Wednesday July 21, 2010 Severe T-Storm Event

Storm Prediction Center Storm Reports Graphic showing the scope of the Wednesday July 21, 2010 Northeast outbreak of severe thunderstorms and isolated tornadoes

Storm Prediction Center Storm Reports Graphic for the Wednedsay July 21, 2010 Event 

Widespread severe weather struck the Northeast with many reports of significant wind damage, large hail, and a few tornadoes in New York, New Jersey, and across all of the New England states. (One of the tornadoes occurred in central Litchfield County, CT, ranked an EF1, with estimated 100 mph winds.) This was a regional major event that spanned from the mid morning hours where it initiated over western and central New York, through the late night hours when the event ended over New England. Multiple rounds of thunderstorms, some supercells, occurred in response to a moderately unstable air mass, unseasonably strong wind shear, significant moisture and heating, dewpoints ranging from 65° to 70° and temperatures ranging through the mid to upper 80s on average, all interacting with an approaching a moderately strong upper air trough and jet streak along with a northward moving weak surface warm front and approaching surface cold front. The players all set the stage for the long duration severe weather outbreak.

Interestingly, however, much of the local region was spared the strongest of the storms, with a significant doughnut hole over the area through much of the afternoon and early evening. (The SPC storm report graphic above illustrates the relative minimum of severe reports in the local area as compared to the rest of the Northeast.) Severe weather was most widespread over northeast New York, northern Vermont, and northern New Hampshire and southern Maine during the afternoon along the warm front. A second area of widespread significant severe weather occurred over central and southern New York, then into MA and CT during the afternoon where a weak lead short wave low pressure trough aloft acted on an atmosphere that was more unstable than it was over eastern New York. A few isolated severe t-storms did occur locally from the early to late afternoon as a result of that short wave trough's passage, mainly in the Catskills, mid Hudson valley, and Berkshire and Litchfield counties. But most of the rest of the region was out of it.

The main thunderstorm and scattered severe weather event locally developed during the evening over eastern New York and western New England as the main upper air trough, jet streak, and surface cold front moved into the region. These features acted on an atmosphere that was largely left unstable as few thunderstorms had occurred previously during the day. The result, despite a loss of daytime heating, was the development of several short lines and clusters of locally severe t-storms forming and moving through the region between 6pm and 10:30pm. Frequent lightning, strong wind gusts and some hail occurred as these storms moved through the local area, affecting areas from the Adirondacks through the Capital Region to Berkshire County, MA most. Areas south of Albany, through the Catskills and mid Hudson valley, hit by earlier rain and t-storms, were largely not affected by the evening round.

Severe Weather Reports Collected by the Albany and Binghamton NWS offices. These reports are used to verify the warnings that were issued for the event and do not cover all of the damage that may have occurred in the region due to the T-Storms. (43 Severe weather reports were received for the local 21 counties in the WRGB weather coverage area for this event. This was a moderate event locally.)

Town County Severe Report Time of Severe
Deposit Delaware Trees and power lines blown down 1:27pm
Pittstown Rensselaer Wind damage: Trees blown down on Cooks Buro Rd, power outages reported (Supercell T-Storm) 1:54pm
Hancock Delaware Trees blown down throughout the town 2:00pm
Franklin Delaware 1.25" diameter hail (Half Dollar Sized) 2:10pm
6 Miles East of Franklin Delaware 1.25" diameter hail 2:11pm
Williamstown/N. Adams Berkshire 1/2" Hail, measured 43 mph wind gust (sub-severe)
2:25-2:30 pm
6 miles SW of Delhi Delaware Wind damage, trees blown down 2:35pm
North Adams, MA Berkshire Wind damage, large tree down on a house (Supercell T-Storm) 3:05pm
Millerton Dutchess Wind damage, trees and wires blown down 3:06pm
Amenia Dutchess Wind damage, trees down on multiple vehicles 3:06pm
Sharon, CT Litchfield 90 mph straight line winds (NWS damage survey conclusion) numerous trees blown down in a 200 yard path width (Supercell T-Storm) 3:05-3:10pm
Cornwall, CT Litchfield Large trees down on Route 7 3:25pm
Litchfield, CT Litchfield 1/2" to 1.75" diameter hail throughout Litchfield (Supercell T-Storm) 3:44 pm
Litchfield, CT Litchfield EF1 Tornado (100 mph winds) path width 100 yards, path length 1/4 Mile (NWS damage survey conclusion) 3:35pm
Litchfield, CT Litchfield 1.75" diameter hail 3:50pm
Cornwall, CT Litchfield Wind damage, many trees blown down 3:50pm
Thomaston, CT Litchfield EF1 Tornado, 100 mph winds, path width 50 yards, path length 200 yards 3:58pm
Terryville, CT Litchfield EF1 Tornado, 100 mph winds, path width 50 yards, path length 200 yards 4:05pm
4 miles ENE Poughkeepsie Dutchess Wind damage, branches, trees, and wires blown down on Sleight-Plass Road 4:27pm
Lagrangeville Dutchess Trees and wires blown down 4:33pm
Dover Plains Dutchess Many trees and wires blown down 4:40pm
Hancock Delaware Several trees and power lines blown down, 0.88" diameter hail 5:30pm
5 miles ESE Mckeever Herkimer Trees and wires blown down 6:13pm
Speculator Hamilton Wind damage, trees blown down 6:45pm
Pottersville Warren Trees blown down on Route 9 6:54pm
Ohio Herkimer Trees and wires blown down 8:00pm
Newport and Ohio Herkimer 1.25" diameter hail and wind damage, power pole broken, trees blown down 8:10pm
Schuyler Corners Herkimer Trees blown down 8:25pm
Oppenheim Fulton Wind damage, trees blown down 8:40pm
4 miles SE of Galway Saratoga Trees blown down 9:09pm
Ballston Spa Saratoga Estimated 55 mph to 60 mph wind gusts, large limbs blown down 9:16pm
5 miles SW of Saratoga Saratoga Trees blown down on East Grove Street 9:17pm
Ballston Lake Saratoga Trees blown down on Ashdown Road 9:18pm
SE of Burnt Hills Saratoga Trees blown down on Lake Hill Road 9:18 pm
Pittsfield, MA Berkshire 0.88" diameter hail (not severe) 9:32pm
Bennington, VT Bennington 1.00" diameter hail (severe) 9:55pm