Ask Greg

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: Tornadoes certainly do occur in both those areas, but geographic factors lead to a much lower prevalence there than in parts of the United States. For example, a French study of significant (F2 and stronger) tornadoes there identified 58 between 1960 and 1988, and established that the frequency of such tornadoes was about 1/15th that of the U.S. Great Plains region. Notable tornadoes have been reported in most other European countries as well. It's likely we don't hear about more of them because they are both infrequent and often deemed of primarily local rather than international news value.
Aug. 28, 2009 | Tags: tornadoes

Answer: Clouds that are deep enough to produce heavy rain, lightning and hail contain a tremendous amount of water in the form of cloud droplets, rain drops, ice crystals and hail, all of which can scatter, reflect and absorb light. If you happen to be on the opposite side of such a cloud from the sun, it will appear dark due to the lack of light passing though it, and likewise it will become rather dark underneath the storm. On the other had, if you see the same storm cloud, but you are between the sun and the cloud, it will appear bright white due to the light it reflects and scatters back toward you.
Aug. 27, 2009 | Tags: atmospheric optics, clouds, thunderstorms

Answer: Since hurricanes are large and often long-lived storms systems that can have serious impacts and typically garner great interest from the public, they are given names that make referencing a particular system simpler for meteorologists, news organizations, emergency management and response personnel and the public at large. This is especially useful in cases where two or three storms may be active in the same basin simultaneously. It would be much more cumbersome to identify each storm by constantly changing latitude/longitude, for example, and if storms were simply given an identification number or letter, those would likely not be as easy to remember as a "human" name.
Aug. 26, 2009 | Tags: hurricanes, preparedness

Answer: It's unclear whether the "hurricane" references on the show are to large synoptic winter low pressure systems driven by horizontal temperature gradients (similar in many ways to the nor'easters that affect the U.S. Atlantic coast), which on rare occasion may produce sustained surface winds reaching 74 mph or higher, or whether they are referring to a phenomenon called a "polar low," which some meteorologists have referred to as arctic hurricanes. These systems rarely if ever produce hurricane force winds, but are quite intense nonetheless, and in addition can have some thermal properties (warm core, no frontal boundary) and an appearance on satellite (a clear "eye") similar to tropical cyclones. Even though the northern waters are not warm by any means, the important issue with driving these cyclones, whether in the tropics or polar regions, is the difference in temperature from the sea surface to the middle/upper atmosphere. You can learn more about these systems and see some interesting satellite images at nsidc.org/arcticmet/patterns/polar_low.html, and www.eumetcal.org.uk/polarlow/cometplows/polarlows/print_index.htm.
Aug. 25, 2009 | Tags: cold, hurricanes

Answer: A process called near field coupling can occur in which strong electric fields associated with lightning can induce large voltages and currents in conductive materials, in some cases sufficient to cause damage to sensitive electronics. However, at the small size of cordless phones, cell phones and the like, this doesn't appear to be a major issue and virtually all lightning safety literature supports the use of these items in place of corded phones during a thunderstorm (assuming you are otherwise in a well-protected location, of course).
Aug. 24, 2009 | Tags: lightning, thunderstorms

Answer: There had been 4 tropical depressions at the time you wrote in, but the first one back in late May never reached tropical storm strength, and therefore was never named. Depressions 2, 3 and 4 did reach tropical storm strength, so they took the a, b and c names (Ana, Bill and Claudette) from this year's list.
Aug. 23, 2009 | Tags: hurricanes

Answer: That reading you recalled of 77 degrees is oppressively humid in itself for this part of the world, and a level that is rarely reached. However, the State Climate Office carried out a records search that shows the Raleigh-Durham airport has recorded dew points of 80 degrees or higher on eight days since 1948. The only two days to reach above 80 were July 24, 1965, when the dew point held at 81 for three hours late in the day, and on August 10, 2007 when there was one observation, shortly after a brief shower on a very hot day, with the dew point spiking to a super-steamy 82 degrees.
Aug. 22, 2009 | Tags: humidity/dew point, records/extremes

Answer: A few people have asked about that, given a relatively quiet start to the 2009 season through early August. Historically, a number of seasons have ended up with no named tropical cyclones all the way through July. The 1914 season takes the prize for being "slow," however, with its first and only tropical storm forming on September 15th and lasting until the 19th. No hurricanes formed in that year. Late formation does not necessarily equate to weak systems, of course. In 1992, the first named system of the year did not form until August 16th, and went down in history as Category 5 "Andrew."
Aug. 21, 2009 | Tags: hurricanes, past weather

Answer: To figure that out, you need one more piece of information. When we refer to one inch of rainfall, for example, that means the amount of rain that would stand one inch deep in a level flat container with vertical sides. To calculate the amount of water involved in your case, you would have to find out how far out from the base of the tree you need to water evenly, then compute the area in square inches (remembering the old "pi times radius-squared" equation). Since you're looking for a one-inch depth, this will also be the volume in cubic inches of water needed, which can then be converted to gallons.
Aug. 20, 2009 | Tags: rain

Answer: Updates to seasonal outlooks from NOAA and from Colorado State University that were released in August decreased the predicted number of storms for the 2009 season, due largely to the developing El Nino pattern in the Pacific. The updated forecast from NOAA calls for 7-11 named storms and 3-6 hurricanes, while the updated forecast from CSU predicts 10 named storms and 4 hurricanes. Note that the average numbers for the period 1950-2000 are 9.6 named systems and 5.9 hurricanes.
Aug. 19, 2009 | Tags: el nino/la nina, hurricanes