Investigation of Lightning Patterns Over New Jersey and Surrounding Area

Al CopeNational Weather Service

Mount Holly, NJ

Adam GonsiewskiMillersville University

Introduction• Research on lightning patterns in New Jersey and surrounding

areas, with a focus on the summertime months of June, July, and August, was conducted during the summer of 2010 at the National Weather Service Forecast Office in Mount Holly, New Jersey.

• The goal was to see whether or not lightning had different tendencies across the region based on month, hour of the day, 500 mb flow direction, synoptic regime, and day classification (event, contaminate, or null).

• This work was designed to coincide with a related study on summertime convective initiation over New Jersey, being conducted by NWS Mount Holly and Kean University.

Procedure1. Obtain CG-Lightning from Vaisala for 2004-08. Extract a subset of lightning

data over the study area.

2. Use spreadsheet program to sort the data by month, hour of the day, upper-air flow, synoptic regime, and day classification (event, contaminate, and null).

3. Create tables and graphs showing lightning distribution by day and time.

4. Write a FORTRAN program to put the data into a 21km x 22km grid array (sort lightning by location).

5. Upload the array output from the FORTRAN program onto www.GPSvisualizer.com in order to produce flash frequency maps.

The map to the left shows the total summertime lightning strikes from 2004-2008 across the region.

The overall lightning distribution shows a maximum over the Chesapeake Bay region extending north across eastern PA.

There is a minimum in strikes off the coast of New Jersey (due to colder waters?)

2004 2005 2006 2007 20080

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500000Total Lightning Flashes by YearN

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Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec0

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Total Lightning Strikes by Month 2004-2008N

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Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec0

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Inter-Annual Flash Variability by Month

2004 2005 2006 2007 2008 Average

Num

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10 11 12 13 14 15 16 17 18 19 20 21 22 23 0 1 2 3 4 5 6 7 8 90

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250000Total Lightning Flashes by Hour (2004-08)

Beginning Hour (UTC)

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10 11 12 13 14 15 16 17 18 19 20 21 22 23 0 1 2 3 4 5 6 7 8 90

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April May June July August September

Hour Beginning (UTC)

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SW W NW Other0

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5000Summertime Flashes by 500 hPa Flow

% Days % Flashes Flashes/Day

500 hPa Wind Direction

Perc

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f Fla

shes

12 13 14 15 16 17 18 19 20 21 22 230

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50000Hourly Flashes by 500 hPa Flow and Day Type

SW Event SW Contam W Event W Contam NW Event NW Contam

Hour Beginning (UTC)

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HP LP CF WF SF TROF0

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5000Summertime Flashes by Synoptic Type (12Z-00Z)

% Days % Flashes Flashes/Day

Synoptic Type

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Daytime T-Storm Trends:SW vs. NW Flow Aloft

Daytime T-Storm Trends:Cold Front vs. High Pressure

Conclusions

• Lightning activity peaks in late afternoon (diurnally) and in mid-summer (annually)

• For any given month, large inter-annual variation is possible

• Diurnal maximum becomes earlier from spring into summer

• Half of all summer lightning occurs with SW flow aloft; half is associated with cold fronts

• Diurnal trends vary somewhat with flow aloft and surface synoptic pattern

Future Work

• Obtain and analyze lightning data from additional years

• Examine diurnal trends past 00Z• Create contoured analyses of flash density

Acknowledgements

• Lightning data provided by Vaisala (gratis)

THE END