Ask Greg

Recent Questions

Question: What affect will North Carolina see from a La Nina, should one arise after the waning of the current El Nino? — Kimberly Wiegand

Answer: The recent El nino is now considered over and conditions are in the "neutral" range regarding equatorial sea surface temperatures in the central and eastern Pacific. However, there is a La Nina watch in place now as development of La Nina is considered likely by later this summer. The influence of any particular La Nina event, similar to that of El Nino, can vary a good bit depending on it's intensity (how much cooler water temperatures are than normal) and the state of other large-scale patterns that it interacts with. That said, on average La Nina has its primary influence on North Carolina during the cooler half of the year, and on average leads to warmer than normal temperatures and lower than normal precipitation. During the warmer months, there is little influence on day-to-day weather here, but it does have a tendency to increase the number and intensity of tropical cyclones in the Atlantic, which can indirectly lead to greater than normal precipitation here due to the higher chance that a couple of these cyclones or their remnants will pass through the area.
Jun. 20, 2016 | Tags: el nino/la nina

Question: If I am not mistaken, I remember that back in the summer of 1999 we had here in the Triangle 21 straight days of 100 degree weather - beginning in July & ending in August. Is this true? — Patrick

Answer: Not quite, but 1999 was indeed a very hot summer with a lot of days in the 90s and 100s, including 12 days at 100-plus, more than any other year in records going back to 1887. The longest stretch of consecutive days reaching 100 or higher in Raleigh was 6, which occurred in July 2012. In 1999, the longest consecutive stretch of days that hot was 3. We did have 23 days in a row at 90 or higher in July to August 1999, but that streak comes in second to a 24-day stretch that occurred in July to August 1995.
Jun. 19, 2016 | Tags: heat, past weather, records/extremes

Question: Never seen a straight rainbow, until Sunday afternoon June 5th. Does that mean anything? — Gail S

Answer: We did some follow-up checking about the location in the sky, the type of weather conditions, and more specifics about the colored band you saw, and based on the added information and a photo you sent in, it was clear that what you saw was not a rainbow, but a form of halo that can occur when the sun is very high in the sky and there are some thin cirrus clouds made up of well-formed six-sided plate-like ice crystals that are mostly oriented with their flat sides parallel to the ground. The result is called a "circumhorizon arc," and they are typically visible several times a year, though you have to happen to be looking in the right area at the right time. Because the sun has to be at least 58 degrees above the horizon, they can only occur here between late March and mid-September (in Fall and Winter the sun never climbs that high over us). You can read more about them, see some other photos in a gallery, and find some diagrams that explain how they form, at www.atoptics.co.uk/halo/cha2.htm. The photo you took of the arc you asked about here is posted at www.wral.com/weather/image/15777736/?ref_id=15777729.
Jun. 18, 2016 | Tags: atmospheric optics, cool sites

Question: There is a big sailboat race from Indian Island in Pamlico to Ocracroke 6/18. Can you please tell us about the forecasted closed low pressure on the coast this coming weekend? — Charlie B Blackbeard Sail Club

Answer: At times, we have to answer these questions up to several days in advance, and are doing so on this one. For that reason, we tend to avoid specific forecast-related questions here. In this case, we wanted to mention that as of early in the week prior to the race, there are some notable questions with regard to the position and intensity of low pressure, which various computer models indicated could, by Sunday, be anywhere from hugging the South Carolina coast, with clouds and rain for eastern NC, to several hundred miles offshore (the more common solution), leaving eastern NC with sunshine, low humidity and breezy north winds. By the time you read this, with any luck newer projections based on newer observations will have raised the confidence level regarding the weekend forecast - check in on our web and on-air forecasts, including the recreational forecast section here, for updated information on the coastal forecast for Sunday and the potential position of any nearby low.
Jun. 17, 2016 | Tags: wral.com

Question: Our insurance company needs to know what day some damaging hail occurred in the Cary area recently. Do you know? — Vickie

Answer: We found two days back-to-back when hail meeting severe weather criteria (meaning one-inch diameter or greater) was observed in and around Cary. On May 2nd at about 4:25 PM, there were several reports of hail measuring 1-2 inches in diameter, while the following day brought another round of hail, this time at about 6:10 PM and mostly having diameters of about one-half to one inch.

Should any of you wish to search for this kind of information directly, a good source is the Local Storm Reports Database at the State Climate Office web site. You can find it at climate.ncsu.edu/lsrdb/index.php. In this case, we used the portion of the page with the blue shaded box, and restricted the search to Wake County, also using the "advanced options" to search the time frame from May 1st to June 12th and to only look for storm reports related to hail (chosen under the "Thunderstorm Hazards" section).
Jun. 16, 2016 | Tags: cool sites, hail, past weather, severe weather

Question: This is possibly an actual meteor question, not very weather related. The night of Tuesday, June 7th at about 8:55 I watched what looked like big speeding sparks cross part of the sky and go black, as "falling stars" often do - immediately thinking some bits of meteorite just landed over Nash County. (I was driving east on 561 a mile outside of Louisburg, and I'd guess the display was in the direction of Castalia.) But this is what floored me - the bright explosive display was clearly BELOW the high clouds, and actually appeared to disappear in a normal, fluffy defined cloud a bit lower. Is this common for extraterrestrial debris? I was initially afraid I was seeing the failure of something man-made, but then rational thought kicked in and said "MAYBE it was space rocks, and they actually appear that low?" BTW I thought for sure my dash-cam caught it, but it was just out of range, but of course. — Erika

Answer: This was a decent week for "fireball" observations around here - we also received reports from the following night and from Friday, June 10th, the subject of yesterday's question and answer here. In your case, you observed a bright meteor that was reported to the American Meteor Society by at least 94 people from as far south as SC to as far north as NY and PA. You can see a map of the reports, and click on any reports to read their remarks about what they saw, at www.amsmeteors.org/members/imo_view/event/2016/1992.

We suspect your impression that the meteor was below high cirrus clouds was a matter of angle, distance and perception relative to the curving surface of the earth. Meteors generally decelerate to speeds too slow to produce visible light by the time they descend to about 50-60,000 feet above the surface, while the high clouds you noted would have been somewhere in the range of about 20-30,000 feet up. The clouds could appear at a higher angle above the horizon due to their relative proximity to you, while the more distant meteor path looks lower. Based on other reports, you probably saw the fireball in the northeastern sky, and it happened to reach the point where it became invisible while it was behind the lower cloud you mentioned that was much closer to you. There's a nice FAQ about fireballs, meteors and meteorites (the parts of some meteoroids that make it all the way to the ground) at www.amsmeteors.org/fireballs/faqf/.
Jun. 15, 2016 | Tags: astronomy, atmospheric optics, cool sites

Question: Was traveling on 40 east near mile marker 267 and we saw a green light falling, looked if it had sparks trailing. Sorta like a shooting star. About 10:00 PM Friday night, June 10. — Donnie Parker

Answer: What you saw was a very bright meteor often referred to as a "fireball." This one was seen over a large area (due to the great altitude involved) and many people reported a similar sighting. So far, such reports have been received by the American Meteor Society from six states. You can see the "fireball event" page that consolidates and maps those reports at www.amsmeteors.org/members/imo_view/event/2016/2028.
Jun. 14, 2016 | Tags: astronomy, cool sites

Question: Weather in the US seems to generally track from West to East, but storms in the Atlantic generally form near Africa and track from East to West toward the US. Why the difference? Does it have to do with the jet stream? — Michael Drum

Answer: This is largely based on the difference in latitude between much of the U.S. and the typical formation areas of those tropical systems that develop west of Africa, well to our south. As you noted, the jet stream, which forms partly as a response to strong temperature gradients (frontal bands) in the mid-latitudes, tends to flow west to east and to move smaller disturbances along in that same direction for much of the year. However, in the warmest months of the year, notable frontal zones and the jet stream tend to migrate north and become weaker over most of the U.S.

In addition, there is a persistent, semi-permanent subtropical high pressure area that often stretches across much of the north Atlantic Ocean. Trade winds on the south side of this high tend to blow from the east across the most common tropical cyclone formation areas, steering the storms toward the west. When the storms reach the western end of the high, which can vary some in location and strength, they often turn (known as "recurvature"), first to the north or northwest, and eventually northeast or occasionally east, when they reach sufficiently high latitudes and come under the influence of the jet stream.
Jun. 12, 2016 | Tags: general meteorology, hurricanes

Question: I have lived on Holt Lake near Four Oaks for 5 years. I watch the iControl radar and the storms seem to be scared to death of Holt Lake. They slow down, weaken, or try to go around. What is it? — Rupert Hester

Answer: Moving areas of precipitation, 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 Holt), 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 the Four Oaks area from time to time.

You touched on one aspect of this whole issue that can be quite interesting, though, and that is indeed 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 echo. 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 tend to 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. It is also the case that since intense storms often cover a fairly small percentage of the region, by definition most of them tend to pass north, south, east or west of a given location in any single event, and sometimes a series of events, before the one day or two that that location gets hard hit. This is evident to us because of the fact that we frequently receive questions like yours (what makes storms split up when they approach my town and redevelop later?) from pretty much every part of our viewing area!
Jun. 11, 2016 | Tags: general meteorology, thunderstorms, weather radar

Question: We received a message stating we had a Baron Tornado Warning. What did this mean? — Judy Warf

Answer: We found in following up that you were located in the White Hill area of Lee County when this occurred, when some strong to severe storms were scattered around the region on Sunday, June 5th. There were not any tornado warnings issued by the National Weather Service that day, and in fact no tornadoes occurred. However, we suspect that you saw an alert by way of the WRAL Weather App, on which we collaborate with a company called Baron Services. In addition to the standard watches and warnings from NWS, the app includes the option to have notifications when radar and lightning data indicate the approach of especially strong storms, storms with lightning, and storms that indicate rotation based on radar velocity data. In this case, the app might post an alert for a "Twisting storm approaching," accompanied by a value for the "Baron Tornado Index," or BTI. That index is a 0-10 scale indicating how likely a storm is to be producing a tornado. We noticed that while no severe thunderstorm or tornado warning was ever issued for the Lee County area that day, there was a cell southwest of Lee moving that direction that had some low to mid-level rotation associated with it for a short time. Detection and automated analysis of that cell may have resulted in the message you saw.
Jun. 10, 2016 | Tags: preparedness, severe weather, tornadoes

Questions 41 - 50 of 5014.


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.