2011 by the Numbers

• -7°F: the lowest temperature reported in North Carolina during the year, on January 9 at Mount Mitchell
• 0.5 inches: the amount of snow measured at Beech Mountain on October 1, making it the earliest snowfall on record in North Carolina
• 9: the number of days at or above 100 degrees in Raleigh, the most since 1999 (12 days) and the second-most on record
• 30: the number of reported tornadoes on April 16, which beat the old single-day record of 20 (April 7, 1998)
• 62.6°F: the average temperature in Raleigh during 2011, making it the third-warmest year on record
• 86 mph: the maximum sustained winds of Hurricane Irene when it made landfall near Cape Lookout on August 27. The storm was a category one at landfall but had been at category three strength just 36 hours before.
• 45,294: the number of acres burned in the Pains Bay wildfire. The Dare County blaze started with a lightning strike on May 5 and was 100% contained by June 27.
• $5.2 million: the amount of damage to Ben Martin Elementary School in Fayetteville from an EF3 tornado during the April 16 outbreak

2011 Was Warm — and Perhaps the Most Extreme Year?

2011 was warm in North Carolina — the 10th warmest on record for statewide averages.

Temperature and Precipitation by Climate Division
Departures from Normal for 2011
Based on Preliminary Data

It was also a bit dry in central and eastern NC. The dryness is most evident in southeastern parts of the state, as shown in the radar-based precipitation map below.

Precipitation for 2011: Percent of Normal
Based on estimates from NWS Radar
Data courtesy NWS/NCEP

However looking back at the year's average temperatures and precipitation totals can be a bit misleading, as most of our society’s sensitivities to climate aren’t seen with annual averages. Instead, we see our sensitivities in the climate extremes. And 2011 may likely be most remembered as a year of extremes.

January — Very cold conditions, especially early. Statewide, January 2011 was the 16th coldest on record, and there were several significant snow events.
February — 29th warmest on record
April — 11th warmest April on record, record-breaking tornado outbreaks
May — Driest May on record for many locations east of I-95
June — Top 10 warmest June on record for most of NC, and top 5 driest for areas east of I-95
July — Top 5 warmest July on record for most of NC
August — Hot, dry conditions expand the drought, then Hurricane Irene devastates NE NC
October — early season cold snap brings SNOW to high elevations, 25th coldest October on record
November — flooding from 10+ inches in western NC, statewide totals rank as 18th wettest on record
December — Top 5 warmest on record for much of NC

So while the annual averages may not seem extreme, almost every month brought an impact to North Carolina. Indeed, we couldn’t find another year in our records that has this same combination of extreme events of relative magnitude in one calendar year. Based on our limited records of severe weather, 2011 will likely go down as the most extreme year given the snowstorms, the severe tornado outbreaks, the excessive heat and drought, and the landfall of Hurricane Irene.

Below is a table of Local Storm Reports provided by the National Weather Service.

Cold Start, Warm Finish to Winter

The first few months of 2011 were really a tale of two winters after a cold and snowy end to 2010, which included the first white Christmas in more than 20 years for much of the state. In January, two low pressure systems moving along the coast brought winter precipitation to the state on the 10th and the 22nd. In addition to these winter weather events, North Carolina experienced very cold temperatures. Based on the monthly average mean temperature, it was the 12th-coldest January in Asheville, the 15th-coldest in Charlotte, and the 5th-coldest in Wilmington.

January average mean temperature rankings for locations across North Carolina
Courtesy of the Southeast Regional Climate Center's Climate Perspectives tool

One of the main reasons behind January's cold, snowy pattern was a negative-phase North Atlantic Oscillation (NAO) for most of the month. As our Global Patterns page explains, a negative NAO is associated with a strong upper-level high pressure system over eastern Canada that helps funnel cold, Arctic air into the Southeast and allows storms to track up the east coast. However once February rolled around, the NAO switched from predominately negative to predominately positive, which led to above-average temperatures and a reduced amount of wintry weather. In fact, most of the state saw only a dusting of snow in February, associated with an event on February 10 that brought the heaviest snow — about four inches of accumulation — to the northeastern coastal counties.

February average mean temperature rankings for locations across North Carolina
Courtesy of the Southeast Regional Climate Center's Climate Perspectives tool

The cold January and warm February were complimented by a near-normal March in which the statewide average temperature was only 0.18°F above normal. The vast differences in temperature during January, February and March (cold to warm to near-normal) meant that average temperatures at most locations ranked as near-normal for the three-month period.

April 16th Tornado Outbreak

The weather dealt North Carolina a hard blow on April 16, 2011 with a tornado outbreak that left homes and businesses ruined, lives lost, and many North Carolinians shaken. This outbreak was part of a 3-day event that spawned numerous tornadoes across the southern tier of the US.

Tracks of April 16th tornadoes. Source: National Weather Service, Raleigh, NC

The tornadoes and storm damage NC experienced can be placed into the broader picture of tornado incidences in April 2011 for the US as a whole, which now ranks as the most active tornado month, at 753 tornadoes, since record keeping began (the previous record was set in May 2003 at 542 tornadoes)¹. For 2011 as a whole, there were 1,894 recorded tornadoes in the US with North Carolina seeing 113 of these². This contrasts sharply with the annual average number of tornadoes for NC: 26³. In fact, April 16th alone surpassed this average. Therefore, can it be said that this tornado outbreak was unheard of in North Carolina? The answer to this is more complicated than a simple 'yes' or 'no.' Since tornado record keeping began, there does not appear to be another single event in North Carolina where so many tornadoes occurred in such a wide range across the state in such a small time frame⁵. But before record keeping, who knows? North Carolina has seen tornado outbreaks and has incurred significant tornado damage in its history, and will probably see tornadoes in its future. The climate of NC is such that tornadoes are a not-uncommon occurrence in the spring and residents of the state should be aware of this fact and have a plan in place in the event a tornado is headed their way.

Downtown Raleigh following tornado passage Image credit: Jarles Alberg	Golf-ball sized hail stones from Clinton, NC Source: WRAL news http://www.wral.com/weather/image_gallery/9458338	Tornado damage from Camp Lejeune/Jacksonville, NC Image Courtesy: NWS, Newport/Morehead City, NC http://www.erh.noaa.gov/mhx/EventReviews/20110416/Damage1.JPG

Links to sources of information:

1. Breakdown of 2011 US tornadoes information by NOAA:
   http://www.noaanews.noaa.gov/2011_tornado_information.html
2. 2011 Severe Weather Summary from SPC:
   http://www.spc.noaa.gov/climo/online/monthly/2011_annual_summary.html
3. NOAA's SPC Warning Coordination Meteorologist’s page (also has links for downloading GIS data of tornado tracks for each year since 1950):
   http://www.spc.noaa.gov/wcm

Additional information:

• Write up about April 16th tornadoes by the Newport/Morehead City NWS Office:
  http://www.erh.noaa.gov/mhx/EventReviews/20110416/20110416.php
• Write up about April 16th tornadoes by the Raleigh NWS Office:
  http://www4.ncsu.edu/~nwsfo/storage/cases/20110416
• Video showing satellite imagery of 3-day system that spawned tornadoes in NC on April 16th:
  http://www.noaa.gov/extreme2011/midwest_se.html

Summer Heat and Drought

After a record-breaking heat during the summer of 2010 (summer 2010 was the hottest on record statewide), most everyone was hoping for a cooler summer in 2011. However, it certainly didn't play out that way. The summer of 2011 ranked as a top 5 warmest summer for most locations in NC. Several locations tied or exceed the number of days with maximum temperatures greater than 90°F, and many locations in eastern NC also tied or broke the records for number of days with temperatures more than 100°F.

Drought in 2011 wasn't nearly the severity experienced in 2007 or 2008, but it did roar its ugly head, especially in eastern NC. Drought conditions emerged in May east of I-95, and persisted through the rest of the summer. D3 (Extreme Drought) peaked in mid-July, when more than half of NC was under moderate to severe drought.

Hurricane Irene

In late August, the hot summer and drought was interrupted by Hurricane Irene, which brought heavy rain, high winds and flooding during its rendezvous with the North Carolina coast. Even though it made landfall as a Category 1 hurricane, Irene was a powerful and damaging storm. More than 15 inches of rain was observed in Bayboro, and at least 6 inches fell across much of the coastal plain. In addition, tropical storm-force (greater than 39 mph) wind gusts were measured as far inland as Winston-Salem, with wind gusts exceeding 100 mph reported as the eye wall moved through Carteret County.

The map below shows Local Storm Reports issued by the National Weather Service on August 27.

The Outer Banks received the worst damage due to a combination of the rain, wind and storm surge. Winds blowing across the Pamlico Sound created a somewhat unusual sound-side surge of up to seven feet at the Oregon Inlet Marina. That storm surge caused two breaches of Highway 12, the only road connecting the Outer Banks towns to the mainland. Irene's damage in North Carolina is estimated at $71 million, and at least six deaths in the state are attributed to the storm. Irene was certainly a reminder of the power of Mother Nature and the sometimes volatile climate in our state.

Photo obtained from the Raleigh News & Observer website. Photographer: Chuck Liddy

Autumn: Unusually quiet and mild? Only on average.

After the extremes in winter, spring, and summer, the autumn season in North Carolina seemed unusually calm. Temperatures in September, October, and November were generally closer to normal. Similarly, rainfall was overall close to normal, with wetter conditions in September and November and drier conditions in October and December. However, the statewide monthly averages hide some extremes observed. In early October, cold temperatures brought an early taste of winter to western NC with the earliest measurable snow on record in North Carolina. Storms in western North Carolina in November brought more than 10 inches of rain and flooding to stream, rivers, and streets in the mountains. Storms largely disappeared in December, which brought spring-like conditions and temperatures that were generally in the top 5 for much of NC.

As 2011 came to an end, many North Carolinians enjoyed an unusually warm holiday season. The warm, drier conditions in December were due, in part, to the La Niña pattern and a positive North Atlantic Oscillation. What a contrast to how the year began.