Sunday September 4, 2011
Severe T'Storm-Tornado Event

An EF1 Tornado, maximum winds of 110 mph, touched down at Florida NY in Montgomery County and quickly tracked to the east - northeast through Cranseville, then to the western portions of Glenville in Schenectady County between 5:20pm and 5:35pm on Sunday September 4, 2011. Significant damage to trees and power lines occurred along the entire 7 mile path. Cranseville, just east of Amsterdam, took the brunt of the storm with windows blown out of homes and multiple buildings with partial roof damage. The parent supercell t'storm continued to track across southern Saratoga, northern Rensselaer, and southern Bennington counties through 8:00m producing frequent violent cloud to ground lightning, strong wind gusts with pockets of straight line wind damage to trees and power lines, and torrential rainfall. This was the most violent t'storm of the day, however, t'storms were numerous throughout the Catskills, Adirondacks, Mohawk valley to Vermont into the night with reports of widespread flash flooding due to repeat thunderstorms over southern Herkimer County.

Set Up:
A tropical air mass was in place over the region with dewpoints ranging from 70°-74° and air temperatures climbing into the low 80s with partial sunshine during the afternoon after a layer of morning low clouds burned off in the wake of a quick round of downpours and t'storms moved out of the region between noon and 2pm. Moderately strong speed shear existed in the atmosphere (winds increasing in speed with height) with the shear increasing through the late afternoon and the evening. Directional wind shear (turning of the wind with height) was considerable with surface winds from the SE at 10-15 mph on average (enhanced in south to north oriented valleys), coupled with winds aloft steadily turning to SW then to West with height. The combination of moderate speed shear and favorable directional shear coupled with the moist boundary layer air mass and moderate instability (CAPE, convective available potential energy, values of 1500 to 2500 j/kg) produced a favorable environment for severe t'storms across the region. The trigger for the storms was a diffuse pre-frontal low pressure trough over central New York running well in advance of a slow moving cold front approaching western New York. This trough acted as the convergence boundary to focus new t'storm development by the mid afternoon over the western Mohawk valley and Adirondacks.

The Tornado:
A unique combination of factors likely played a role in the tornado development over Florida in Montgomery County, an area that has had tornado development before. The first factor in tornado development was the merger between a severe t'storm tracking northeast through Schoharie County with a t'storm moving west down the Mohawk valley. The merger occurred roughly at the confluence of the Schoharie Creek and Mohawk river near Florida. The Schoharie valley, being roughly south to north oriented, served to further back and increase the southeast surface wind and thus enhanced the low level wind shear (turning of the wind) at that location to a level which support the development of a tornado. (This localized enhancement to low level wind shear in and close to the north south valleys in eastern New York and western New England is well documented to play a role in tornado genesis if other favorable weather conditions are present.) As the two storms merged in the strongly sheared low and mid level environments a deep layered strong rotation quickly developed causing a tornado to rapidly form then move to the east northeast at 30 mph. As the storm moved away from the source of strong low level wind shear its rotation rapidly weakened and the tornado lifted as it moved through the western side of Glenville in Schenectady county, traveling a total of seven miles. The parent supercell t'storm, however, continued to track east across Ballston Lake in Saratoga County, where the photo below of a wall or funnel cloud was taken, then into Rensselaer County, and finally through southern Bennington County where a measured wind gust of 64 mph was recorded at the Bennington automated observation station at 7:28pm. Pockets of straight line wind damage to trees and power lines as well as frequent violent lightning occurred all along this storm's total path.


Wall Cloud, or Possibly a Funnel Cloud, West of Exit 11 Ballston Lake
Late Sunday Afternoon September 4, 2011
Photographer: Dan Bernhard

Supercell Wall Cloud, or Funnel cloud just west of exit 11 of the Northway, Ballston Lake, NY Sunday late afternoon September 4, 2011

NWS ALBANY TORNADO REPORT

Location
From 2 miles southwest of Cranseville in Montgomery County to the town of Glenville in Schenectady County

Time
5:20pm to 5:35pm

Maximum EF Rating
EF1 (Top winds of 110 mph)

Estimated Path Width
Widest damage path of 1/2 mile

Estimated Path Length
7 Miles

No Injuries or fatalities

Summary
Sunday afternoon a tornado touched down near the town of Florida in Montgomery County. It moved northeast to the western end of Glenville in Schenectady County. Damage was extensive along the entire path length...with the most significant damage in the town of Cranseville where damage included numerous trees snapped off and uprooted, broken windows to homes, shingles stripped off roof tops, some roofs partially blown off, numerous sheds and out buildings destroyed.

 

STORM REPORTS September 4, 2011
The reports listed do not represent all of the wind damage or flash flooding which may have occurred in this event, but rather were collected and disseminated by the National Weather Service for the purpose of verifying the the warnings which were issued for the event.

Town County Storm Report Time
Fairfield Herkimer Wind Damage: Two trees blown down 3:35pm
1 Mile W. of Stratford Fulton Hail: 1" diameter 3:50pm
Salisbury Center Herkimer Wind Damage: Large tree limb down across from 412 Dairy Hill Rd. 4:05pm
Fairfield Herkimer Wind Damage: 2 Power poles down 4:35pm
2 Miles SE of Amsterdam Montgomery Funnel Cloud, Trees blown down blocking the NYS Thruway between mile markers 171 and 172 5:20pm
Cranseville Montgomery EF1 Tornado: Significant damage to trees, power lines, poles, partial roofs blown off, windows blown out 5:23pm
3 Miles ESE of Amsterdam Montgomery EF1 Tornado: Tornado crossing the Thruway, video showing the storm 5:25pm
Glenville Schenectady EF1 Tornado: Widespread tree and power line damage 5:30pm
Herkimer Herkimer Flash Flood: Streams out of their banks and roads washed out 5:45pm
Mohawk Herkimer Flash Flood: Streams out of their banks and roads washed out 5:45pm
Frankfort Herkimer Flash Flood: Streams out of their banks and roads washed out 5:45pm
2 Miles SE of Mohawk Herkimer Flash Flood: Streams out of their banks and roads washed out 5:45pm
Ilion Herkimer Flash Flood: Streams out of their banks and roads washed out 5:45pm
Mohawk Herkimer Wind Damage: Trees and wires blown down on Walnut Street, Henry Street, Michigan Street, and Columbia Street 5:47pm
Ballston Lake Saratoga Wind Damage: Numerous trees and power lines blown down 5:56pm
2 Miles SE of Little Falls Herkimer Wind Damage: People trapped between two fallen trees, no injuries 5:59pm
5 miles SW of Saratoga Springs Saratoga Wind Damage: Many large limbs blown down 6:00pm
Middleville Herkimer Flash Flood: Widespread flash flooding 6:00pm
2 miles ENE of Clifton Park Saratoga 3/4" Diameter Hail and Wind Damage with numerous limbs blown down 6:12pm
Mechanicville Saratoga Wind Damage: Trees blown down 6:18pm
Buskirk Washington Wind Damage: Trees blown down 6:32pm
Schaghticoke Rensselaer Wind Damage: Trees and wires blown down, one injured, Fairgrounds shut down 6:32pm
Pittstown Rensselaer Wind Damage: Trees and wires blown down 6:32pm
Tomhannock Rensselaer Wind Damage: Trees and wires blown down at the Tomhannock Reservoir 6:48pm
Frankfort Herkimer Flash Flood: Moyer Creek overflowed at Brice Rd., surrounding three homes 7:03pm
Hoosick Rensselaer Wind Damage: Tree on house on Pine Valley Road 7:04pm
Frankfort Herkimer Flash Flood: Water going over the bridge at W. Main Street near Cemetery Rd. 7:09pm
Hoosick Rensselaer Flash Flood 7:18pm
Hoosick Falls Rensselaer Wind Damage: Tree blown down on a house on Kokely Ave 7:19pm
Bennington, VT Bennington T'Storm Wind Gust of 64 mph 7:28pm
Bennington, VT Bennington Wind Damage: Trees blown down 7:51pm

 

 

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