Major Severe T-Storm Outbreak
Four years ago to the day, May 31, 1998, one of the most violent outbreaks of severe Thunderstorms and tornadoes to develop in the Northeast hammered all of eastern New York and western New England with widespread severe thunderstorms and several damaging tornadoes including the Mechanicville/Stillwater storm. Although, not as intense as the 1998 event, a substantial severe weather outbreak comprised of multiple lines and clusters of storms rampaged through eastern New York and western New England from 1:30pm through 7:30pm on Friday, May 31. The Albany National Weather Service office issued thirty nine severe thunderstorm and two tornado warnings during this event. In 1998, the office issued a total of forty six warnings, most of which were tornado.
It became apparent several days in advance of the outbreak that many of the necessary parameters to create and sustain severe weather would be evident over the Northeast on the 31st. Very warm and moist air had been entrenched over the region for much of the week preceding the event with dewpoint temperatures in the mid 60's. On the 31st, a very strong upper air low pressure system moved into the region on a northwest steering flow. The upper level low brought both spin, or wind shear to the region, as well as cold air aloft to create significant instability. A surface cold front and low pressure trough preceding the front acted as the low level convergence boundaries for the eighty degree humid air to rise, thus forming the updrafts that created the thunderstorms. Low level winds gusted to 25 mph from the south. Mid and upper level winds veered with height into the west and increased in speed to approximately 80 knots at about the 20,000 foot level. The veering of 45 to 50 degrees was sufficient to produce the necessary shear for a few discrete supercell thunderstorms (rotating storms) to form ahead of and in conjunction with the two main lines of severe T'storms.
The first line of thunderstorms developed on the pre-frontal low pressure trough during the early afternoon and rapidly became severe. Strong bow echo structures were noted on radar in conjunction with widespread damaging straight line winds and a weak, short lived F-0 tornado in Johnstown, NY. (F-0 winds range from 40-73 mph) A supercell (rotating) thunderstorm formed immediately ahead of the line in Rutland county, Vermont, where 60 mph straight line winds and hail occurred. Another discrete supercell formed in advance of this line and produced 1.75" diameter hail at New Paltz in Ulster county at 2:23pm. Damaging thunderstorms from this first round moved through the remainder of eastern New York and into western New England through 3:30pm.
Not even before the first line of storms had exited the Channel 6 coverage area, did the second line of severe T'storms enter from the west. This line, closer to the parent upper level low and thus fueled and driven by the upper level winds and therefore more greatly influenced by a wind sheared environment, was comprised, especially on it's southern end, of discretely rotating supercell storms. (Supercells form in highly wind sheared environments) These supercells produced primarily hail and damaging straight line winds. However, several F-0/F-1 tornadoes, winds of approximately 75 mph, did touch down in Otsego county, near Cooperstown, southern Delaware county in the town of Lordville, and in southern Dutchess county over Whaley lake near Wingdale. The last storm with this line exited Litchfield county, CT by 7:30pm ending the multiple round extended severe weather outbreak over eastern New York and western New England. The cold front passed through the region around midnight with nothing more than a few clouds and a noticeable drop in the dewpoints through the pre-dawn hours of June 1.
The following table is a listing of reported storm damage from this outbreak.