Multiscale Analysis of the 1 June 2011 Northeast U.S. Severe Weather Outbreak and Associated Springfield, Massachusetts Tornado

On 1 June 2011, the 12th killer tornado in New England since 1950 tracked 63 km (39 mi) from Westfield to Charlton, MA resulting in 3 fatalities, 200 injuries, and EF3 damage.  At least fourteen supercells produced six confirmed tornadoes and six hail reports ≥7 cm (≥2.75 in) in diameter across eastern New York and New England.  This paper takes a multiscale look at meteorological factors contributing to this event. The synoptic pattern evolution closely resembles the composite mean shown by Banacos and Ekster (2010) for significant severe weather events in the northeast United States associated with an elevated mixed layer (EML).  The presence of an EML and rich boundary-layer moisture (surface dewpoints 20-22oC) supported surface-based CAPE >4000 J kg-1 by early afternoon on 1 June.  A strengthening prefrontal trough within the moist and unstable boundary layer, together with increasing low and deep-layer shear created an environment favorable for tornadic supercells.  In particular, storms moved into an environment with increasing values of 0-1-km AGL bulk shear, increasing storm relative helicity, and lower lifted condensation level heights.  Values of these parameters were largely consistent with significant-tornado occurrence in proximity studies.  Tornadic signatures in WSR-88D and experimental CASA 3-cm dual-polarization radar data are described, in addition to a remarkable three-body scatter spike associated with lofted debris near peak apparent intensity of the EF3 tornado.