Ask Greg

Recent Questions

Question: I noticed that rain on Wednesday Sep 24th came from SE to NW and seemed to be in a counterclockwise rotation. Is this a tropical system that just developed late or is it a different type of system that moves in this manner? — Robert

Answer: There was not a tropical cyclone in the area that day, but some significant moisture from the western Atlantic area was pulled into the system that brought moderate to heavy rain our way. That system was made up of a nearly stationary surface front along the coast, with a trough of low pressure at successively higher levels in the atmosphere that tilted westward so that the trough axis at, say, 10,000 feet up was stretched more or less along the I-95 corridor well inland. Winds through that trough didn't make a complete circle, but did curve in a counterclockwise manner that gave the appearance of rotation that you noted.
Oct. 3, 2014 | Tags: past weather, rain

Question: Was there any tornado activity reported the night of September 23-24th? During the night our front door was ripped off by a powerful wind that snaked up our stairs--sounded like a horde of very large animals running down the upstairs hall--was over quite quickly. — Leonne Harris

Answer: There were no tornado reports from that night, and there were also no "local storm reports" concerning wind damage from non-tornadic gusts. We also checked whether any warnings were issued that night, and it appears that none were. We also looked at several stations' wind reports, and found that while winds generally ran from the northeast at about 5-15 mph, there were some peak gusts in the 20-30 mph range associated with the bands of shower activity that passed through that night. Of course, very localized effects may have produced some higher winds that were not picked up at any of these stations, but based on the lack of tornado and wind reports, it appears your situation was very unusual for that night.
Oct. 2, 2014 | Tags: past weather, tornadoes, winds

Question: I really love looking at weather radars and observing forecasts in my area. I really want to be a meteorologist when I am older. I was wondering is it possible for it to snow when the temperature is above 32 degrees? — Eric Magoon

Answer: For snow to form, the temperature at the altitude where the snow crystals grow does have to be below 32 degrees, and in fact to get a decent snow usually requires there be a moist layer that is in the range of about -4 to 14 degrees F. However, those crystals, and the snowflakes that are often composed of multiple crystals stuck together, can sometimes survive falling through a shallow layer of air that is above freezing near the surface. In that way, at ground level it can indeed snow at temperatures above 32 degrees, and on rare occasion it can do so with surface readings well into the 40s. Good luck to you if you decide to pursue meteorology in the future!
Oct. 1, 2014 | Tags: cold, snow

Question: When wind direction is given for my town, Rocky Mount, NC, why is the direction on my yard's weather vane often showing a different direction even though the wind is substantial and not being blown about by gusts? Is this a normal for wind directions in most places? — Carlisle

Answer: Winds do tend to be fairly variable in direction, although at higher speeds they do tend to be a little more uniform over space and time. Even then, local topography, the orientation of wind relative to obstacles like buildings and wooded areas, and the complexities of flow near the surface in the presenace of such obstacles. You don't mention how high your vane is off the ground, but the standard wind measurements reported by airport weather stations are taken at 10 meters, about 33 feet, off the ground in an open, usually rather flat area. Finally, you're probably aware of this, but just to make sure, the direction of winds reported in weather observations give the direction the wind blows from, rather than the direction the wind blows towards. One thing you can do is look at winds reported not only for Rocky Mount, but for several surrounding airport stations. If many of those are in good general agreement and your vane differs significantly, you may have either some significant localized effects, or a vane that isn't calibrated quite correctly.

Sep. 30, 2014 | Tags: general meteorology, winds

Question: Are global models truly global, or northern- and southern-hemispherical? For regional models (European, Canadian) how do they handle a weather system just outside and upstream of their region? — Chris

Answer: Global models, as implied in the name, do indeed represent the atmosphere around the entire world, and when you see a regional map from the American GFS (Global Forecast System), Canadian GEM (Global Environmental Multiscale) and European (usually referred to as the ECMWF, or European Center for Medium Range Weather Forecasting, also called the Integrated Forecast System) and a couple of others run by the United Kingdom Met Office and the U.S. Navy, you are in fact seeing just a section of that model presented for a limited portion of its global domain.

On the other hand, there are regional models that do run, usually at higher time and space resolutions that provide greater detail, over more limited portions of the globe. These models have to have horizontal "boundary conditions" provided along their edges, and these values are often provided by the initialization and/or forecast fields from the larger global models. There can, as you alluded to, be problems simulating systems that move into the domain of these models from more distant locations, so the domain and time frame over which these models are run are usually chosen to be large enough (domain) and short enough (duration of the forecast) so that these "edge effects" mainly impact portions of the domain outside the area of primary interest.

Sep. 29, 2014 | Tags: general meteorology, maps & codes

Question: Where can I find daily air quality information, such as green, yellow etc? Since I have asthma, this is important information for me to have. — Nadine

Answer: On our main weather page, look for the "Resources" link in blue letters near the top. Then scroll down a bit on the resulting page and you'll see a link to "NC Air Quality Forecast." That will take you to a forecast page prepared by the NC Division of Air Quality that provides expected levels of ozone and particulate pollution, and where those forecasts fall on the color-coded scale from green (good) to purple (very unhealthy).
Sep. 28, 2014 | Tags: air quality,

Question: When was the first "official" day of fall? My calendar says September 22nd, but when I Google the question I get September 23rd. So... now I am coming to "the expert." :-) — Faye B

Answer: The traditional definition of the first day of Fall is based on Astronomy, and is the day on which the Autumnal Equinox occurs. This year, that was at 10:29 PM EDT on Monday, September 22nd. However, when you look up the time of the equinox, it is sometimes given in "Universal Time," which corresponds to the time at the Zero-degree meridian, which runs through Greenwich, England. At that location, 10:29 PM EDT for us is their 2:29 AM on September 23rd, so the fact that parts of the world are already into the next day on the calendar when the equinox happens may account for some of the variation in dates you noticed. Just to make things even more complicated, those of us in the weather and climate business usually think of the seasons in terms of typical mid-latitude weather conditions, and consider September 1st the beginning of "meteorological Fall!"

Sep. 27, 2014 | Tags: astronomy, general meteorology

Question: In your answer about the safety of submerged scuba divers you neglect one possible issue. Many divers maintain a diving flag above their diving location to warn away small boats. These flags are sometimes pulled by divers using a line, or are anchored nearby diving operations. During a lightning strike, this line could form a path of least resistance, and allow the lightening to conduct current down the path. — Mark Erickison

Answer: That's a good addition to the recent question and answer. We would think that a flag buoy connected via a non-conductive line wouldn't lead to much of an increase in current conducted into the water, although perhaps an argument could be made that there might be a slight enhancement due to the interface between the line and water. One certainly wouldn't want to be near a "diver down" buoy line that was composed of metallic cable or a chain, though.

Sep. 26, 2014 | Tags: lightning, weather & health

Question: Do you promise to continue at WRAL and NOT retire for at least 10 more years? The viewers are not ready for an un-O'Fishel weather team. That's just my 2¢ worth. — Denise Hughes

Answer: Denise, thanks very much for your kind words and support. I don't have any plans to leave or retire anytime soon. I also know that every day is a gift, and should not be taken for granted. So I try to take life one day at a time. Ten years is a long time :-)
Sep. 25, 2014 | Tags:

Question: What is the record for the fewest 90 degree days in August? — Neil G.

Answer: We just finished off an August (2014) with relatively few days reaching 90 or higher, in this case six. However, you might be surprised to find that the record for fewest is actually zero, which occurred in 1969. In records for the Raleigh area that stretch back to 1887, there are three other years (1887, 1889, and 1971) in which only one day in August reached or exceeded that threshold.
Sep. 24, 2014 | Tags: heat, records/extremes

Questions 21 - 30 of 4377.

Ask Greg Your Question Now!

Please understand that the volume of Ask Greg questions makes it impossible to answer every one or to list them all here. You may find it helpful to search for your own question using the form at the top of this page to see if it has been posted in our database.

When you submit a question you understand that your question and e-mail address will be sent to our editorial staff. Accordingly your question will not be subject to the privacy policy of this site.