Tracking Outflows from Severe Thunderstorms Using NSF EarthScope USArray Pressure Sensors

The NSF Earthscope USArray Transportable seismic network, a dense array of over 400 seismic stations deployed in a grid with 75km station spacing, provides real-time monitoring of seismicity as well as surface barometric pressure from instrumentation housed within enclosed vaults. On June 22nd 2010 several of the stations in North and South Dakota, Nebraska and Kansas observed sudden and dramatic increases in surface pressure (~2.0 to 3.5 mb in less than 5 minutes, with a gradual increase following). Doppler radar, local observations and infrared satellite images confirmed the passage of severe thunderstorms coinciding with these pressure jumps. On further investigation, it was determined that the USArray stations observing the pressure jumps were actually observing outflow gust fronts from the thunderstorms. Analysis of additional severe thunderstorms events on separate occasions also confirms the passage of thunderstorm outflows coinciding directly with pressure jumps among the various USArray stations. The data presented within this paper will reveal the temporal nature and speed of these outflows using the high-resolution continuous 1sps pressure data from several USArray stations as a backbone. Additional data will be provided from Doppler radar and satellite images as well as local observations. The overall utility and viability of the USArray pressure data will then be discussed as a supplemental aid for now-casting severe weather events.