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Eastern Pennsylvania Supercells of 30 June 2015-draft
By
Richard H. Grumm
National Weather Service State College, PA
1. Overview
A surge of modestly deep moisture (Fig. 1) moved through Maryland and eastern Pennsylvania
ahead of a weak surface cyclone to the west (not shown). The surge of high PW air was
accompanied by a strong low-level jet. This produced strong low-level wind shear in the 10m to
850 hPa layer (Figs. 2 - 4) over eastern Pennsylvania, LCL heights generally below 1000m, and
CAPE in the 1200 to 2400 JKg-1 range over the region. The combination of high CAPE and
strong wind shear favored the development of supercell thunderstorms.
Several supercells developed over portions of Maryland and eastern Pennsylvania. Most of these
storms produced wind damage (Fig. 5) and based on video evidence potentially produced a
tornado in eastern Pennsylvania. The strong shear, reasonably high CAPE favored supercells and
the low-LCL heights heightened the probability of tornadoes. In addition to the high CAPE, the
SRH was relatively high in eastern Pennsylvania (Fig. 6) as was the supercell composite index
(Fig. 7).
This paper will focus on some of the discrete supercells which developed on 30 June 2015 from
a radar perspective. The models and analysis data pointed to a relatively high supercell day
which verified in eastern portions of Pennsylvania and adjacent States.
2. Supercells of note
One of the first supercells of the day developed in Lancaster County and moved northeastward
eventually entering Berks County, PA. A video of the tornado1 with this storm appeared on
social media, taken from near Morgantown, PA. This storm was sampled at over 10kft by
KCCX, KDIX, and KDOV. The terminal Doppler radar TPHL sampled the storm much closer to
the surface revealing the hook and strong velocity couplet (Fig. 8) at 1750 and 1800 UTC. A
loop of TPHL data revealed a weak mesocyclone west of Gap at 1716 UTC and moving to the
northeast. The velocity data peaked out several times between 1800 and 1810 UTC indicating a
strong mesocyclone and in implied TVS as it moved toward and near Honey Brook, PA. This
mesocyclone tracked up and east of the Berks and Lebanon County borders and weakened
significantly after 1830 UTC.
This tornado, the Honey Brook tornado was rated as an EF1 tornado by a National Weather
Service survey team. It downed numerous trees which blocked several roads, downed power
lines, and damaged several private residences and out building.
1
Storm survey team interviewed the video photographer and determined the video was taken in Lancaster County
of the tornado in westernmost Chester County which moved toward Honey Brook. PHL PNS is in appendix.
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A second strong supercell developed near Burnham central, PA around 1836 UTC. This storm
tracked to the east northeast (Fig. 9). The storm moved eastward showing rotation, a ZDR
column and peak Z around 65 dBZ at times along with a trackable mesocyclone. Cross sections
implied the 50 dBZ cores barely reached 20Kft in this storm. Images at 1929 (Fig. 10), 1945
(Fig. 11) and 2042 (Fig. 12) show this was a long-lived storm.
No tornado damage was determined to have been caused by this supercell. It did produce wind
damage and one area of focused damage suggesting a microburst.
The third significant supercell develop from a storm which split The parent storm originated
along the Snyder-Union County border prior to 2326 UTC 30 June (Fig. 13). Strong
mesocyclone spun-up rapidly as shown in the 2347 UTC image (Fig. 14) and the circulation
about the mesocyclone peaked just west of Danville around 0003 UTC (Fig. 15) near the village
of Riverside. The tight circulation was one of the stronger vortices observed on the KCCX radar
in several years.
Cross sections revealed that the Riverside storm (Fig. 13-15) rarely had 50 dBZ cores much
above about 20kft. These were relatively low-topped supercells. Despite this, the Riverside
tornado was rated an EF1 tornado by a National Weather Service survey team.
3. Summary
A nearly ideal supercell environment set up in eastern Pennsylvania and adjacent States during
the afternoon and evening hours of 30 June 2015. The strong 0-1km shear, high helicity, and
high CAPE suggested the potential for supercells. Several supercells developed across the
region. Three of the higher impact storms in east central Pennsylvania were presented here from
a radar perspective.
These data show that all three storms had mesocyclones. The storm over Lancaster and Berks
counties was sampled too high to truly detect the mesocyclone and potential tornado. However,
the 1 minute 0.4 degree TPHL TDWR did an excellent job sampling the storm and the strong
low-level cyclonic circulation. Clearly, the TDWR data was able to capture the low-level
circulation with the Honeybrook tornado.
The Burnham and Riverside storms were tracked on the KCCX WSR-88D. Both storms showed
rotation and the Riverside storm showed strong rotation in both the base velocity and storm
relative velocity data. The Riverside tornado had a strong signal in the KCCX WSR-88D
velocity and storm relative velocity products.
There were at least 4 other supercells some were shorter lived and others split. The storm which
formed the Riverside storm was a shorter-lived supercell thunderstorm.
4. Acknowledgements
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NSSL MRMS page and NSSL on demand page
5. References
http://employees.oneonta.edu/ellistd/meteorology/fujita1977.pdf
http://eyewall.met.psu.edu/rich/she.gif
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Figure 1. HRRR 00-hour forecasts of precipitable water (mm) and shading for values of 40 mm or greater. Data in hourly increments form a) 1800 to f) 2300 UTC
30 June 2015. Return to text.
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Figure 2. As in Figure 1 except for valid 1800 UTC 30 June showing a) 850 to 10m bulk shear (ms-1), b) 850 to 500 lapse rates, c) LCL height in m
and d) CAPE. Return to text.
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Figure 3. As in Figure 2 except valid at 2100 UTC. Return to text.
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Figure 4. As in Figure 2 except valid at 2300 UTC. Return to text.
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Figure 5. Storm reports from the Storm Prediction Center. Data as of 1839 UTC 1 July 2015. Survey team results are
not in these data. Return to text.
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Figure 6. HPC 0-3km helicity valid at 1800 UTC 30 June 2015. Return to text.
http://www.spc.noaa.gov/exper/mesoanalysis/new/archiveviewer.php?sector=16&parm=scp&underlay=1
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Figure 7. As in Figure 6 except for SPC supercell composite parameter and radar at 1800 UTC. Return to text.
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Figure 8. TPHL TDWR 0.4 degree reflectivity and 0.4 degree storm relative velocity of the lower levels of the supercell in extreme eastern Lancaster
County at 1750 UTC and 1800 UTC. This storm was captured on video with a potential tornado on the ground. Return to text.
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Figure 9. KCCX radar valid at 1836 UTC showing clockwise from upper left, 0.5 degree SRM, V, KDP, and Z. At this zoomed perspective Burnham does
not appear. White arrow shows approximate location of Burnham and yellow arrow the track. Return to text.
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Figure 10. As in Figure 9 except valid at 1929 UTC. Return to text.
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Figure 11. As in Figure 9 except valid at 1945 UTC. Return to text.
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Figure 12. As in Figure 9 except for velocity in lower panels and valid 2042 UTC. Arrow shows the weakening storm. Return to text.
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Figure 13
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Figure 14
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Figure 15
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Appendix of PNS
PNS for KPHL
A NATIONAL WEATHER SERVICE SURVEY TEAM ACCOMPANIED CHESTER COUNTY
EMERGENCY MANAGEMENT OFFICIALS TO ASSESS DAMAGE IN HONEY
BROOK. TREES WERE UPROOTED AND OR SNAPPED ALONG THE DAMAGE PATH.
DEBRIS WAS SCATTERED ACROSS THE ROADWAYS AND FARM FIELDS.
SEVERAL ROADS WERE IMPASSABLE DUE TO DOWNED TREES AND POWER LINES.
THE MOST SIGNIFICANT DAMAGE OCCURRED ALONG A LINE FROM GIVEN ROAD
TO TALBOTVILLE ROAD. DAMAGE TO PRIVATE RESIDENCES INCLUDED ROOF
PANELS TORN OFF ALONG WITH A MOBILE HOME UNSEATED FROM ITS
MOORINGS. TWO PEOPLE WERE TRAPPED WITHIN THE MOBILE HOME AND HAD TO
BE RESCUED BY THE LOCAL FIRE DEPARTMENT. A BARN ALONG TALBOTVILLE
ROAD HAD ITS ROOF TORN OFF AND WALL DAMAGED DURING THE STORM.
TREES TO THE SOUTH OF AN EASTWARD FACING HOME ON TALBOTVILLE ROAD WERE
NOTED TO BE LAYING IN AN EASTERLY DIRECTION WHILE TREES TO THE NORTH
OF THE HOME WERE NOTED TO BE LAYING IN A WESTERLY DIRECTION, INDICATIVE
OF TORNADIC DAMAGE. IN ADDITION, THERE WAS CLEAR VIDEO OF A FUNNEL CLOUD
ALONG THE RIDGE LINE LOOKING SOUTHWARD TOWARDS HONEY BROOK.
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PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
748 PM EDT WED JUL 1 2015
...TORNADO CONFIRMED NEAR RIVERSIDE IN NORTHUMBERLAND COUNTY
PENNSYLVANIA...
LOCATION...RIVERSIDE IN NORTHUMBERLAND COUNTY PENNSYLVANIA
DATE...JUNE 30TH 2015
ESTIMATED TIME...815 PM EDT
MAXIMUM EF-SCALE RATING...EF1
ESTIMATED MAXIMUM WIND SPEED...100 MPH
MAXIMUM PATH WIDTH...100 YARDS
PATH LENGTH...1 MILE
BEGINNING LAT/LON...40.9238N/76.6440W
ENDING LAT/LON...40.9253N/76.6235W
* FATALITIES...0
* INJURIES...0
* THE INFORMATION IN THIS STATEMENT IS PRELIMINARY AND SUBJECT TO
CHANGE PENDING FINAL REVIEW OF THE EVENT(S) AND PUBLICATION IN
NWS STORM DATA.
...SUMMARY...
THE NATIONAL WEATHER SERVICE IN STATE COLLEGE PA HAS CONFIRMED A
TORNADO NEAR RIVERSIDE IN NORTHUMBERLAND COUNTY PENNSYLVANIA ON
JUNE 30TH 2015.
A STORM DAMAGE SURVEY WAS CONDUCTED ON WEDNESDAY THE 1ST OF JULY
SOUTH OF THE TOWN OF RIVERSIDE IN NORTHUMBERLAND COUNTY.
MOST OF THE SURVEYED DAMAGE WAS AT A RESIDENCE NEAR THE
INTERSECTION OF MOSER AND SNYDERTOWN ROADS. DAMAGE BEGAN JUST TO
THE WEST OF PINE SWAMP ROAD ABOUT 1 MILE WEST OF THE RESIDENCE.
MULTIPLE TREES WERE DAMAGED AS THE TORNADO MOVED EASTWARD ACROSS
A WOODED AREA AND A FIELD BEFORE CROSSING SNYDERTOWN ROAD.
AN EYEWITNESS VIEWED THE TORNADO FROM AN ADJACENT PROPERTY AS IT
BEGAN TO DAMAGE THE RESIDENCE AT MOSER AND SNYDERTOWN ROADS.
A CHAOTIC DEBRIS FIELD WAS OBSERVED AT THE RESIDENCE WITH DEBRIS
STREWN IN MULTIPLE DIRECTIONS. HOWEVER...THERE WAS A CLEAR PATTERN
OF BOTH COUNTER-CLOCKWISE AND CONVERGENT WIND FLOW.
THE MOST EXTENSIVE DAMAGE WAS TO A SMALL BARN AND A SHED. DEBRIS
FROM THESE STRUCTURES HEAVILY DAMAGED A CAR. THE CAR ITSELF WAS
MOVED A SHORT DISTANCE AND THE WINDOWS WERE BLOWN OUT. TREES WERE
UPROOTED AND SNAPPED. PIECES OF WOOD WERE IMPALED INTO THE GROUND
IN A CONVERGENT PATTERN AND ONE 2 BY 4 IMPALED THE CAR. SIDING AND
TRIM WERE DAMAGED ON A HOUSE. THE TORNADO APPEARED TO THEN LIFT
AND END WITH NO DAMAGE OCCURRING AT THT RESIDENCE TO THE EAST
ON MOSER ROAD.
THIS INFORMATION CAN ALSO BE FOUND ON OUR WEBSITE AT
WEATHER.GOV/CTP.
FOR REFERENCE...THE ENHANCED FUJITA SCALE CLASSIFIES TORNADOES
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INTO THE FOLLOWING CATEGORIES:
EF0...WIND
EF1...WIND
EF2...WIND
EF3...WIND
EF4...WIND
EF5...WIND
SPEEDS
SPEEDS
SPEEDS
SPEEDS
SPEEDS
SPEEDS
65 TO 85 MPH.
86 TO 110 MPH.
111 TO 135 MPH.
136 TO 165 MPH.
166 TO 200 MPH.
GREATER THAN 200 MPH.
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