Faith Eherts
Consulting Meteorologist
April 23, 2015
Case Six
An EF0 tornado was reported to have occurred in Jefferson County, PA (approximately
outlined with a white box) around 4:35 pm on May 31st, 2008. The county manager is required
to document whether the tornado touched down in the town of Brockway, PA (marked with a
white star on the following maps) in Jefferson County. I was asked to assist with this decision.
Note: Since all things meteorology are based around where meteorology was founded –
Greenwich, England – all time stamps are reported in GMT time to avoid time zone confusion
among international peers. Therefore, a tornado reported at 4:25pm in the USA’s Eastern Time
zone would be recorded as 20:25 GMT. For this reason, the following radar snapshots range
from 4:18 to 4:27pm Eastern Time (20:18 to 20:27 GMT).
Based on an analysis done of available NEXRAD weather radar data via the National
Oceanic and Atmospheric Administration (NOAA), it can be proven that the most basic
conditions necessary for a tornado to occur were present in Jefferson County. Mainly, this
involved the presence of a significant supercell thunderstorm. Precipitation can be found on
radar imagery via their color contrast compared to the dark background, which has been fitted
with state boundaries and major roadways to help orient the observer as to where this bird’s
eye view is oriented. Below, you’ll notice the thick yellow border of western and northern
Pennsylvania as well as route I-80 traversing central PA over a black background. The surfacebased radar best situated to view this part of the state is located in State College, PA. This
vantage point can easily be located due to the large “cloud” symmetrically oriented about the
center of the state. This is known as a radar anomaly, and is simply due to the presence of bugs
and other such near-by interferences with the radar beam. However, real precipitation can
easily be pinpointed due to its more defined color scheme and natural shape/structure. With
green being light rain and red indicating a more “severe” part of a storm, an easy-tounderstand spectrum of colors can be analyzed. Specifically, a supercell storm can be identified
via its generally round (as opposed to oblong) shape and rotating nature over time. Since the
reported tornado is supposedly an EF0 – the lowest, least damaging tornado rating possible – it
is not surprising that this storm is relatively disorganized.
In the following images, it is clear that Brockway is, in fact, located quite a distance to
the east of a few separate significant thunderstorms. No large tornado is likely to form within
this cluster of storms due to the lack of a single defined area of rotation, never mind one near
Brockway at the time reported. However, a brief and insignificant tornado is perfectly likely to
have occurred in extreme northwestern Jefferson County based on the location of the storms at
the time in question. A relatively isolated and strong storm clipped the northwestern corner of
Jefferson County around 4:25pm on May 31st, 2008, but Brockway is located well east of this
area.
For these reasons, I conclude that the ingredients necessary to form a non-significant
EF0 tornado in Brockway, Pennsylvania were not present at this date and time.
A
May 31st, 2008, 20:18:45 GMT = 4:18:45 pm
B
20:23:20 GMT = 4:23:20 pm, the reported time of the tornado.
C
20:27:55 GMT = 4:27:55 pm