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Answer: It depends a little on what you mean by speed, but the most important measure of that in a practical sense is that the angular velocity of earth's rotation leads it to spin just over once around (361 degrees) in a solar day, while the moon's angular velocity averages about 13 degrees per solar day, so it takes 27.3 days for the moon to circle the earth. Another way to look at speed, of course, is forward speed in miles per hour. On the earth, the surface at the equator is moving eastward about 1040 mph due to rotation, while the moon's forward speed in orbit is almost 2300 mph. However, a spot at the equator only has to travel around 24,900 miles in a single rotation, while the moon has to travel about 1.5 million miles in a single orbit.
Sep. 26, 2009 | Tags: astronomy

Answer: Our bodies lose heat more rapidly when the wind is blowing, which makes it "feel" colder than it really is, and wind chill is an estimate of the air temperature that would be required to produce the same rate of cooling in the absence of significant wind. A good explanation, an easy to use chart, and the formula used for calculations can be found at www.nws.noaa.gov/om/windchill/index.shtml.
Sep. 25, 2009 | Tags: apparent temperature, cold, cool sites, winds

Answer: Quite a few tropical cyclones form in the southern hemisphere, although the numbers are much higher in the north. Most southern hemisphere storms occur over the western South Pacific and across the southern Indian Ocean between Africa and Australia. On the other hand, they are extremely rare over the South Atlantic. You can get a visual sense of their worldwide distribution using a map of all tracks from 1945-2006 at upload.wikimedia.org/wikipedia/en/0/0f/Tropical_cyclones_1945_2006.png.
Sep. 24, 2009 | Tags: cool sites, hurricanes, maps & codes

Answer: Hazel swept across our state on October 15th of that year. As far as what the year was like overall, we can look back at some of the yearly statistics for a very rough idea. In 1954, the Raleigh-Durham airport recorded 41.6 inches of rain, about 4.6 inches below normal, with measurable rain falling on 102 days, compared to a normal of 119, and it appears it was a fairly bright year, with 99 days listed as "cloudy," versus a normal of 118. Snowfall totaled 8.9 inches, almost two inches above the normal of 7.0, with over an inch of snow falling on 4 separate days. Temperature-wise, the year was fairly close to normal, with an average high of 72.1 degrees (normal 70.9) and low of 48.1 (normal 48.8). It is notable that those numbers masked some sizable extremes, though, as the high reached 90 or above 59 times (normal 40) while the low dropped to freezing or colder 77 times versus a normal of 51.
Sep. 23, 2009 | Tags: hurricanes, past weather

Answer: The decrease you're asking about actually begins a little sooner than you might think. The "normal" high for Raleigh-Durham, as derived by the National Climatic Data Center based on thirty years of data ending with the most recent "zero" year and rounded to the nearest degree, drops from its peak value of 90 on July 22 to 89 for July 23. The rate of decrease from day to day is very slow for a few weeks, dropping to 88 on August 6, then picks up pace as we head on into the fall. You can find a listing of those daily normals at www.erh.noaa.gov/rah/climate/data/rdu.daily.normals.html.
Sep. 22, 2009 | Tags: cool sites, heat, past weather

Answer: Lightning itself doesn't really explode, but if it heats a contained liquid to the point of almost instantaneously vaporizing it, an explosion may result. In the case of trees, this can result from the sudden heating of sap or water under the bark or occasionally within the wood. The very rapid expansion of liquid into vapor can blow patches of bark off, or sometimes split the tree. Damage can be obvious or somewhat hidden within, and the health of the tree may not always correspond to its outward appearance after a strike.
Sep. 21, 2009 | Tags: lightning

Answer: There are two principle ways pressure is measured. Mercury barometers consist of a glass tube filled with mercury that is inverted and placed in a reservoir that is exposed to the air. The force per unit area of the mercury column will then balance the force per unit area of the atmosphere (its weight, more or less) atop the reservoir. Higher pressure forces the column higher, and vice versa. A smaller, more convenient and portable device for measuring pressure is the aneroid barometer, in which a sealed flexible metal chamber from which air has been removed will compress when outside pressure is higher and vice versa. The chamber is then linked mechanically to a pointer and calibrated scale from which the pressure can be read. That is a very brief description, and you might like to search aneroid and mercury barometers on the web for some pictures that will help better illustrate their operation.
Sep. 20, 2009 | Tags: instruments

Answer: The size of the "squares" would depend on the spacing interval chosen for the map in question. We frequently use maps with a spacing of every 5 degrees latitude and longitude and occasionally include a second set of lines with one degree spacing. The question then becomes, how much distance is associated with each degree? For latitude, each degree is roughly 60 nautical miles or 69 statute miles. For longitude, the same numbers apply at the equator, but since longitude lines all converge at the poles, the distance between them decreases with increasing latitude and is equal to 60 nautical miles times the cosine of the latitude. At 35 degrees north for example, a degree of longitude covers about 43 nautical miles, or 49 statute miles. For a concise discussion of longitude and latitude, see www.nationalatlas.gov/articles/mapping/a_latlong.html.
Sep. 19, 2009 | Tags: hurricanes, maps & codes

Answer: Like many processes in meteorology, it would be nice if there was a straightforward, simple answer to that! However, many other factors come into play in causing precipitation to form or dissipate and in causing pressure to rise or fall, and it is possible in specific circumstances for developing precipitation to result in pressure changes, and for pressure changes to trigger precipitation. Overall, though, it is probably reasonable to say that the more common and dominant relationship of the two you mentioned is for falling pressure to contribute to the formation of rain.
Sep. 18, 2009 | Tags: general meteorology, rain

Answer: You probably noted in the class that most significant tornadoes form on the right rear flank of supercell thunderstorms, relative to the direction of storm movement. If the supercell is a "discrete" storm, out on its own, then most of the rain, thunder and lightning would be over when the tornado moves through or very shortly afterward. However, sometimes the tornadic supercell can be just one part of a larger group or line of thunderstorms, in which case additional areas of rain, lightning and perhaps hail may pass across the same area. In rare cases, there can even be multiple tornadic cells that cross the same or nearly the same location.
Sep. 17, 2009 | Tags: severe weather, thunderstorms, tornadoes