1. An Examination of High Impact Severe
Weather Events in the Mid-Atlantic Region
Joe Egan
Valparaiso University
Major: Meteorology
Weather-Ready Nation
National Weather Service/ WFO State College, PA
Richard Grumm (Mentor)
Charles Ross (Secondary Mentor)
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2. Outline
• Objectives
• Background
• Methodology
• Climatology
• Case Studies
• Summary
• My Next Steps
• Acknowledgements
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3. Objectives
• Severe thunderstorms are quite frequent in
the Mid Atlantic in late spring and summer
– Wind Damage main threat, often in narrow lines
• My Interests:
– Weather History
– Forecasting Convection
– Keeping Public Informed
• Hypothesis: Derechos and spearhead echoes
are responsible for large amounts of wind
damage in the Mid Atlantic
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4. Background
• Most widespread severe wind event: Derecho
– 240+ mile concentrated swath of wind damage
– Severe (58mph+) wind reports along path
– Several “well separated” 75mph+ wind gusts
– Source: Storm Prediction Center
•Types of Derechos
– Progressive
– Serial
– Hybrid
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Damage in Washington, D.C.from 29 June
2012 Derecho (Bloomburg/AP)

5. DATE REMARKS CATEGORY
7/7/2003 DERECHO from IL to PA Progressive
7/8/2003 DERECHO in OH/PA Progressive
8/26/2003 DERECHO from IN to coast; including PA Progressive
5/21/2004 DERECHO from IN to VA, including PA Progressive
6/30/2005 DERECHO in OH and PA; also in south Plains and in Ozarks Progressive
8/4/2010 DERECHO from OH through WV and PA to VA Progressive
4/19/2011 DERECHO in OH Valley and SE, including in east OH/west PA Serial
7/11/2011 DERECHO from OH to PA/MD/VA and in VA (from KY) Progressive
6/28/2012 DERECHO in PA and NJ (into morning of 6/29) Progressive
6/29/2012 DERECHO from IL to Mid Atlantic Progressive
7/26/2012 DERECHO in PA, NJ, WV, MD, eastern OH Serial
6/12-13/2013 DERECHO in OH and western PA (late night of 6/12 into AM of 6/13) Progressive
6/25/2013 DERECHO from OH to PA, MD, and NJ Progressive
7/10/2013 DERECHO in OH and PA Serial
7/8/2014 DERECHO in PA, MD, and northern VA Serial
5/11/2015 DERECHO in OH, PA along/east of I-71 Serial
Data Table of Large Derechos
Dates link to Storm Reports images June 2012 “Super Derecho”
5
Hole in reports partially
due to communications
outages but appeared in
other events.
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6. Derecho Examples
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Map Courtesy: Storm Prediction Center

7. SHE Background
• Focus on Spear Head Echoes
(SHEs; Fujita and Byers 1977)
– Contain appendage pointed
in direction of motion
– “Parent Echo” ahead of SHE;
ingested into SHE
– Main threat: Wind Damage
(downdraft CAPE; SPC)
– Too short-lived to be
derechos
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Image Courtesy: Fujita and Byers (1977)

8. Methodology
• Created a general severe weather climatology
from 2000-June 2015 using SPC Storm
Reports
• Documented linear patterns of wind damage
in Mid Atlantic
– Classified PA events as Derecho, classic
SHE, frontal SHE, or hybrid
• Examined radar data from select events with
NCDC archive radar data and GR2Analyst
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9. 5/18/2016 9

10. 5/18/2016 10

11. SHE/Derecho Climatology
• Average 27-28 SHE/Derecho events per year in Mid
Atlantic
• Climate period (2000 – 2014*)
• Includes SHEs/derechos along cold fronts
• Nearly 90% occur between May and September
– Through June 2015
• 180 events affected PA (through June 2015)
– 16 Derechos
– 86 classic SHEs (non-frontal)
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*Did not use 2015 for SHE/Derechos
average; year incomplete

12. Case Study: 7 July 2012
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Notice the
coherent
line in the
wind
reports in
PA
Map Courtesy: Storm Prediction Center

13. Case Study: 7 July 2012
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Images created with GR2 Analyst and NCDC archive radar dataStorm-following

14. Case Study: 7 July 2013
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Map Courtesy: Storm Prediction Center
Notice the
coherent
line in the
wind
reports in
PA

15. Case Study: 7 July 2013
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Images created with GR2 Analyst and NCDC archive radar data
Storm-
Following

16. Case Study: 4 August 2010
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Map Courtesy: Storm Prediction Center
Notice
the
coherent
line in
the
reports
in SE OH
into WV

17. Case Study: 4 August 2010
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1928 UTC 2106 UTC
Images created with GR2 Analyst and NCDC archive radar data
Parent Echo
Spearhead
Echo

18. Summary
• SHEs and derechos account for a significant number
of Mid Atlantic severe weather reports
– Average of 27-28 events in Mid Atlantic per year
• SHEs:
• Shorter-lived but locally as damaging as derechos
• Often account for significant amount of severe reports
during many events
• Recognition of SHEs on radar important to ensure
timely, accurate warning decisions
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19. Future Research
• Synoptic and mesoscale conditions
favorable for SHEs and Derechos
– Difficult to forecast (SPC)
– Downdraft CAPE and cold pools
• Communication of threats to life and
property
– Outreach events critical
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20. My Next Steps
• Rising Senior at Valparaiso University
• Considering attending Graduate School
• Career Goal: Operational Meteorology
– Public or Private Sector
– Emergency Management
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21. Acknowledgments
• Thank you to my mentors, Richard Grumm
and Charles Ross, for taking me on
• Thank you to the staff of the NWS WFO in
State College
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22. References
• Bloomberg, 2013: The 11 Most Damaging U.S. Weather Disasters of 2012. Accessed 8 July 2012.
[Available online at http://www.bloomberg.com/slideshow/2013-01-03/the-11-most-damaging-u-s-
weather-disasters-of-2012.html#slide8]
• Fujita, T. T, and H. R. Byers, 1977: Spearhead echo and downbursts in the crash of an airliner. Mon. Wea.
Rev., 105, 129–146, doi:10.1175/ 1520-0493(1977)105,0129:SEADIT.2.0.CO;2
• GR2 Analyst Software Package
• Grumm, Richard and Elyse Colbert/NWS State College, 2012: End of heat-event severe event of 7 July
2012. Accessed 10 June 2015. [Available online at
http://cms.met.psu.edu/sref/severe/2012/07Jul2012.pdf]
• Grumm, Richard and Elyse Colbert/NWS State College, 2013: Severe Event of 7 July 2013. Accessed 8 July
2015. [Available online at http://cms.met.psu.edu/sref/severe/2013/07Jul2013.pdf]
• NCAR, 2014: Image Archive. Accessed 27 June 2015. [Available online at
http://www2.mmm.ucar.edu/imagearchive/]
• NOAA, 2015: MRMS Single Product Map Viewer. Accessed 11 June 2015. [Available online at
http://nmq.ou.edu/applications/qvs_2d_maps_main.html]
• NOAA/NWS/ERH, 2013: Derecho Event 29 June 2012. Acessed 29 June 2015. [Available online at
http://www.erh.noaa.gov/rlx/science/derecho/]
• NOAA/NCEP/NCDC, 2015: HDSS Access System. Accessed 19 June 2015. [Available online at
http://www.ncdc.noaa.gov/has/has.dsselect]
• NOAA/NWS/NCEP/SPC, 2015: About Derechoes. Accessed 24 June 2015. [Available online at
http://www.spc.noaa.gov/misc/AbtDerechos/derechofacts.htm]
• NOAA/NWS/NCEP/SPC, 2014: Downdraft CAPE. Accessed 25 June 2015. [Available online at
http://www.spc.noaa.gov/exper/mesoanalysis/help/help_dcape.html]
• NOAA/NWS/NCEP/SPC, 2015: Severe Weather Summaries. Accessed 10 June 2015. [Available online at
http://www.spc.noaa.gov/climo/online/]
• NOAA/NWS/NCEP/SPC, 2015: SPC Severe Weather Events Archive. Accessed 10 June 2015. [Available
online at http://www.spc.noaa.gov/exper/archive/events/]
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