An 8 Year Lightning Climatology of North Carolina Jonathan Blaes, NOAA/NWS Raleigh, NC Morgan Brooks, NOAA/NWS Milwaukee/Sullivan, WI

Motivation Cloud-to-ground (CG) lightning is one of the leading causes of weather-related fatalities in the U.S., second only to flooding (Curran et al. 2000). “Storm Data” (NOAA/National Weather Service 2011) ranks North Carolina sixth in the U.S. for the number of lightning fatalities between 1995 and 2010 and fifth during our study period of Lightning climatologies have shown a broad maximum of CG flash density over the southeastern U.S. (Orville et al. 2011), but these studies have not closely examined the lightning distribution over North Carolina.

Motivation North Carolina's convective weather is heavily influenced by a unique and diverse set of geophysical features. This climatology explores the influences of the season, time of day, various geophysical features, and mesoscale processes on the spatial and temporal distribution of CG lightning across the state. This project provides a context and initial dataset to support complementary lightning related projects.

Audience Participation What month has the greatest amount of CG lightning in NC? [April, May, June, July, August, or September] What time of day has the greatest/fewest CG lightning strikes on average per year? For the following locations: AVL, CLT, ECG, EWN, FAY, GSO, ILM, RDU… - Which has the greatest/fewest CG lightning strikes on avg per year? - Which has the greatest/fewest days with CG lightning on avg per year? - How many days with lightning is needed to reach 50% of the annual total? Where is the lightning capital of NC? [Cape Hatteras, New Bern, Goldsboro, Lumberton, Charlotte, or Asheville]

Map of Apr 1994 – Feb 2003 Flash Rate Density Example Total Flash Density Analysis

Map of Average U.S. Lightning Flash Density Example CG Flash Density Analysis

Examples of CG Flash Density Analysis

North Carolina Topography

North Carolina Annual Precipitation

North Carolina Soil Types

North Carolina Land Use

Methodology An eight year data set ( ) of U.S. National Lightning Detection Network (NLDN) CG lightning data across North America was constructed. The data was quality controlled to remove positive flashes less than 15 kA. The point data, constructed with latitudinal and longitudinal pairs, were then ingested into ArcGIS software where the “Point Density” tool was used to create a 5 km 2 analysis. Statistical point data for eight selected cities were derived using a 25 km 2 grid box centered over the associated airport location (AVL, CLT, ECG, EWN, FAY, GSO, ILM and RDU). A total of 4,162,622 CG lightning strikes were analyzed over the study period.

NLDN Data The NLDN consists of over 100 remote, ground-based sensing stations located across the U.S. that instantaneously detect the electromagnetic signals given off when lightning strikes the earth's surface. These remote sensors send the raw data via a satellite-based communications network to the Network Control Center operated by Vaisala Inc. in Tucson, Arizona. The NOAA NWS purchases the data from Vaisala and then distributes it to field and forecast offices. The NLDN records: - Time - Location - Polarity (positive or negative) with the peak signal strength (of first return strike) - Multiplicity (number of return strokes per CG flash) 2003,1,1,15,0,26, , ,-12,6

Annual Flash Density

Seasonal Flash Density

Seasonal Flash Density Percent of Annual

Seasonal Flash Density Percent Positive

Monthly Flash Density Apr May Jun Jul Aug Sep

Monthly Maximum of 1,360,268 strikes in July, followed by 941,651 in August, and 928,860 in June. Total of 3,230,779 strikes in June, July, and August which account for 77.6% of the annual total. Combined total of 48,604 strikes in November, December, January, and February which account for just 1.1% of the annual total.

Hourly

Hourly Flash Density 16Z17Z 18Z19Z 20Z 21Z

Hourly Flash Density 02Z 21Z22Z 23Z00Z 01Z

Hourly Maximum of 487,188 strikes during the 21 UTC hour, and a minimum of 25,057 strikes during the 13 UTC hour. 59.2% of all strikes occur between UTC.

Site Specific ILM has the greatest number of strikes per year, 13% more than the second greatest location (FAY) while GSO has the fewest. The top three locations in number of strikes per year, ILM, FAY, and EWN are located in southeastern NC where sea breeze boundaries, the Sandhills convergence zone, and the Piedmont trough can complement one another and produce convection. AVL has the greatest number of days with strikes (nearly 57) and the second fewest number of strikes per year. All 8 locations experience days with excessive lightning with 50% of the total annual lightning occurring on just 4 to 6 days.

Site Specific Monthly July has the most flashes out of any month for all eight sites closely examined The percent of flashes during July at the eight sites ranged from 44% to 29% and the average was 36.0% A dramatic decline in flashes from August to September reflects the climatologically drier fall The minimum month varied among November, December, January, and February

Site Specific Hourly

Earlier peak at AVL and ILM, likely results from stronger geographical forcing mechanisms On average, 23% of flashes at AVL occur during the peak hour, 16% at ILM, and 12% at RDU The three sites in central NC, CLT, GSO, and RDU had the latest peak time, 22Z

Audience Participation What month has the greatest amount of CG lightning in NC? [April, May, June, July, August, or September] What time of day has the greatest/fewest CG lightning strikes on avg per year? 21 UTC/13-14 UTC For the following locations: AVL, CLT, ECG, EWN, FAY, GSO, ILM, RDU… - Which has the greatest/fewest CG lightning strikes on avg per year? ILM/GSO - Which has the greatest/fewest days with CG lightning on avg per year? AVL/ECG - How many days with lightning is needed to reach 50% of the annual total? ~4-5 days Where is the lightning capital of NC? [Cape Hatteras, New Bern, Goldsboro, Lumberton, Charlotte, or Asheville] Tabor City, roughly half way between Lumberton and Wilmington

Additional Information Additional analysis images and other charts are available online at the URL below. Jonathan Blaes

Acknowledgements Special thanks to Gail Hartfield who has lead much of the lightning research at NWS Raleigh. Michael Moneypenny and Bradley McLamb provided ArcGIS help. Terry Click and Ron Humble provided assistance with data extraction. Rebecca Duell and Lindsey Anderson (NC State University) provided assistance with the data analysis. Dr. Brett McDonald (NOAA/NWS Riverton WY) provided a portion of the AWIPS NLDN lightning data. Dr. Gary Lackmann (NC State University) and Dr. Larry Carey (University of Alabama in Huntsville) provided guidance and direction for this project.

References Curran, E. R. Holle, and R. Lopez, 2000: Lightning casualties and damages in the United States from 1959 to J. Climate, 13, 3448–3453. Koch, S. E., and C. A. Ray, 1997: Mesoanalysis of summertime convergence zones in central and eastern North Carolina. Wea. Forecasting, 12, 56–77. NOAA/National Weather Service cited 2011: U.S. Natural Hazard Statistics. [Available online at Orville, R. E., and G. R. Huffines, 2001: Cloud-to-ground lightning in the United States: NLDN results in the first decade, Mon. Wea. Rev., 129, 1179–1193. Orville, R. E., G. R. Huffines, W. R. Burrows, and K. L. Cummins, 2011: The North American Lightning Detection Network (NALDN)—analysis of flash data: 2001–09. Mon. Wea. Rev., 139, 1305–1322. Wootten, A., S. Raman, and A. Sims, 2010: Diurnal variation of precipitation over the Carolina Sandhills region. J. Earth Syst. Sci. 119, No. 5, October 2010, pp. 579–596

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Extra Slides

DateLocationAgeSexLocationActivityVictim 10-Jun-11Durham Cnt45MFieldFeeding livestockSteven Taylor 4-Jun-10Madison Cty25FNear mountain topHikingBethany Lott 15-Jun-10Graham19MUnder treeHad been playing soccerHoracio Alejo-Ascensio 8-Jun-09Fairview65MIn fieldClearing brushDonald M. Lynch 27-Jul-09Southern Shores49MBeachJoggingMatthew Glomb 25-Sep-09Wrightsville Beach18MBeachSwimmingJohn Edward Sackett 7-Jul-08Lea Island16MUnder beach houseBoating-fishing/taking shelterLucian Ellis 8-Jun-06Cherry Point27FTarmac of air baseWalking Aug-06Chapel Hill17MYardTaking clothes off clothes lineBryan Howard NC Lightning Fatalities