WRAL.com: Raleigh, Durham, Fayetteville

The most direct way to find your question is to search for the name you used when you submitted it (first name, last name or both). If you did not include a name, then you can search using keywords from your question. Of course, since many weather-related terms are common to a lot of the questions we receive, this may turn up a number of others in addition to your own.

Thanks again for sending your questions to Ask Greg!

Answer: Yours is the only report we've received of oddly colored frost or ice so far. In checking around with other employees, most of us have seen frost or ice covered windows a few times in the last month or two but the ice in question has generally appeared to be of the typical clear, translucent or white variety. We wondered if perhaps you or someone else may have run some blue-tinted washer fluid onto the windshield the evening before, which might account for such a coloring of the ice and frost. On the night in question, skies were partly cloudy in the evening and mainly clear the rest of the night with no precipitation reported, so the ice and frost would have had to be deposited directly from the air, unless you had a very low-probabilty encounter with a "blue ice/blue water" leak from a passing jetliner's waste system.
Mar. 9, 2013 | Tags: controversy, dew/frost

Answer: While there is an ongoing effort to detect and categorize larger asteroids or other objects in near-earth space that could pose a collision threat, objects as small as the meteor that exploded above Russia (though large for a meteor with a diameter variously reported at 7-15 meters and "the size of a bus") would be inherently difficult to detect at a great distance without a huge undertaking in terms of monitoring efforts, and probably wasn't noticed until it reached the atmosphere. Given its entry speed of 40,000 mph or so, that would have left little or no time for any meaningful warning.
Mar. 8, 2013 | Tags: astronomy, preparedness

Answer: It's probably most accurate to say that we use a combination of models, some of which are also used by our weather service counterparts and some of which are not, so there's a notable overlap but not an exact duplication. As you noted, some years ago we entered into a cooperative project with NC State University, the State Climate Office and the NC Supercomputing Center to adapt and optimize a computer model called MM5, originally developed by the National Center for Atmospheric Research and Penn State University, for application over our part of the country. We called the resulting model, which we ran in both a high-resolution version covering the central and eastern U.S., and a lower resolution version extending well into the Pacific and Atlantic oceans, "NC WeatherScope" for on-air use. That modeling system is still among those we use on-air and behind the scenes, but we also have the ability to show on-air versions of several other proprietary medium to high resolution models (known variously as ADONIS, VividCast, MicroCast, RPM, etc) and can also display output from National Weather Service models and modeling systems such as the NAM, GFS and SREF, along with occasional views of output from the ECMWF ("European" model). So as not to have a laundry list of labels to apply to the different views, we simply label output from any of the models we'd like to show according to the output presented (precipitation, clouds & rain, potential snow accumulation, upper flow & rotation, etc) and generically call any of those "FutureCast."
Mar. 7, 2013 | Tags: maps & codes

Answer: There is a "frost point," which is analogous to dew point when the amount of moisture in the air is such that the temperature would have to fall to freezing or below in order for the air to be saturated with respect to an ice surface. As you noted, any further cooling, or any further addition of moisture to the air in that case, would cause the water vapor to be deposited directly from vapor to ice crystal form, so long as there is an appropriate surface for the frost to attach to. That is commonly the case with objects like grass, leaves, the tops of cars, etc. In the open air, this will only occur in the presence of aerosols having appropriate molecular structures. These are called "ice nuclei," and serve as the initial formation points for ice cloud particles and snow crystals.
Mar. 6, 2013 | Tags: clouds, general meteorology, humidity/dew point

Answer: You're right that the moist, high-wind-shear area in the right front quadrant of a land-falling hurricane often (not always) triggers a swarm of short-lived and usually rather weak tornadoes. It would be overstating things to say a hurricane can never set off a violent EF5 tornado, but the environment around hurricanes is generally characterized by deep moisture and warm air aloft that limits the kind of extreme instability and explosive updrafts that are usually associated with the most intense tornadoes. This is reflected somewhat in the fact that most hurricanes, in spite of being huge convectively-driven storms systems, produce relatively little lightning.
Mar. 4, 2013 | Tags: hurricanes, tornadoes

Answer: In recent weeks we've transitioned to a pattern that features more frequent development of upper level troughs to our west, which then generate low pressure waves at surface that travel along fronts moving through the region. All of this has made rain and occasional wintry precipitation more common than it had been (but not to 40 days & nights magnitude!). Before we launched into this pattern, parts of the area were in moderate drought, so with any luck the wetter period will help get us back to more normal levels of soil moisture, stream flows, reservoir volumes and groundwater status.
Mar. 3, 2013 | Tags: rain, water resources

Answer: We can't be quite certain which temperature you are referring to on our web site or what station you have set to show up for temperature on your Desktop Weather application. In general, though, the temperature shown in the upper right corner of our web site is from a sensor here at the TV station and is updated almost real-time, whereas temperatures from airport weather stations are updated once per hour (for sites with ASOS stations like RDU) or once every twenty minutes (for sites with AWOS stations, as a number of smaller airports in the area use). These differnces in update times can lead to differences in the numbers. Of course, it is also possible that there are notable differences in actual temperatures between one location and another, and that would likewise be reflected in the readings posted on the web site and shown in a Desktop App.
Mar. 2, 2013 | Tags: instruments, maps & codes, wral.com

Answer: We can only surmise that you've been a little unlucky with respect to being in the right place and time to see rainbows for a while, as the conditions that lead to them haven't really changed all that much and they continue to be frequently seen and photographed. The basic ingredients for seeing a nice rainbow are for the sun to be fairly low in the sky, for there to be some breaks in the cloud cover on the side of the sky where the sun is located, and for there to be some rain falling on the opposite side of an observer from the sun, with the rain illuminated by direct sunlight. For much more on rainbows, see www.atoptics.co.uk/bows.htm.
Mar. 1, 2013 | Tags: atmospheric optics, cool sites, rain

Answer: It very likely was, as "snow pellets" is another common name for graupel, which is made up of snow crystals or snowflakes that have become sufficiently coated with rime ice (tiny supercooled droplets that freeze on contact) during their development or descent to take the form of white, rounded pellets. Graupel is not unusual in North Carolina, though it does often melt into rain before reaching the surface. Graupel is also known variously as "soft hail," the aforementioned "snow pellets," or "rice snow." We've even had some of our web visitors write to ask about it here, and suggest calling it "slow" or "sneet!"
Feb. 28, 2013 | Tags: snow, winter weather

Answer: We don't have much to go on regarding what information you'd like to have for your investigation, but you might find it helpful to look over the records page for that date that you can access through our "Almanac" page - a direct address for the information is www.wunderground.com/history/airport/KRDU/1984/12/7/DailyHistory.html. If it would help to have the information in the larger context of a weather map for that date or surrounding ones, you can retrieve such historical maps from the NOAA Central Library at docs.lib.noaa.gov/rescue/dwm/data_rescue_daily_weather_maps.html. Good luck!
Feb. 27, 2013 | Tags: maps & codes, past weather