Two Part Severe T-Storm and Tornado Event
Monday July 21, 2003

The events of Monday, July 21 shattered what had been one of the quietest severe weather seasons on record for eastern New York and for western New England.  And the end of the 2003 severe weather drought came with a high end, widespread two part severe thunderstorm and major tornado event. 

The day began with only marginal parameters in place for severe weather over the region, with one exception. And that exception was the large scale pattern which featured an anomalous deep low pressure trough that was actively digging into the Ohio Valley. The trough created a deep layered and fast southwest flow of air over the Northeast.  In fact winds at the jet stream level topped 90 knots, with winds closer to the surface, at about 5000 feet off the ground, as strong as 40 knots.  Winds of this strength are more common in April and May, rather than July and represented a considerable amount of wind energy available in the atmosphere that was in place prior to the outbreak, and is quite favorable in supporting severe weather if other parameters are in place.  Dewpoint temperatures, representing the moisture content in the low levels of the atmosphere, were sufficiently high to support thunderstorms, in the upper 60's.  But a discernable convergence boundary to form storms, the amount of sunshine, and thus the level of instability, were in question early in the day.  Without a convergence boundary, or enough instability, thunderstorm development is difficult.  The position of the upper level low pressure trough, even though it provided quite a bit of wind energy, was quite far to the west of the region and thus in a somewhat unfavorable position for severe thunderstorms in the local area.

By midday it was becoming more clear that small scale weather features, rather than the large scale features, would be key in triggering and supporting severe weather during the afternoon and again during the evening.

A weak warm front type feature became evident, early in the afternoon, draped across central New York to central New England, which acted as a local lifting mechanism and also acted to increase the low level wind shear. (Wind shear is a change in wind direction and speed.)  The more shear available, the greater the chance for severe weather. Sunshine also heated the area for several hours during the morning and the early afternoon allowing temperatures to warm to around 80 degrees, increasing the local instability.

Severe Weather Event Part I:
Rain developed across northern New York, to the north of the warm front with a small thunderstorm pendant attached on the southern periphery of the rain shield.   The thunderstorm pendant resided just to the north of the warm front in the area of greatest wind shear, humidity, and instability, and thus rapidly intensified as it approached the Capital Region by mid afternoon.  The cluster of storms became severe over Schoharie county where wind damage was reported at 3:17pm.  Wind damage occurred a short time later in western Greene county, then in Schenectady and Albany counties.   For a brief time, Doppler radar indicated rotation over southern Schenectady and northern Albany counties prompting a tornado warning at 3:41pm.  No tornado damage was confirmed, but straight line wind damage occurred along the storm's path.   The discontinuous damage path extended from southern Schenectady and northern Albany counties through southern Saratoga, northern Rensselaer, and southern Washington counties.  The cluster weakened as it passed through Bennington county but still went on to produce torrential rain. 

This was only part one, of what later in the evening would develop into a major severe weather outbreak with the occurrence of a supercell thunderstorm that produced a family of tornadoes.

Severe Weather Event Part II, Tornado Outbreak:
The severe weather that occurred during the evening of July 21 was in large part driven by a very strong mesoscale low pressure system that formed very early in the day over Iowa.  The tiny spinning low and it's attendant thunderstorm complex, called a mesoscale convective system,  tracked from Iowa across the the southern Great Lakes states to Northwest Pennsylvania by late afternoon.  This National Weather service radar image shows the intense system as it moved along the New York, Pennsylvania border late in the afternoon.  Damaging wind and tornadoes were occurring at this time in Pennsylvania.

The system followed an east to northeast track crossing the New York, Pennsylvania border very early in the evening, then moving just north of the Capital Region by mid evening, and into New England north of Rutland county, VT early at night.  The following two radar images show the progress of the system through the region.

6:44pm EDT
9:26pm EDT

The tightly spinning and intense nature of the "Meso" low created a highly wind sheared low level environment, highly supportive of tornado producing thunderstorms.  In fact, the dramatic drops in barometric pressure ahead of the system caused the winds in the Hudson Valley to blow almost due east for a time into the "Meso" low, yielding between seventy and eighty degrees of shear or in other words, turning of the wind.  The fast nature of the winds aloft with the very favorable upper level jet stream configuration, and the high surface dewpoints leading to sufficient instability, and the very organized nature to the line of thunderstorms associated with the "Meso" low meant an imminent severe weather outbreak for eastern New York and western New England. The Storm Prediction Center had issued a Severe Thunderstorm Watch during Part I of the event, which remained in effect until 10pm. 

The first severe thunderstorm warnings went out for Otsego and Delaware counties at 6:20pm as the lines of storms slammed into those counties with force.  The Binghamton Doppler radar indicated a 65 mph rear inflow jet into the line of storms in Delaware county, which helped sustain the widespread damaging wind machine.  The Albany Doppler radar, to the east of the line, showed 75 mph winds a couple of thousand feet off the ground along the storm front's leading edge.  It was later confirmed in Delaware county that straight line winds of  80 and 90 mph occurred causing widespread damage through the county.  Severe thunderstorm warnings then went up for Schoharie and Greene counties at 6:57pm. 

The main event then unfolded as the storms in western Greene county merged with other thunderstorms in eastern Greene county.  The storm merger and subsequent interaction with the higher dewpoint air and the highly wind sheared environment in the Hudson valley, allowed a supercell thunderstorm (a rotating thunderstorm) to rapidly spin up and produced the first, of what would be a family of tornadoes, in Palenville.  A tornado warning was issued for eastern Greene county at 8:06pm.  Doppler radar indicated that the circulation formed and intensified very quickly within the supercell.  And once formed, maintained its strength for over two hours as it tracked, with increasing speeds, up to 55 mph, to the northeast through northwest Columbia, Rensselaer, and finally Bennington county through 10:00pm.  The supercell was imbedded within a larger area of thunderstorms that were simultaneously producing damaging straight line winds though Ulster, Dutchess, Columbia, Rensselaer and Berkshire counties.   Lightning within the supercell became almost continuous along it's path and 1.5 to 2.5 inches of rain fell.  The supercell exited far northeast Bennington county, VT  by 10:15pm, marking the conclusion of the severe weather outbreak.

Tornado Warning Time Table: 

8:06pm: Tornado Warning Issued for Greene County until 8:45pm
8:20pm: Tornado Warning Issued for Northern Columbia County until 8:45pm
8:43pm: Tornado Warning Issued for Northeastern Columbia and Southern Rensselaer Counties until 9:30pm
9:27pm: Tornado Warning Issued for Bennington County, VT until 10:15pm

Albany National Weather Service Damage Assessment Results: Tornado Confirmations

Greene County: Palenville, F1 Tornado Confirmed: 73-112 mph winds
Tornado width 50 yards on the ground for 1/2 mile

Greene County: Catskill/Kiskatom, F2 Tornado Confirmed: 113-157 mph winds
Tornado width 150 yards

Greene County: Coxsackie, F0-F1 Tornado Confirmed: 75 mph winds
Tornado width 50 yards (Note: This was the same tornado that struck Catskill)

Rensselaer County: Nassau, F1 Tornado Confirmed: 73-112 mph winds
This tornado produced a discontinuous path of three quarters of a mile in length ending just north of Route 20 with multiple vortices indicated.  The average width of the tornado was 75-100 yards. Widespread straight line wind damage was also found near Kinderhook Lake, and along both Route 203 and Camp Holly Road in Niverville.  The straight line winds were estimated in excess of 80 mph

Columbia County: Kinderhook, F2 Tornado Confirmed: 113-157 mph winds
The tornado touched down in the extreme Northeast end of the town of Kinderhook on County Route 28B.  The path began on Ottoville Road and extended on a a quarter mile in length with an average width of 50 yards.

Columbia County: Stuyvesant, F0 Tornado Confirmed: 40-72 mph winds
This tornado occurred along Country Route 26A and had a path length of one half mile and a width of 60 yards.

Columbia County: Newton Hook, Town of Stuyvesant, F0 Tornado confirmed, 40-72 mph winds
This tornado occurred right across the river from Coxsackie, and was likely the same tornado that produced damage in Coxsackie.  The path was discontinuous and extended four tenths of a mile with an average width of 125 yards.

Bennington County, VT: North Pownal to Bennington, F0 to F1 Tornado Confirmed, 75 mph winds
The tornado first touched down in North Pownal and traveled north into Bennington.   The path was 50-150 yards wide and seven miles long.

Graphic Showing the Path of the Parent Supercell Thunderstorm with confirmed Tornado touchdowns labeled

The following is a listing of other damage reports associated with both the afternoon and evening severe events on July 21, 2003

Town Name

County

Damage Report

Approximate Time of Damage

Walton Delaware Wind damage, numerous trees and wires downed 2:30pm
Middleburgh Schoharie Wind damage, wires down 3:17pm
Lexington Greene Wind damage, trees down 3:46pm
Schenectady Schenectady Wind damage, trees and wires down 4:00pm
Guilderland Albany Wind damage, trees down 401pm
Colonie Albany Wind damage, large trees down, wires down 4:11pm
Clifton Park Saratoga Wind damage, trees and wires down 4:15pm
Hudson Falls Washington Wind damage, trees down 4:30pm
Cambridge Washington Wind damage, wires down 4:30pm
Schaghticoke Rensselaer Wind damage, trees down 4:37pm
Pittstown Rensselaer Wind damage, trees down 4:40pm
Hoosick Rensselaer Wind damage, trees down 4:41pm
Exeter Otsego Wind damage, trees down 6:57pm
Edmeston Otsego Wind damage, trees down 6:59pm
Walton Delaware Trees uprooted, roof torn off a building 7:00pm
Delhi Delaware Widespread wind damage, county wide 7:15pm
East Fishkill Dutchess 1 inch diameter hail 7:05pm
Ulster County Ulster County wide straight line wind damage 8:00pm
Bethlehem Center Albany Numerous trees down 8:16pm
Esopus Ulster Numerous trees down 8:20pm
Catskill Greene Tornado, homes destroyed 8:23pm
Hudson Columbia Wind damage 8:25pm
Stockport Columbia 1.75" diameter hail 8:30pm
Lenox Dale, MA Berkshire Wind damage, numerous tress down 8:58pm
Bethlehem Center Albany Trees down on Delaware Avenue 9:00pm
Rensselaer Count Rensselaer County wide wind damage 9:00pm
West Cornwall, CT Litchfield Trees and wires blown down 9:12pm
Easton Washington Wind damage, trees down 9:15pm
Bennington, VT Bennington Widespread wind damage to trees and power lines 9:30pm

Photographs of Tornado Damage From WeatherNet 6 weather watcher James Meehan from Chatham, Columbia County

Lines Down along Route 9 in Valatie, Columbia County and Damage to Structures from fallen trees in Niverville, Columbia County

Damage to this hoouse and trees in Niverville, Columbia County

Damage along State Farm Road, Niverville, Columbia County

 

 

 

 

 

 

Photographs of Tornado Damage From WeatherNet 6 weather watcher Steve Meicht from Catskill, Greene County

Damage to a home along Route 32 in Catskill, Greene County Debris Field along Route 32 in Catskill, Greene County

More damage along route 32 in Catskill, Greene County