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Recent Questions

Question: My second grader son has been asking me questions such as "what is the dew point and how high can it get?" — Anonymous

Answer: Dew point is a measure of how much invisible water vapor is in the air, so that the higher the dew point, the more water vapor and vice versa. Dew point is expressed as a temperature, and if the actual temperature of the air becomes equal to the dew point, the air is considered saturated with water vapor so that any further cooling of the air or increase in water vapor will result in condensation, or a change of the water vapor molecules into liquid water. This can lead to the formation of clouds, fog or precipitation when moist air is cooled. In our area, dew point rarely climbs higher than the mid 70s, but there are rare excursions to higher values, with the highest reading on record at the RDU airport being 82 degrees for a short time on August 10, 2007.
Jul. 2, 2014 | Tags: humidity/dew point, records/extremes

Question: Years ago you very seldom heard of a tornado in this area. Now we have them every summer, all summer. Why? — Darryl

Answer: There are a couple of points in answering here. The main reason we seem to have more tornadoes than many years ago seems to be an increase in population and spread of population to more previously rural or unpopulated locations, and perhaps more so the deployment of Doppler Weather Radar covering almost the entire state. This allows detection and documentation of tornadoes that may be quite weak and may only exist for a minute or two, many of which would have gone unreported in the past. One reason we believe this to be the case is that the number of weak tornadoes (EF-0 and EF-1, for example) has increased considerably over time, while the number of more intense and longer-lasting tornadoes (EF-3 and EF-4, which are hard to miss even in the absence of enhanced radar coverage) has stayed about the same.

The other issue is to note that we do have a peak in the likelihood of tornadoes, especially the stronger ones, in the mid-late Spring and early to mid Fall, while there are still relatively few during the summer. While summertime thunderstorms can be locally intense due to heat and humidity, producing strong wind gusts and sometimes large hail, we usually lack the proper ambient wind speed and wind shear profiles to cause the storms to become the supercells that are most prone to generate tornadoes.
Jul. 1, 2014 | Tags: past weather, thunderstorms, tornadoes

Question: What is the latest date for the first named storm for the Atlantic Basin? — John Lobenstein

Answer: That turned out to be a more difficult answer to track down that we first expected, as published records and extremes for the Atlantic basin almost all involve the earliest and latest formations, rather than the latest initial development. We turned to a former NCSU meteorology student and resident of the Triangle, Dr Michael Brennan, who is now a lead forecaster at the National Hurricane Center, and he was able to query a database there and find that the latest known formation of the first system reaching a sustained wind speed of 35 kt or higher was Tropical Storm 1 in 1914, which reached tropical storm intensity on September 15th of that year and went on to be the only known Atlantic Tropical Cyclone of that season. In those days, the storms were not named, of course, and there are also come caveats involved in the fact that storms could potentially go unnoticed for some time before being detected and assessed for intensity. In the decades since regular reconnaissance (whether by aircraft or satellite) has been available, the latest first formation was Tropical Storm (later Hurricane) Arlene, which was named on August 30th, 1967.
Jun. 30, 2014 | Tags: hurricanes, records/extremes

Question: I have lived in Apex, NC for 16 years. It is not uncommon to see a rain shower on your radar approaching Apex but just before it gets here it splits and goes around Apex. Sometime coming back together on the other side of town! I know Apex is the high point of the railroad but is it that much higher than the surrounding area to make this happen? Is it Lake Jordan? Or is is just my perception and nothing else? — Guy

Answer: Convective showers and thunderstorms are subject to a large number of influences, some local and some larger scale, that can cause them to vary substantially in size, shape and intensity over short periods of time. While it is possible for lakes (like Jordan), rivers and topography in general to affect low level temperature and humidity fields in a way that can feed into the behavior of some nearby showers and storms, it can be very difficult to generalize about what those effects are, or to separate those influences from any number of others for a particular episode or series of episodes such as you've noticed in Apex from time to time. One aspect of this whole issue that you may find interesting, though, is one of perception. Radar imagery of most showers and thunderstorms, especially at some distance from the radar site, tends to make them appear larger than they really area, and causes some individual cells to appears merged into one larger area. One result of this is that less area may be affected by rain, or by heavy rain and storminess, than one might expect when scanning radar loops. In addition, people focus very closely on how these cells behave near their location, but not so closely on how other cells are evolving in locations they are less interested in. This is evident to us because of the fact that we frequently receive questions like yours (what makes storms split up when they approach my town?) from pretty much every part of our viewing area!
Jun. 29, 2014 | Tags: general meteorology, thunderstorms, weather radar

Question: While looking at wind maps of the world recently, I noticed it appears the jet stream has all but died in the northern hemisphere. Should we be worried? See: Earth - Animated Map of Global Wind and Weather - earth.nullschool.net — Robert

Answer: It is typical for the jet stream to both retreat northward and weaken in intensity as we head into the late spring and summer, and as far as we can see in checking some recent and projected maps, it doesn't appear all that atypical for the season. We opened the web page you cited, and noticed that it defaults to a depiction of wind fields for the surface layer (about 33 feet above the ground or water). For anyone else who visits that page, note that by clicking the "earth" label at the lower left corner of the page, you can make several choices regarding what information is mapped. When we switched the wind depiction to the 250 mb level, the jet stream was clearly evident, though it was weaker in the northern hemisphere than the south (where winter is in full swing and the jet stream is both strong and extended away from the pole). As an example, see earth.nullschool.net/#current/wind/isobaric/250hPa/orthographic.
Jun. 28, 2014 | Tags: cool sites, general meteorology, winds

Question: Thursday, June 12th we had a severe storm in Lee County. Particularly on Chris Cole Road in the Tramway area. We are convinced there was some sort of small tornado that came through that area because the amount of damage we received however there were only reports of strong winds. Is there someone that can be contacted to come out and verify if it was or was not a tornado since there is a visible path of snapped trees and such? It's just so weird how it only affected such precise area and no where else. — Jodi Yow

Answer: Storm damage surveys are carried out by the National Weather Service office responsible for issuing warnings in the area struck by a possible tornado. They will usually conduct a survey if radar depictions, eyewitness accounts or other factors indicate that a tornado may have occurred. In deciding whether to contact them and suggest a survey, it is worth keeping in mind that some especially intense straight-line wind gusts can exceed the intensity of some tornadoes, and in some cases the intense winds can follow very narrow "burst swaths" that produce a well-defined path of damage. The can even create swirling winds to either side of the wind core that can mimic some of the rotational nature of tornadic winds. If you'd like to contact the NWS office in Raleigh, they list a public phone of 919 515-8209 (8A-9P daily) and also accept e-mail through rah.webmaster@noaa.gov.
Jun. 27, 2014 | Tags: severe weather, spotters/skywarn, tornadoes

Question: Has the current heat index been removed from the WRAL site? It doesn't seem to appear on the Current Conditions page. — John

Answer: Instead of appearing on the current conditions page, both heat index and wind chill (as appropriate) appear on maps of our local area in the "Map Center" portion of our site. Just click the Map Center link in the "Maps & More" box in the upper right of our main weather page, and then select the "other maps" section, where can select "temperatures." The temperature map will have a "more views" box above it, where you can see the various temperature-related maps, including those for heat index and wind chill.
Jun. 26, 2014 | Tags: apparent temperature, maps & codes, wral.com

Question: We are fairly new to the Raleigh area after spending 23 years in Charlotte. My husband I notice that there always seems to be a slight breeze here, that we didn't notice in Charlotte. Are we crazy? Or can you enlighten us on this question? Thanks! — Sarah Harmon

Answer: We took a look at the average annual wind speed for both the Raleigh-Durham and Charlotte airports, and found them to be 7.5 mph for Raleigh and 7.4 mph for Charlotte. That difference probably wouldn't be noticeable. However, differences in localized topography, vegetation, building size and structure, bodies of water, etc, can certainly lead to micro-climates that fall outside the larger scale patterns, and it is certainly possible that you lived in one around Charlotte that often limited the wind speed near your home, while your current location is one that exposes you to more noticeable winds more frequently.
Jun. 25, 2014 | Tags: normals, winds

Question: Did Fayetteville have a 100-degree day in 2013? — Josh

Answer: The summer of 2013 was a rather mild one across our overall region, and neither of the archived official reporting stations in the Fayetteville area reported reaching 100 or higher in that year. At the Regional airport (FAY) there had been 14 such days in 2011 and five in 2012. In 2013, the highest reported temperature there was 98 degrees, which was reached on four days, once in June and three times in August.
Jun. 24, 2014 | Tags: heat, past weather, records/extremes

Question: I saw the long term forecast for our summer season and it called for cooler than normal temps. What's happened? It certainly doesn't seem to be working out that way. — Tony

Answer: We can't be sure from your question where and when you saw the forecast you're referring to. We went back and checked summer temperature outlooks from the Climate Prediction Center and found that all of the outlooks for summer issued from January through April indicated all of NC in the "above normal" category for temperature. The forecast from May showed the eastern half of the state in the above normal category while the western half was in the "equal chance" category, meaning an equal probability of having below, near, or above normal average summer temperatures.
Jun. 23, 2014 | Tags: heat

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