Case Jan 02-03 2006 --Squall line moves through early afternoon...leaving stable conditions, stratus and low LCLs over region through early night hours. --Boundary layer recovers from west during the evening...strong 500mb shortwave provides triggering mechanism for new development of convection. Convective mode initially is multicell and linear in nature. --Storms become more isolated as mid lvl dry air encounters storms while they pass over the downwind side of the cape axis and begin feeling the effects of stronger shear along the western edge of a strong low lvl jet.

250 MB 01/02/06 12Z 01/03/06 00Z

500 MB 01/02/06 12Z 01/03/06 00Z

850 MB 01/02/06 12Z 01/03/06 00Z

00Z FFC Sounding 00Z TLH Sounding -- Cold/Dry Mid Lvl Air Advecting East -- Note the mid level environment advecting from the west for our 2 tornado events. Note the environmental conditions advecting from the south of our 2 tornado events. TLH: 0-6km Shear of 72 Knots, veering winds near sfc FFC: Dry air above 850mb, lapse rates 7.7C/km -- Low Lvl Moisture Advecting North --

Parameters at 01Z SBCAPE 750-1000 J/kg 0-3km Cape 125 J/kg CIN 0 to -50 J/kg LCL 500-600 m LFC 1400-1500 m LI -5 to -6 C 500-700mb LR 7-7.5 C/km 0-6km Shear 60-65 kts 0-3km Shear 40 kts 0-1km Shear 30-35 kts 0-3km Helicity 300-350 m^2/s^2 0-1km Helicity Sfc Wind 10 kt @ 190 925mb Wind 20-25 kt @ 240 850mb Wind 20 kt @ 250 700mb Wind 25 kt @ 260 500mb Wind 35 kt @ 240 300mb Wind 100-105 kt @ 260 Note very strong shear and veering of winds in the low lvls Note abundant 0-3km Cape Note unstable 700-500mb lapse rates Note very low LCLs and LFCs Note low CIN Note that storm was heading into higher 0-1km and 0-3km helicity environments while heading east into the (LLJ) Other interesting Finds -- Note 300mb jet core maxima directly over tornado events -- Note events occurring near strongest sfc theta-e advection over entire region (4C/s). -- Note DCAPE minimum within higher values where tornadoes occurred (600

Note wedge of high pressure developing along the eastern Appalachian Mtns Note western edge of LLJ Looks like mid lvl dry air filtered over the storms (500mb shortwave provided kick) at the time the storms entered the enhanced area of low lvl winds (western edge of LLJ). Storms became more isolated at this point as they encountered a tremendous amount of shear and outran the highest SBCAPE environment (downwind axis of cape). Speed convergence zone (at sfc) happened to run perpendicular to storm motion (may be due to the LLJ mixing to the sfc as the sfc temps increased to the low 60s the further south you went). Storms ended up paralleling this feature with unimpeded flow from the south (tail-end charlie type storm). Subtle speed convergence noted in the obs and SPC meso data (enough to do the trick though). Convergence seen through 500 mb. Strong diffluence aloft being under the core of a 300mb jet. 500-700mb Lapse rates near 7 C at time of tornadoes! Due to dry air and shortwave pushing through. Note mid 60 temps and dewpts Note slight backing of the wind Note sfc convergence

Tornadoes occur on downwind side of SBCAPE axis. SBCAPE / SFC WIND @ 01Z SBCAPE / 925 MB WIND @ 01Z Tornadoes occur on downwind side of SBCAPE axis. Tornadoes occur along western edge of LLJ. Tornado event times 0122Z and 0215Z Note events occurred after sunset Note SBCAPE advected over region, was not present well before the storm got to the location. Note tail-end charlie storm with unimpeded flow from the south.

Conclusion 500mb shortwave initial kicker of thunderstorm development. Strong mid level lapse rates occur with dry/cold air from the west and low level moisture from the south. Favorable parameters for tornadic supercells Tornadoes developed on downwind side of SBCAPE axis while entering western edge of LLJ. Storms ran parallel to sfc speed convergence zone with unimpeded flow from the south into tail-end charlie storm.

Jan 03, 2006: 0103Z 0.5 degree Dual mini supercells with well-definied inflow notches/hook echoes are moving into northern Johnson County. Weak rotational couplet is seen in the eastern-most storm, embedded within the inflow notch.

Jan 03, 2006: 0108Z 0.5 degree As cells collide, hook echoes/inflow notches diminish in distinction. Best circulation exists in a subtle inflow indicated by arrow.

Jan 03, 2006: 0114Z 0.5 degree Interesting appendage appears in the northern/eastern cell. Selected rotational couplet associated with this reflectivity feature.

Jan 03, 2006: 0120Z 0.5 degree This is the time of the tornado report. The tvs signature is nearly co-located with the location of tornado damage. Note the reflectivity notch and correlated rotational couplet.

Johnson County Tornado January 2, 2006 Rotational Velocity (In+Out/2) TIME (EST)

Johnson County Tornado January 2, 2006 NROT Value TIME (EST)

Jan 03, 2006: 0201Z 0.5 degree This line originated with the Johnson county storms. Signatures are much weaker at this point. Sampled a decent couplet within a subtle weak echo region.

Jan 03, 2006: 0206Z 0.5 degree Rotation remains weak and broad, yet an interesting reflectivity feature sparks some interest.

Jan 03, 2006: 0211Z 0.5 degree Sampled the subtle weak echo region indicated by the arrow. This appears to be the transitioning notch seen in the previous volume scan.

Jan 03, 2006: 0216Z 0.5 degree Reflectivity and SRM at the time of the tornado report. Note that the rotation is still quite broad and NROT is unimpressive. In fact, NROT values within this storm are on a downward trend from this point on. The only feature of interest is the peculiar reflectivity circulation seen in the center of the storm. Attempted to sample weak rotation associated with this feature.

Jenkins County Tornado January 2, 2006 Rotational Velocity (In+Out/2) TIME (EST)

Jenkins County Tornado January 2, 2006 NROT VALUE TIME (EST)