Severe Hail Storms, Monday June 15, 2009

Prolific hail producing thunderstorms developed over eastern New York and western New England by the mid to late morning on Tuesday June 15, continuing through the evening. The event was primarily comprised of severe multicell thunderstorms forming in a high instability-low wind shear environment. (Multicells propagate through back building. For example, an initial cell will develop, become severe, put out a cold outflow causing it to weaken, but then generate a new cell on its flank. The process continues until the storm environment becomes unfavorable for additional development.) The convection developed in response to the passage of a strong short wave trough (a pocket of very cold air aloft, close to -20 degrees Celsius at the eighteen to twenty thousand foot level in the atmosphere ) in conjunction with the passage of a 115 knot jet core (200mb level) over Pennsylvania. The passage of the upper level jet core over Pennsylvania put much of New York and western New England in the jet's favorable left front quadrant where large scale lift in the atmosphere is enhanced.

Surface conditions, seemingly, were not particularly favorable for the development of severe convection with maximum temperatures ranging through the upper 60s to low 70s and dewpoints in the mid 50s. However, the coldness of the air aloft was more than sufficient to compensate for the lack of significant heating and surface moisture to yield significant instability (Convective Available Potential Energy ranging from 1500 to 2000 Joules/kg). The combination of the high instability, which created significant buoyancy to the air, which when combined with the large scale ascent caused by the passing jet core and upper level short wave trough, allowed strong updrafts to develop yielding intense thunderstorm development.

Rather weak wind fields existed in the low and mid levels of the atmosphere which precluded significant organization of the thunderstorms and also partially explains the lack of damaging wind in the event. Fairly moist conditions also existed through a reasonably deep layer in the atmosphere which reduced the amount of evaporational cooling that could occur aloft, which reduced the rate at which downdraft air flowed out of the thunderstorms, limiting the strength of the ground level winds. A few of the strongest cores did produce ground level winds ranging from 40-45 mph due largely to frictional effects of the hail and torrential rain dragging that air down to the ground. Therefore, large hail was the main severe weather mode for the event as the cold mid level environment was quite favorable for the formation and maintenance of hail as it fell, allowing lots of it to make it to the ground. The weak steering flow in the atmosphere also explains the slow forward motion/propagation of the storms (15 mph on average) which created a situation where long duration hail falls occurred in some locations with hail falling for up to fifteen minutes or more, leaving accumulations of one to two inches on the ground. The slow motion also meant terrain played an important role in where storms initially developed and how they behaved. This was especially the case with the first round of storms as significant back building occurred over Bennington County Vermont in essence creating a situation of almost stationary torrential hail producing thunderstorms sitting over the same locations for one to two hours. Flash flooding was reported in Vermont, especially in downtown Bennington and across northern Warren and Washington counties as a result of terrain induced back building of the storms. Flash flooding also occurred in and around Pittsfield, MA due to slow moving back building storms dumping torrential rains in short periods of time.

The event began with scattered thunderstorms during the mid to late morning forming over the Adirondacks and higher elevations in western New England as what appeared to be a lead upper level impulse triggered development. A second upper level impulse caused additional thunderstorms to develop during the mid to late afternoon and evening which eventually supported the particularly intense multi-cell cluster which blasted parts of eastern Schenectady, southern Saratoga, and northeast Albany counties with torrential rain and accumulating hail between 5pm and 7pm. The Capital Region storm briefly developed some weak mid level rotation, due to storm based motions, with a wall cloud observed over Albany and rotation observed by National Weather Service meteorologists at the Albany NWS office on Fuller road. Brief rotation was noted as this storm cluster tracked southeast into western Rensselaer County before weakening slightly on its trek through Columbia and southern Berkshire County, then out of the region after 9pm.

This radar image is of the storm cluster over northeast Albany County at 6:28pm. Hail ranging in size from 1/2" to 1" diameter, on average was falling from the slow moving storm at this time throughout the region shaded in light purple. (The light purple color indicates an area of high reflectivity on the radar showing the most likely region for hail)

Click here for a series of additional radar images

Click here for hail and storm pictures

Severe Multicell thunderstorm over northeast Albany County, 6:28pm, June 15, 2009 

Saratoga Springs was hit twice by two small in size, but intense hail storms, the first between 2pm and 2:30pm with the primary hail core tracking right over SPAC. Hail up to the size of 3/4" and a twenty degree temperature drop were recorded through WeatherNet 6 spotter Gary Burton. Shovels were reportedly necessary to clear hail in and around Saratoga Springs with this storm. The second hail storm, taking almost the identical track, moved over Saratoga Springs and SPAC between 4:30pm and 5:00pm.

Most of the hail throughout the region ranged in size from 1/2" to 3/4" with some reports of hail the size of golf balls (1.75" in diameter) The larger hail stones were more the exception than the rule, however. The skew towards smaller hail explains the few reports of car, window, siding, and roof damage from the event. Many occurrences of decimated foliage and gardens, however did occur.

The tale below lists the severe weather reports collected by the Albany and Binghamton National Weather Service offices for the purpose of verifying the severe thunderstorm warnings that were issued. The listing is a sampling of what occurred across the region and is therefore not a complete list of all the hail that occurred from the event, only what was reported.

Storm Reports for the Tuesday June 15, 2009 Event

Town

County Storm Report

Time of Occurrence

Kerhonkson

Ulster Penny Sized Hail (3/4" Diameter) 12:10pm
Kerhonkson Ulster Penny Sized Hail Again 12:44pm
Near Hancock Delaware Nickel Sized Hail (0.88" Diameter) 1:45pm

Putnam

Washington Flash Flood, County Route 2 Washed Out 2:15pm
Saratoga Springs Saratoga Penny Sized Hail, Covered the ground 2:20 to 2:40pm
Bennington, VT Bennington Quarter Sized Hail (1" Diameter) @ Morse State Airport 2:25 to 2:35pm
Cragsmoor Ulster Nickel to Quarter Sized Hail 2:36pm
Awosting Ulster Nickel Sized Hail 2:50pm
Near Pine Bush Ulster Nickel Sized Hail 2:55pm
Bennington, VT Bennington Flash Flood, cars stalled in downtown flood waters 3:00pm
Pittsfield, MA Berkshire Nickel Sized Hail 3:10pm
Stockbridge, MA Berkshire Penny Sized Hail 3:10pm
Near Pittsfield, MA Berkshire Nickel Sized Hail 3:35pm
Pittsfield, MA Berkshire Flash Flood, school bus stalled in flood waters 3:40pm
Oneonta Otsego Golf Ball Sized Hail, (1.75" Diameter) 4:10pm
Morris Otsego Nickel Sized Hail 4:10pm
Corinth Saratoga Quarter Sized Hail 4:12pm
Oneonta Otsego Quarter Sized Hail 4:22pm
Walton Delaware Nickel to Quarter Sized Hail (2" to 3" Accumulation) 4:22 to 4:24pm
Andes Delaware Nickel to Ping Pong Ball Sized Hail (1.5" Diameter), Hail covered the ground 4:55 to 4:57pm
Hamden Delaware Nickel Sized Hail, hail covered the ground and cars 5:00pm
Ames Montgomery Nickel Sized Hail 5:00pm
Galway Saratoga Penny to Quarter Sized Hail on Galway Lake 5:15pm
Charlton Saratoga Nickel Sized Hail, covering the ground 5:40pm
Galway Saratoga Wind damage, a tree and wires blown down 5:41pm
Glenville Schenectady Quarter Sized Hail 5:45pm

Scotia

Schenectady Nickel Sized Hail 5:45pm
East Glenville Schenectady Penny Sized Hail 5:50pm
Rexford Saratoga Penny Sized Hail 6:00pm
Niskayuna Schenectady 1/2" Diameter to Penny Sized Hail, Driven by 40 mph gusts, hail covered the ground @ CBS6 with torrential rain 6:02pm
Colonie Albany Penny Sized Hail 6:10pm
5 Miles NNW of Albany Albany Quarter Sized Hail 6:14pm
Latham Albany 1/4" Diameter Hail 6:20pm
Guilderland Albany Hail up to Golf Ball Sized, covering the ground, significant damage to vegetation 6:20pm
Albany Albany 1/4" to 3/4" Diameter Hail 6:20pm
North Bethlehem Albany Quarter Sized Hail 6:25pm
Cohoes Albany Quarter Sized Hail 6:25pm
Albany (NWS) Albany Penny Sized Hail measured @ NWS office on Fuller Road 6:28pm
Colonie Albany Quarter Sized Hail 6:32pm
2 Miles W of Albany Albany Quarter Sized Hail near Buckingham Pond 6:35pm
Westerlo Albany 1/2" Diameter Hail 6:40pm
Brunswick Rensselaer Wind Damage, one tree down 6:40pm
Albany Albany Quarter Sized Hail at Point of Woods Drive 7:04pm
East Greenbush Rensselaer Wind damage, wires down on Mannix Road 7:05pm
Coeymans Hollow Albany Golf Ball Sized Hail 7:05pm
Ravena Albany Penny Sized Hail 7:15pm
Kinderhook Columbia Penny Sized Hail, wind gust to 41 mph 7:17pm
Kinderhook Columbia Penny Sized Hail 7:19pm
Valatie Columbia Nickel Sized Hail 7:20pm
Chatham Center Columbia Pea to Penny Sized Hail 7:42pm