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Recent Questions

Question: Can the Nuclear Plant have an effect on my weather? I live about three miles N.E. of the plant. — Duncan Humphrey

Answer: It is possible for facilities like this to have some effects on weather, although in many cases the impacts are pretty minor. That may be the case more so for the Harris plant than some others, since there is only one cooling tower there, compared to several more than that for some other plants, and we've also see examples of impacts from co-located nuclear and coal power plants that have as many as 5 or 6 towers and exhaust stacks to emit heat, water vapor and particulates that can either create clouds and occasionally showers or storms where they otherwise would not exist, or enhance those that are already passing over the area. In your case, there may be days when the general wind pattern is to blow from the southwest that your temperature and humidity levels would be a little higher than places off to your northwest or southeast, and in some cases there may be a noticeable cumuliform cloud overhead in an otherwise mostly clear sky. If the atmosphere is already close to an appropriate profile of temperature and humidity to produce shower activity, the heat and moisture in a plume from the plant could at times trigger a shower a little earlier than surrounding areas as well.
Sep. 13, 2016 | Tags: air quality, general meteorology

Question: Does the state require annual equipment calibration before accepting weather data from a weather station? — Steve

Answer: Most "official" weather instruments used by government agencies does require routine preventive maintenance and periodic calibration checks. The exact requirements depend on the applications involved, and generally are more strict and exacting for use by the National Weather Service and for climate monitoring purposes, and somewhat less so for more local agricultural monitoring networks and so on. Generally, the equipment is subjected to quality control monitoring of data received remotely, very basic monthly inspections, more detailed quarterly or tri-annual checks involving the use of well-calibrated portable reference instruments used to compare readings against those being checked. If the readings differ beyond prescribed thresholds, the existing instrument is replaced or repaired as appropriate. In some cases, there is also an annual re-certification requirement.
Sep. 12, 2016 | Tags: instruments, maps & codes

Question: Is there somewhere in North Carolina that would calibrate and certify barometers and possibly other weather measuring devices as well? — Steve Wildermuth

Answer: We were unable to think of anyone available to do the kind of calibration/certification on home weather euipment that you asked about. You might want to check with some online vendors of home weather stations and see if they have any programs for repair or calibration that can be done by mailing in the equipment. However, some equipment, such as most barometers, have a means of adjusting the reading and performing your own calibration, so long as you have reasonably accurate numbers to compare to. What we often recommend, as Checking your barometer readings against a nearby airport on a day when there is a weak pressure gradient across the region (no big storm systems nearby or sharp frontal passages imminent). Match your barometer to that and you should be in good shape, since for monitoring a single site you're more interested in changes of pressure more so than the absolute value. For temperature, a good way to check against nearby stations is to do those comparisons several times over a few days, and look for periods of time when it is rather cloudy and windy, as these conditions minimize the variability of temperature over short distances. You could also check at least one verifiable data point for your thermometer by placing the probe in a slurry of crushed ice and water. The temperature should read very close to 32 degrees F or 0 Celsius.
Sep. 11, 2016 | Tags: instruments

Question: Are there data sources publicly available that track the major pressure systems (i.e. Azores) in a fashion that is similar to hurricane tracking applications? — Matt B.

Answer: We can't think of anything that sounds exactly like what you're asking for, but we can point you to a ocuple of possible resources. First, there is a cyclone genesis and tracking page maintained by the NWS Environmental Modeling Center. You can go to www.emc.ncep.noaa.gov/gmb/tpm/emchurr/tcgen/, and click on the initial time you're interested in from he list of model runs on the left. This site focuses, as do most if not all, on low pressure systems and not on highs. You'll see a wide variety of models and map areas, and can click any "green checked" box for a view of anticipated storm tracks on that part of the earth, including good coverage of the Atlantic in the rows labeled "NW Atlantic." There are also some observed storm tracks (tropical and extratropical) for the northern hemisphere available from the Climate Prediction Center at www.cpc.ncep.noaa.gov/products/precip/CWlink/stormtracks/strack_NH.shtml.

You can also check general model trend for the north Atlantic that include surface and upper air projections that allow for following the positions of lows and highs using any number of sites with model graphics. These extend anywhere from around 180-240 hours into the future. One example is the Atlantic projection at the Penn State e-wall, at mp1.met.psu.edu/~fxg1/ewalltropatl.html.
Sep. 10, 2016 | Tags: cool sites, hurricanes, maps & codes

Question: I have heard there was a storm that formed off the coast of Africa heading to NC and if it hits it will be a big storm but haven't heard anything else about it. Is this true? — Emily

Answer: You sent your question on Labor Day, and at the time there was no system in the Atlantic that matched that description. There is a wave moving off of Africa a couple days later that has a chance of slowly developing into a tropical cyclone, but projections thus far do not indicate an especially strong system, and also tend to track it into the mid-Atlantic without any impact on the USA. As we're in the heart of hurricane season, of course, that doesn't preclude the development of additional disturbances that could impact our state, so we all need to continue to monitor the tropics through the next month or two.
Sep. 9, 2016 | Tags: hurricanes, preparedness

Question: How small can a microburst be? I read some pages on the NOAA website that indicated they were usually less than 2.5 miles, but how small can they realistically be? — Gary Roberson

Answer: A microburst is a form of downburst, meaning a volume of air descending rapidly from a thunderstorm, impacting the surface and spreading outward. As you noted, microbursts are defined as downbursts that extend for less than a 2.5-mile diameter. However, there isn't a real lower limit on the possible size of an area impacted by microburst winds, since they can occur on a continuum from the 2.5-mile limit on down to the point where no winds at the surface reach the threshold to cause damage to crops, trees or structures. It isn't unusual for mixing of ambient air to the sides of some downdrafts to cause the strongest winds to reach the surface in small streaks or pockets, which can make for scattered and very localized areas of damage.
Sep. 8, 2016 | Tags: thunderstorms, winds

Question: Take a look at the WRAL 24-hr rainfall map. What is up with the rainfall in Greenville? It looks like they are reporting rain from Hermine in centimeters rather than in inches. — Dave Salman

Answer: We noticed that, too, and in fact there were a couple of different locations that we were not directly plotting the values on our maps where we saw that color contours in the background had areas that were obviously contaminated with readings that were too high, so that we turned off that background layer for on-air purposes. We aren't absolutely sure what the problem was yet, but have seen instances in the past with reports from the type of automated sensor used at the Greenville airport in which display software adds up rainfall cumulative rainfall totals as if they were sequential un-related values instead, leading to a significant over-calculation of the reported amount. Other nearby stations, along with radar-based estimates, make it appear most areas in the vicinity of Greenville received around 6-8 inches of rain Thursday through Saturday from the combination of a frontal boundary and Hermine.
Sep. 7, 2016 | Tags: instruments, maps & codes, rain

Question: I'm dying on the inside. When will the heat stop? I'm going to melt before autumn comes. — Kayla

Answer: We can't really promise a particular time, but of course we are heading out of summer and into Fall in the coming weeks, so the overall trend will be downward. However, after a bit of a comfortable break due to the combination of a cold front and Hermine, our temperatures appear as if they will run a good bit above normal for much of the week to come, before sinking to more typical levels after the coming weekend - still warm, but most likely lower 80s instead of upper 80s to mid 90s.
Sep. 6, 2016 | Tags: heat

Question: I'm watching the 10:00 pm forecast and they say current temperature is 85. WRAL web site at the exact same time says it's 82.... why? — Toolman

Answer: There are a couple of ways this may have been the case, depending on where you were looking for data on the web site. One involves the fact that we have a weather station on our roof that provides a temperature for our station location, while there is a separate temperature measured at the RDU airport that we use on many of our on-air maps and current conditions graphics. These sensors are far enough apart that different readings are not especially unusual. In addition, while the value from the sensor on our roof is almost continually updated, the automated station at RDU normally sends a new observation once per hour. If temperatures are trending up or down through that period, that can also lead to a discrepancy between the two values. You can check both readings by clicking the "Current Conditions" link on our main weather page.
Sep. 5, 2016 | Tags: instruments, maps & codes, wral.com

Question: Can't a line of storms redevelop if it is in an unstable air mass? — Amy

Answer: When a line of storms exists, there can be a sizable number of ways in which it was generated, ranging from frontal boundaries to outflows from previous storms to passing upper level disturbances, and how persistent the line is can depend on the strength and orientation of any of those factors, along with the 9overall level of instability in the surrounding airmass. In some cases, the surrounding environment may become less supportive of storms and the line will simply decay and the storms will come to an end. Given enough instability, however, and a lack of opposing forces, there are other times when the remnants of a line, or outflow boundaries that were produced by that line, can redevelop and continue to produce newly forming showers and storms.
Sep. 4, 2016 | Tags: general meteorology, thunderstorms

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