June 11, 2008 - Chapman, KS EF3 Tornado

Documented by: Scott F. Blair

The nighttime tornadoes on 11 June 2008 presented several challenges to storm observers to clearly identify specific storm features. Beyond the typical issues with observing storms in the dark, these storms were borderline high-precipitation supercells and fast-movers.

The photo above (left) is the only known photo of the tornado as it moved through Chapman, KS around 0319z. The photo (right) identifies several discernable storm characteristics, most notably the large cone tornado in the center of the picture. This photo is a 10mm wide angle and a time exposure for roughly a 10 second period and has been contrast enhanced.

While it might seem quite bright outside, this was far from the case. In reality, we had no view of the tornado until several large power flashes illuminated the condensed tornado. Additionally, virtually all the lightning was within the vault region and not in the hook echo region (as typically the case with lightning distribution). This resulted in no lightning backlighting the tornado; such is the case with this photo where all illumination is front-lit.

Immediately before this photo was taken, direct phone contact was established between the National Weather Service in Topeka, KS and an off-duty NWS employee from WFO Topeka. This served as the first confirmation of an ongoing tornado. In addition, another off-duty NWS employee from WFO Pleasant Hill forwarded further information via Spotter Network to the NWS in Topeka. It is this type of relationship that serves to strengthen the mission of the NWS by providing detailed severe weather information to the public and media outlets, ultimately assisting to save life and property.

The observing spot was just north of I-70 along Milford Lake Rd. The tornado was approximately 4 miles to the southwest and moving towards our location. In fact, the tornado skirted this location only 2 minutes after we left. The yellow dot represents the viewing location and the red line depicts the tornado track. While this type of position relative to the storm was not desired, it was likely the only clear view of the tornado per HP characteristics. Inflow winds were modest with northeasterly speeds estimated around 15 kts; albeit with northeast winds a spotting clue that the environmental winds have been augmented by a low-level circulation that is approaching.

The images above, 0.5deg base reflectivity (left) and storm relative velocity (right), display the supercell immediately after it passed Chapman around 0323z. The enhanced reflectivity is the 'debris ball' signature whereas the velocity depicts strong gate-to-gate shear indicating the tornado vortex (the tornado is too small to be resolved by the WSR-88D). The yellow dot represents the observing location as described in the previous paragraph. Note the relatively 'dry inflow notch' in advance of the tornado. This was the zone that allowed for the best viewing; generally underneath the vault and between the forward-flank shelf and rapidly wrapping rear-flank shelf and accompanying precipitation.

The tornadic circulation eventually wrapped in rain as it approached I-70 with the tornado dissipating shortly after crossing the interstate. The photo above was taken around 0325z from I-70, just east of the previous viewing location. The area of interest in now fully rain-wrapped with the RFD shelf surging northeastward.

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