Thursday August 8, 2019
Severe T'Storm Outbreak (QLCS - Squall Line)

Shelf cloud over Halfmoon, Saratoga County, Thursday August 8, 2019 - Photo Credit: Sean OrganPhoto Credit: Storm Chaser Sean Organ: Leading edge shelf cloud, Halfmoon, Saratoga County
Thursday August 8, 2019

This was the third consecutive and culminating day of severe weather across eastern New York and western New England punctuated by the passage of a robust squall line (QLCS-quasi-linear-convective-complex) which impacted all areas from the Mohawk valley to Saratoga Springs, Washington, and Bennington counties on south during the late afternoon and early evening that was also preceded by a couple of isolated severe cells over southern Saratoga, Rensselaer, and northern Berkshires counties. The line was highly photogenic with spectacular shelf cloud formations, much like the one shown in the image above, along the leading edge, formed as warm moist air in advance of the storm is lifted over the cool thunderstorm outflow which acts as a mini cold front. Wind gusts routinely ranged from 40-50 mph with some gusts from 55-60 mph (measured gust to 59 mph at Latham at 5:37pm and a measured 63 mph wind gust near Austerlitz at 5:55pm) resulting in numerous pockets of wind damage throughout the region. The image below illustrates the main zones where wind damage was reported.

Damage report and main wind damage paths, Thursday August 8, 2019

The day's set-up, like the previous day, featured a warm and humid air mass which through heating effects warmed into the mid 80s with dewpoints ranging through the mid 60s. Some cooling aloft came from an approaching upper level low pressure trough which aided in increasing the thunderstorm fuel, or instability with CAPE (convective available potential energy) values up to 2000j/kg. Mid level wind fields were a little stronger than on Wednesday but not substantially and turning of the wind from the surface through the boundary layer was modest. The atmosphere locally was set-up to support isolated to widely scattered showers and t'storms, a few of which could become severe producing brief microburst type wind damage and hail. And that did occur, primarily in the Mohawk valley, southern Adirondacks, Lake George-Saratoga-Capital Region to Vermont and the northern Berkshires from the late morning through the mid afternoon with a number of small t'storm cells randomly developing, most not severe. The exception was a more organized and back building cluster of thunderstorms over Saratoga, Washington and Rensselaer counties between 3 and 4pm that briefly became severe producing hail and locally gusty wind with another very small isolated cell between 5 and 5:45pm that tracked from near Sand Lake in Rensselaer County through Cheshire, Adams, and Savoy in Berkshire County, producing hail and strong wind gusts as well as frequent lightning.

The main event, however, was the passage of an organized squall line which moved from west to east across the region, with a forward speed of 45-50 mph, from 3:45pm to 7pm after originating over western New York during the morning. The thunderstorm complex was long lived developing an impressive cold pool which was the feature that allowed its eastward propagation and maintenance of the line's ability to produce strong wind gusts over such a distance and over such a long period of time.

Signals were mixed, however, as to whether or not the line could continue to maintain its intensity as it moved into the local area as it appeared to become cold pool dominated. In other words, the rain cooled air that the storms produced began to outrun the leading edge of the line effectively cutting off the warm moist air in advance that was feeding it. It's a typical process in the lifecycle of a QLCS. However, the air over eastern New York, especially in the Hudson valley, was significantly unstable and primed to support strong thunderstorms should any arrive.

What ultimately happened was a pulse cycle in the line as the cold pool caused weakening and fragmenting it as it got into the Mohawk valley and Schoharie County with the line breaking up and radar echoes weakening. Yet, it was still producing pockets of damaging wind during this period. Then, when the line came into Saratoga County, the Capital Region, and the Hudson valley, the fresh new pocket of warm unstable air allowed fast and significant regeneration with rapid intensification which allowed it to continue to produce pockets of wind damage as it tracked into the Berkshires before ultimately weakening over central Massachusetts around 8pm. The following two Instant Doppler 6 radar images illustrate the line as it was strengthening in the Hudson valley between about 5:45pm and 6:15pm

Instant Doppler 6 base reflectivity image at 5:53pm August 8, 2019 - 50 nautical mile scan - Intense squall line arcing from Saratoga Springs to Rensselaer and Columbia counties

Instant Doppler 6 image around 5:53pm August 8, 2019 

Instant Doppler 6 base reflectivity image at 6:06pm August 8, 2019 - 75 nautical mile scan

Instant Doppler 6 image around 6:06pm August 8, 2019 

Photo Credit: Jason Cross: Leading edge shelf cloud, Saratoga Springs, Saratoga County
Thursday August 8, 2019

Albany Doppler Radar image showing a severe thunderstorm over Saratoga Springs around 6pm August 7, 2019 

NWS Storm Reports for Thursday August 8, 2019. Note, these reports are used to verify the NWS warnings which were issued for this event and therefore do not necessarily represent an accounting for all of the wind damage which may have occurred.

Town County Severe Weather Report Time
Schaghticoke Rensselaer Wind Damage: Trees blown down 3:40pm
Hartwick Otsego Wind Damage: Trees and wires blown down 3:42pm
Oneonta Otsego Wind Damage: Trees and wires blown down 3:57pm
German Flatts Herkimer Wind Damage: Trees blown down 4:00pm
Middlefield Otsego Wind Damage: Trees and wires blown down 4:06pm
Bovina Center Delaware Wind Damage: Numerous trees blown down over roads 4:29pm
Middleburgh Schoharie Wind damage: Trees down in Middleburgh and in multiple locations in the County 4:50pm
Knox Albany Wind Damage: Trees and wires down at the intersection of Knox-Gallupville Rd, and Berne-Altamont Rd 4:52pm
Burtonsville Montgomery Wind Damage: Trees down across Burtonsville Rd 4:55pm
Knox Albany Wind Damage: Trees down in Knox 5:00pm
Westerlo Albany Wind Damage: Multiple reports of trees and wires down along County Route 1, Route 143 and State Route 32 5:02pm
Tribes Hill Montgomery Wind Damage: Tree and wires blown down 5:05pm
Fort Johnson Montgomery Wind Damage: Tree down on oak Street in Fort Johnson 5:08pm
Tribes Hill Montgomery Wind Damage: Tree down on wires along Maple Ave. in Tribes Hill 5:10pm
Cairo Greene Wind Damage: Trees and wires down in Cairo and several other locations in Greene County 5:20pm
Ravena Albany Wind Damage: Tree down at Winnie Avenue and Dempster Street 5:20pm
Coeymans Albany Wind Damage: Tree down on Fares Rd. 5:20pm
Adams, MA Berkshire Wind Damage and marble sized hail, trees down 5:27pm
Athens Greene Wind Damage: Route 383 north and southbound closed due to downed wires 5:33pm
Latham Albany Measured wind gust to 59 mph 5:37pm
Halfmoon Saratoga Wind Damage: Trees down in Halfmoon Township 5:40pm
Halfmoon Saratoga Wind Damage: Route 236 north and southbound closed at Route 9 due to downed poles and wires 5:40pm
Halfmoon Saratoga Wind Damage: Power pole downed near the intersection of Routes 9 and 236 2:42pm
Chatham Columbia Wind Damage: Trees down in Chatham and many other locations in Columbia County 5:45pm
Stottville Columbia Wind Damage: Large tree branches down, estimated wind gusts to 60 mph 5:45pm
Stillwater Saratoga Wind Damage: Trees down 5:45pm
Shawangunk Ulster Wind Damage: Tree down on wires 5:50pm
Clintondale Ulster Wind Damage: Trees and wires blown down 5:55pm
Austerlitz Columbia Measured wind gust to 63 mph 5:55pm
Stockbridge, MA Berkshire Wind Damage: Trees and wires blown down on Interlaken Rd 6:05pm
Stockbridge, MA Berkshire Wind Damage: Several white pines sheared 20-30 feet off the ground and large dead poplar downed 6:05pm
Fairview Dutchess Wind Damage: State Route 115 closed at Cream Street due to downed trees and wires 6:06pm
Lee, MA Berkshire Wind Damage: Tree down blocking one lane of the Mass Pike westbound 6:08pm
Pittsfield, MA Berkshire Wind Damage: Multiple reports of trees and wires blown down in and near the city 6:10pm
Lenox, MA Berkshire Wind Damage: Trees and wires blown down 6:15pm
Lee, MA Berkshire Wind Damage: Trees and wires blown down 6:15pm

Storm Reports: Thursday August 8, 2019

Storm Prediction Center Storm Reports For August 8, 2019