Thursday July 16, 2009 Severe T'Storm Event
Mohawk Valley-Capital Region-Mid Hudson Valley Supercell

Another severe hail storm marched down the Mohawk valley into the Capital Region from the mid to late afternoon on Thursday July 16. It was the fourth hail storm of the season in the town of Guilderland with gigantic chunks of ice reported in an almost continuous path from southern Herkimer County through Montgomery, Schenectady, and Albany counties, then into the mid Hudson valley and Litchfield County, CT as the storm merged with others during the evening. This was a classic supercell thunderstorm (a storm with a rotating updraft) typically long lived and capable of producing long tracks of severe weather in the form of large hail, damaging wind, and tornadoes, providing sufficient low level turning of the wind is present. In this case, the storm's rotation rate was sufficient to aide in producing hail up to tennis ball sized (2.5" in diameter) and pockets of wind damage along its path. Low level wind shear, was not sufficient for tornado production.

The event unfolded after the passage of a warm front during the morning. Dewpoints steadily climbed from around 60° early in the day to between 65° and 70° during the afternoon in a narrow warm sector bounded by an approaching cold front over western New York. Moderate wind shear in both direction and speed was present in the atmosphere, coupled with sufficient instability supplied by the warming and moistening boundary layer (air temperatures in the low 80s prior to severe weather, and dewpoints in the upper 60s) and dropping temperatures aloft. a Small clusters of t'storms developed near Syracuse by the early afternoon which tracked east down the Mohawk valley becoming the supercell that brought the latest round of huge hail to parts of the region.

After moving through the Capital Region roughly between 5pm and 6pm, the supercell merged with other storms which had formed in a broken line through the Catskills to form a large slow moving mass of severe thunderstorms which went on to produce additional hail, damaging wind, and locally flooding rainfall in Columbia, Dutchess, and Litchfield counties through 9pm. Rainfall amounts of 1.5" to 2.5" occurred in parts of southern Columbia, Dutchess, and Litchfield counties as the storms moved through.

A significant power outage occurred in parts of Schenectady and Saratoga counties as a result of lightning strikes on two major transmission lines in Spider Falls.

Severe Weather Reports

The reports listed in the table were compiled by the Albany National Weather Service offices for the purpose of verifying the severe thunderstorm warnings that were issued for this event and does not necessarily represent the total number of severe weather occurrences that materialized with this event. It should be noted that he vast majority of severe weather reports listed below resulted from the one supercell thunderstorm.
Town County Storm Report Time
Herkimer Herkimer Quarter Sized Hail on Main St. (1.00" diameter) 3:23pm
Herkimer Herkimer Quarter Sized Hail on Prospect Street 3:25pm
Unadilla Forks Otsego Wind damage, numerous trees blown down 3:37pm
Herkimer Herkimer Wind damage, tree down on Steuben Street 3:32pm
Herkimer Herkimer Quarter Sized Hail on Steuben Street 3:32pm
Herkimer Herkimer Wind damage, tree down along Route 5 3:33pm
Little Falls Herkimer Penny Sized Hail (3/4" diameter) 3:37pm
Nelliston Montgomery Quarter Sized Hail 4:02pm
2 Miles No. of Canajoharie Montgomery Golf Ball Sized Hail @ Lock 15 of the Erie Canal (1.75" diameter) 4:03pm
Nelliston Montgomery Penn Sized Hail 4:07pm
5 Miles NNW of Canajoharie Mongtomery Nickel Sized Hail (0.88" diameter) 4:10pm
Palatine Bridge Montgomery Half dollar Sized Hail, damage to windows and crops reported (1.25" diameter) 4:10pm
Palatine Bridge Montgomery Wind damage, trees blown down 4:10pm
Altamont Albany Golf Ball Sized Hail 5:15pm
5 Miles W. of Colonie Albany Penny Sized Hail 5:16pm
5 Miles SW of Rotterdam Albany Golf Ball Sized Hail 5:20pm
Guilderland Albany Golf Ball Sized Hail 5:20pm
2 Miles W. of Rotterdam Schenectady Nickel Sized Hail 5:21pm
4 Miles WNW of Colonie Albany Quarter Sized Hail 5:21pm
Guilderland Albany Quarter Sized Hail @ Hiawatha Golf Course 5:24pm
Guilderland Center Albany Hen Egg Sized Hail (2.00" diameter) 5:25pm
Guilderland Albany Nickel Sized Hail 5:25pm
Mckownville Albany Tennis Ball Sized Hail (2.5" diameter) 5:25pm
Rotterdam Schenectady Quarter Sized Hail 5:29pm
2 Miles NW of Albany Albany Quarter Sized Hail 5:30pm
5 Miles WNW of Colonie Albany Penny Sized Hail 5:31pm
3 Miles NW of Albany Albany Half Dollar Sized Hail, @ the NWS Office on Fuller Road 5:32pm
3 Miles NW of Albany Albany Quarter Sized Hail, Driver @ I-87 and I-90 5:33pm
Guilderland Albany Golf Ball Sized Hail 5:34pm
3 Miles WNW of Albany Albany Hen Egg Sized Hail (2.00") 5:34pm
5 Miles West of Albany Albany Nickel Sized Hail, Krumkill Road 5:35pm
4 Miles NW of Albany Albany Nickel Sized Hail, Crossgates Commons 5:36pm
1 Mile North of Albany Albany Quarter Sized Hail 5:40pm
2 Miles WNW of Albany Albany Nickel Sized Hail 5:40pm
Albany Albany Penny Sized Hail 5:44pm
Delmar Albany Penny Sized Hail 5:45pm
2 Miles NNW of Albany Albany Penny Sized Hail 5:46pm
6 Miles WSW of Albany Albany Penny Sized Hail at Trumpeter Place 5:47pm
Albany Albany Ping Pong Ball Sized Hail, South Allen Street (1.5" in diameter) 5:49pm
East Greenbush Rensselaer Penny Sized Hail, Town Hall Parking Lot 6:00pm
Taghkanic Columbia Quarter Sized Hail 6:22pm
Dalton, MA Berkshire Penny Sized Hail 6:50pm
Port Ewen Ulster Measured wind gust to 64 mph 7:05pm
Whiteport Ulster Wind damage, trees blocking the south bound lanes of the Thruway 7:15pm
Salisbury, CT Litchfield Wind damage, trees blown down on Route 41 and Route 44 7:31pm
Lakeville, CT Litchfield Wind damage, trees blow down on Route 41 and Route 44 7:35pm
Falls Village, CT Litchfield Quarter Sized Hail and wind damage 7:45pm
Salisbury, CT Litchfield FLASH FLOOD: Several roads reported under water 8:00pm
Ancram Columbia FLASH FLOOD 8:10pm
Torrington, CT Litchfield FLASH FLOOD 8:30pm
New Preston, CT Litchfield Ping Pong Ball Sized Hail 8:55pm

Radar Images

#1: ENX (Albany NWS Doppler Radar) Base Reflectivity, lowest tilt: Supercell thunderstorm approaching Herkimer and LIttle Falls at 3:21pm, Thursday July 16, 2009. The curved area between Herkimer and Little Falls is called an inflow notch and represents the area of updraft feeding into the rotating storm. The lack of radar echo in the notch indicates rainfall and hail that is being suspended aloft by the updraft. The black shaded area at the center of the storm represents the region of greatest reflectivity in the storm which corresponds to the region of largest hail. Hail up to quarter size (1.00" in diameter) was falling from the storm at this time.

Albany National Weather Service Doppler Radar image of the supercell t'storm in southern Herkimer County at 3:21pm July 16, 2009 

#2: ENX (Albany NWS Doppler Radar) Base Reflectivity, lowest tilt: The large hail producing supercell, accompanied by weaker t-storms on its southern flank, located near East Stone Arabia in Montgomery County at 4:07pm.

Albany National Weather Service Doppler Radar image, supercell t'storm over Montgomery County, July 16, 2009 

#3: ENX (Albany NWS Doppler Radar) Base Reflectivity, lowest tilt: The supercell in Schenectady County at 4:53pm. The severe weather analysis program tripping on a strong rotation within the storm, noted by the red circle (shear marker). Hail sizes began increasing from quarter sized to half dollar and ping pong ball sized.

Supercell over Schenectady County, July 16, 2009, 4:53pm

#4: ENX (Albany NWS Doppler Radar) Base Reflectivity, lowest tilt: Supercell thunderstorm tracking into northern Albany County at 5:12pm. The rotating updraft was weakening a bit at this point which allowed the giant hail that the updraft had been suspending to begin crashing down to the ground. Within ten to fifteen minutes of this image, hail up to tennis ball sized (2.5" in diameter) began hitting the ground in and around Guilderland.

Weakening supercell moving into Albany County, producing up to tennis ball sized hail, 5:12pm July 16, 2009 

#5: ENX (Albany NWS Doppler Radar) Base Reflectivity, lowest tilt: 5:12pm, supercell over Albany/Schenectady counties with a developing line of non-severe t-storms extending to the SW into the Catskills. One lone severe hail producing t'storm over southern Columbia County. The line expanded as it moved east into the mid Hudson Valley, Berkshire and Litchfield counties going on to produce additional large hail and localized flash flooding in southern Columbia, northern Dutchess, and Litchfield counties.

Wider radar image illustrating the devleoping line of t-storms into the Catskills 

 

Photographer: CBS6 viewer Roseanne Palumbo: Gigantic hail in Guilderland, July 16, 2009 Photographer: CBS6 viewer Nicole Hart: Large hail in Guilderland, July 16, 2009
Large hail in Guilderland, July 16, 2009.  Large hail in Guilderland, July 16, 2009.