87th AMS Annual Meeting

Wednesday, 17 January 2007
Lake-effect Thunderstorms
Exhibit Hall C (Henry B. Gonzalez Convention Center)
Scott M. Steiger, SUNY, Oswego, NY; and R. Orville and J. Keeler
Lightning during the cool season (November-February) is a relatively rare occurrence across the northern United States. However, extreme instability results when cold air is advected over large bodies of relatively warm water, as is the case in the late fall and early winter in the Great Lakes region. The high water and heat flux rates also aid in creating significant quantities of supercooled water and graupel in lake-effect clouds, necessary ingredients for strong cloud electrification.

An intense band of lake-effect precipitation developed over Oswego County in upstate New York on 2 December 2005. The National Lightning Detection Network recorded 5 cloud-to-ground (CG) flashes during this event. However, National Weather Service snow spotters located on the SUNY Oswego campus noted total (intracloud + CG) flash rates of 1 flash (2 min)-1 for approximately 30 minutes (total flashes during this period ~ 15). Heavy graupel was observed several times during this period, consistent with charge separation hypotheses. There is also evidence that a synoptic-scale short-wave interacted with the band during its electrically active state. This likely deepened the boundary layer and the cumulus growth.

We plan on presenting data from other cases, but the 2 December 2005 event was the most electrically active lake-effect event in recent memory for Oswego. We will also show how often these events occur throughout the lake-effect season in the eastern Great Lakes region. Lastly, we propose the implementation of a total lightning network (e.g., LMA, LDAR II) in this region to better understand the charge structure in lake-effect clouds and how lightning initiates within them. This is an important problem as the public is at risk because they don't expect lightning during winter precipitation. Lake-effect clouds are not as turbulent as summertime convection, hence lending them more susceptible to study by research aircraft and balloon soundings.

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