The June 1, 2011 Hail Monster Event across Eastern New York and Western New England

During the late morning and afternoon of 1 June 2011, most of upstate New York (NY) and New England was in a warm sector ahead of a strong cold front approaching from southeastern Canada, the eastern Great Lakes and the Ohio Valley. A humid and unstable air mass was over the Northeast. Surface dewpoints were in the 17-21°C range ahead of the boundary and 5-10°C in the wake of it by the late afternoon. A prefrontal surface trough was evident in the surface analysis in the early afternoon over eastern NY, which helped aid the strong to severe convection that developed. Convection rapidly developed ahead of the cold front and its associated prefrontal surface trough over eastern NY and western New England between 1500 UTC and 1800 UTC. The severe weather continued into New England through the early evening with large hail, damaging winds and tornadoes. The first of five baseball-size (≥7.0 cm) or larger hail reports occurred at 1700 UTC in Saratoga Springs, NY. Mammoth hail stones of 8 cm in diameter at Shaftsbury, VT, and about 10 cm were measured in Windsor, MA located in the Berkshires. The vast majority of the severe weather in the Albany forecast area was from large hail (≥ 2.5 cm) with nearly 3 dozen reports. There were about a dozen significant (≥ 5.0 cm) hail reports that occurred across eastern NY and New England from the entire event.

A closed 500 hPa upper level low was approaching the Northeast from central Ontario. Mid and upper-level heights fell over NY and New England ahead of a short-wave trough quickly encroaching from the Great Lakes Region. A strong mid-level jet streak of 50-75 knots moved into northern NY and New England, which helped enhance the convection with some upper level divergence over east-central NY and western New England. The thermodynamic environment was very volatile with an abundance of instability in place. A special 1600 UTC sounding at Albany revealed a surface-based convective available energy (SBCAPE) value of 3452 J kg-1, Downdraft CAPE value of 1000 J kg-1, wet-bulb zero height of 10.5 kft AGL, and mid-level lapse rates of 7.0°C km-1. The 1600 UTC Local Area Prediction System (LAPS) analysis had SBCAPEs of 2000-5000 J kg-1 over eastern NY and western New England. The 1200 UTC KALB sounding had a well-defined elevated mixed layer approximately between 700 hPa to 500 hPa, which back trajectories showed it originated from northern Mexico. The 0-6 km deep layer bulk shear increased in excess of 40 knots in the 1600 UTC KALB sounding with several supercells firing ahead of the cold front. The supercells became hail monsters with tall updrafts and massive elevated reflectivity cores associated with them.

A multi-scale approach will be used in analyzing the major severe event from the synoptic-scale to the storm-scale, in order to understand the convective environment that produced the anomalously large hail stones in the Northeast. The poster will show observational data used in the analyses including surface and upper air observations, satellite imagery, and KENX WSR-88D 8-bit radar data. The storm-scale analysis will utilize a variety of radar tools (Four-Dimensional Stormcell Investigator) and techniques.