Labor Day 2013 Severe Weather

Storm Summary

Severe weather made its way across western and central New York during the 2013 Labor Day holiday. Thunderstorms developed rapidly during the late morning hours of Monday September 2nd in an unstable air mass ahead of a cold front approaching from southern Ontario, Canada. Surface temperatures of around 80°F, running above normal for early September, combined with uncomfortably humid dewpoint temperatures of around 70°F provided warm and moist air to fuel the storms. Mid-level temperature lapse rates of 7°C/km and Convective Available Potential Energy values of 2000 to 3000 J/kg allowed storms to build to 40 kft with the strongest storms building over 50 kft. Uni-directional vertical wind shear of around 25 to 30 knots provided an environment for long-tracked storms while intense storm updrafts made for a large hail threat. Evaporational cooling of the decending hail cores within the storms increased downdraft speeds creating a damaging wind threat on the ground. Large hail and damaging winds were observed across southern Chautauqua county in the early afternoon. Storms then impacted portions of central NY east and southeast of Lake Ontario into the early evening with numerous reports of large hail and strong thunderstorm winds taking down trees and power lines.

WPC surface analysis from 2 pm EDT. Low pressure is centered north of Georgian Bay with a cold front across far Western New York. Surface observations show a warm moist environment east of the front which helped fuel the storms.

Observed upper-air sounding for Buffalo, NY from 8am EDT. In this thermodynamic diagram called a SKEW-T Log-P, notice the area bounded to the right of the red vertical temperature trace which highlights the unstable environment aloft and the nearly uni-directional winds with height...key ingredients for severe thunderstorms with intense updrafts and strong winds.

SPC convective outlook from 1230 pm EDT. Western and central New York was included in a slight risk for severe weather including large hail and damaging winds.

Radar Loop

Loop of one hour interval KBUF radar images from 1100 am to 700 pm EDT showing the severe thunderstorms that developed ahead of the cold front as it swept across New York. Also overlaid are cloud-to-ground lightning strikes and warning polygons. Notice the red colors which show the most intense storm cores.

Hail Swaths

This image shows swaths of Maximum Expected Hail Size (MESH) produced by some of the severe thunderstorms that moved across the region. The swaths are created by algorithms developed at the National Severe Storms Laboratory (NSSL) and Cooperative Institute for Mesoscale Meteorlogical Studies (CIMMS) using radar data from the NEXRAD network. This results in 1 km x 1 km resolution of sampled estimated hail size between 800 am and 600 pm on Labor Day. Referring to the color scale at the top, the green colors indicate hail of one to one and three-quarter inch in diameter which was observed over southern Chautauqua, northern Cayuga, western Oswego and Onondaga counties. Download the KMZ file of these swaths here .

Lakewood, NY Hail Core

This animated image shows a three dimensional volume of radar reflectivity from the severe thunderstorms which produced large hail and damaging winds around Lakewood, NY south of Chautauqua Lake as sampled by the KBUF radar. The loop begins at 1231 pm and ends at 1258 pm. The view is looking north near the state line south of Jamestown, NY. The light blue color shows weak reflectivity echoes highlighting the overall storm structure while the pink colored area is measured as reflectivity greater than 60 dBz and can be interpreted as the core of heaviest precipitation which included large hail. Also note how the hail core extended up above the freezing level (yellow line at about 13 kft) and -20°C level (red line at around 23 kft) before crashing down over the Lakewood area. As the hail core decended it also brought down strong winds which took down trees and power lines in the area.

Storm Reports


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Storm Photos

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