Changing Skies Over Central North Carolina VOLUME 10, ISSUE 1 SPRING 2013 NOAA’S NATIONAL WEAT HER SERVICE RALEIGH, NC Understanding a Derecho: What Is It?

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Changing Skies Over Central North Carolina VOLUME 10, ISSUE 1 SPRING 2013 NOAA’S NATIONAL WEAT HER SERVICE RALEIGH, NC Understanding a Derecho: What is it?

INSIDE THIS One of the biggest severe and record gusts were rec- duce destruction similar to ISSUE: weather events of last year orded at Fort Wayne, IN, that of tornadoes, the damage was the derecho that crossed Zanesville, OH and Hunting- typically is directed in one Forecast 2 the Midwest into the Mid ton, WV. While the derecho direction along a relatively Formats Atlantic states in late June. only clipped North Carolina, straight swath. As a result, The storm affected 11 states there was plenty of buzz for the term "straight-line wind Wireless Emer- 3 including IL, IN, OH, PA, KY, the next several weeks and damage" sometimes is used gency Alerts WV, MD, VA, NC, DE and the buzzword was “derecho.” to describe derecho damage. NJ. Unfortunately, 22 people Soon every thunderstorm By definition, if the wind dam- New NWS 3 were killed, mostly from was being called a derecho. age swath extends more than Director trees falling on homes and So as we approach severe 240 miles (about 400 kilome- vehicles. Over 5 million peo- season we thought this would ters) and includes wind gusts Precipitation 4 ple were without power. This be a good time to talk about of 58 mph (93 km/h) or Modeling was the first derecho to real- derechos and their various greater along most of its length, then the event Drought Update 8 may be classified as a derecho. StormFest 9 Wind Strength By definition, winds in NWS Welcomes 10 Blake Ellis a derecho must meet the National Weath- er Service criterion for severe wind gusts (greater than 57 mph) at most points along the derecho path. But in stronger derechos, winds may exceed 100 mph. For example, as a derecho roared through northern Wisconsin on July 4, 1977, winds ly capture widespread major characteristics. media attention as it rolled of 115 mph were measured. through big markets like Chi- Definition More recently, the derecho cago, Indianapolis, Baltimore, that swept across Wisconsin Washington D.C. and Tide- A derecho (pronounced simi- and Lower Michigan during water, VA. This was a pro- lar to "deh-REY-cho") is a the early morning of May 31, gressive derecho that cov- widespread, long-lived wind 1998 produced a measured ered 600 miles in 10 hours storm that is associated with wind gust of 128 mph in east- averaging 60 mph. Wind a band of rapidly moving ern Wisconsin, and estimated speeds within the derecho showers or thunderstorms. gusts up to 130 mph in gusted from 80 to 100 mph Although a derecho can pro- (continued on page 6) P A G E 2 Print and Mobile Options for Your Forecast

The NWS office in Raleigh is vance. That is a lot of infor- print and display their neigh- always searching for new mation! This forecast infor- borhood forecast for their and better ways to serve the mation can be presented in customers, employees, and people of central NC. In a variety of ways, tailored students on a daily basis. addition to our dense obser- for specific users (such as Here is how to get to this vation network, detailed fire weather partners) or page: aviation forecasts, and full for general use. One such suite of watch/warning/ way is the Printable Fore- 1.) Go to www.weather.gov/ advisory products, we pro- cast Page – a simple, unclut- raleigh (our local web page). duce hourly forecasts of tered, single-page display of 2.) Click on your location on temperatures, humidity, rain the 7-day forecast. This is a the map to see your local chances, wind, and numer- great way for businesses, forecast. ous other weather parame- hotels, schools, government (continued on page 5) ters, all out to 7 days in ad- agencies, and others to

“The NWS office in

Raleigh is always

searching for new and better ways to serve the people of

Central NC.”

An Example Printable Forecast Page From NWS Raleigh

CHANGING SKIES VOLUME 10, ISSUE 1 P A G E 3

Wireless Emergency Alerts on Your Mobile Device

Imagine this: You’re driving vice no matter where you are. won’t have to open it up to down the highway, humming read it. NOAA’s NWS will broadcast along to your favorite tunes, warnings via WEA for weather The Wireless Emergency when the cell phone stowed in emergencies that are most dan- Alert system relies on “best- your bag suddenly makes a gerous to life and property: tor- effort” networks, so delivery strange noise. To investigate, nadoes, flash floods, hurricanes, of alerts at a given place and you take the next exit and safely extreme wind, blizzards and ice time is not guaranteed. The pull over to check the screen. storms, tsunamis, and dust new alert system is not a re- Good thing you did: Your phone storms. Severe thunderstorm placement for other alert sys- just alerted you to a tornado a warnings will not be part of the tems, and you should not rely on it as a sole source of emergency information. A weather alert sent through WEA is intended to notify the public that a warning has been issued and that you should seek additional information. Remember: Not all phones are capable of An Example of a Wireless Emergency Alert receiving Wireless Emergency Alerts. few miles away in the same initial rollout of broadcast mes- Cell service customers can county you’re driving through. sages because they are so fre- opt out of weather alerts, but Sound plausible? It is. Last June, quent; however, these will con- we strongly discourage you America’s wireless industry tinue to be broadcast by NOAA from doing so. These weather rolled out a new nationwide text Weather Radio, media outlets alerts are a vital public service emergency alert system, called and Internet-based services. that ultimately helps America Wireless Emergency Alerts When your phone receives a become a more weather- (WEA), which will warn you WEA message, it will alert you ready nation. Armed with late when weather threatens. with a unique ring tone and vi- -breaking weather warnings, The text alert service is free and bration. These 90-character people will have the timely automatic – there’s no need to messages are a “heads up” to information they need to sign up or download an app, and prompt you to seek further in- make smart decisions about this service will not use any of formation about the threat. how to protect themselves, your paid text messages or The message will look like a their families, their friends and minutes. As long as your cell text, but it’s not a traditional neighbors, and their personal phone is WEA-capable, you’ll get text message most people are property. wireless alerts for the most dan- used to. This text message will -Nick Petro gerous types of weather from automatically pop up on your NOAA’s National Weather Ser- cell phone’s screen and you P A G E 4 Do More Models Make it Merrier?

A winter storm from the past Feb- ruary provides a good example of the utility of ensembles. Predicted liquid equivalent precipitation from the SREF members and the SREF mean for the February 16-17 winter storm is shown at left. The plot is viewed from right to left with amount of precipitation in tenths of an inch shown in the verti- Short Range Ensemble Forecast (SREF) members showing various cal axis and the “A winter storm forecasts for liquid equivalent precipitation amounts. color of the lines indicating likely from the past A weather forecast is an esti- al forecasting that allows for precipitation type. At about mate of the future state of a rapid and scientifically- the same time as the SREF February provides a the atmosphere. It is created based comparison of multiple output shown at left, one of good example of the by estimating the current model forecasts. The ensem- our primary models, the state of the atmosphere using ble forecasts give the fore- NAM, indicated 0.03” of liq- utility of observations and then calcu- caster a much better idea of uid equivalent precipitation lating how this state will what weather events may during the event, while the ensembles..” evolve in time using a Nu- occur at a particular time. By other primary model, the merical Weather Prediction comparing these different GFS, indicated 0.34”, a big (NWP) computer model. forecasts the forecaster can spread between the two. The Forecasters have always un- decide how likely a particular SREF output suggests that derstood the value of exam- weather event will be. If the confidence in precipitation ining multiple NWP forecasts forecasts vary a lot then the amount is low as its members to help produce a more relia- forecaster knows that there have values ranging from ble forecast. Instead of run- is a lot of uncertainty about 0.05” to 0.78”. A majority of ning just a single forecast, an what the weather will actual- the SREF members are clus- ensemble approach runs the ly do, but if the forecasts are tered in the 0.10” to 0.30” computer model a number of all very similar forecasters range with a few outliers times from slightly different will have more confidence in indicating much greater starting conditions, model predicting a particular event. amounts. In the end, SREF frameworks, or model config- Forecasters at the NWS Ra- mean value indicated 0.28” urations. The complete set of leigh use a number of ensem- which was very close to the forecasts is referred to as the ble forecast systems, with the observed 0.39”. ensemble family, and individu- most commonly used system al forecasts within it, ensem- called the Short Range En- -Jonathan Blaes ble members. semble Forecast (SREF). The SREF is composed of 21 dif- Ensemble prediction is a rela- ferent members, with the tively new tool for operation- average value of all of the forecasts called the “mean”.

CHANGING SKIES VOLUME 10, ISSUE 1 P A G E 5

Print and Mobile Options for Your Forecast (continued from page 2) 3.) Scroll down about halfway, for easy access on a daily basis. member, we update our fore- just under the 7-day forecast, cast every 3 hours, and often under the “Additional Forecasts Another tool at your disposal is more frequently, so you’ll always and Information” header. Click the NWS Mobile Weather site. get the latest forecast. on the second option from the On your smartphone or tablet, top left, “Printable Forecast”. simply go to mobile.weather.gov As always, your feedback on to access the site. This is a quick these tools, and suggestions for 4.) Choose “Print” from the top and easy way to view your local, other ways that we can give you right to print a one-page fore- current conditions and get ei- the information that you need, cast with graphics and text. ther a quick forecast or the de- are greatly appreciated! You can now bookmark this tailed outlook for your neigh- forecast in your web browser, borhood while on-the-go. Re- -Gail Hartfield

Screenshots From the National Weather Service Mobile Weather Site

New National Weather Service Director Selected Louis W. Uccellini, Ph.D., has was responsible for directing been selected to become the the planning, science and tech- next assistant NOAA adminis- nology, and operational respon- trator for weather services and sibilities related to NCEP’s the 16th director of NOAA’s Central Operations and Envi- National Weather Service. ronmental Modeling, as well as Since 1999, Uccellini has led seven national centers, includ- the NWS’ National Centers for ing the National Hurricane Environmental Prediction, Center in Miami, Storm Predic- which in 2012 moved to a new tion Center in Norman, Okla., state-of-the-art facility in Col- and Space Weather Prediction lege Park, MD. At NCEP, he (continued on page 10) P A G E 6 Understanding a Derecho (continued from page 1)

Lower Michigan. that produce the damaging though they may travel for winds. hundreds of miles. In other The winds associated with cases, the progressive derechos are not constant The type of derecho most derecho and associated bow and may vary considerably often encountered during echo system begin relatively along the derecho path, the spring and fall is called a small, with a narrow path, sometimes being below serial derecho. These are but over time grow to ex- severe limits (57 mph or produced by multiple bow ceed 250 miles in width. The less), and sometimes being echoes embedded in an line of thunderstorms of a progressive derecho often begins as a single bow echo that evolves into a short squall line, typically with more than one embedded bowing segment. Progressive derechos may travel for many hundreds of miles along a path that is relatively narrow compared to those of serial derechos. extensive squall line Often they are associated very strong (from 75 mph (typically many hundreds of with an area of weak low to greater than 100 mph). miles long) that sweeps pressure at the surface. This is because the swaths across a very large area, of stronger winds within the both wide and long. This Derechos and Heat general path of a derecho type of derecho typically is Waves “Some of the most are produced by what are associated with a strong, called downbursts, and migratory low pressure Some of the most intense summer derechos, especially intense summer downbursts often occur in system. those of the progressive derechos, especially irregularly-arranged clusters, along with embedded The second type of derecho type, occur on the fringes of major heat waves. Examples those of the microbursts and burst swaths. is called a progressive Derechos might be said to derecho. These are associ- include the July 1983 "I-94" progressive type, be made up of families of ated with a relatively short derecho in the upper Missis- downburst clusters that ex- line of thunderstorms sippi Valley, the Mid-July occur on the fringes tend, by definition, continu- (typically from 40 miles to 1995 derechos in New York and Canada, and the more of major heat ously or nearly continuously 250 miles in length) that recent Ohio Valley / Mid- for at least 240 miles. may at times take the shape waves.” of a single bow Types of Derechos echo, particu- larly in the Two main types of derechos early stages of may be distinguished. This development. classification largely is based In some cases, on the overall organization the width of a and behavior of the associ- progressive ated derecho-producing derecho and convective system and re- its associated flects, in part, the dominant bow echo sys- physical processes responsi- tem remain Synoptic Setup for Derechos Near ble for the thunderstorms relatively nar- Heat Waves row even

CHANGING SKIES VOLUME 10, ISSUE 1 P A G E 7

through August), with more During a typical heat than 75% occurring between wave over the central April and August (see graph at and eastern United left). As might be expected, States, a large, station- the seasonal variation of ary upper-level high derechos corresponds rather pressure area usually is closely with the incidence of present over the south- thunderstorms. central states. Persis- tent westerly winds on Derechos in the United States the poleward side of most commonly occur along the high allow EMLs two axes. One extends along generated over the the "Corn Belt" from the up- Rocky Mountains to per Mississippi Valley south- Derecho Climatology by Month extend eastward into east into the Ohio Valley, and the Ohio Valley and the other from the southern Atlantic derecho of June 2012. Northeast, well beyond their Plains northeast into the mid The relationship is more than usual range over the Plains. Mississippi Valley (figure be- statistical. It turns out that the Warm air aloft associated with low). During the cool season meteorological conditions favor- the base of the EML acts as a (September through April), able for large-scale heat waves "cap" or "lid" that prohibits derechos are relatively infre- often also are conducive to thunderstorm development derechos. In the United States, along much of the extent of this is especially true from the the EML, southward into Upper Missisippi Valley and Up- the heat wave-associated per Great Lakes into the Ohio "high." But on the northern Valley and Northeast. fringe of the EML, where low-level uplift frequently is The primary link between heat focused along a stationary waves and derechos is the pres- front marking the northern ence of an elevated mixed layer, edge of the heat wave, up- or EML. An EML is a layer of drafts that form in the mid-tropospheric air that origi- strongly heated air near the nates over the arid, elevated ground may breach the cap, terrain. EMLs exhibit sharp de- resulting in an explosive creases in temperature with release of instability. If oth- height. The large vertical tem- er conditions are favorable perature differentials (or "steep" (e.g., low-level moisture is abun- quent but are most likely to lapse rates) in EMLs are analo- dant along the front, winds are occur from east Texas into gous to those observed over largely unidirectional, parallel to the southeastern states. Alt- black-topped roofs and parking it, and increase with height), hough derechos are extremely lots on sunny days. Such thermal additional storms may erupt in rare west of the Great Plains, stratification encourages the concentrated fashion along the isolated derechos have oc- formation of strong updrafts boundary, yielding a band of curred over interior portions that can lead to the develop- downstream-developing storms of the western United States, ment of thunderstorms. In fact, and, on occasion, a full-blown especially during spring and the frequent presence of an EML derecho. early summer. on days otherwise favorable for thunderstorm formation to a Derecho Climatology -Brandon Vincent and large extent accounts for the Ryan Ellis (source: NWS intensity of the storms common- Derechos in the United States Storm Prediction Center) ly encountered over the Great are most common in the late Plains. spring and summer (May P A G E 8 Spring Drought Update central NC have all risen above their target elevations and now contain enough water to last through the summer, even if our rainfall deficit lingers through the spring.

Drought impacts have ac- cordingly declined significant- ly early in 2013. Nearly the entire state west of Inter- The western half of the Tar Even near normal rainfall is state 95 (~70% of the state) Heel state benefitted greatly of great benefit during the was categorized as abnormal- “The western half of from a wet period from late cool months, however, as ly dry or worse on January the Tar Heel state December into January. The evaporation is low and de-

benefitted greatly

from a wet period from late December

into January.”

east, however, has been mand from other sources, 1st, as compared to ~25% on slow to catch up, and is such as agriculture and pub- March 15th. Only a small running a deficit for the year lic use, is also reduced. The area (~7 counties) of south- to date. water supply reservoirs in central NC remained categorized as suffer- ing from moderate drought by the U.S. Drought Monitor ( http://drought.gov/ drought ).

-Mike Moneypenny

CHANGING SKIES VOLUME 10, ISSUE 1 P A G E 9 May 4th Marks Fourth Annual StormFest career paths, notable weather events in their professional careers, weather safety, careers in meteorology, and challenges in their industry. The panel typically fields ques- tions from the audience.

In addition to meeting some of your National Weather Service forecasters and staff, you will have the opportunity to personally interact briefly with the meteorologists you see on television every day. Stormfest is a lot of fun, and one of its main purposes is to North Carolina Museum of Natural Sciences in Raleigh, NC get people ready for severe weather. Visitors will have the opportunity to learn how The fourth annual Stormfest at providing demonstrations and a variety of organizations in- the North Carolina Museum of educational material for adults crease community severe Natural Sciences will take place and children. At past Storm- weather awareness, prepared- Saturday, May 4. Hosted by fests, participating organizations ness, and response. Some WFO Raleigh and the museum have included the American Red demonstrations and hands-on in collaboration with the Ameri- Cross, the North Carolina Bap- activities will aid in under- can Red Cross and local media, tist Men, Central Carolina Sky- standing severe weather safety this event typically draws weath- warn, the North Carolina State and what the organizations do er enthusiasts and others from Climate Office, the Salvation help keep people safe. across the state. The event al- Army, and local chapters of the lows everyone the opportunity American Meteorological Socie- Put the activity on your calen- to experience and learn more ty, among others. A favorite dar now for Saturday, May 4. about severe storms in North activity among those visiting the Stormfest hours will be the Carolina. museum for Stormfest has been museum hours of 9 AM to 5 a panel discussion each with on- PM. The museum is located in At Stormfest, NWS staff mem- air morning and Chief Meteorol- downtown Raleigh at 11 West bers, local media and TV mete- ogists from the major television Jones St. General admission orologists, researchers, storm stations serving the Raleigh- to the museum is free. chasers, emergency officials and Durham market. The moderat- several public service organiza- -Darin Figurskey ed discussion, entitled “Ask the tions will be available all day Experts”, has focused on their New NWS Director (continued from page 5) Center in Boulder, Colo. Uc- Uccellini received his Bache- cellini is also a fellow of the lor of Science (1971), Master American Meteorological So- (1972), and Ph.D. (1977) NOAA’s National Weather Service ciety and just completed his degrees from the University Raleigh, NC term as the society’s presi- of Wisconsin-Madison. He dent. has published more than 60 1005 Capability Drive Uccellini, 63, began his weath- journal articles and chapters Suite 300 er career at the Goddard in books, and is known for Centennial Campus, NCSU Space Flight Center's Labora- coauthoring the widely ac- Raleigh, NC 27606 tory for Atmospheres as the claimed two-volume book, Phone: 919-515-8209 section head for the Northeast Snowstorms. A Fax: 919-515-8213 Mesoscale Analysis and Mod- native of Bethpage, N.Y. on Forecast Line: 919-515-8225 eling Section in 1978. In 1989, Long Island, Dr. Uccellini is a he joined the NWS as chief of resident of Columbia, MD. the Meteorological Opera- He and his wife, Susan, have tions Division and then be- three children. came director of the Office of -NOAA Meteorology in 1994.

William Blake Ellis Joins WFO Raleigh Electronics Team On December 31, 2012, “jumping in with both NWS Raleigh welcomed feet” to make sure all a new addition to the types of systems and family. William Blake equipment have been Ellis arrived at our office working well. on New Year’s Eve as a new electronics techni- -Darin Figurskey cian. Blake was formerly an Aerospace Specialist Supervisor at Pope Air Force Base, and most New electronics recently served as a Sen- technician Blake ior Manufacturing Engi- Ellis running with a neer Technician for UTC Aerospace Systems in 20-pound vest dur- Wilson. A resident of ing the 2012 Memo- Clayton, Blake has a rial Day Murph ac- Bachelor's Degree in tivities in Clayton. Business Administration from Campbell Universi- Photo courtesy of ty. Blake has been a the examiner.com. welcome addition to the Raleigh office, and has been active learning NWS operations and