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Question: What happened over Bath, NC today that caused rain clouds to disperse in a growing ring around 6:45 am this morning (07/19/2017)? I saw it on weather radar. — Phil Parry

Answer: Those were not rain, or clouds, but instead a concentration of tens of thousands of purple martins that roost at a site on the far side of the Pamlico River and a little ways downstream from Bath, actually close to the PCS Phosphate plant near Aurora, NC. The expansion you are seeing begins just before sunrise most days, and shows the martins as they swarm outward and upward to go out in search of food to start the day. This kind of image on radar is known as a "roost ring." It's something we covered in a bit more detail in a blog post from a number of years back. See www.wral.com/weather/blogpost/1631522/ for more, and note that the post references an image "above." To see that image, you'll actually scroll down and click on a thumbnail a little below the text toward the right side.
Jul. 24, 2017 | Tags: cool sites, weather radar, wral.com

Question: We had a pretty severe thunderstorm in Archer Lodge yesterday afternoon and as I was watching the dual Doppler, I noticed out flow boundaries from two different cells that seemed to converge over our area. Would that lead to a more intense storm? — Doyle McGlone

Answer: There may be a small effect on intensity of storms that form when outflow boundaries converge because that process might deliver a more intense initial lifting of air to start the process, but we're not aware that there's a strong correlation there. Converging boundaries may increase the odds of new storm formation at that location a bit more than a single boundary passing through (which can also set off new development), but the intensity of the resulting storm is likely more related to the overall structure of the atmosphere in terms of the vertical profiles of temperature and humidity prior to the arrival of the boundary, along with how larger scale winds vary in speed and direction with height. When those variables all favor an intense storm, the manner in which it is triggered plays a fairly small role by comparison.
Jul. 23, 2017 | Tags: general meteorology, thunderstorms, weather radar

Question: I have a unusual question that I have searched the Internet and cannot find an answer. About a month ago in Rocky Mount we had tornado warnings it was very windy and the rain was hard and I thought my roof is going to fly off. Anyway I did have some damage to my roof and need to know the date in which that happened. — Tammy Weatherly

Answer: Based on the date you sent your question and the time frame you mentioned, we're pretty sure you're referring to a tornado warning that was issued at 5:39 PM on June 5, 2017. The warning was cancelled at 5:52 PM. While no tornado was observed or confirmed with the storm, there were strong gusts and heavy rain, as you mentioned, and there were storm reports in the warning area for flash flooding and also for a tree blown down onto a mobile home at Brook Valley Mobile Home park.
Jul. 22, 2017 | Tags: past weather, severe weather

Question: I'm trying to figure out the best time to mow my lawn today so that I'm mowing at the most comfortable / least humid time. The hourly forecast shows that from 11AM to 8PM the dew point will be steady at 72 degrees. However, relative humidity fluctuates from 64% at 11AM to 54% at 4PM. Am I better off mowing at 11AM (with a temperature of 86 degrees) or 4PM (with a temperature of 91). Or, with a steady 72 degree dew point, will it feel just as uncomfortable no matter what time of day I choose? Having just travelled home from Las Vegas where the 105 degree temperature and low humidity resulted in my not having a single drop of perspiration in my eyes, I realize that I much prefer high heat / low dew point to being coated in perspiration with little to no evaporation cooling me down. — Matthew Walter

Answer: You make a good point at how much different it can be dealing with heat in the absence of much humidity. On a day like the one you mentioned around here, you'd probably be best served looking at the combination of temperature and humidity, not just the humidity value. One way to approach that would be to take the forecast air temperature and the dew point (or relative humidity) and calculate the heat index at various points during the day. Whenever that is lowest may be the best time for cutting the grass or other strenuous activities. Of course, the choice can be complicated a bit by whether different times of day will put you in more direct sun or in shade, or whether there might be a strong breeze that helps a bit at some point in the day, so keep those factors in mind as well. There are any number of calculators on the web to estimate the heat index with temperature and either dew point or RH as humidity inputs. One example is at www.weather.gov/ffc/metcalc.
Jul. 21, 2017 | Tags: cool sites, heat, humidity/dew point, weather & health

Question: I have noticed over the last year or so that WRAL calls the Triangle Raleigh, Durham, Fayetteville. What happened to Chapel Hill? In any weather alert notification the counties of Alamance, Chatham, Durham are mentioned, NOT Orange. What's the deal? — David

Answer: We're a little surprised that you've gotten that perception. While Fayetteville is certainly a very important part of our viewing area, we don't consider that a part of the Triangle, which we continue to consider roughly the area bounded by Raleigh, Durham and Chapel Hill. As for weather alerts, those are generally based on watches, warnings or advisories issued by the National Weather Service, so the counties included will be those which they listed in the issued product. It may simply be that in some of the recent severe events, Orange County was fortunate to be missed by the most intense storms that warnings were issued for.
Jul. 20, 2017 | Tags: maps & codes, preparedness, severe weather

Question: Given that the shortest and longest days of the year (solstices) are when the sun is over the respective tropical meridian, it marks the beginning of winter or summer. It seems to me that the season would straddle the short and long days. Is my logic failed? — Aat

Answer: If we're interpreting your question correctly, your logic is exactly the reason we refer to both "traditional" or "astronomical" seasons, which are defined as starting with the solstices and the intervening equinoxes, and "meteorological" or "climatological" seasons, which align more so with the highest and lowest average temperatures for summer and winter, with the transition seasons falling in between. For mid-latitude regions like ours, this results in "meteorological summer" running from June 1st to August 31st, and "meteorological winter" from December 1st to the end of February. One could, in principle, adjust these even more finely into roughly three-month periods that start and end on dates that would vary some depending on latitude and regional topography, but that would probably become a fairly unwieldy source of additional confusion. We would guess that "meteorological" winter, spring, summer and fall probably correspond fairly closely to what you had in mind, and this definition tends to be used in keeping and referencing weather and climate records.
Jul. 19, 2017 | Tags: astronomy, general meteorology, maps & codes

Question: Outflow boundaries from storms...are these phenomena only recently detectable by our technology? — Tom Noffsinger

Answer: They have been well-known as a feature of thunderstorm structure and effects for quite a long time, but have become increasingly detectable through the decades. Once reasonably high-resolution visible satellite imagery became available in the late 1970s and early 1980s, outflow boundaries could clearly be seen on that imagery in the vicinity of thunderstorms, but the imagery itself was updated infrequently and had a considerable time lag. Most weather radar at the time, and into the late 1980s and early 1990s, was in the form of WSR-57 and WSR-74 National Weather Service instruments that produced about half the output power of the WSR-88D ("NEXRAD") Doppler radars that replaced them. The added power, and upgraded receiver sensitivity, of those radars (along with the power, sensitivity and shorter wavelength of privately owned radars like our DualDoppler 5000) have made the boundaries more routinely visible in the last 10-20 years. Because the outflow airmasses tend to be rather shallow, their boundaries are still seen mainly when they occur fairly close to a radar site, since the upwardly tilted radar beam can pass over top of them at greater distances from the transmitter.
Jul. 18, 2017 | Tags: general meteorology, thunderstorms, weather radar

Question: Hi! Is there a calendar online that shows when we last had rain; specific daily rainfall amounts for the area (instead of aggregate monthly or yearly data for the area (or less helpfully - the State))? Getting the right amount of water to my summer garden is tricky and being able to look back and determine how much water it needs would be helpful - relying on my memory alone is a faulty system. — Anonymous

Answer: There are a number of resources we can suggest, keeping in mind that rainfall can vary a good bit over a short distance. In terms of looking at specific dates and how much was received in rain gauges at individual stations, you can use the "Almanac" function of our web site to check a selected date - when you do that, the default is to show a single day's info for RDU. However, you can then change the view to "monthly," which will allow you to quickly scan a table of observations near the bottom of the page that includes daily precipitation observations for the entire month - you can also use the "Search for Another Location" box to change the observation site to another town. Another place to look for a fairly dense network of daily precipitation observations is the Community Collaborative Rain, Hail & Snow network, at www.cocorahs.org. Once you learn your way around the site a bit, you can get good localized history of recent precipitation for the region there. Another option is a National Weather Service Precipitation Analysis page that uses radar estimates of precipitation, adjusted to fit with rain gauge reports, to plot daily contours of precipitation that you can step through. The advantage here is that radar fills in some of the gaps between fixed observation sites. The page also allows you to view precipitation amounts summed over the past week, past month, past 90 days, etc, and to view how those amounts compare to normal. The address is water.weather.gov/precip/, and you might like to go to the "location" button, select "WFO," choose "Raleigh" and click on the county borders for a good view of our area.
Jul. 17, 2017 | Tags: cool sites, past weather, rain

Question: Why is it that when I'm looking at the live online radar, I'm seeing areas of blue in the Triangle area? Is that where the Doppler radar is reflecting off water or lakes? — James

Answer: When the Dual Doppler
5000 radar includes a display of some of the lowest reflectivity values (often shaded blue), which are good to have in picking up drizzle or light sprinkles, outflow boundaries from storms, and light snow in the winter, they can become rather enhanced when we have temperature and moisture profiles that are favorable for "anomalous propagation" that bends the radar beam down a bit and increases returns from the ground and from low altitude non-meteorological targets like dust, insects and birds. This is most noticeable when there is both a temperature inversion near the surface and a rapid decrease in humidity with increasing height. When you lapse the radar in these situations, you can often notice the ground returns staying in the same place or jumping around somewhat randomly, while precipitation echoes move along with steering winds. This time of year, you may also notice some movement with the low-level winds in the light, non-meteorological returns as they pick up on the concentrations of insects or dust.

Jul. 16, 2017 | Tags: weather radar, wral.com

Question: Where is the dew point forecast on this website? — Jimmy Pines

Answer: Dew point is included in the hourly forecast on our site. The one thing to note is that it isn't shown by default when you first access the hourly forecast section. Instead, once you do that, look for the "More Details" link just below the initial list of hourly information. Once you click that, you will see dew point, relative humidity and wind speed/direction added to the previous information for each forecast time.
Jul. 15, 2017 | Tags: humidity/dew point, wral.com

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