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The most direct way to find your question is to search for the name you used when you submitted it (first name, last name or both). If you did not include a name, then you can search using keywords from your question. Of course, since many weather-related terms are common to a lot of the questions we receive, this may turn up a number of others in addition to your own.

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Answer: Assuming you mean days that reached 100 degrees or greater rather than exactly 100 for the high, the record stretch was set at the Raleigh-Durham airport just last summer. A six-day period from July 3-8, 2012 saw high temperatures of 101, 101, 101, 100, 102 and 105 to set the record.
Jun. 17, 2013 | Tags: heat, records/extremes

Answer: At the time of your message, Tropical Storm Andrea had maximum sustained winds of 45 mph, but its forward motion was northeastward at 28 mph. All the same, your point is well taken and serves to illustrate some of the complications attendant to the real atmosphere compared to some of the simplifying assumptions we often make regarding weather features. If Andrea was a giant spinning piece of plastic, for example, then every part of the plastic would move along at 28 mph toward the northeast, and any place on land in contact with it would be brushed by at least that speed, plus or minus any rotational component as you move away from the center. In the real atmosphere, however, the storm is not an object, but really a process made of rising and sinking air that flows into and out of it, and embedded water droplets and ice crystals. Winds are locally enhanced and suppressed by convection, friction with the surface below reduces speeds near the ground and helps induce turbulence that drives gusts and lulls, and even the low pressure center can move in part due to constantly reforming in a new position and not always by a simple linear forward movement of the entire air mass. A few hundred to a few thousand feet above the surface, winds would come somewhat closer to meeting the conceptual model you have in mind due to the relative lack of friction effects there, but would still be subject to a number of complicating factors.
Jun. 16, 2013 | Tags: hurricanes, winds

Answer: While rainfall rates and duration are related to flooding that may result, there is not a direct and simple relationship between rainfall and flooding levels, since that relationship depends on things like the previous saturation level of the ground, prior elevation of river and stream surfaces, the shape and size of rain-producing clouds relative to the shape and size of the drainage basin for a given body of water and so on.

The "100-year flood" is the elevation that water from a given stream or river has only a one percent chance of reaching in any given year, or to put it differently, has a 100-year "return interval." What this level is varies and is specific to particular locations along individual waterways. It is calculated based on historical measurements of the water level. It is important to note that as with other statistical measures, the fact that a flood level has a 100-year recurrence interval simply describes its probability, and doesn't guarantee that there will be 100 years between one instance and the next.

One can also calculate the historical likelihood of certain rainfall amounts occurring within a specified amount of time at a particular location. Here you've asked about 3 inches of rain falling in one hour. The probability of that rain rate varies from place to place, but to give an example, at the Raleigh-Durham airport the amount of rain with a one percent chance of occurring within one hour is 3.08 inches, and represents the "100-year one-hour rainfall rate" for that site.

There is a nice web page that provides tables and graphs of rainfall probability based on duration and rainfall amount located at hdsc.nws.noaa.gov/hdsc/pfds/pfds_map_cont.html?bkmrk=nc. Also, the USGS has a good discussion of the 100-year flood" concept at ga.water.usgs.gov/edu/100yearflood.html.
Jun. 14, 2013 | Tags: cool sites, flooding, rain

Answer: Wind shear is a difference in wind speed and/or direction over a distance, and plays a role in many weather processes. In this sense, the shear mentioned in regards to the tornadoes is the same in a basic sense as that involved in potentially disrupting the development or intensification of a tropical cyclone. In the case of tropical systems, we are usually interested in the vertical difference in wind speed between a near-surface layer and something close to the upper troposphere (often around 30-40,000 feet in the lower latitudes). There are exceptions to any general rule like this, but if this shear exceeds roughly 20 knots it is usually not favorable for tropical cyclone growth.

Conversely, vertical shear is a positive factor in the development of supercell thunderstorms, which act as the parent storms for most if not all significant tornadoes. Supercells develop most readily in environments where the vertical wind shear between the surface and about 20,000 feet reaches around 35-45 knots or more. Tornadoes are especially favored if in addition there is a strong directional shear in the lowest few thousand feet of the atmosphere such that winds turn clockwise with increasing height, and if downdrafts from the storm create even more concentrated small-scale vertical shear along a shallow outward spreading gust front.
Jun. 13, 2013 | Tags: general meteorology, hurricanes, tornadoes

Answer: We now have a page (WRAL Weather Alert Center) on our site that consolidates access to all of our Alert products. This includes the free WRAL Weather Alert apps for iPhones, iPads, iPod Touches and Android phones and tablets, as well as the fee-based WeatherCall program that will place a phone call to up to three designated numbers when your chosen address falls within a warning area. You can find all the info, along with links to download the apps or sign up for WeatherCall, at www.wral.com/weather/page/12171988/.
Jun. 12, 2013 | Tags: severe weather, wral.com

Answer: It's unclear whether the app you were looking at indicated a mesocyclone based on the detection alogorithm utilized by the National Weather Service in its NEXRAD radar network, but a version of that algortithm was found in a 2005 study to result in tornadoes for about 30% of mesocyclone detections overall. The algorithm was updated a few years later and appears likely to now identify and highlight some smaller and weaker mesocyclones than the older version. We were unable to find documentation as to whether this may have reduced that percentage, but that may be a reasonable supposition. In any event, detection of a mesocyclone may also indicate a storm organization strong enough to produce damaging downburst winds or large hail even if no tornado forms, so it's worth paying attention to a storm that generates a radar detection of that sort. However, it is also possible that the mesoscale detection itself is in error, or that a noisy velocity signature leads to some transient detections that do not show consistency over time or vertically, in which case they may be less likely to signal a high chance of severe weather, and therefore less likely to trigger a warning by the National Weather Service.
Jun. 11, 2013 | Tags: maps & codes, severe weather, weather radar

Answer: For Holly Springs and most of central North Carolina, prevailing wind directions are from the southwest (from a compass direction of 230 or 240 degrees) ten months out of the year. The months of September and October are the exceptions, with a prevailing wind for those months from the northeast (030 to 040 degrees). Keep in mind that these are long-term averages, and there can quite a bit of short-term variability of wind direction in any given year, month or week.
Jun. 10, 2013 | Tags: normals, winds

Answer: There were no tornado reports logged in our state on Monday, but there were some storms that occurred in a generally, but not entirely, unfavorable environment for organized storms and rotation. There was one report of a funnel cloud near Jackson in Northampton County. We looked at archived radar data for the time you reported, and there was a cell in the area that briefly took on a reflectivity shape that can be associated with rotation and strong updrafts. There was not a strong Doppler velocity signature of rotation, but there was a hint of weak rotation for a short time. and we can't rule out that you may have seen a brief funnel cloud. With these kinds of storm cells there can also be random fractus clouds that give an illusion of a tornado-like structure, and it may also be possible that gusty winds and updrafts in the vicinity of the storm cell could have triggered a whirlwind not unlike a dust-devil, but also not a classically organized tornado. Unfortunately, while there are a number of possibilities such as these, we can't be certain based on the information available to this point exactly what you may have witnessed.

Jun. 9, 2013 | Tags: past weather, tornadoes

Answer: There is not an absolutely confident way to be sure every occurrence of hail in any given location is recorded and can be checked later. The best system we have now is a system of local storm reports issued by Noational Weather Service offices when they receive observations of hail from weather stations, storm spotters, emergency responders, the media or public. You can explore these reports through a nice interface that the State Climate Office of NC has developed at www.nc-climate.ncsu.edu/lsrdb/index.php. On this page, you'll see two ways to view the reports. On left is a day by day national report button. Select a date (in your case, March 1 of this year, for example) and you will see a large map showing all storm reports nationwide for that day. The reports are color-coded, and you can deselect any report types you'd rather not plot. You can also zoom the map in for more detail, pan it around (open hand pointer) and mouse over individual dots (when the pointer shows a pointing finger, you can click for a text description of the report).

The other search tool in blue to the right can be narrowed down to focus on a single county, like Cumberland. By clicking the "advanced options" link there, you can also choose the date range you're interested in, and can narrow down the type of report to only tornadoes, for example, or in your case only hail. This part of the tool is great for screening. However, if no one sent a report of hail from your location to the NWS, then it may not show up here. In that case, it can be useful to look at the larger day by day map, which can quickly be stepped a day ahead or back, and look for groups of reports that may be from other nearby counties. That can be an indication of a day on which storms may have produced some hail, for example, that didn't happen to get reported in your specific area. You can also try a collection of reports from a volunteer precipitation obsever network called CoCoRAHS. See this page to search for hail reports - www.cocorahs.org/ViewData/ListHailReports.aspx.

Jun. 8, 2013 | Tags: cool sites, hail, past weather

Answer: The general circulation of the atmosphere is broken into cells that transport, in a fairly complex way, warm air from the tropics northward and cold air at the poles southward. As air flows in either direction, the rotation of the earth leads to a turning in wind direction, to the right of the original flow direction in the northern hemisphere. This effect is called the Coriolis force. While the overall pattern of flow is rather complex, in a general sense it results in bands of predominant flow within the troposphere, having a predominant component from the east near the equator and in the tropics south of about 30 degrees latitude and also north of about 60 degrees. In between, the mid-latitudes favor a predominant flow from the west. These westerlies are concentrated and most intense in the jet stream, the position of which both depends upon and influences more localized temperature variations. While the west to east flow in the midlatitudes (where we are located) is highly variable, with troughs and ridges and embedded low and high pressure circulations, the overall west to east flow causes most weather features to move in more or less that direction. Hurricanes often start out at lower latitudes in the tropics where they are subject to steering flow from the east, but they sometimes drift far enough north to encounter the midlatitude westerlies, in which case they too can take on a motion toward the east or northeast.


Jun. 7, 2013 | Tags: coriolis, general meteorology