Wednesday May 31, 2017
Severe Thunderstorm Event
Colonie 90 mph Microburst - Wappinger (Dutchess County) brief EF-1 Tornado

Photographer: Sean Organ- The photograph shows a cloud lowering in the region of this thunderstorm's updraft as it was developing over eastern Montgomery and western Schenectady counties on Wednesday May 31, 2017. The darker area in the background is a downdraft region where rain and small hail was falling at the time of the shot. Pea sized hail was reported in and around Amsterdam close to the time this photograph was taken.

Cloud lowering with rainshaft in a developing thunderstorm over western Schenectady County, May 31, 2017


Scattered severe thunderstorms erupted in the Capital Region, mid Hudson valley as well as across New England during the afternoon and evening on May 31, 2017 in an unstable environment characterized by chilly air aloft, (500mb temperatures around -17° C to -18° C) and surface temperatures in the mid 70s, warmed due to a period of strong heating from the mid morning into the early to mid afternoon. Surface dewpoints were not particularly high, though, generally ranging through the upper 50s, boosted somewhat by evaporation from a wet ground due to rainfall from the previous day. CAPE values (convective available potential energy) ranged from 1000 to 1500 j/kg resulting from the thermodynamic environment, (cold air aloft, warmer at the ground) more than sufficient to sustain healthy thunderstorm updrafts. Strong wind fields also once again existed aloft (as had been the case in the previous severe weather events in May 2017) with significant turning of the wind with height (directional shear) a highly favorable ingredient for severe thunderstorm generation and some rotating updrafts. Low level shear magnitudes, however, were small, meaning the surface winds were not particularly strong, which indicated a low tornado threat across the region.

THE EVENT:
Showers and a few thunderstorms initially developed along a broken line across western New York during the late morning and early afternoon, moving east into the Adirondacks and Otsego county between 2 and 3pm. The environment across this portion or our area was less unstable than the air over the immediate Hudson valley so the thunderstorms at this point were not severe. Intensification, however, began along the leading edge of these thunderstorms as they moved further east where two cells developed brief rotation over east central Warren County going on to produce hail across northern Washington and Rutland counties through 4pm. Simultaneously, the cluster of thunderstorms that had tracked through Otsego county redeveloped over Montgomery and Schenectady counties between 3:30 and 4pm where small hail and strong wind gusts were developing. The radar image below shows two strong cells over eastern Montgomery and western Schenectady counties where small hail was occurring in and around Amsterdam. These cells would merge, rapidly intensify and develop a briefly rotating updraft (supercell structure) which supported widespread hail across Schenectady county and a 90 mph microburst over a small part of Colonie at 4:13pm. The explosive development occurred due to the storm intersecting a more unstable and slightly more humid environment where the surface wind was backed (more southeasterly) in the Hudson valley, causing it to rapidly become severe.

Intensifying thunderstorm cells over eastern Montgomery and western Schenectady counties at 3:53pm May 31, 2017

By 4:18pm the storm cells had completely merged with the now severe thunderstorm producing widespread hail across Schenectady County. The updraft was rotating at this point with a clear hook echo near Lisha Kill in Albany county and arguably a second weaker circulation northeast of Altamont. Approximately five minutes prior to this radar image, in the vicinity of Colonie, the rotating updraft unleashed a 90 mph microburst at the intersection of Kings and Cordell Roads which spanned a mile to Morris Road uprooting trees and taking down power lines.

Severe thunderstorm over Schenectady County, 4:18pm May 31, 2017

This image is the lowest tilt velocity scan from the Albany Doppler radar at 4:21pm May 31, 2017. The image shows the rotational couplet just over the Schenectady County line into Colonie shortly after the time of the microburst. The circulation did not last long, quickly dissipating as it moved southeast in the direction of Loudonville.

Albany Doppler radar velocity scan at 4:21 May 31, 2017 
Hail analysis at 4:27pm May 31, 2017: The image shows the hail core associated with the rotating updraft largely over eastern Schenectady County. Up to 3/4" diameter hail was falling at CBS6 at this time with larger hail stones up to 1.75" in and around Schenectady. The hail core weakened as the circulation weakened with generally small hail of 1/2" diameter or less over southern Saratoga county as the cell moved east.

Albany Doppler hail analysis at 4:27pm May 31, 2017 
Radar image at 4:37pm May 31, 2017 showing the severe thunderstorm extending from north of Malta in Saratoga County to Colonie. Small hail was falling over Cohoes and Waterford at this time. The majority of the severe weather from the event in the local area occurred as a result of this storm and was confined largely to Schenectady and northern Albany counties, occurring between 4:15pm and 4:45pm.

Albany Doppler radar image at 4:37pm May 31, 2017 

Pockets of wind damage also did occur into Rensselaer County with some large hail from a separate cell in Greene County at 4:40pm. The radar image below shows the line of storms extending from southern Washington County on south through Rensselaer County, northwest Columbia and eastern Greene counties at 5:01pm..

Albany Doppler radar image at 5:01pm May 31, 2017 
At 5:44pm the storms were no longer severe but still producing heavy rain and small hail across Bennington, Berkshire and central and northern Columbia Counties. Additional development, however, was underway over Ulster County in what would become a second line which would sweep the mid Hudson valley with large hail and a brief tornado touchdown in Wappingers in southern Dutchess County at 7:14pm.

Albany Doppler radar image at 5:44pm May 31, 2017 
The new line of thunderstorms was fully formed by 7:00pm with severe weather in progress with the cell near Poughkeepsie as a fully rotating updraft had developed which was producing large hail at the time and a rotating wall cloud

Albany Doppler radar image at 7:00 pm May 31, 2017 

At 7:12 pm, two minutes before a brief tornado touch down in Wappingers, this strong hook echo was evident on radar indicating the strong rotation in the storm at the time.

TORNADO REPORT: (Albany NWS)

Location: Wappingers - southern Dutchess County

Estimated Time: 7:14pm

Rating: EF-1 - Peak winds of 100 mph

Path Width: 1/4 Mile

Path Length: 1.25 Miles

Impact: Damage to both hardwood and softwood trees as well as a shed roof lifted.

Albany Doppler radar image at 7:12 pm May 31, 2017



Wall cloud over Wappingers Falls, Dutchess County - Photograph contributed by Shane K Snyder via Facebook

Wall cloud over Wappingers Falls, Dutchess County, Wednesday evening May 31, 2017

Photograph contributed via facebook by Jim Reidy Jr - Thunderstorm shelf cloud moving into Albany, May 31, 2017

Thunderstorm shelf cloud over Albany, May 31, 2017

Photograph contributed by Mark Parrella - Hail in Niskayuna around 4:20pm May 31, 2017

Hail in Niskayuna, May 31, 2017 

Photograph contributed via facebook by Bill Lawrence - Severe thunderstorm wind damage in Poestenkill, Rensselaer County, May 31, 2017

Damage in Poestenkill, Rensselaer County May 31, 2017 

Photograph by Sean Organ - Dramatic cloud lowering over a farm between Florida, NY and Scotia NY Wednesday afternoon May 31, 2017.

Dramatic cloud lowering with the developing thunderstorm between Florida and Scotia, May 31, 2017 

Storm Prediction Center Storm Reports Graphic for Thursday May 18, 2017 showing the locations of reported storm damage.

SPC Storm Reports for Wednesday May 31, 2017 


NWS Storm Reports for Wednesday May 31, 2017. 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
Hague Warren Measured 1" diameter hail 3:39pm
3 Miles SW of Darrowsville Warren Measured 0.88" diameter hail (Nickel Sized) 3:40pm
Glen Montgomery T'Storm wind damage, tree blown down onto a road 3:50pm
Colonie Albany 90 mph microburst, began at the intersection of Kings Road and Cordell Road spanning a mile to Morris road. Microburst path width of 100 yards, significant damage to trees and power lines 4:13pm
Rotterdam Schenectady Estimated 1" diameter hail 4:15pm
South Schenectady Schenectady Measured 1" diameter hail 4:18pm
1 Mile NE of Ft. Hunter Albany T'Storm wind damage, tree blown down on East Lydius Street 4:18pm
Niskayuna Schenectady T'Storm wind damage, Tree blown into a house on East Country Club Drive 4:20pm
1 Mile SW of Stanford Heights Albany T'Storm wind damage, trees and wires down and a transformer on fire on Cordell Road 4:22pm
1 Mile NNW of Niskayuna Schenectady Measured 1.75" diameter hail 4:21pm
2 Miles SW of Lisha Kill Albany T'storm wind damage, multiple trees blown down 4:22pm
1 Mile So. of Maywood Albany T'Storm wind damage, trees down on Albany Street 4:22pm
1 Mile So. of New Salem Albany T'Storm wind damage, trees down at the intersection of New Scotland Road at Stove Pipe Road 7:24pm
Niskayuna Schenectady Estimated 0.88" diameter hail 4:25pm
2 Miles W of Malta Saratoga T'Storm wind damage, trees and wires blown down 4:26pm
1 Mile N of Stanford Heights Schenectady T'Storm wind damage, trees and wires blown down 4:30pm
Mohawk View Albany T'Storm wind damage, tree down across a road 4:30pm
1 Mile ESE of Loudonville Albany T'Storm wind damage, tree down on Princess Lane 4:34pm
Loudonville Albany T'Storm wind damage, tree down on Osborne Road 4:35pm
Schenectady Schenectady Estimated 1" diameter hail 4:36pm
1 Mile ESE of Loudonville Albany T'Storm wind damage, tree blown down on Cherry Tree Road 4:36pm
1 Mile SSE of Place Corners Greene Estimated 1" diameter hail 4:40pm
Watervliet Albany T'storm wind damage, tree down at the intersection of 14th Street and 2nd Ave. 4:40pm
1 Mile N. of Sycaway Rensselaer Measured 0.88" diameter hail 4:46pm
1 Mile SSE of Ives Corner Rensselaer T'Storm wind damage, trees and wires blown down 4:45pm
1 Mile SSE of Poughkeepsie Dutchess Measured 1.75" diameter hail and strongly rotating wall cloud 6:50pm
Arlington Dutchess Measured 1" diameter hail 6:56pm
Hopewell Junction Dutchess T'Storm wind damage, trees down 7:14pm
Wappinger Dutchess Brief EF-1 Tornado - Tree tops snapped off, house impaled by branches, shed blown down and partial collapse of a house on Maloney Road, near Route 376 7:14pm
East Fishkill Dutchess T'Storm wind damage, trees down 7:27pm
Hurd Corners Dutchess T'Storm wind damage, multiple trees down 7:30pm