June 4, 2004 Severe Weather Outbreak|
Synoptic Overview -
A stationary front extended southwest to
northeast across central North Carolina during the late morning and afternoon hours of June 4. A weak wave of low
pressure was stalled along the front. In the upper levels, trough was slowly moving eastward across
the Ohio Valley at 500 MB with a closed circulation over western North Carolina at 850 MB.
Thunderstorms developed south of the frontal zone in a warm and unstable airmass and
then moved north and northeast. Several thunderstorms became severe with a few thunderstorms
Severe Weather Reports -
The severe weather reports were clustered near the frontal zone as convection that developed
in the warm air south of the front became enhanced near and along the font. There were approximately
six reports of tornado touchdowns with dozens of reports of funnel clouds. Flooding became
an increasing problem as thunderstorms redeveloped and repeatedly moved over the same areas
dropping several inches of rain and producing flash flooding.
There were several factors limiting wind damage and tornado touchdowns. While directional wind
shear along the boundary was impressive, the magnitude of the winds in the low and mid levels
was lacking. This limited the amount of wind shear available to the storms. The direction
of storm motion had a significant northerly component which caused the storms to quickly move
across the frontal boundary.
Had the surface front been oriented more north to south or had
the storm’s steering winds moved the thunderstorms parallel to the front, the individual storms would
have been exposed to frontal boundary wind shear for longer periods of time. This
would have likely extended the life time of the rotating mesocyclones that only lasted 1–2 radar
scans (about 5 to 10 minutes). Had the mesocyclones persisted for longer durations, there may
have been more funnel clouds reaching the ground as tornadoes.
The mesocyclone that did produce
a tornado across Johnston, Wayne, and Wilson Counties was persistent, causing damage all the way
into Martin County. It was also very deep, with the radar MESO algorithm showing a mesocyclone depth from
1,500 feet to 12,000 ft at one point. This storm also display good rotation on the radar's 0.5 Storm relative
velocity imagery, while most other storms had weak to no rotation in the lowest