Wednesday August 21, 2019 - Severe Weather Outbreak
Brief Spin Up Tornadoes In Johnstown, Saratoga Springs and Windham, VT
Severe Troy City Flash Flood

An active day of convection culminated during the afternoon and early evening with numerous severe thunderstorms which produced wind damage, hail, flooding rainfall (severe flooding in the city of Troy,) and three brief spin up tornadoes, one in Johnstown, NY at 2:24pm, the second in Saratoga Springs at 3:35pm, and the third in Windham, VT at 5:05pm.

These brief tornadoes evolved out of transient meso-vortices within a short line segment (small QLCS - quasi-linear convective system) as it tracked along and just south of a warm front that was draped across Fulton, northern Saratoga, Washington and Bennington counties during the afternoon. This warm front acted to back the surface wind flow enough to enhance the low level shear in the warm and humid air mass that was in place coupled with a low lifted condensation level, to allow for brief tornado circulations to reach the ground and produce damage. Unlike classic supercell thunderstorm tornadoes, which can become violent and last for long periods of time in some cases, the tornadoes in this case were brief and on the weaker end of the scale.

The Johnstown, NY Tornado - Fulton County

Albany NWS Tornado Report - Johnstown

The Albany National Weather Service team in their comments noted that a very small area of damage was discovered that extended a short distance from Johnson Avenue to Pleasant Avenue in the city of Johnstown that was consistent with damage a tornado would produce. Damage was confined to uprooted trees with peak winds estimated to have ranged from 85-90 mph. Essentially, this tornado produced the same type of damage that the many microbursts (straight line wind) from other severe thunderstorms caused in the region throughout the season.

The Saratoga Springs, NY Tornado - Saratoga County

Albany NWS Tornado Report - Saratoga Springs

The Albany National Weather Service team found several hardwood trees uprooted and snapped on Gilbert Road with one downed tree specifically showing convergent flow into the storm due to it having fallen in a south to north configuration which would be consistent with an area of rotation in a storm that was moving from SW to NE as this storm was. Further, extensive damage at a residence near the intersection of Route 29 and Schallen Road occurred where dozens of hardwood trees snapped or uprooted and were felled in all different directions with several trees at the back of the residence blown down in the opposite direction of the storm's movement. This tree damage configuration strongly indicated rotation at that location, according to the NWS team. Additionally, a tin roof on a large barn was peeled upward on the northeast-facing side of the barn, indicating that the wind swirled from a northeasterly direction in that area while the main area of the storm was moving from southwest to northeast. No damage, however, occurred to a well constructed house on the property which is what lead to the conclusion that the maximum wind speed intensity was close to 105 mph. Anything wind stronger and damage would have been likely to the well constructed house.

Image generated by the Albany National Weather Service office showing the short path of the tornado which was not too far east of the Saratoga track - Wednesday August 21, 2019.

Albany NWS Tornado Saratoga Springs Tornado Path Image 

WINDHAM, VT TORNADO

TIME: 5:05PM

MAXIMUM EF SCALE RATING: EF-1

ESTIMATED MAXIMUM WIND SPEED: 105-110 MPH

ESTIMATED PATH WIDTH: 350 YARDS

ESTIMATED PATH LENGTH: 3/4 OF A MILE

The Albany National weather service damage assessment team found a swath of almost continuous damage in a 3/4 mile by 350 yard area. "There was shingle and siding damage to several homes with many dozens of trees violently snapped or uprooted. Outdoor furniture, shingles, and siding were observed to have been tossed hundreds of yards."

The following three radar images illustrate the development of the thunderstorms along the warm front in the Mohawk valley with a track into Saratoga County between roughly 1:30 and 3:30pm

Radar and Warnings graphic at 1:23pm - Wednesday August 21, 2019 - Linear zone of developing thunderstorms extending from Hamilton County south into NW Fulton and southern Herkimer counties. These thunderstorms were not severe at this time.

Radar and Warnings, 1:23pm Wednesday August 21, 2019

Radar and Warnings graphic at 2:26pm - Wednesday August 21, 2019 - The radar showed a linear zone of thunderstorms at this time, but with small scale rotating vortices, especially on the southern end. This was about the time the brief spin up tornado occurred in Johnstown, Fulton County.

Radar and Warnings, 2:26pm Wednesday August 21, 2019 

Radar and Warnings graphic at 3:34pm - Wednesday August 21, 2019
- The radar showed an intense linear complex of thunderstorms entirely in Saratoga County. There were several transient meso-vortices within the line at this time with the strongest over Saratoga Springs producing a brief spin-up tornado at about the time of this image with the touchdown just east of the track. The national weather service had an enhanced severe thunderstorm warning in effect for the storm at this time indicating large hail and winds up to 80 mph possible.

Radar and Warnings, 3:34pm Wednesday August 21, 2019 

Ultimately the line segment of violent storms in Saratoga County expanded south into the Capital Region and linked with the line of downpours and thunderstorms moving through the Catskills to form a long narrow squall line which moved through the Capital Region, mid Hudson valley and Berkshires through the early evening. Torrential rain caused some of the most serious flooding on record in Troy (around three inches of rain observed in an hour or so,) with pockets of wind damage in the mid Hudson valley and Berkshires. The sequence of Instant Doppler 6 radar images below illustrates the development of the broader severe QLCS and its progress through the region.

Instant Doppler 6 Image at 5:01pm - Wednesday August 21, 2019 - A line of intense thunderstorms extended from Bennington County, VT through the Capital Region and Catskills. The most intense storms were in the Albany and Troy area at this time producing torrential rainfall, hail up to quarter size, and flooding along with frequent vivid lightning and strong wind gusts.

Instant Doppler 6 Image at 5:01pm Wednesday August 21, 2019 

Instant Doppler 6 Image at 5:32pm - Wednesday August 21, 2019 - Storms were intensifying across eastern Greene and southern Rensselaer counties at this time as well as in Bennington County, VT.

 Instant Doppler 6 Image at 5:32pm Wednesday August 21, 2019

Instant Doppler 6 Image at 6:02pm - Wednesday August 21, 2019 - Intense line of thunderstorms in southeast Rensselaer, Columbia and NW Berkshire County at this time

Instant Doppler 6 Image at 6:02pm Wednesday August 21, 2019

Instant Doppler 6 Image at 6:38pm - Wednesday August 21, 2019 - Thunderstorms in the process of moving out of Berkshire and Columbia counties at this just about marking the end to the severe weather event.

Instant Doppler 6 Image at 6:38pm Wednesday August 21, 2019 

THE DAY'S SET-UP:
A number of factors came together to set the stage for severe weather with the main players being an area of low pressure, which tracked west of the region which forced its surface warm front (a key player) to move into the Mohawk valley-Saratoga region an southern Vermont during the afternoon. A series of upper level impulses which moved through causing some cooling aloft which helped to enhance instability and updraft strength. Adding fuel was a hot and humid air mass at the surface characterized by temperatures climbing into the mid 80s and dewpoints well into the 60s to around 70° which helped to support CAPE (convective available potential energy) values up to 2000j/kg, sufficient for strong thunderstorms. Wind shear in the atmosphere was moderate with up to 35 knots of speed shear aloft and significant turning of the low level wind, especially in the vicinity of the warm frontal zone. That localized turning of the wind was the key ingredient to support the brief meso-vortices to form allowing for the three brief spin-up tornadoes to occur along and south of the warm frontal boundary.

Conditions, however, were somewhat muddy early in the day as a round of active convection went through early in the morning consisting of torrential downpours and one severe thunderstorm around 5:30am that blew down a few trees and wires around Galway and Charlton. The Instant Doppler 6 image below shows fairly widespread downpour and thunderstorm coverage at 6:15am. These storms formed along the advancing warm front, which once it pushed north had the net effect of bringing in an even warmer and more unstable air mass into the region mitigating the stabilizing effect this convection could have had on the atmosphere. An additional narrow line of downpours and thunderstorms moved across the entire region from the late morning into the early afternoon, but that too, did little to cause stabilization as the air rapidly destabilized due to an advancing upper level disturbance which caused upper level cooling, offsetting any surface cooling that may have occurred due to the midday convection. In fact a period of sunshine developed after the midday line causing temperatures to rise quickly setting the stage for the main severe weather and flooding event from the mid afternoon through the early evening.

Instant Doppler 6 Image at 6:15am - Wednesday August 21, 2019

Instant Doppler 6 Image at 6:15am Wednesday August 21, 2019

RAINFALL
It is worth noting that the combined water from all three convective events produced pockets of rainfall in excess of three inches for the day in places like Copake where 3.21" fell, Red Hook, where 3.27" fell, Schaghticoke, where 3.52" fell, Troy where 3.03" fell, Stratford, where 3.00" fell, Ballston Spa, where 3.09" fell, and Buskirk where 2.85" fell.

NWS Storm Reports for Wednesday August 21, 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
Charlton Saratoga Wind Damage: Wires and large limbs down on Stage Road 5:08am
Charlton Saratoga Wind Damage: Wires and limbs blown down on lake Hill Road near Charlton Girls School 5:09am
Red Hook Dutchess Torrential Rain: 1.41" in 25 minutes from 4:10 to 4:35am 5:41am
Caroga Lake Fulton Wind Damage: Route 111 closed due to a downed tree 1:44pm
Cranberry Creek Fulton Wind Damage: Tree blown down on route 30 between Mayfield and Northville 2:10pm
Johnstown Fulton Tornado: EF-1 Tornado confirmed with small area of tree damage, peak winds estimated to be 85-90 mph 2:24pm
Johnstown Fulton Straight Line Wind Damage: Trees blown down onto a barn 2:26pm
Ballston Spa Saratoga Wind Damage: Wires blown down 3:25pm
Ballston Spa Saratoga Wind Damage: Trees and wires blown down on West High Street 3:25pm
Ballston Spa Saratoga Wind Damage: Trees and wires blown down on Mourningkill Drive 3:25pm
Wilton Saratoga Wind Damage: Several reports of tree limbs blown down 3:25pm
Greenfield Center Saratoga Wind Damage: Limbs down on wires 3:25pm
Saratoga Springs Saratoga Wind Damage: Large tree blown down, damaging three parked cars on Union Avenue 3:30pm
Saratoga Springs Saratoga Tornado: EF-1 Tornado confirmed east of the track, peak winds estimated to be 105 mph 3:35pm
Northumberland Saratoga Wind Damage: Trees and wires down 3:45pm
Round Lake Saratoga Large Hail: Measured 1.00" diameter hail 3:49pm
Stone Ridge Ulster Wind Damage: Tree limbs down 3:49pm
Rosendale Village Ulster Wind Damage: Tree blown down on wires at Route 32 and Creek Locks Road 4:07pm
North Easton Washington Wind Damage: Tree blown down 4:10pm
Round Lake Saratoga Flash Flood: Left lane of the Northway between Exit 11 and Exit 12 closed due to flooding 4:20pm
Kerhonkson Ulster Wind Damage: Tree blown down 4:20pm
Charlton Saratoga Heavy Rain: Daily Total: 2.20" 4:44pm
Fish House Fulton Heavy Rain: Daily Total: 2.50" 4:45pm
Latham Albany Large Hail: Measured 1.00" Diameter hail 4:45pm
Cohoes Albany Large Hail: Measured 1.00" Diameter hail 4:49pm
Cohoes Albany Wind Damage: Trees and wires blown down 4:55pm
Standfordville Dutchess Wind Damage: A few trees blown down 4:55pm
Cohoes Albany Flash Flood: Urban flooding in the city 5:00pm
Troy Rensselaer SEVERE FLASH FLOOD: Widespread major flooding in Troy, with deep water rushing down Sixth Street, Federal Street, and Hoosick Street. A few feet of standing water in many downtown locations. Roadways closed due to damage and debris on Federal Street, Sage Avenue and Peoples Avenue 5:15pm
Speigletown Rensselaer Torrential Rain: Daily Total: 2.30" 5:17pm
Wynantskill Rensselaer Wind Damage: Trees and wires blown down on Route 66 between Route 355 and Snyders Corners Road 5:18pm
Malta Saratoga Torrential Rain: Daily Total: 2.38" 5:20pm
Watervliet Albany Flash Flood: Portions of Route 7 near the intersection with Route 787 closed due to flooding 5:30pm
Wynantskill Rensselaer Flash Flood: Road closed at Chalet CT and Zermat Drive due to Flash Flooding 5:30pm
Beacon Dutchess Measured wind gust of 50 mph 5:40pm
Stuyvesant Columbia Wind Damage: Tree blown down on Route 9J near Gibbons Road 5:40pm
Kinderhook Columbia Wind Damage: Wires down 5:45pm
Loudonville Albany Flash Flood: All lanes on Central Avenue closed near Vatrano Road due to flooding 5:45pm
East Greenbush Rensselaer Flash Flood: Route 9 near Elliot Avenue had a lane blocked due to flooding 5:45pm
Chatham Columbia Wind Damage: Tree blown down 5:50pm
Brunswick Rensselaer Flash Flood: Route 278 closed due to flooding 6:00pm
Lenox, MA Berkshire Wind Damage: Tree blown down 6:20pm
Lee, MA Berkshire Wind Damage: Wires blown down 6:25pm
Galway Saratoga Torrential Rain: Daily Total: 2.31" 6:29pm
Becket, MA Berkshire Wind Damage: Tree blown down 6:40pm
Buskirk Washington Torrential Rain: Daily Total: 2.84" 7:00pm
Sycaway Rensselaer Flash Flood: Some street flooding on South Lake Drive 7:25pm
Manchester, VT Bennington Torrential Rain: Daily Total: 2.19" 9:57pm

 

Storm Reports For Wednesday August 21, 2019

Storm Prediction Center Storm Reports For August 21, 2019