Ask Greg

Recent Questions

Question: How is it that "hurricanes" are now reported in the Pacific? — Kirk Hilton Proctor

Answer: We're not certain why you enclosed the word hurricanes in quotes, but hurricanes have long been a part of the weather regime (and reported as such) for the central and eastern North Pacific Ocean, where the Central Pacific Hurricane Center (CPHC - Honolulu, HI) and National Hurricane Center (NHC - Miami, FL), respectively, are responsible for tracking, forecasts and warnings, just as the NHC does for the Atlantic basin. When tropical cyclones in any of these basins have sustained winds reaching 74 mph or higher, they are referred to as hurricanes, so long as they remain east of the International Date Line (the 180-degree meridian). The same kind of storm in the northwest Pacific is referred to as a typhoon, while similar storms in the south Pacific and Indian Oceans are generally referred to as some variation of "Severe Tropical Cyclone." Different naming conventions apply to storms depending on which basin they are in. You can see a description of those naming systems and lists of names for all basins worldwide at www.wmo.int/pages/prog/www/tcp/Storm-naming.html.
Oct. 22, 2014 | Tags: cool sites, hurricanes

Question: Do you think we will have a lot of snow or ice this winter? — Linda

Answer: Unfortunately, we just don't have a lot of reliable signals to use in forecasting details regarding how much snow or ice may occur in an upcoming season. There are some techniques that can take advantage of such things as predictions of El Nino or La Nina sea surface temperature conditions in the Pacific Ocean, and the amounts of Fall snow cover in Siberia, for example, but these tend to relate to winter temperature trends, and to a lesse extent overall precipitation trends, more so than to snow and ice specifically. Recent projections for Winter 2014-15 from the National Weather Service have our area with an equal chance of above, near or below normal winter average temperature, and within an area with a slightly higher chance of above normal precipitation as opposed to near or below normal precipitation.
Oct. 21, 2014 | Tags: winter weather

Question: What is the ideal temperature and dew point combination for fog in Southern Wake County? — John

Answer: There isn't a single ideal combination, and the formation of fog can be affected greatly by a number of factors beyond a simple combination of a surface measurement (4-5 feet off the ground) of those two variables. In a general sense, if dew point and temperature are very close together or the same, the air is saturated and there is at least some potential for fog. At colder temperatures, there is less water vapor in the air and so fog may tend to be less likely to be realized or tend to be less dense, while warmer temperatures favor thicker fog. Also, fog formation is more likely if the soil is cool (relative to air temperature) and moist, if vegetation is actively transpiring moisture, if winds are very light, if clouds at higher levels are lacking and if the amount of moisture in the lowest levels of the atmosphere tends to increase a bit with height rather than decreasing.
Oct. 20, 2014 | Tags: atmospheric optics, clouds, humidity/dew point

Question: I was just reading some of the posts and saw the suggestion of storing food in your dishwasher, even a washing machine when your power goes out and packing it with ice! Unfortunately, without power, neither will automatically drain, thus leaving your food sitting in water that will enable bacterial growth. — Chuck

Answer: Very good point, and anyone thinking of using those suggestions would probably be well advised to place any unsealed food that might be stored in a dishwasher up in the racks so that meltwater would not be in contact with the food, and can then drain away when power is restored, or if practical to leave most of the ice in watertight plastic bags until after the power is back on. Note that the other answer (available by using the AskGreg search box to find the word "dishwasher") also includes links to extensive lists of power outage tips from FEMA and the Red Cross.

Oct. 19, 2014 | Tags: preparedness, severe weather

Question: July 1, 2014 : what was the temperature, humidity for this day? — Beth

Answer: At the RDU airport, we kicked off the month of July this year with a low of 74 degrees and a high of 93. The lowest dew point of the day was 62 degrees and the highest was 72, with relative humidity ranging from a maximum of 71% in the morning to a minimum of 47% in the afternoon. You can check these kinds of numbers anytime through the Almanac section of our web site, using the "get historical data" section.

Oct. 18, 2014 | Tags: past weather, wral.com

Question: Can you tell me how meteorologists take account of contrail clouding into your weather forecast? Everyday planes leave long contrails that turn into clouds that produce rain. Everyday they cover my sun over my Farm. How do you meteorologists take this into your weather forecast? — Sue

Answer: High altitude aircraft can indeed leave long, persistent condensation trails in their wake when atmospheric conditions at flight level are in the appropriate ranges for temperature and ambient humidity (along with relatively limited amounts of turbulence and wind shear). When we notice these conditions on days with little likelihood of other, lower clouds that may obscure the view of higher altitudes, we'll occasionally mention that in our forecasts. On such days, especially when naturally produced cirrus cloud cover is lacking, contrails can spread and induce the formation of cirrus cloud that would not otherwise occur.

On many other days, however, conditions are not favorable for contrails to form or persist, and they will either be absent or only exist for a very short distance behind the aircraft. On some of these days, conditions are otherwise favorable for some natural cirrus to form, or we simply see clear blue skies (assuming there are not intervening lower clouds in place).

In regards to taking these into account in our forecasts, apart from including a mention of patchy high cloudiness or occasional contrails, there isn't much other direct impact. If the high clouds appear fairly extensive, we may reduce temperature forecasts a bit in the daytime, or increase low temperature predictions for overnight. In most cases, the presence or absence of contrails has little impact on precipitation forecasts, which depend much more heavily on moisture at lower levels of the atmosphere.

In a broader sense, aircraft emissions at high altitudes do result in a small increase in water vapor and thus humidity at those levels than would occur otherwise. That water vapor becomes part of the overall atmospheric moisture budget, and is included in humidity measurements taken with radiosonde balloons and by instrumented aircraft, and therefore feeds into initializations of the computer forecast models we use to predict the future state of the atmosphere. In that way, changes due to aircraft emissions are taken into account in forecasts implicitly even if a specific mention of contrails isn't made.
Oct. 17, 2014 | Tags: clouds, controversy

Question: I live just West of Jordan Lake (Chatham County) and have noticed on many occasions that rain moving towards the east will diminish as it approaches the Jordan Lake area. Is the lake itself a factor that causes this? — Tom Coleman

Answer: Moving areas of rain, including convective showers and thunderstorms, are subject to a large number of influences, some local and some larger scale, that can cause them to vary substantially in size, shape and intensity over short periods of time. While it is possible for lakes (like Jordan), rivers and topography in general to affect low level temperature and humidity fields in a way that can feed into the behavior of some nearby showers and storms, it can be very difficult to generalize about what those effects are, or to separate those influences from any number of others for a particular episode or series of episodes such as you've noticed in Chatham County from time to time. One aspect of this whole issue that you may find interesting, though, is one of perception. Radar imagery of most showers and thunderstorms, especially at some distance from the radar site, tends to make them appear larger than they really are, and causes some individual cells to appears merged into one larger area. One result of this is that less area may be affected by rain, or by heavy rain and storminess, than one might expect when scanning radar loops. In addition, people focus very closely on how these cells behave near their location, but not so closely on how other cells are evolving in locations they are less interested in. This is evident to us because of the fact that we frequently receive questions like yours (what makes storms split up or dissipate when they approach my town?) from pretty much every part of our viewing area!
Oct. 16, 2014 | Tags: general meteorology, rain, weather radar

Question: For 62 years, I thought "there" and "their" were homonyms. They aren't. They are homophones. Homonyms are words that are spelled exactly the same but have completely different meanings. Bear is a homonym... A brown bear can bear a great weight. Weight and wait, like bear and bare, are homophones. — Jim Murphy

Answer: For anyone wondering what this entry has to do with weather, we recently answered a question about closed captioning used in some of our on-air forecasts, and made note of some of the humorous translations of words that sound alike that sometimes pop up. (You can find the original question by using the search box at the top of the AskGreg page and entering "closed captioning").

In that answer, we used the word homonym where homophone would have been the appropriate term. Thanks Jim for catching that! We've updated the previous answer in our database. Incidentally, it's interesting to note that in the examples Jim provided, wait and weight are strictly homophones, while bear and the other meaning of bear qualify as both homonymns (same spelling, different meanings), homographs (same spelling, different meanings) AND homophones (same sound, different meanings).
Oct. 15, 2014 | Tags: wral.com

Question: How do you find out how much rain you received on a previous day and date, specifically, how much rain did i get zip 27603 9/23,24,25, 2014. It rained all night the 23rd and all day the 24th. I know it takes a lot of rain to receive 2 inches. I think we received 1 1/2 inches. Is that about right? I have tried 3 or 4 web sites with no luck. — Vicky

Answer: We checked a site run by the State Climate Office and found rainfall at a station not far from you (Lake Wheeler) that rainfall during that period totaled 1.25". We also checked readings from numerous sites that are part of a volunteer observation network, a number of which are peppered around you general part of Wake County, and found a range fro that time frame from about .5" on the low end to around 2 inches. This general range was in agreement with radar-based estimates for that time span from the NWS Precipitation Analysis page that indicated roughly 1.5" around your part of the county. The sites we used take a bit of effort to learn your way around, but if you'd like to have a look they are www.nc-climate.ncsu.edu/cronos, www.cocorahs.org/ViewData/ListDailyPrecipReports.aspx and water.weather.gov/precip/.
Oct. 14, 2014 | Tags: cool sites, past weather, rain

Question: A hint....When power is off for an extended amount of time, pack your dishwasher with ice. The insulation allows the ice to melt slowly an acts as a mini refrigerator. Your food stays cold, but I wouldn't depend on it for meats ,etc. As the ice melts, the water goes down the drain! — Cameron

Answer: That's an idea we hadn't heard, but it might work reasonably well, and you could probably apply the same reasoning to storing some food in a clothes washer, assuming in both cases that sufficient amounts of ice are readily available. There is also the option of using coolers, which are also insulated. They would not drain away melted water automatically, but there might be situations where having that water remain available for washing, rinsing or other non-drinking uses would be beneficial as opposed to discarding it as it melts. For a more comprehensive list of tips on preparing for or enduring an extended power outage, check the lists at www.redcross.org/prepare/disaster/power-outage and www.ready.gov/blackouts.


Oct. 13, 2014 | Tags: cool sites, preparedness

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