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Recent Questions

Question: How did monthly precipitation in 2016 compare to that in 2015? — Tony Stephenson

Answer: We hadn't finished 2016 entirely when this answer was drafted, so some small changes are possible. However, for the entire year at RDU, 2015 brought 57.1 inches, while 2016 had totaled up to 50.9 inches so far. That makes both years quite wet, as the "normal" yearly rainfall (defined by the 1981-2010 average) is 43.3 inches. Months that were especially different between the two years included May, when 2016 saw 3.2 inches more than 2015, July (with 3.1 inches more in 2016), November (in this case, 2016 saw 6.5 inches less than 2015, and was especially dry while the same month in 2015 was especially wet). As of this writing, December 2016 had received 4.3 inches less rain than the previous year.
Jan. 1, 2017 | Tags: normals, past weather, rain

Question: Can you please post your solstice explanations from last night's news cast for our science class today? — Samantha Pontrelli - Wake Forest High School

Answer: Unfortunately, we weren't able to post that segment in time for your class - the general idea of the discussion, however, was that the day of the winter solstice would be the one on which the daylight period between sunrise and sunset was shortest of the year, but that sunrise and set do not approach one another at the same rate leading up to the solstice and vice versa. Instead, sunset begins to become later a couple weeks prior to the solstice, but at a rate that is slower than that at which the sunrise gets later. After the solstice, sunrise continues to get later for a couple weeks, while the sunset becomes later at a faster rate, making the daylight period gradually longer again. These differences are related to the combination of earth's tilted rotation axis and its slightly elliptical orbit around the sun. If your class is interested in some of the details on how sun times vary through the year, you might like to do some research on the "Equation of Time." The day to day change in day length in the weeks around the solstices are quite small, while the rate of change increases to a maximum in the period around the equinoxes in March and September. Our guest blogger Tony Rice recently posted about the yearly variation in day length and its rate of change, and that might be an interesting article for your class to look over. You can find it at www.wral.com/solstice-reminds-us-of-sunlight-s-wave-patterns/16360674/
Dec. 30, 2016 | Tags: astronomy, cool sites, wral.com

Question: On "Average," how did the low, high temps by month fare this year compared to 2015? — Tony Stephenson

Answer: Note that we're answering this a few days before 2016 is over, so there could be some minor changes by the time December ends. That said, when you average the high temperatures for both years through late December, you find they ran about .7 degree F warmer in 2016 than the previous year, while the low temperatures for 2016 averaged one-half degree warmer than 2015. Taken together, the overall mean temperature for 2016 wound up .6 degree warmer. Of course, this averaged value masks or offsets some larger variations that occurred on a seasonal basis. Especially notable, for example, was that February 2016 has a mean temperature 9 degrees warmer than the same month in 2015, March 2016 was warmer than the previous year by 7.1 degrees, and December so far has averaged 10.6 degrees colder than the same period in 2015. You can investigate all this in more detail, if you'd like, using the "Monthly Summarized Data" and "Seasonal Time Series" functions at xmacis.rcc-acis.org/
Dec. 29, 2016 | Tags: cold, cool sites, heat, past weather

Question: When is the last day of 2017 that snow or even a ice storm can be anticipated? — John

Answer: There's really no way to be specific with an answer to that, as no technique exists by which to forecast specific snow or ice events more than a week or two in advance, and generalized seasonal outlooks for how temperature and precipitation are most likely to compare to normal seasonal values can't provide meaningful information about the timing of individual events either. What we can do is look at history, and note that climatological records show that our latest measurable snow recorded in Raleigh occurred on April 18, 1983, when 1.8 inches of snow was observed, while our latest snowfall of any kind, amounting only to a trace amount that could not be measured, occurred on May 2nd, 1939. Of course, snow as late in the cool season as these dates is quite rare, but they do give an idea of what the extremes have been in the past.
Dec. 28, 2016 | Tags: past weather, records/extremes, snow

Question: Will it be raining Christmas Eve from 5:30 to 7:30? Santa visits our neighborhood and we like to keep the big guy dry! We love your broadcasts and have watched you for many years. — Marge Bye

Answer: Unfortunately, this is the kind of question that is hard to get to in a timely fashion through the "AskGreg" forum. We thought we'd answer anyway just to note that when it comes to short term or custom time frame forecasts, it's usually best to either catch us on the air or to check our online forecast. When there is some timing that we can apply to the forecasts, we'll usually note it in the text description part of the 7-day forecast, and you can also check the hourly forecast to see how the precipitation chance is varying. On Christmas Eve, the rain chance dropped through the afternoon to around 20% later in the day and into the evening, but there was a lingering very narrow line of light rain that covered a small amount of the area at any given time. Depending on your location, you may have had a brief encounter with that, but hopefully the very light amounts of rain involved (less than one-hundredth of an inch) didn't cause problems!
Dec. 27, 2016 | Tags: maps & codes, past weather, wral.com

Question: You had a neat chart on the other night comparing sunrise/sunset times, with an explanation I understood... & forgot! Any chance of a link to that piece, or graph & transcript? Might help me answer my wife's question: 'Yesterday at 7AM it was a lot lighter than today! I didn't expect it to get lighter in one day, but this is so wrong!' — Bill Lewis

Answer: If we're thinking of the right chart, it was a line graph with the times of sunrise and sunset, and illustrated how they do not both change in corresponding opposite directions at the same time around the solstice, but instead the date of earliest sunset and latest sunrise are offset by several weeks. Even so, the combined sunrise and sunset times are such that the winter solstice has the shortest period between rise and set. We'll look into posting the graphic as a blog, but in case you don't catch it you can see sunrise and set times for a year in a table generated from the Naval Observatory web site at aa.usno.navy.mil/data/docs/RS_OneYear.php, and see the relationship between the two times. Note that the table is rounded to the nearest minute, and in the days surrounding the solstice the times can change by just a few seconds from day to day so that several days may round off to the same value. This is also a reason to suspect that your wife's observation about light at 7 AM was probably more influenced by differences in location and thickness of clouds, rather than the timing of sunrise, since sun continues to rise a little later each day until a week or so into January.
Dec. 26, 2016 | Tags: astronomy, cool sites

Question: Will we get any snow before winter is over? — Crystal Hardison

Answer: There's now way to really be certain, and it's true that we do have a rare winter on occasion with no measurable snow. However, most years we do have at least a couple of episodes with snow falling, sometimes in very small amounts and less frequently reaching much larger totals. As we write this (a few days before it appears online) our chance of snow appears quite small through the end of December, but beyond that we simply don't have a way to make a confident prediction farther into the season. We have a weak La Nina winter underway, which historically correlates to winters that are drier and warmer than average. However, snowfall is more variable than overall precipitation and is not very predictable, on a seasonal level, based on the state of La Nina or El Nino.
Dec. 25, 2016 | Tags: el nino/la nina, snow, winter weather

Question: What's the chance of tornado activity with the weather back and forth like it is? — Tracy

Answer: "Back and forth" is one way to describe fairly active patterns that move significant warm, unstable air north and cold, stable air south on a frequent basis. Periods in which this kind of pattern is especially strong do raise the chance of severe weather, including tornadoes, and that is the reason that tornadoes are at least possible in our state any time of year. However, even in rather active winters with a lot of temperature swings and passing large-scale low pressure systems and upper-level troughs, the overall trend is for the chance of tornadoes to remain considerably lower than it is in the Spring and to a lesser degree in the Fall. Tornadoes are rather rare events in general for our area, but just to give an example, Wake County has had two confirmed tornadoes during the winter (Defined as Dec-Feb) in the 66 years since January 1950, each of which affected just a very small fraction of the county.
Dec. 24, 2016 | Tags: tornadoes, winter weather

Question: Why was the forecast high for Tuesday, Dec 20th 46 degrees, but when you checked the hourly forecast, the highest temp was 41 degrees occurring at 2 to 3 in the afternoon? — Mel Nelson

Answer: There are two things that can contribute to this. For one, the highest temperature of the day can occur between hours, so that on occasion any two hourly times may bracket the time of the maximum value. This would usually only result in a difference of a degree or two, though. A more pertinent factor is the manner in which our web site is set to retrieve hourly forecast information. While the main 7-day forecast numbers (highs/lows), weather icons, wind speeds and directions, and text descriptions for the Raleigh area are directly entered by WRAL WeatherCenter meteorologists, the hourly values, in addition to 7-day forecasts that you might use the "change location" feature for, are retrieved from a gridded information resource called the National Digital Forecast Database (NDFD), which is populated through a combination of computer modeling and adjustments by National Weather Service meteorologists. At the time you checked the hourly forecast, that database was indicating a max temperature in Raleigh for Tuesday around 42 degrees while we were projecting 46. By Tuesday morning, we were still expecting around 46, while the NDFD forecast high had increased to 45, with its hourly forecast showing 44 degrees at 2-3 PM. Use of the NDFD allows us to include the ability for you to use the "change location" function on our main weather page to check forecasts for distant locations in our state, or anywhere across the United States.
Dec. 23, 2016 | Tags: maps & codes, wral.com

Question: If warm air comes from the southwest and the northwest, then where does cold air come from? — Aliyah

Answer: The development of colder or warmer air than is currently in place over a given area is actually much more complex than that, and includes factors such as the presence or absence of clouds and precipitation, whether on the large scale air over the region is rising or sinking, and the extent to which warmer or cooler air than average has been carried especially far north or south by other weather systems upwind of our location. Because of that, it is possible under the right circumstances for warmer air or colder air to flow in from any direction. Even with all that being the case, it is true that in a broad, general sense, warmer air tends to originate south of us and vice versa, so colder air most often moves in with winds having a northerly component (northwest, north, northeast, etc) while warmer air is more likely to move in with winds having a southerly component.
Dec. 22, 2016 | Tags: cold, fronts & airmasses, general meteorology, heat

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