Analyzed surface temperatures (red/purple), dew points (brown/green), and wind barbs from SPC at 01 UTC on Friday, May 9, 2008
Surface winds across the Northwest Piedmont have backed slightly to the southeast and dew point temperatures
are in the lower to mid 60s. Surface temperatures range in the lower to mid 70s.
850 MB heights, temperatures (red/blue), dew points (green), and wind barbs (black) from SPC at 01 UTC on Friday, May 9, 2008
A broad trough of low pressure can be seen in the 850 mb pattern across
the Ohio and Tennessee valleys. A moderate southerly flow at around 40 knots is present across Georgia and South
Carolina. Temperatures up to 18 degrees C can be seen across South Carolina with the southerly flow producing
good warm advection and lift across central and western North Carolina.
Analyzed low level lapse rates in the 0-3 km layer (blue, green, and orange) from SPC at 01 UTC on Friday, May 9, 2008
A lapse rate is the rate of temperature change with height and the image below
is for the layer from the surface to around 10,000 feet. Note the surface based, low level
lapse rates shown below range in the 6.5 to 7.0 deg C/km across include much of central North
Carolina. Values less than 6 degrees C/km represent "stable" conditions, while values near 9 degrees
C/km are considered "absolutely unstable."
Analyzed surface based convective available potential energy (SBCAPE) (red) and surface based
convective inhibition (blue lines - shaded) from SPC at 01 UTC on Friday, May 9, 2008
SBCAPE values ranged between 500 and around 1000 J/kg across the Northwest Piedmont and
Triad area. There was around 50 to 100 J/kg of convective inhibition (CIN) in this region as well
suggesting that the convection was not entirely surface based initially.
Analyzed most unstable convective available potential energy (MUCAPE) (red) and lifted parcel level
(dashed black lines and shaded in yellow and green) from SPC at 01 UTC on Friday, May 9, 2008
MUCAPE values ranged between 1000 and around 1500 J/kg across the Northwest Piedmont and
Triad area. The shading area across western portions of the Northwest Piedmont suggests that
the greatest instability was not surface based and that parcels were lifted at around 500 meters
above the surface.
0-3 Km Storm Relative Helicity (blue) and storm motion (brown) from SPC at 01 UTC on Friday, May 9, 2008
Note the 0-3 Km SRH values in excess of 250 units and approaching 300 units in the
Western Piedmont and Triad area.
Analyzed Lifting Condensation Level (red, blue, and green) from SPC at 01 UTC on Friday, May 9, 2008
The LCL height is the height at which a parcel becomes saturated when lifted dry adiabatically.
The importance of LCL height is thought to relate to sub-cloud evaporation and the potential
for outflow dominance. Low LCL heights imply less evaporational cooling from precipitation
and less potential for a strong outflow that would likely inhibit low-level mesocyclone development.
Thunderstorms that produce tornadoes generally have a lower LCL height with LCL heights
less than 1,000 meters typically favorable for tornado development. The LCL values during this
event were around or just less than 1000 meters across the Northwest Piedmont.
NWS Composite Reflectivity Imagery from 0130 UTC on Thursday, May 8, 2008 (930 PM EST).
The composite reflectivity imagery is from the approximate time in which the analysis imagery above is valid.