National Weather Service United States Department of Commerce

Numerous funnel cloud reports were received from portions of Northwest Ohio Thursday afternoon (Figures 1,2, and 3). The funnel clouds were associated with rain showers similar in the circled area in Figure 4.  It is interesting that the funnel clouds were associated with shallow convection as indicated by the lack of any lightning and shallow cloud tops of less than 16,000 feet. Even though atmospheric conditions were not favorable for the development of tornadoes (strong deep shear, high instability, and increased low-level shear), the right conditions were in place for the development of weak funnels.  Increased low-level cyclonic vorticity (or spin) was located right along a nearly stationary surface boundary as indicated in the 1743 UTC surface weather plot (Figure 5).  This increased vorticity was in the presence of rather steep low-level lapse rates of 7 C/km and increased surface based instability (indicated by the convective available potential energy ‘CAPE’ analysis) as seen in Figure 6. Although CAPE was rather low (approximately 500 J/kg), the weak wind field in this case may have increased the chances for the development of weak funnels. The lack of any turbulent disruption to the flow typical with stronger winds, supported a nearly un-obstructed environment to the stretching of low level vorticity into an updraft (or the shower). Stronger winds would have likely led to the disruption of the funnel’s formation given the very marginal conditions present for their development.

This type of vortex development, which is different from the typical strong shear high CAPE events, would have been classified as a non-mesocyclone tornado had the funnel reached the ground. Non-mesocyclone tornadoes typically occur in this area in the presence of moderate CAPE high low level vorticity (the land spout case typical with strong heating along a surface boundary in the presence of a strong updraft). In the land spout case, strong surface heating can lead to stretching of the low level vorticity (spin) present into a strong updraft, which further enhances the vortex. This can lead to the development of a tornado under certain conditions.

Thursday’s case was unique in that the instability and low-level shear were very weak. The only factors that were present were decently strong low level lapse rates and slightly increased surface vorticity along the surface trough. It is hypothesized that the rather steep lapse rates allowed for the enhancement of vorticity through stretching in the vertical. This enhanced vorticity was then ingested into the rain shower’s updraft where further stretching occurred, leading to the development of several weak short-lived funnels. The rather weak wind field present Thursday likely allowed this process to occur nearly uninterrupted as turbulence was minimal with the light to calm low level winds present.


Figure 1. Picture of a funnel cloud near Delphos. Photo taken by Zac Elwer.

Figure 2. Picture of a funnel cloud near the Allen County Airport. Photo taken by Deana Kramer.
 Figure 3. Picture of a funnel cloud just west of Kalida. Photo taken by Patti Hipsher.

Figure 4. Doppler radar imagery taken from the KIWX radar. Circled area inidicates where some of the funnels were witnessed. Note the very weak reflectivity.

Figure 5. Surface plot at 1743 UTC 6 June 2009. The grey circle indicates the approximate position of Kalida where some of the funnel clouds were witnessed. Note the light winds with cyclonic circulation present.

Figure 6. Local model analysis of surface based CAPE (red contours), 0-2 km laps rates (purple contours/image), and surface wind. Note the overlap of the steeper lapse rates and the CAPE axis near Kalida where several funnels were reported.