atmospheric set up was conducive for supercellular
thunderstorms to form on this day. A dual jet stream structure (Figure 1)
enhanced lift over the area while a vigorous negative tilt mid level trough (Figure 2) provided strong positive vorticity advection. Strong vertical wind shear as seen
on the MHX 00Z sounding (Figure 3) provided the ability for storms to
violently rotate while surface heating during the afternoon increased
surface based instability.
surface, a cold front was poised to the west over the North Carolina
mountains at 7 am Saturday morning as a warm front moved north to the near
the North Carolina/Virginia border (Figure 4). Thunderstorms would break out ahead
of the cold front, first over central North Carolina during the early
afternoon hours and move into Eastern North Carolina by late afternoon and
early evening. Strong surface based instability and low-level wind shear
led to the thunderstorms very quickly becoming tornadic.
these factors were contributors to the intensity of the thunderstorm that
developed which formed into discrete supercell
structures. These discrete supercell
thunderstorms produced violent tornadoes that caused damage of up to EF3
intensity on the Enhanced Fujita Scale (Figure 5) for rating
Figure 1. 250 mb Analysis at 00Z April
17, 2011 showing dual jet structure over the Eastern United States.
Figure 2. 500 mb Analysis at 00Z April
17, 2011 showing mid-level trough becoming negatively tilted.
Figure 3. The 00Z April 17, 2011
Newport/Morehead City (MHX) sounding showing strong low-level wind shear.
Figure 4. Surface map at 7 am April 16,
2011 showing a cold front approaching Western North Carolina as a warm
front moves north of the area.
Figure 5. The Enhanced Fujita Scale
Velocity image showing strong rotational
couplet (yellow circle) near Snow Hill around 545 pm April 16, 2011. An
EF-3 tornado was on the ground at this time.
Another rotational couplet observed near Hargett’s Crossroads in Jones County around 710
pm April 16, 2011. The result was an EF-2 tornado.
Another rotational couplet on the east
side of Jacksonville around 815 pm April 16, 2011 which led to a EF-3
tornado which produced extensive damage in the Piney Green area and again
near Riverdale in Craven County.
Storm Prediction Center
GR2 Analyst Software
NOAA Daily Weather Maps