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Question: The local pool certainly seems cooler after a significant rain. Are there any generalizations you can make about the temp of the rain during a typical summer storm? — Nadine
Answer: There are, although the situation is complicated enough that some generalizations are indeed necessary, since the temperature of rain reaching the surface depends on its initial temperature in the formation region aloft, the transfer of energy into the drops (warming) as they fall toward the surface, the cooling of the drops as they evaporate (offset in some cases by condensation of additional moisture onto the drops as they fall through warmer, humid air), the size of the drops, and the presence or absence of hail in the storm (even if the hail melts before reaching the surface. All that said, it is common in summer storms for rain temperatures to range anywhere from mid 50s to around 60 degrees in the presence of significant hail, to upper 60s to mid 70s otherwise. Of course, given that summer storms often develop or roll in when temperatures near the surface are in the 80s or 90s, this can indeed have a sharp cooling effect!
Jul. 9, 2016 | Tags: general meteorology, rain, thunderstorms
Question: I've been living in NC my whole life. I'm now 31 years old. For the past couple of years we have not seen a hurricane that was able to come inland, passed Raleigh. I know that is a great thing. When can you tell if the weather is right for a hurricane to form? Is the water too cold for one to come? — Carter A Mickens
Answer: There are several factors meteorologists keep an eye on in regards to potential formation of tropical cyclones. The development of these storms typically requires a combination of high humidity, low vertical wind shear, and warm sea surface temperatures (generally around 80 degrees or higher). The shear and moisture conditions, along with potential weak disturbances involving some spin in the lower atmosphere, can vary a good bit day-to-day or week-to-week, leaving some areas favorable for supporting development and others unfavorable at any given time. Ocean temperatures tend to vary more slowly. Those have been, and should continue to be, favorably warm from the southern NC coast east and southeast, as well as over the Gulf of Mexico.
Jul. 8, 2016 | Tags: general meteorology, hurricanes
Question: I saw where the dew point was 76 on Monday night, July 4. If not the record for this area, what is? — Doug Black
Answer: The dew point at RDU did indeed reach 76 degrees at 8 and 9 PM the evening of Independence Day this year. That was a rather high value even for this time of year, and certainly contributed to a noticeably muggy feel to the air. However, it wasn't a record reading. The highest we know of at the Raleigh-Durham airport occurred on August 10, 2007 when there was one observation, shortly after a brief shower on a very hot day, with the dew point spiking to a super-steamy 82 degrees. The temperature at that time was 89 degrees (after a high of 104 shortly before the shower) for a relative humidity of 80 percent and a heat index value of 110. This was one of only two days since records began at RDU on which the dew point there has climbed above 80 degrees (the other was July 24, 1965, when the dew point reached 81), and there have only been six other days there when it reached as high as 80.
Jul. 7, 2016 | Tags: humidity/dew point, records/extremes
Question: Looking at the almanac, NC has had almost 40" above normal rainfall in the past 5 years. Even the 30, 60, 90-day almanac shows consistently higher than normal amount of rainfall here. I thought it was just my imagination but we really are getting a lot more than normal rain here in NC. What's up with that, in your opinion? — D.
Answer: You're correct, but it is really pretty difficult to provide a satisfying answer beyond the fact that "normal" is a 30 year average value (ending with the most recent "zero" year and updated every ten years) that results from years having a fairly wide spread of rainfall amounts, and in which some multi-year longer scale variations are evident when you look at a really long-term plot of annual totals. in the case of the past 5 years, for example, 2015, 14 and 13 all were notably wetter than normal, but the 4 years prior to that were all at or below normal. Historically, in records going back to 1887, we see some stretches with a steady average but large swings year to year, interspersed with a number of stretches of 4-6 years that favor more frequent above (late 1940s to early 50s, mid 1990s to around 2000) or below (1880s to early 1890s, mid 1960s to around 1970) amounts. We'll have to wait a few more years to see how this year and the past three stack up in that historical sense, and whether any further long-term patterns become evident.
Jul. 6, 2016 | Tags: past weather, rain
Question: What does it take for a storm to cause power issues or outages? — Scott Wayne Stephenson
Answer: Most commonly, thunderstorms can lead to power outages by either producing wind gusts that reach near 60 mph or higher, thereby taking down some large limbs or sometimes trees, which may in turn snap or short-circuit some power lines. It is also possible for lightning strikes to lead to some power outages, though this is somewhat less common with well grounded, protected power transmission systems. Larger storms systems, like tropical cyclones, can lead to large areas with high winds and heavy rain, leading to widespread power losses and numerous trees toppling. In rather rare instances, intense tornadoes may be strong enough to damage power generation facilities and cause issues.
Of course, those all address typical warm-season storm types. During the winter, heavy, wet snow and, even more so, thick glaze icing due to freezing rain, can directly stretch or snap power lines, bend or break branches and topple trees and power poles, all leading to significant power outages.
Jul. 5, 2016 | Tags: severe weather, thunderstorms, weather & health, winter weather
Question: I have had people family members and friends tell me that if a tornado is strong that it can pull, blow or take people and things out of basements. Is this true or false? — Casey Cartwright
Answer: Basements are generally considered quite a safe location to seek shelter in tornadoes, as being below ground level would remove a person from being directly in the line of intense horizontal winds should the tornado strike directly. There would still be some danger from very intense tornadoes, of course, if the home above were largely destroyed and some parts of it fell into the basement. However, even if the building is largely blown away and the basement were left open to the sky, it is very doubtful that people or other reasonably heavy objects positioned low within the basement would be swept out of it. The chance of this would be minimized even more if the person taking shelter were to lie down or crouch low within the basement, in order to minimize the surface area exposed to any wind that swirls in.
Jul. 4, 2016 | Tags: preparedness, tornadoes, weather & health
Question: How during a La Nina can we both have increased hurricane seasons and on the other side of the coin we get droughts in the Southeast like the one in 2007? — Anton
Answer: Your question points out the importance of recognizing the difference in long-term or average trends and relationships, versus the complexities and variability that is involved in results for individual seasons or years. On average, La Nina conditions (especially in the cooler months) lead to lower than normal precipitation in the southeast, while also promoting greater than normal Atlantic tropical cyclone activity, which can sometimes enhance precipitation in our area during the later summer and fall due to tropical cyclones or their remnants passing over the region. However, depending on the state of some other large scale patterns and oscillations, these results may not hold for a particular year, or may be overshadowed by other effects. In 2007, we actually started the year coming out of an El Nino, which often leads to cool season precipitation that's above normal. Dry conditions set in rapidly during the spring, however, and then a hot mid to late summer exacerbated the problem. While the tropical season was fairly active overall, with 17 cyclones (15 of them named), most occurred well to our east or south, and only one (Gabrielle) managed to brush our state, and did so without producing widespread significant rain. As might be expected fairly often with La Nina, the winter of 2007-09 remained dry and drought persisted, before a break set in as we moved into Spring 2008.
Jul. 3, 2016 | Tags: drought, el nino/la nina, hurricanes
Question: Hi! I know this is a more specific question, but I'm not sure how to get the answer other than to go to "The Fish!" I am trying to find out what time rain entered the Raleigh/Knightdale area on 6/28/16. — Erica Hinton
Answer: An exact time for a particular spot is touch to pin down due to a few scattered sprinkles and showers that occasionally formed and dissipated out ahead of a more widespread, steady band of rain and showers that morning. Based on radar and surface station observations, however, for Raleigh the first sprinkles and patches of rain tracked in from the west and southwest around 8 AM or just after, while the steadier rain began to pick up closer to 9 AM. In both cases, the timing would have been about 15 to 30 minutes later for Knightdale.
Jul. 2, 2016 | Tags: past weather, rain, weather radar
Question: Are we going to see thunderstorms that are severe on Saturday? — Amy
Answer: We're setting this answer in place a couple of days in advance, and so far the weekend forecast appears unsettled, though with a fairly low level of confidence regarding specific details and timing. There are some factors regarding the potential storms on Saturday, such as shear between surface and mid-level winds, and sharply decreasing temperatures though the lowest several thousand feet of the atmosphere, that can lead to at least a small chance of storms that produce localized wind gusts to severe levels (58 mph or higher). However, we'd suggest you check our online and on-air forecasts for any updates regarding the potential for severe storms. You could also check for recent updates regarding severe potential from the Storm Prediction Center, at their web site at www.spc.noaa.gov/products/outlook/. We often highlight those outlooks in the Weather Feed section of our web site, and on our WRAL Weather Facebook page.
Jul. 1, 2016 | Tags: cool sites, severe weather, wral.com
Question: A few years ago we set a record for most 90 degree (or more) days in a year. There have been few 90 degree days this year. What is the record for the least 90 degree (or more) days and are we close? — Neil Gustafson
Answer: We haven't wuite finished out June at the time of answering your question, but it appears we're unlikely to see additional 90-degree days before it's over. if that holds up, we will have seen 11 days at or above 90 in Raleigh through the end of June. The average number of days at that point, in records going back to 1887, is 13, so we're not far behind the typical pace. The least we've ever had in Raleigh for the entire year was 11, back in 1889, noting that the average number for the entire year is 42. In more recent decades since reports have come from the RDU airport, the lowest yearly number was 15, which occurred in both 1969 and 1972. The least we've had through June was 1, in 1979, a year that went on to see 18 days at or above 90.
On the other end of the extremes, the most we've had through June was 32, in 1944, and the record number for a year was in 2010, with 91 days.
Jun. 30, 2016 | Tags: heat, normals, past weather, records/extremes
Questions 51 - 60 of 5043.
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Published: 2007-10-09 14:40:00
Updated: 2014-06-24 16:06:51