Wednesday, November 17, 2010
Heavy Convective Rain Event/Ghent EF1 Tornado

A strengthening low pressure system racing northeast on a track west of the Appalachians, taking it on a line up through Kentucky, Ohio and west of the St. Lawrence valley from late Tuesday night November 16 through Wednesday November 17, produced heavy rain, isolated severe weather, and regional strong wind gusts on its trek through the Northeast. On average, 1/2" to 1.25" of rain fell, with locally 1.5" to 2" of rain in terrain favored areas (much of this in a two to three hour period early Wednesday morning.) Isolated wind damage and a confirmed EF1 (95 mph wind estimate) tornado in Ghent, Columbia County occurred with the passage of a strong convective line between 4am and 6am Wednesday morning. And in the storm's wake, strong gradient wind gusts up to 45 mph buffeted the region from Wednesday afternoon into the night. With the storm's passage well west of the region, mild air with temperatures well into the 50s occurred through the duration.

The rain came in two distinct installments with the first largely a light rain or drizzle from the mid afternoon on Tuesday November 16 through approximately 10pm. An average of .15" to .35" of rain fell with the first round. The second round of rain, tied closely to a strong surface front and powerful upper air disturbance transiting the region was much more intense and included a narrow and fast moving convective line of torrential rain embedded within a broader area of moderate rainfall. This intense convective line moved from west to east across the region between 4am and 6am Wednesday morning accompanied by strong gusty wind in some areas. A t-storm developed within the line which went on to produce small pockets of significant wind damage to trees in the Claverack area and a confirmed (NWS storm survey) EF1 tornado in Ghent (winds estimated to 95 mph) The occurrence of the wind damage and brief tornado, although not common in November, is not unprecedented as strong storms with intense and highly sheared wind fields (ingredients favorable for severe weather) often transit the region at that time of the year. What is typically lacking is sufficient instability for severe weather to develop. In this case, a strong and highly sheared wind field existed, with very strong winds residing only about 3000' off the deck. Just enough instability developed, with temperatures in the low 50s and dewpoints near 50° in the mid Hudson valley coupled with cooling temperatures aloft, for a tall enough updraft to form which effectively tapped into the high momentum air aloft and then mixing that air down to the ground in brief damaging downbursts. The high shear supported the brief tornado spin up in Ghent.

Storm Report from the Albany National Weather Service Damage Survey

Ghent:
EF1 Tornado: Maximum wind speed 95 mph, 300 yard width, 2 mile sporadic damage path
Damage: Mostly to trees and power lines...minor damage to structures due to falling trees
Damage was most concentrated at the intersection of Soller Heights Road and county Road 9
Time: Approximately 5:18am

Claverack
Downburst: Maximum wind speed 85 mph
Damage confined primarily to trees and power lines
Time: Approximately 5:10am

Rain tapered to scattered downpours through Wednesday morning, then tapered further to widely scattered sprinkles and light showers through the afternoon and evening. A tight pressure gradient around the departing storm coupled with increasing instability in the atmosphere due to the air cooling aloft more quickly than at the surface worked in tandem to increase the gradient winds across eastern New York and western New England through the afternoon and evening. Westerly winds ranged from 15-30 mph with gusts occasionally ranging from 40-45 mph.

WeatherNet Storm Total Rainfall Reports for the November 16-17, 2010 Event

Town County Rainfall Report Town County Rainfall Report
Pittsfield, MA Berkshire 0.80" Savoy, MA Berkshire 0.95"
Lanesborough, MA Berkshire 0.95" Alford, MA Berkshire 0.95"
Sharon, CT Litchfield 0.94"      
           
Feura Bush Albany 1.12" Cohoes Albany 0.66"
Latham Albany 0.64" Colonie Albany 1.05"
East Berne Albany
2.00"
South Berne Albany 2.30"
Albany (Airport) Albany 0.71" Voorheesville Albany 0.64"
           
Ancramdale Columbia 0.75" Livingston Columbia 0.54"
Chatham Center Columbia 0.50" North Chatham Columbia 0.53"
Kinderhook Columbia 0.62" Germantown Columbia 0.51"
           
Hopewell Junction Dutchess 0.57" Arkville Delaware 1.25"
           
Northville Fulton 0.75" Johnstown Fulton 1.12"
           
Catskill Greene 1.02" Freehold Greene 1.30"
Greenville Greene 1.22" Elka Park Greene 1.51"
Haines Falls Greene 1.18" Cairo Greene 0.91"
           
Indian Lake Hamilton 0.76" Wells Hamilton 1.33"
Blue Mountain Lake Hamilton 0.80"      
           
Fonda Montgomery 0.69" to 0.79" Glen Montgomery 0.64"
Amsterdam Montgomery 0.68" Palatine Bridge Montgomery 0.51"
Hessville Montgomery 0.83"      
           
Cherry Valley Otsego 0.80" Worcester Otsego 0.70"
           
Center Brunswick Rensselaer 0.49" Stephentown Rensselaer 0.80"
Speigletown Rensselaer 1.60" Taborton Rensselaer 0.60"
           
Charlton Saratoga 0.67" Wilton Saratoga 0.68"
Ballston Spa Saratoga 0.61" Malta Saratoga 0.72"
Clifton Park (Oaks) Saratoga 0.92"      
           
Scotia Schenectady 0.71" Princetown Schenectady 0.80"
           
Richmondville Schoharie 0.88" Jefferson Schoharie 0.70"
Fulton Schoharie 0.65" Schoharie Schoharie 1.15"
Cobleskill Schoharie 1.02" Gilboa Schoharie 1.00"
           
Phoenicia Ulster 2.03" West Shokan Ulster 2.02"
Saugerties Ulster 0.75" Esopus Ulster 0.51"
Kingston Ulster 0.55" Kerhonkson Ulster 1.45"
Whiteport Ulster 0.79"      
           
Brant Lake Warren 1.09" Warrensburg Warren 0.95"
Queensbury Warren 1.13" Lake Luzerne Warren 1.10"
           
Cossayuna Washington 0.46" Fort Edward Washington 0.86"
           
Woodford, VT Bennington 1.19" Danby, VT Rutland 0.92"

 

Photographer: WeatherNet 6 spotter Jim Meehan. Wednesday November 17, 2010. Straight line wind and tornado damage in Ghent, NY, Columbia County  
Wind damage from Ghent, NY, Columbia County, November 17, 2010 
   
Albany Nexrad (ENX) Base Reflectivity image of the convective line a minute before 5am, just prior to the downburst in Claverack and brief tornado in Ghent, Wednesday, November 17, 2010  
Albany Nexrad image, 5am, November 17, 2010