Ask Greg

Question: I was reading about "whippoorwill storms," and wondered where these would occur and how the name arose.

Answer: That was a new term for us, but it is defined in the Glossary of Meteorology as the first bad or stormy weather in spring after a period of warm weather. No further etymology is given there regarding origins of the term or where it might be commonly used. It may have arisen due to a warm spell in spring being a favored time of year for beginning to notice whippoorwills calling in the evening.
(2008-05-09)

Question: What are some colleges that have good meteorology programs?

Answer: There are far too many high quality programs to list in this space, but to mention just a few of the better programs one could include Penn State, Oklahoma, Wisconsin, N.C. State, MIT, Washington, Florida State, Texas A&M, Illinois and Ohio State. For more comprehensive listings, including contact information, see www.nssl.noaa.gov/edu/schools.html and www.nwas.org/links/universities.html.
(2008-05-08)

Question: What is the meteorological basis behind the old sailor's ditty "Red sky at night, sailor's delight?"

Answer: Given our complex atmosphere, a very simple rule of thumb like that one cannot be expected to verify in every case, but that doesn't mean it has no scientific basis. Since mid-latitude weather systems generally travel from west to east, early evening sunlight shining red on clouds overhead or to the east can indicate a departing storm system, and vice versa, but there are many exceptions to this.
(2008-05-07)

Question: Could you point me to a source for downloading historical weather data into an Excel spreadsheet?

Answer: For historical data in the sense of long term average, or "normal" values, you can go to water.dnr.state.sc.us/climate/sercc/climateinfo/historical/historical_nc.html, select the site you're interested in, and then click on either "NCDC 1971-2000 Normals" and "Daily Summary Stats" to get tables of data you may find useful. You may have to experiment a bit to copy and paste into your spreadsheet.
(2008-05-06)

Question: What other reason would allow for new record cold temperatures even if global warming occurred?

Answer: We noted regional variations yesterday. Also, our records are based on limited time series that began largely in the 1800s. A highly variable quantity like temperature will tend to have an expanding envelope of record highs and lows over time. Unless the rate of increase in global average temperature exceeds the rate of decrease of extreme low temperature, record lows can continue to be broken.
(2008-05-05)

Question: Does wet snow behave any differently than dry snow?

Answer: When the surfaces of individual snow crystals are close to the freezing point or just beginning to melt, the crystals become "sticky" and easily adhere to one another. This sometimes results in very large "snowflakes" that are actually agglomerations of many snow crystals. For similar reasons, wet snow tends to pack together more readily, so is easier to use for making snowballs and snowmen.
(2008-05-04)

Question: Do tsunamis all travel at the same speed, or do they have their own individual characteristics?

Answer: Many characteristics of tsunamis depend on the particulars of the initiating event, be it an earthquake, landslide or volcanic explosion. However, the long wavelengths of tsunamis leads them to behave as "shallow-water" waves, with a forward speed proportional to how deep the water is. In open ocean, they can travel at 250 to 600 mph, slowing considerably as they reach shallower waters near land.
(2008-05-03)

Question: What is the difference between "wet snow" and regular snow?

Answer: Wet snow falls through air that is close to or sometimes a little above freezing on its way to the surface, leaving it partially melted or prone to partial melting on contact. This results in wet snow having a lower snow to liquid ratio than the dry, powdery form that is more likely to occur when the air is well below freezing throughout the lower atmosphere and at the surface.
(2008-05-02)

Question: Why would a satellite image show very cold clouds in red? Isn't red indicative of warm temperatures?

Answer: Weather maps showing air temperatures are often color-coded with higher temperatures in "warm" colors such as reds, and chilly temperatures in "cool" colors like shades of blue. However, for infrared satellite imagery, where clouds are visualized on the basis of their temperature, there is no such standard rule, and the colors may be arranged in any way that best highlights features of interest.
(2008-05-01)

Question: My husband says that when you do weather on TV, you are standing in front of a blank wall. Is that true?

Answer: He's correct. A system called ChromaKey replaces anything in the picture that is a certain color (in this case, a bright green but otherwise blank wall in our studio) with satellite, radar and other graphics from computers in the WeatherCenter. We have video monitors in front of us and to either side that display the same image you see at home, so that we can point to the right places.
(2008-04-30)

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