Wednesday September 8, 2021
Severe T'Storm Event - 70 mph Gust at the Albany Airport

It was a late show, the 11th hour, at the very end of the severe weather potential window for the local area on Wednesday September 8, 2021 that a significant burst of violent thunderstorms erupted from what had been a slow moving benign line of rain and thunder that had formed well in advance of a cold front over central New York earlier in the day. Vivid lightning, pockets of damaging wind, and locally torrential rainfall escalated quickly between 6 and 7pm in the Hudson valley from eastern Warren County south through the Capital Region with rapid storm intensification that resulted in numerous reports of downed power lines, branches, and trees in the zone shaded in red on the map below with most of the severe weather occurring between 6 and 9pm.

Local Storm Damage Zone and Report Locations 9/8/2021 

Punctuating the event was a series of strong downburst wind gusts across northern Albany County with a 53 mph gust clocked at the Voorheesville New York State Mesonet site at 7:25pm which was then followed by an extreme 70 mph wind gust at the Albany International Airport at 7:44pm. The 70 mph gust at Albany is the strongest convectively induced wind gust to have occurred at the airport since an 82 mph gust on May 31, 1998, which was associated with a brief tornado at the airport on that big severe weather day. Prior to that, a 77 mph gust was clocked at the airport on July 15, 1995 when an early morning super derecho passed through. And more recently, on October 7, 2020, a 67 mph gust occurred at the airport as a derecho moved through on that day. The 70 mph gust at the Albany airport in this event is the 3rd highest convectively induced gust at Albany on record (good wind records date back to 1987) and also the highest gust on record at Albany for the month of September.


Peak wind gust at the Albany Airport, 7:44pm September 8, 2021 

Albany Doppler Base Velocity Image: 7:44pm - The radar indicated 65 mph winds just off the ground in and around Colonie and Latham at this time. This was the pocket of high wind aloft that was further accelerated in the downburst over the Airport resulting in the recorded 70 mph gust and the subsequent tree and power line damage reported in the area. This was straight line wind as no rotation was observed on the radar.

 7:44pm Albany Doppler Base Velocity Image: September 8, 2021

Albany Doppler Base Reflectivity Image: 7:45pm

7:45pm Albany Doppler Base Relfectivity Image: September 8, 2021 

THE EVENT
The atmosphere on this day was characterized by warm, windy, and humid conditions with temperatures topping off in the upper 70s to lower 80s, a strong gusty gradient southerly flow, with frequent 25-30 mph gusts through the day, and dewpoints that climbed into the mid, and in a few places, upper 60s. A 2pm special data collecting weather balloon launch at Albany revealed strong wind shear, both in speed and direction, meaning winds increased considerably from the surface through the mid levels with strong veering of the wind with height, or in other words, a wind shift from southerly to west-southwesterly aloft. This wind profile created an environment favorable for organized and even rotating thunderstorms. Bulk shear across the area ranged from 35-50 knots, which is strong. Instability was fairly high, especially for September, with surfaced based CAPE (convective available potential energy) ranging from 1000-1500 j/kg during the peak heating hours of the day, another ingredient favoring strong convective development.

Mitigating the set-up, however, was the indication of some subsiding, or sinking air in the upper levels of the atmosphere through the day and rather poor mid level lapse rates, meaning the air aloft was not particularly cool. Both of these factors acted to suppress convective development and in fact did so effectively through the majority of the day as little cloud cover developed in advance of the frontal clouds which came in during the mid to late afternoon from the west. This mitigating factor, however, did allow the instability to build up through the afternoon under what was more or less a capped environment.

Realizing all of the above, the forecast question during the afternoon then became, would the frontal band of rain and thunder that had been slowly developing over central New York earlier in the day reach the warm and unstable air mass in the Hudson valley prior to the diurnal cooling which would rapidly take place with the setting sun during the evening, or would it be late? And further, given the highly wind sheared environment, which requires less instability to support severe weather than a low shear environment, how quickly during the evening would the parameters become less favorable for supporting severe storms? As little as an hour timing difference of the line fast or slow would make a big difference in their intensity on arrival.

These were the questions, I, as well as other forecasters, including those at the Storm Prediction Center were grappling with which was evident by the lack of a severe thunderstorm watch prior to the event, although one had been discussed. A watch only went into effect for Greene, Columbia, Berkshire, Ulster, Dutchess, and Litchfield counties around 8pm, after most of the severe weather locally had occurred. And in the end, aside from some minor wind gusts, there was no severe weather in the counties where the watch was in effect, locally.

In the end, the convective line, mainly the northern part of it, encountered the more unstable air mass just before the favorable window closed with storms intensifying within the line, initially in Fulton and Montgomery counties and then north into Warren and Saratoga counties. Tall updrafts rapidly formed allowing effective momentum mix down of the strong winds aloft to the ground in localized damaging downbursts. As the individual line segments evolved the forward motion of the northern end of the line accelerated with that forward speed both increasing the surface wind gust potential while at the same time allowing the storms to take full advantage of the remaining instability after the sun had gone down which ultimately allowed them to continue producing severe weather through the immediate Capital Region and into Washington County and Vermont before subsequently weakening as the instability waned through the mid evening time frame.

To the south, in the Catskills and mid Hudson valley, where the instability was a little higher than across the rest of the region and the wind shear just as strong, no severe weather occurred. This largely may have been due to timing as the line was slanted in a northeast to southwest configuration (illustrated in the radar images of the event below) which meant the southern portion came into the Hudson valley later in the evening when the instability was diminishing. However, heavy rain did occur with areas of urban and poor drainage and localized flash flooding being reported, especially in southern Greene County.

This event is a good case in point illustrating how sensitive convective weather is to the smallest fluctuations in atmospheric conditions and how only a tiny parameter change, whether it's a few degrees in temperature or dewpoint at the surface or aloft, or timing, or background wind conditions, which can make the difference between no storms, weak storms, or violent storms. It's always fascinating to me to watch as each event has its own fingerprint.

The following series of radar images chronicle the progress of the convective line through the region between 5 and 10pm

5pm Albany Doppler Radar Image: Non severe slow moving line of downpours and thunder impacting Hamilton, Herkimer and Otsego counties


5pm Albany Doppler Radar Base Reflectivity Image: September 8, 2021

6pm Albany Doppler Radar Image: Intensifying convective line with a severe cell producing wind damage in and around Amsterdam at this time.


6pm Albany Doppler Radar Base Reflectivity Image: September 8, 2021

7pm Albany Doppler Radar Image: Intense convective line from western Rutland and Washington counties south through Saratoga, western Albany, SE Schoharie, western Greene and western Ulster counties. T'Storms were severe in Washington county producing pockets of wind damage and frequent lightning at this time.


7pm Albany Doppler Radar Base Reflectivity Image: September 8, 2021

8pm Albany Doppler Radar Image: Intense convective line from Rutland and northwest Bennington counties south through Rensselaer, NW Columbia, eastern Greene and western Ulster counties. Severe thunderstorms were in progress across Rutland and Rensselaer counties at this time with pockets of damaging wind and frequent lightning.

 8pm Albany Doppler Radar Base Reflectivity Image: September 8, 2021

9pm Albany Doppler Radar Image: Strong thunderstorms persisted at 9pm in Columbia and northern Berkshire counties, although weaker than earlier in the evening. Heavy rain and frequent lightning, however, were in progress at this time.

9pm Albany Doppler Radar Base Reflectivity Image: September 8, 2021 

10pm Albany Doppler Radar Image: The previously organized line of thunderstorms had dwindled to areas of rain and rumbles with some heavy downpours in progress at this time in Columbia and Berkshires counties.

10pm Albany Doppler Radar Base Reflectivity Image: September 8, 2021 

Wind Damage on McCaffrey Road - Amsterdam, Montgomery County - Photos by Tom Dimezza

Wind damage in Amsterdam, Montgomery County 9/8/2021 

Wind damage in Amsterdam, Montgomery County 9/8/2021 

NWS Storm Reports for Wednesday September 8, 2021. 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
Amsterdam Area Montgomery Wind Damage: Multiple reports of trees and power lines blown down, tree onto a home and vehicle on McCaffrey Road, outhouse overturned 5:59pm
Galway Saratoga Wind Damage: Tree blown down on Jockey Street 6:11pm
Warrensburg Warren Route 9 in the town of Warrensburg and one mile north of Route 28 closed due to downed trees 6:13pm
3 Miles NNE of Porter Corners Saratoga Wind Damage: Tree blown down on Tannery Hill Road and Minor Road 6:22pm
Hague Warren Wind Damage: Downed trees between Walker Lane and Stonebridge Road in Hague 6:28pm
1 Mile North of Lake George Village Warren Significant Wind Damage: Numerous trees snapped and uprooted along an approximately half mile stretch with visible damage off of exit 22 north of Route 9N 6:30pm
Lake George Village Warren Downed trees near Exit 22 and Route 9N on the Northway 6:33pm
1 Mile SE of South Glens Falls Saratoga Tree blown down on Bluebird Road 6:44pm
Glens Falls Warren Measured 51 mph gust at the Glens Falls NYSM site 6:45pm
Kingsbury Washington Wind Damage: Trees and wires blown down 6:45pm
2 Miles NE of Argyle Washington Wind Damage: Tree blown down on Tripp Road 7:03pm
Hebron Washington Wind Damage: Trees and wires blown down 7:20pm
Voorheesville Albany Measured 53 mph wind gust at the Voorheesville NYSM site 7:25pm
North Easton Washington Wind Damage: Tree blown down on Route 113 7:34pm
Delmar Albany Wind Damage: Downed trees, road blocked 7:35pm
2 Miles WNW of Albany Albany Wind Damage: Large tree limb down on Soc Ring Road 7:35pm
Westmere Albany Wind Damage: Wires down on Johnston Road between Ashford Drive and Ildra Lane 7:35pm
Colonie Albany Wind Damage: Large tree limbs down 7:40pm
Middle Falls Washington Wind Damage: Wires blown down 7:41pm
Albany Airport Albany Measured 70 mph wind gust 7:44pm
4 Miles NE of Nassau Rensselaer Wind Damage: Trees down on Curtis Hill Road 7:56pm
Grafton Rensselaer Wind Damage: Downed tree on State Route 2 8:17pm
5 Miles NE of Grafton Rensselaer Wind Damage: Down tree between Fox Hollow Road and Route 22 12:02am/8th
2 Miles ENE of Palenville Greene Wind Damage: Downed tree near Ramsey School Road and Route 23A 8:25pm
North Bennington, VT Bennington Wind Damage: Wires blown down 8:25pm
Coxsackie Greene Flash Flood: Route 285 at Lawrence Ave had all lanes closed due to flooding 8:50pm
Stuyvesant Columbia Flood: Minor flooding on State Route 9J 8:54pm
Pittsfield, MA Berkshire Wind Damage: Wires blown down on Wahconah Street 9:30pm


Storm Reports: Wednesday September 8, 2021

Storm Prediction Center Storm Reports For September 8, 2021 

WeatherNet 6 Storm Total Rainfall - September 8 Through the Thursday Morning September 9, 2021

Town County Rainfall Report Town County Rainfall Report
Pittsfield, MA Berkshire 1.47" Hancock, MA Berkshire 3.07"
Clarksburg, MA Berkshire 2.40" Savoy, MA Berkshire 1.60"
           
Delmar Albany 1.07" Loudonville Albany 0.91"
Albany (ASOS)* Albany 0.49" Glenmont Albany 0.82"
Colonie Albany 0.75" South Berne Albany 1.25"
           
Livingston Columbia 1.40" Taghkanic Columbia 1.41"
Germantown Columbia 1.50"      
           
Roxbury Delaware 1.36"      
           
Athens Greene 1.60" Halcott Greene 1.78"
           
Indian Lake Hamilton 1.00"      
           
Petersburg Rensselaer 1.32" Speigletown Rensselaer 1.25"
           
Clifton Park Saratoga 0.43" Saratoga Springs Saratoga 1.00"
Halfmoon Saratoga 0.44" Lake Desolation Saratoga 0.54"
Galway Saratoga 0.72" Ballston Spa Saratoga 1.00"
           
Glenville Schenectady 0.34" Schenectady Schenectady 0.39"
Rotterdam Schenectady 0.29" Duanesburg Schenectady 0.24"
           
Huntersland Schoharie 0.65" to 1.16" Jefferson Schoharie 0.75"
           
Phoenicia Ulster 2.67"      
           
Greenwich Washington 1.67" Hebron Washington 1.52"
Hartford Washington 1.06" to 1.36" Granville Washington 0.71"
           
Landgrove, VT Bennington 0.95" Woodford, VT Bennington 1.42"
West Rutland, VT Rutland 0.75"