Ask Greg

Question: Why didn't the recent tsunami reach the northwest coast of Australia?

Answer: There were some reports of abnormal waves and tides there, so the tsunami did reach that coastline, but only in a very weak form. It appears the orientation and nature of the thrust-fault earthquake that triggered the tsunami was such that it focused most wave energy more or less toward the west and east from the origination area, with comparatively little energy directed south toward Australia.
(2008-05-16)

Question: If the temperature equals the dew point so that humidity is 100 percent, could you assume it is raining?

Answer: No you can't, since the reported relative humidity is usually measured about five feet off the ground, and may not represent the atmosphere above, where the air may be too dry for rain, or even for clouds to form at times. If the surface humidity is 100% and the air is cooled further, fog or mist may begin to form. There may also be dew condensing onto objects such as grass, cars and windows.
(2008-05-15)

Question: "Tsunami" is not listed in my dictionary. What is the definition of a tsunami?

Answer: The U.S. Geological Survey defines tsunami as a sea wave of local or distant origin that results from large-scale seafloor displacements associated with large earthquakes, major submarine landslides, or exploding volcanic islands. They are sometimes referred to as tidal waves, although there is no connection between tsunami and the tides associated with lunar and solar gravitational effects.
(2008-05-14)

Question: Can we have global warming and still break record cold temps in many places in the world?

Answer: If average global temperature increases, there are still a couple of reasons to expect new record cold temperatures to be set in many locations. One of those is that most climate change models do not exclude regional variations in which a warming in average global temperature could involve above average warming in some locations, little change in others, and even a cooling trend for some regions.
(2008-05-13)

Question: I was at Grandfather Mtn last October 16th and the wind made it hard to walk. How strong was it?

Answer: You did pick a windy time to visit, as records indicate an average wind speed of 107 mph at the Swinging Bridge visitor center that day. That location exceeds 100 mph about six times per year, and clocked a peak wind of 196 mph in April 1997. At www.grandfather.com/media/database.php, you can query an archive of temperature, precipitation and wind observations taken at the site since 1955.
(2008-05-12)

Question: My third grade class at Vass Lakeview Elementary would like to know if it can snow at 42 degrees.

Answer: It is fairly unusual for snow to reach the ground at temperatures much beyond the mid to upper 30s, because this typically indicates a layer of warm air near the surface deep enough to melt snowflakes that fall into it from colder layers aloft. However, there are rare cases in which the decrease in temperature with height is especially rapid, allowing for snow at 40 degrees or warmer.
(2008-05-11)

Question: When and why did Kerr Lake's "normal" level drop from 300 feet to less than 298 feet?

Answer: Kerr Lake is operated for purposes of flood control, power generation, recreation, and fish & wildlife support by the Corps of Engineers. A complex set of operating instructions results in the "normal" level for the lake varying throughout the year, from as high as 302 feet in the spring to as low as 295.5 feet through the winter, with a decline along this "guide curve" during the autumn months.
(2008-05-10)

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)


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