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Answer: Comet PANSTARRS was visible low in the western sky around or a little after sunset in that time frame, but your comment about "tracking south to north" raises some questions, as the comet would appear as more or less a stationary object in the sky, similar to any star or planet in the vicinity in regards to movement. If you meant that you saw an object move quickly across the sky while you were watching, then that sounds more like a meteor than the comet. We checked to see if any especially bright meteors, called "fireballs," were seen around that time, but none were reported that evening in our area (you could have seen a fainter meteor that wouldn't show up in fireball logs). There was a bright fireball sighted the previous evening just before 7 PM, with reports from several states, including the western half of NC. You can see some photos of comet PANSTARRS at earthsky.org/space/comet-panstarrs-possibly-visible-to-eye-in-march-2013 to get an idea as to whether it may have been what you saw. Keep in mind that camera exposures can be adjusted to make the comet stand out a little more than it might to the naked eye, and also, as noted before, that the image seen in the photos would have appeared to be standing still in the sky.
Apr. 1, 2013 | Tags: astronomy, atmospheric optics

Answer: There are a few things that play a role in this. Of course raindrops and the rainwater itself typically would be odor-free, but that is not the case with materials that may exist on the ground or on other surfaces that the rain drops fall onto. The most common odor associated with rain is produced by spores from a microorganism in the actinomycetes family, which develop during dry periods and are splashed into the air in the form of a fine aerosol when rain begins. This odor actually has a name, "petrichor," and is a kind of dank, woodsy smell. There area sometimes also aromas associated with the rain falling on roadways and lofting bits of tires and petrochemicals into the air, and finally, when thunderstorms are nearby there can also be a faint odor of ozone, which is created along the lightning channel and has a sharp, somewhat chlorine-bleach-like character. Under the right circumstances, the wind can carry some or all of these odors ahead of a moving area of rain, giving an olfactory alert that precipitation may soon begin!
Mar. 31, 2013 | Tags: folklore, rain

Answer: There is a lag in the number of Atlantic tropical cyclones such that the peak activity on average occurs from late August to early October or so rather than at the time of the strongest incoming solar radiation of the year (in late June). This is partially related to a similar lag in the maximum sea surface temperature (on average), as well as to some other favorable factors for supporting development of tropical cyclones that also tend to peak in that time frame. These include the frequency and intensity of low pressure disturbances called easterly waves moving out of west Africa and across the tropical Atlantic, and a yearly minimum of vertical wind shear that tends to occur in the tropics through this time frame. The reduced vertical shear allows storms to develop and maintain organization more efficiently, whereas greater amounts of such shear tends to disrupt or weaken, and in some cases prevent altogether, the development of named storms.
Mar. 30, 2013 | Tags: hurricanes

Answer: The radar return by itself actually can not tell us with certainty what kind of precipitation is occurring at the ground, so there are a number of techniques that have been applied in radar display software over the years to color-code echoes to show the estimated precipitation type at the surface. This has usually been done with an algorithm that combines nearby recent surface observations (precipitation type and temperature) with data collected from sounding balloons or aircraft, and also considers computer model projections and/or analyses of the vertical temperature and moisture structure of the atmosphere. By using all these inputs, a reasonably good selection of precipitation type can be made for most areas, but it is not a perfect solution and has to be treated as an approximation.

Newer radars with dual-polarization capability, such as our Dual Doppler 5000 and recent upgrades being installed at National Weather Service sites, do have some capacity to more directly make those determinations. The precipitation type being sampled by the radar beam can be reasonably well estimated based on several parameters measured by the combination of horizontally and vertically polarized signals, but is subject to some ambiguity. In addition, while dual-polarization is pretty good at estimating the type of precipitation at the height of the radar beam (which increases with distance from the radar site), it can not determine whether that precipitation type changes between the altitude sampled and the ground below, so combining the dual-pol technology with the other methods mentioned above is usually a good idea.
Mar. 29, 2013 | Tags: rain, snow, weather radar

Answer: If we're interpreting your question correctly, you're referring to the numbers in white that are located in the black potion of the "tubes" on the 7-day graphic. Those are the expected low temperatures. They are offset a bit to the left on the tube compared to the location of the high temperature above, in order to give the sense of timing involved. On a typical day, the minimum temperature will occur around sunrise or within an hour or so afterward, followed by the highest temperature during the mid-afternoon hours.
Mar. 28, 2013 | Tags: maps & codes, wral.com

Answer: The increasing day length and higher sun angle through this time of year is certainly important, but can be overcome in terms of how our temperatures stack up relative to long-term averages ("normal") if the large-scale weather pattern is one that transports fresh supplies of colder air into the region, generally from the north or northwest. If we had day after day of full sunshine, with light winds and little resulting advection of air in from higher latitudes, part of the heat would go into the ground each day, where some is transferred to warming the air by contact and convection and some goes into warming soil temperatures, and some of course would be lost by radiation to space. This outgoing radiative heat loss is strongest during the day but is overwhelmed by the incoming radiation from the sun. At night, of course, the solar radiation is gone and temperatures cool because the outgoing radiation continues to take heat away.

Some years, the large scale pattern is one that brings air our way frequently from warmer areas to our south and west (as in March 2012) and we warm up rapidly with above normal temperatures. This year we have tended toward a cooler pattern that brings frequent supplies of chillier air our way.
Mar. 27, 2013 | Tags: general meteorology

Answer: We assume you're asking about the March 12-14 event that was widely called the "Storm of the Century." If so, Goldsboro only received an unmeasurable trace of snow from that system, as the heavy snows were concentrated over about the western quarter of the state, where the mountains and foothills received more than a foot on a widespread basis, with some parts of the central and northern mountains reaching 3-4 feet of snow. The weather station at Seymour Johnson AFB recorded 1.3 inches of rain from that storm, along with the trace of snow, and also noted a 71 mph peak wind gust.

You can see a map of the snowfall accumulations from the storm at www4.ncsu.edu/~nwsfo/storage/cases/maps/accum.19930313.gif.



Mar. 26, 2013 | Tags: cool sites, past weather, winter weather

Answer: For the Raleigh area, sunrise that morning will occur at about 7:02 AM EDT. For anyone who'd like to check the sunrise time for another location, there is a good source for that provided by the U.S. Naval Observatory. Just go to aa.usno.navy.mil/data/docs/RS_OneDay.php and select the date, along with the country, state and city or town you're interested in.
Mar. 25, 2013 | Tags: astronomy, cool sites

Answer: Gusts have many contributing factors, but the more routine gusts that we experience on days with moderate to strong winds derive largely from the passage of turbulent eddies that result from mechanical and thermal mixing. Winds flowing across topographical or man-made obstacles develop vortices and rolls that can alternately oppose (and weaken) or reinforce and add to the mean wind as they travel past a point leading to rapid surges and lulls in the wind. If a passing eddie or vortex happens to be stretched along its axis as it moves along, it's rotation speed will increase even more, adding to the strength of gusts it may produce. Similarly, thermals (bubbles of air heated by the surface that become buoyant and rise) lead to upward motion and compensating downward motion that can capture air with greater momentum from several hundred to several thousand feet above the ground, and transport it rapidly to the surface where it can produce sudden increases in wind speed.

A somewhat different mechanism can be involved in the production of severe gusts of wind from some thunderstorms, in which heavy precipitation in the storm can drag air from above downward at rather high speeds, spreading out and producing strong horizontal winds that oftent take on a gusty character. This process is sometimes enhanced if there are layers of dry air being entrained into parts of the storm, or a layer of relatively dry air below the cloud base. In these cases, the precipitation may partially evaporate, cooling the downward rushing air, making it denser and increasing its fall speed - this is often a factor in severe thunderstorm wind gusts.
Mar. 24, 2013 | Tags: general meteorology, severe weather, winds

Answer: In records going back to 1944 at RDU, the high temperature has been 20 degrees or colder 13 times. This includes two days, Jan 16, 1972 and Jan 21, 1985, with highs of 17 degrees. We also maxed out at 18 degrees there on Feb 17, 1958 and Jan 19, 1994.

In the last year or two, the local National Weather Service has produced a set of climate record data for the Raleigh area called ThreadEx that combines observations from several successive observing sites to run the start of the data set back to 1887. Checking that database, we find that the lowest high observed for the Raleigh area was 10 degrees on Feb 13, 1899. There were also observed highs of 13 degrees on Feb 12 that same year and 16 degrees on Dec 30, 1917.
Mar. 23, 2013 | Tags: cold, past weather, records/extremes