outbreak that formed south of a powerful low pressure area, and along or ahead of an especially strong and active cold front, on May 31, 1985. The storm led to tornadoes that formed over Ohio, New York and Ontario as well, with most of them following a west to east track. Overall, there were 43 tornadoes in the outbreak, with 23 of those affecting parts of Pennsylvania. The storms resulted in 89 fatalities, including 22 in Pennsylvania, and since that day there have only been two more tornado days in the entire U.S. with a higher number of deaths. Only once have we in North Carolina had a greater number of tornadoes in our state than Pennsylvania did on that day (there were 30 in NC on April 16, 2011). It's also notable that one tornado in that 1985 outbreak was rated F5, the only twister of that intensity in Pennsylvania history. So far, there has never been an F5 or EF-5 tornado recorded in the Tar Heel state. For more on the 1985 outbreak, including some maps and satellite images illustrating the weather pattern that spawned the tornadoes, see www.weather.gov/ctp/TornadoOutbreak_May311985.
May. 24, 2017 | Tags: cool sites, past weather, severe weather, tornadoes
Question: Please, can you explain me the meaning of averaging time used in measurement of wind speed? — Lara Betty
Answer: In measuring and reporting winds, some standards and definitions have to be applied in order to obtain consistent data from one site to another. To account for the highly variable and often turbulent nature of winds, the concept of averaging is applied. For basic surface wind measurements, it goes like this: Winds at official reporting stations are measured 10 meters above the ground (about 33 feet), and the most common types of automated weather stations take a reading of the wind speed every second. These readings are then averaged over a period of 5-seconds, which is considered to be the "instantaneous" value. These readings are stored and compared to 2-minute averages of those 5-second readings, and if there are fluctuations of the 5-second readings of 10 knots or more during the 10 minutes prior to an official observation, the highest of the 5-second readings in that 10-minute period is reported as the gust speed, while the 2-minute average value is reported as the "wind speed." The system also keeps track of the highest 5-second speed during the entire time since the previous official observation (usually 1 hour earlier), and if that highest value is 25 knots or greater, it will be reported as the "peak wind" during the interval between observations. At the end of each day, the highest 5-second wind from the entire day is reported as the daily peak wind, while the highest 2-minute average value is reported as the maximum daily sustained wind. Generally speaking, turbulent surges and lulls in the wind speed mean that averaging the winds over time lowers the value compared to the highest "instantaneous" values, but also produces a value that is higher than the lowest "lulls" in the wind. The averaging is done to try and obtain a more reasonable report of what is experienced most of the time. So to summarize, when you hear the current wind speed is, say, 13 mph gusting to 26 mph, the 13 mph is a two-minute average, while the 26 mph is the highest 5-second average taken in the previous 10 minutes.
May. 23, 2017 | Tags: instruments, maps & codes, winds
Question: Yesterday I sent you an e-mail requesting the dates of lightning strikes in the Clayton-Archer Lodge area between April 20th and May 6th. The information is needed so I can file a claim for financial help in replacing parts on my heating unit. — Doug Packard
Answer: We are able to display real-time and lapsed lightning strikes as storm systems move through, but do not have access to archives. While historical lightning strike data is available, it is owned and controlled by private companies that require you pay a fee to retrieve strike data or view strike maps for any particular time and location. For those interested in purchasing lightning strike data for research or insurance purposes, see www.uspln.com/forensics.html (especially the links to Lightning Incident Archive Search (LIAS) reports) and www.vaisala.com/en/products/thunderstormandlightningdetectionsystems/Pages/strikenet.aspx, where you'll see a box that serves as a link to purchase lightning reports from CoreLogic. We're not sure how detailed your need for specific data is, and whether it rises to the level of paying for these kinds of reports. We can tell you more generally that thunder was reported at the RDU airport on April 20 and 21, and May 1 and 5, while at the Johnston County airport, thunder was reported on April 24, 25 and 28, in addition to May 1, 2 and 5.
May. 22, 2017 | Tags: cool sites, lightning, past weather, thunderstorms
Question: How can you measure the speed of rainfall by looking at radar from one town to another? Does any of WRAL's apps provide means to measure the speed rain is traveling? — Bobby
Answer: The radar sections of our apps do not have a readout or built-in means of showing what the speed of rain areas is, but you can get a sense of that by using the lapse functions either on the Dual Doppler 5000 displays, where you would choose the view you’re interested in and then select the “1-hour” lapse, or by viewing the iControl radar display and clicking the “play” arrow, which will show about a 50-minute long lapse. You can figure a rough speed by following a rain area or storm cell across an area of known distance and dividing that distance by the elapsed time. For example, on the 1-hour lapse, if a band of rain moves halfway from Raleigh to Rocky Mt, that’s about 25 miles, so the band is moving around 25 mph.
Also, in situations where there are severe thunderstorm or tornado warnings in place, you can read the text of the warning and it will usually include a statement that gives the direction and speed of movement of the storm responsible for the warning.
May. 21, 2017 | Tags: rain, thunderstorms, weather radar
Question: Why doesn't the map used when WRAL airs the weather on TV show NC Hwy 540 (toll road)? — Ron
Answer: You may not have seen the map on air yet when we have it zoomed in sufficiently far to have that part of the road show up. At somewhat wider views, we restrict the roads that show up on the map to interstates like 40, 85 and 540, and then at somewhat closer views U.S. highways, like 1, 64 and 401 appear, but still leave the clutter level of the map on the low side. Zooming in even closer shows NC routes like 147, 55 and the toll portion of 540 that you're asking about. Zooming in even further, when appropriate, brings county roads and surface streets into view on the map.
May. 20, 2017 | Tags: maps & codes, weather radar
Question: No one that I know (especially me) has a clue what dew point means. Whether you report a dew point of 25 or 75, it means nothing. However, everybody I know understands humidity. I could never understand why weather experts insist on reporting dew point vs humidity. If you forecast a high of 85 with humidity of 80%, I know exactly what to expect. Forecasting dew point? Who knows? — Marc Sullivan, Clayton
Answer: The reason many meteorologists use dew point and have been attempting to help the public become more familiar with it is that it is a much more direct measure of humidity level than the relative humidity you prefer (in percent). While relative humidity depends on both the temperature and the amount of water vapor in the air, dew point depends only on the water vapor content. For most people in very warm weather, a dew point in the mid 50s or below feels fairly dry, while upper 50s to low 60s begins to feel a little humid, mid 60s to near 70 feels noticeably humid, and dew points above 70 quickly rise to the oppressive or "steamy" level. In the example you gave, of 85 degrees and 80% relative humidity, the dew point would be a very high 78 degrees (and the associated heat index value would be 97 degrees). That is an unusually high dew point for our area, where having the dew point reach 80 degrees or higher is a very rare and usually short-lived occurrence. You mentioned dew point of 25 or 75 not having a meaning - what it would mean is that the air is quite dry with a dew point of 25 (skin lotion might be a good idea for some people) while it is quite humid at 75 degrees (there is about six times as much water vapor in the air). Depending on the temperature, either of those dew points could be associated with an 85% relative humidity, even though there is such a great difference in the actual moisture content in the air.
May. 19, 2017 | Tags: heat, humidity/dew point
Question: I'm currently having problems with my T.V. and computer. Is there any way to receive a forecast on my phonograph? — Hugh M
Answer: We probably shouldn't take the bait here, but nonetheless will suggest that it may be possible, on days with a record high.
We now return you to our regular programming...
May. 18, 2017 | Tags: folklore
Questions 1 - 10 of 5307.
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Published: 2007-10-09 14:40:00
Updated: 2014-06-24 16:06:51