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Question: I bought a fishing barometer. Is the barometric pressure inside my house the same as it is outside? To get a current relative reading, does the barometer have to be outside the house or will I get and accurate change while the instrument is indoors? — James Siewert

Answer: Unless your home is unusually airtight, you should get the same pressure reading indoors as outdoors at the same elevation. Even in a home that is sealed to an extreme degree, indoor and outdoor pressure tends to equalize rather quickly. Barometric pressure is somewhat unique in that sense, as it is one weather variable that can typically be measured indoors just as well as outdoors. That is not the case with most other quantities, like temperature, dew point, wind, precipitation and so on.
Mar. 9, 2014 | Tags: general meteorology, instruments

Question: I frequently visit a beach on Brunswick County. I used to think that it was always warmer there than Raleigh in the winter. However, this does not seem to be true, for instance, on March 16, 2013, it was 78 at RDU but 61 there. It seems like it is always 60 degrees there when it is 80 in Raleigh, why? — Gerald

Answer: It's not unusual in the late winter and early Spring for some of the immediate coastal areas of southeastern NC to stay considerably cooler than inland areas on otherwise warm days. On the day you were asking about, RDU had a stiff southwesterly wind and saw temperatures climb into the upper 70s. The Wilmington airport had a west-southwest wind (flowing across land areas being warmed by the sun) and topped out at 79. Not so far away, though, the weather station at Southport had a gusty southwest wind that came in off of near-shore ocean water to the south. Water temperature readings from the time show that those waters were ranging between about 52 and 55 degrees that day, which exerted a strong cooling effect on the nearby land, holding the maximum temperature at Southport to 61 degrees.
It's not unusual for the reverse to happen, for example on a cold night in early winter when temperatures are falling rapidly at inland sites but an onshore breeze keeps beach locations considerably milder due to water temperatures that may still be in the 60s.
Mar. 8, 2014 | Tags: general meteorology, past weather

Question: I frequently visit a beach on Brunswick County. I used to think that it was always warmer there than Raleigh in the winter. However, this does not seem to be true, for instance, on March 16, 2013, it was 78 at RDU but 61 there. It seems like it is always 60 degrees there when it is 80 in Raleigh, why? — Anonymous

Answer: It's not unusual in the late winter and early Spring for some of the immediate coastal areas of southeastern NC to stay considerably cooler than inland areas on otherwise warm days. On the day you were asking about, RDU had a stiff southwesterly wind and saw temperatures climb into the upper 70s. The Wilmington airport had a west-southwest wind (flowing across land areas being warmed by the sun) and topped out at 79. Not so far away, though, the weather station at Southport had a gusty southwest wind that came in off of near-shore ocean water to the south. Water temperature readings from the time show that those waters were ranging between about 52 and 55 degrees that day, which exerted a strong cooling effect on the nearby land, holding the maximum temperature at Southport to 61 degrees.
It's not unusual for the reverse to happen, for example on a cold night in early winter when temperatures are falling rapidly at inland sites but an onshore breeze keeps beach locations considerably milder due to water temperatures that may still be in the 60s.
Mar. 7, 2014 | Tags: general meteorology, past weather

Question: When you state "Raleigh/Durham Airport visibility.. 1/4 mi." What does that mean? — Barbara

Answer: It means that in the vicinity of the airport weather sensor, a person would be able to distinguish and identify objects reliably to a distance of no more than one-quarter mile, due to some obstruction that limits visibility, such as fog, smoke, snow, dust or heavy rain. Visibility at airport weather stations is usually measured using an automated sensor, most often a forward scatter meter and less typically a transmissometer, both of which involve measuring the light that reaches a detector after passing through some air, and converting that to the approximate distance a human would be able to see. Some larger airports also have human observers that can "augment" the visibility observations when needed. Visibility plays a significant role in safe flight operations, and can also be important to drivers and traffic, especially when it falls to 1/4 mile or less.
Mar. 6, 2014 | Tags: instruments, maps & codes, visibility/fog/dust

Question: We had some snow on the afternoon in March 1989. After only a dusting it stopped in the early evening.....but then began to snow again several inches more, but not until the wee hours then and then ended that morning. Do you know what date that might have been. All I remember for certain is that it was in March 1989. — Johnsie Segrest

Answer: We checked records from the RDU airport for that month and found that total snow for the month was one-half inch, which occurred in a couple of different event that happened on March 7-8 and on March 22, in both cases mixed with periods of rain and some freezing rain. This didn't seem to fit with your description, and you didn't mention your location at the time, so we also checked for statewide winter weather in March of that year in a database at the State Climate Office. Again, no significant snow storms turned up for the month, although there was one in February (on the 17th-19th) that produced significant snow, including for the Raleigh area.

You can check databases of past snow storms and other historically notable events for our state at the State Climate Office Winter Storm Database (www.nc-climate.ncsu.edu/climate/winter_wx/database.php) and the Raleigh National Weather Service office's "Past Events" page (www.erh.noaa.gov/rah/events/) to see if you might be thinking of a different month or year.
Mar. 5, 2014 | Tags: cool sites, past weather, snow

Question: Say you have two completely different storm systems coming towards each other, and both produce a tornado at the same time. One tornado is rotating clockwise, and the other rotating counter clockwise, and they collide, what happens? Do they cancel each other out, or do they make a stronger and bigger tornado? — Crystal

Answer: This is one of those questions that hard to answer in the sense that the physics of the atmosphere is such that it works against the likelihood of the event we're talking about actually happening. For well-organized supercell thunderstorms (the kind that are prone to produce significant tornadoes that can become intense and last a while), the larger scale conditions that spawn them would lead to the cell following parallel paths that wouldn't tend to intersect. If you did manage to have a clockwise-rotating storm and a counterclockwise moving on paths that would merge them, it is very likely that outflow winds would disrupt the circulations that allow the storms to feed on low-level warm, moist inflow, so that before they ever reached one another they would cause a dissipation of the tornadoes involved.

There have been cases where one supercell produces a series of tornadoes and a decaying one still exists while a new one intensifies. On rare occasion, one can orbit the other as a "satellite" tornado before its circulation either dissipates or is disrupted by the flow around the stronger vortex. If they were able to actually merge, then it's likely the weaker circulation would simply disappear into the stronger one, without a noticeable effect on intensity (keep in mind tornadoes aren't "objects" as such, but instead are processes, in the form of organized movements of air).
Mar. 4, 2014 | Tags: general meteorology, severe weather, tornadoes

Question: Wife has asked, and I am now curious.. what is the height above ground of the camera we see Western Blvd on? Bet there are more than a few people who would like to know that... — Jim Dawson

Answer: That would be what we refer to as the "Raleigh Skycam," which is located near the top of the 300-foot tall relay tower just behind the station in southwest Raleigh. The camera isn't mounted at the very top of the tower, so is probably around 285 feet or so above ground level.
Mar. 3, 2014 | Tags: instruments, wral.com

Question: Has Raleigh or Wake County ever experienced blizzard conditions? If so, when and what storm? — Chris F

Answer: "Blizzard" has a fairly specific definition in meteorological circles, with a couple of fuzzy aspects, and to check on an occurrence you really need hourly observations, a database of which has been available since the 1940s from RDU. The Southeast Regional Climate Center ran a set of queries on that database to see if we'd met those criteria, and found the answer was no, although there were three storms that at least came within shouting distance.

A blizzard means that winds are either sustained at or frequently gusting to 35 mph or higher, and that visibility is frequently below one-quarter mile in snow or blowing snow, and that those conditions exist for a period of three hours or more. Three storms that came fairly close in terms of lots of wind and poor visibility in snow and blowing snow (but with winds that never became quite strong enough to qualify as a blizzard) occurred on 10 Feb 1973, 2 Mar 1980 and 25 Jan 2000.
Mar. 2, 2014 | Tags: past weather, snow, winds, winter weather

Question: How much snow accumulation in the Great Lakes produces a foot of water? — James Kokolis

Answer: We presume you mean how much melted snow would result in 12 inches of liquid water, and that you're probably interested in the classic "lake effect" snows. The answer is highly variable depending on the particulars of a given lake effect event (very cold air blowing across relatively warm lake water). Some studies have been done characterizing these ratios, and they show a great variability, with the lake effect snows producing generally much larger snow to liquid ratios than snows produced by traveling frontal and low pressure storms systems. As one example, in Marquette, MI the median ratio for lake effect snows is about 30:1, but to capture just the middle 50% of the variation takes you from 22:1 up to 43:1, and the extremes can be higher and lower than that. To give a reasonable range for these kinds of snows, then, you could melt down to 12 inches of liquid from 204 inches of snow on the low end of that middle 50%, 360 inches of snow at the median ratio, and 516 inches from the upper end.

This is very different from snow that usually occurs in our area, where the average ratio is fairly close to 10:1, but we are subject to significant variability as well, and the ratios can easily run between 5:1 and 20:1 here, depending on the temperature in the layers at which snow forms and through which it falls.
Mar. 1, 2014 | Tags: general meteorology, snow

Question: I used to like to look at weather maps for the rest of the country. How can I get them back on the new site? — Kay Lindquist

Answer: There are a couple of links on the main weather page that take you to the "Map Center." On that page, you'll find selections for radar and satellite maps. Clicking wither of those brings up that kind of map centered on our state, but you can then click the state label to select from a variety of other views covering different sections of the United States.
Feb. 28, 2014 | Tags: maps & codes, wral.com

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