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Recent Questions

Question: I saw a single pinkish cloud in the sky this evening. In less that 15 minutes it was white again. What caused this? It was absolutely beautiful! — Bettie Thomas

Answer: The photos Bettie mentioned included a variety of clouds of different sizes and heights in the eastern sky near sunset, with most of the clouds a fairly uniform light gray, with a small cloud a little lower and closer that becomes a bright pink for a time. It appears the cloud that turned pink was in just the right position to be struck by a shaft of reddened light from the setting sun, while the surrounding grayish-white clouds were in shadows from other clouds farther west that prevented that same direct sunlight from reaching them. At some point, the clouds to the west also blocked the direct sun from that cloud as well, allowing it to be lit mainly by the same source (light scattered from the sky above and having more of a blueish-white cast) so that it blends in more with the other nearby clouds. If you'd like to see Bettie's photos, they can be seen at www.facebook.com/WRALMikeMoss/photos/pcb.863321963714863/863319263715133/?type=1&theater
Aug. 9, 2015 | Tags: atmospheric optics, clouds

Question: This winter when the forecast is actually for 32 degrees will it be listed as 82? I have noticed several time this summer that predicted highs were listed as 32 degrees. — John F Lobenstein

Answer: We certainly hope not, and we apologize for the issue that you and several others noticed during a recent transition in the method we use to propagate our forecasts out to some mobile and web platforms. We believe that the problem was located and corrected on about the last day of July. We appreciate the feedback and invite all of you to continue to let us know when you see a problem, or if you simply have suggestions for improvements to any of the mobile app and web features.
Aug. 8, 2015 | Tags: wral.com

Question: I want to know if meteorological fronts are only higher latitude phenomenon, because I live in the equator and I haven't seen fronts depicted on the meteorological charts. — Daniel

Answer: "Only" is probably a bit too strong a word, but well-defined large-scale frontal boundaries are very much a mid and high-latitude phenomenon for the most part. The comparatively small variation in incoming solar radiation throughout the year in the tropical locations leads to much weaker horizontal gradients of temperature there, making frontal zones difficult to form and intensify. On rare occasion, especially intense frontal boundaries originating from the mid-latitudes have been observed to penetrate deep into the tropics, and even cross the equator in especially unusual circumstances.
Aug. 7, 2015 | Tags: fronts & airmasses, general meteorology

Question: I was driving to work on morning of 8/3/15 a little before 4am and was on Hwy 55 Bypass heading toward Apex when I saw a large meteor streak through the sky from left to right. When it got to the far right it must have hit the atmosphere because it look like it exploded into this brilliant burst of green. What caused the burst to be green? — Kay

Answer: Meteors that become especially bright are called fireballs, and occasionally they explode, or detonate, just before becoming invisible. The one you saw had been in the atmosphere for a while, since that interaction with air is what makes it visible. When the combination of the speed, size and composition of the meteor, together with the density of the atmosphere, reaches certain thresholds a break-up or explosion can occur. The colors seen in meteors can be complicated a bit by the effects of vision, especially persistent vision in the immediate wake of a bright light. Nonetheless, it can be possible to infer something about the make-up of the meteor by the colors exhibited, since some of the components have characteristic emission colors when they are vaporized by heating. Nickel is known to glow green, and magnesium to glow bluish-white. Some combination of those two materials may have led to the green appearance you saw.
Aug. 6, 2015 | Tags: astronomy, atmospheric optics

Question: How many 90-degee days so far this year, in Fayetteville? — Roy Daugherty

Answer: Through August 2nd, there had been 50 days in 2015 at the Fayetteville Airport that reached 90 degrees or higher. Of those, 48 had occurred by the end of July. At that time in the year, the average number is 42. In 2011, by the end of July the same location had reached or topped 90 degrees 64 times!
Aug. 5, 2015 | Tags: heat, past weather

Question: Global warming is certainly a concern, but I've been hearing about an impending "mini-ice age" caused by fluctuations in the sun's magnetic fields similar to one experienced in the 1600s. Any truth or urban legend? — Jon Lodge

Answer: This seems to be a case of research results reported in one field of study being misconstrued somewhat in mainstream press and various blog posts. The work that prompted it all is the development of an interesting new model for solar activity that appears to produce predictions of sunspot numbers and related activity better than in the past. The new model, developed by researchers at Bradford, Hull and Northumbria Universities in the UK and published in the The Astrophysical Journal last fall, projects a "grand solar minimum" starting around 2030 similar to the "Maunder Minimum" that ran from the mid 1600s to early 1700s. The solar research makes no reference to temperature influences on earth, but because the Maunder Minimum overlapped with the cooler than normal period often referred to as the "Little Ice Age," some reports about the new research have conflated the two. As is often the case, there are complexities that make such an association difficult to make. First, the mini-ice age was underway already when the Maunder Minimum began, and there appears to be evidence it was prompted primarily by repeated injections of sulfur dioxide from a series of especially intense volcanic eruptions. The Maunder Minimum is thought to have added only a small contribution to the cooling during that period. In addition, studies done a few years ago already attempted to calculate what the effect of a new grand minimum would be, and found that based on the forcing variations associated with the lowered solar activity, global temperatures would average about .2-.3 degrees C lower than otherwise. If current projections for warming based on greenhouse gas emissions hold up, that would account from around 1-2 degrees C warming by 2050. While there's some uncertainty in those projections, of course, the fact that lowered solar activity would appear to only partially offset the greenhouse gas effects makes the development of a new mini-ice age seem unlikely, barring some other event like a series of volcanic eruptions similar to those leading up to the Little Ice Age. The new model for solar activity is a recent development, though, and we imagine there will be a number of studies done in the near future that attempt to better quantify what impacts could result from the predicted solar minimum. If you're interested in the paper describing the solar activity model, it is available at computing.unn.ac.uk/staff/slmv5/kinetics/shepherd_etal_apj14_795_1_46.pdf
Aug. 4, 2015 | Tags: climate change, controversy, cool sites

Question: How many 90 degree days so far in Charlotte NC in 2015? — Paul Coppinger

Answer: They've added up quickly for Charlotte this year. Through July 31st, the 90-degree mark had been reached 48 times in 2015. In records going back to 1879, the long-term average number for the entire year is 43, so that average had been topped before we even reached August. The long-term average for the period January through July is 26, and the record for an entire calendar year is 88 in 1954.
Aug. 3, 2015 | Tags: heat, normals, past weather, records/extremes

Question: In late May the Atlantic hurricane season was forecast to be quieter than normal. How many hurricane regions are there? Is there any correlation on regions' activity? — Chris

Answer: There are seven general basins that tropical cyclones form in and move through around the world, though in terms of forecast and warning repsonsibility they are divided up into a bit more complex group of regions. There is a fairly good map and discussion available in a WikiPedia entry at en.wikipedia.org/wiki/Tropical_cyclone_basins. Not all basins have strong correlations with others on an ongoing basis, but there can be some notable relationships under certain circumstances. Probably the most direct and reliable example is the influence of moderate to strong El Nino and La nina events on the Atlantic, Eastern and Central Pacific regions. El Nino patterns, for example, tend to foster wind shear over the tropical Atlantic that suppresses tropical cyclone activity (one of the reasons this season is forecast to have below-normal activity), but also brings warm sea surface temperatures and limited vertical wind shear over the central and eastern Pacific, leading to above-normal activity there, while La Nina can lead to more or less the opposite trend (more active Atlantic, less active Pacific).
Aug. 2, 2015 | Tags: cool sites, el nino/la nina, hurricanes, maps & codes

Question: It seems a record El Nino is predicted for the coming months. What potential impact could this have on our 2015-2016 Winter? — Gary

Answer: We don't have a good sense this early as to whether this El Nino will reach record levels, as current forecasts for the intensity of the event are still based on late spring/early summer observations and model projections, which tend to have somewhat limited accuracy. Just the same, there have been three previous El Nino episodes reaching the levels currently anticipated for later this year and early 2016, and the current state of the Pacific temperature anomalies exceeds the reading for the same time for each of those events, so it certainly bears watching. Current forecasts call for a "strong" El Nino, perhaps bordering on or reaching the "very strong" category.

In general, the average effect of El Nino for central and eastern North Carolina in the winter is to tilt the odds somewhat in favor of cooler than normal temperatures and greater than normal precipitation. The level of correlation associated with those impacts is only moderate, so it's worth noting that in any given El Nino year, the results can vary a good bit. It's also worth noting that because of all the other smaller scale influences that determine the character of wintry precipitation, the correlation between El Nino and snowfall, for example, is very low so that the presence of El Nino doesn't offer much predictive power when it comes to snow.

We took a quick look at the three seasons in the past that featured strong or very strong El Nino patterns, and found the following averages for rainfall, snow and mean temperature at RDU, for the period December through March. Rainfall was 20.1" (compared to an average for the period, for all years since 1887, of 13.96"), while snowfall averaged 7.9" (long-term average 7.1") and mean temperature 45.0 (versus a long-term 44.5).

It's interesting to note that the temperature in these episodes averages near to a little above the lon-term value, while El Nino in general tilts us toward cooler-than-normal levels. However, some of the strongest episodes have a tendency to cause such an enhancement in the number and intensity of southern jet stream disturbances crossing the southeastern U.S. that a number of them may sweep unseasonably warm air into the state at a level that doesn't happen as much with weaker episodes. The strongest El Nino on record, from 1997-98, resulted in a heavy 23.4 inches of rain and a temperature notably above normal at 45.4 degrees, with only 2.4 inches of snow. Of course, all these numbers should be viewed with the caveat that three strong events makes for a very small historical sample. It will be interesting to see how the next 6-8 months play out!
Aug. 1, 2015 | Tags: el nino/la nina, winter weather

Question: What is the hottest day on record that you know of? — Bill

Answer: You didn't mention whether you were interested in local records only, so here's a quick rundown that scales up from local to global. The RDU airport has peaked at 105 degrees on 4 different dates, once on July 23, 1952 and then on three days (June 29th and 30th, and then July 7th) in the very hot summer of 2012. The hottest temperature measured in the state of NC was in Fayetteville on August 21, 1983, when the high was 110 degrees. The hottest measured high in the USA is also the world record, that being 134 degrees reached on July 10, 1913, at the aptly named Furnace Creek, CA (part of Death Valley).
Jul. 31, 2015 | Tags: heat, records/extremes

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