A Storm-Scale Analysis of the 29 May 2013 Tornado Event across East-Central New York

On 29 May 2013, a major severe weather event occurred across much of upstate New York (NY), and portions of western New England. NY and New England had a few dozen severe reports of damaging winds in excess of 50 knots (58 mph) and large hail (greater than 1.9 cm). However, 3 tornadoes were confirmed in the Albany forecast area ranging from EF1 (winds of 86 to 110 mph) to EF2 (winds of 111 to 135 mph). These three tornadoes affected portions of Montgomery, Schenectady, Schoharie and Saratoga Counties late that afternoon. One of these was a long-path tornado that touched down at 6:47 p.m. EDT in the town of Florida, situated on the border of Montgomery and Schenectady Counties. This tornado continued on towards the east-southeast for 13 miles across most of Schenectady County before ending in the city of Schenectady, at 7:04 p.m. EDT. The tornado had a narrow path at the beginning of its track in the town of Florida. The damage was more impressive and widespread in Schenectady County, where the tornado was around a mile wide at times, with EF1 to EF2 damage observed at Mariaville Lake in Schenectady County with a well-built barn destroyed, numerous hardwood and softwood trees sheared and uprooted, and high tension power line towers crushed and destroyed. Two shorter path length tornadoes touched down in Schoharie and Saratoga Counties.

Observational data, as well as short range deterministic Rapid Refresh data suggested a significant severe weather outbreak would occur. Much of the impacted area had just entered a warm sector with a warm front just north of the Mohawk Valley and Greater Capital Region. Upstate NY and New England were situated near the right entrance region of a 250 hPa 85 kt jet streak with an approaching strong upper level short-wave for the afternoon. A moderate instability and high shear pre-convective environment was in place before the severe weather. Surface based convective available potential energy values ranged from 500 to 1500 J kg^-1 with increasing effective bulk shear values of 35 to 50 kts. 0-1 km Storm-Relative Helicity values were in the 150-200 m² s^-2 range. The effective bulk shear values in the 0-6 km layer suggested the possibility of supercells with rotating updrafts capable of producing large hail and tornadoes.

This presentation will focus on a detailed radar analysis of the event, utilizing the new dual polarization data (differential reflectivity, correlation coefficient, and specific differential phase). The impressive tornadic debris signature will be shown with the correlation coefficient data showing debris detected up to 6200 ft AGL. Traditional base and derived WSR-88D radar products will also be shown in conjunction with the Dual-Pol data. The storm-scale analysis will focus on helpful forecast techniques, including applying results from a local rotational velocity (V)-shear study, to determine what caused the tornadoes and how the tornado warning process can be improved.