Like a bomb went off, that's how the damage in the Viall Hill neighborhood in Stillwater (shown below) and surrounding areas was described after a fast moving violent tornado plowed through around 4:30 in the afternoon on Sunday, May 31, 1998.
The tornado was part of an almost unprecedented outbreak, in terms of areal coverage and duration, of severe thunderstorms and tornadoes throughout the Northeast which spanned from the mid afternoon through the early nighttime hours on May 31, 1998 with multiple waves of violent storms moving across eastern New York and western New England. The only "High Risk" severe weather outlook from the Storm Prediction Center on record to date in the Northeast was issued in advance of the event with in the end twenty five tornadoes touching down in New York, Pennsylvania, Vermont, Connecticut and New Hampshire with nine of them in New York. For perspective, ten tornadoes, mostly brief weak ones, will touch down in New York during an entire average severe weather season. Additionally almost 180 reports of damaging straight line wind and just under forty reports of large damaging hail were recorded for the event, a number which only captures what was specifically reported for the purposes of National Weather Service warning verification, and does not necessarily represent all of the damaging wind and hail events which may have occurred. The graphic below highlights the distribution of severe weather reports for the outbreak.
The long track Mechanicville-Stillwater tornado, which went on to produce damage in Schaghticoke and Pittstown in Rensselaer County as well as in Bennington, VT, as well as the long track track tornado which went through Binghamton, were both rated strong to violent at an F-3 intensity. Today's ranking would have the storm classified as an EF-3 on the enhanced Fujita tornado intensity scale, with winds ranging from 136 to 165 mph. (The EF scale was introduced on February 1, 2007 after studies showed it took winds of lower velocities than had earlier been thought to produce the types of damage observed with tornadoes. All historical tornadoes retain their rankings but have the associated lower velocities attached to them vs. what the original Fujita tornado intensity scale had assigned.)
Damage from the storms was widespread throughout the local area with 60,000 Capital Region customers left without electricity and up to 150,000 without electricity regionally. Many areas remained in the dark for up to four days after the outbreak due to the extensive damage to major transmission line infrastructure. Damage was estimated to be from 65-70 million dollars in the Capital Region, mostly from the Mechanicville tornado. Fortunately, and perhaps as a by product of superior warnings by the Albany National Weather Service and Capital Region media outlets, no fatalities occurred in eastern New York or western New England as a direct result of the storms.
The Meteorology and Timeline
A strong cold front responsible for a widespread severe weather producing squall line across eastern New York and western New England on Friday, May 29, moved south of the region and stalled over southern Pennsylvania on Saturday, May 30. A weak bubble of Canadian high pressure, associated with very dry air, moved over New York and New England producing a beautiful Saturday weather wise. Dewpoint temperatures dropped from the muggy 60s on Friday into the upper 30s on Saturday with mostly clear skies.
Meanwhile, in South Dakota, a powerful westerly jet stream flow up to 150 mph above 30,000 feet contributed to a devastating tornado outbreak which resulted in the almost complete destruction of the town of Spencer. It was the most destructive tornado in South Dakota's history and second deadliest with six fatalities reported. The low pressure system responsible for the Spencer tornado had intensified and raced east to northern Michigan by 8:00 am Sunday morning, May 31. The counterclockwise flow around the cyclone pulled the stalled front over southern Pennsylvania north into the Berkshires through the early afternoon. Very warm humid air was now clashing with the cooler dry air over the Berkshires, resulting in an early round of several large, locally damaging thunderstorms which produced heavy rain, frequent lightning, and isolated damaging downburst winds along the warm front. Simultaneously, in the low pressure system's warm sector, a derecho (a highly organized complex of severe thunderstorms which produce widespread wind damage over long distances) was moving across eastern Michigan. The derecho produced convective wind gusts up to 100 mph across Michigan as well as isolated tornadoes. The first of what would be several tornado watch areas was issued early in the morning on the 31st for much of western and northern New York to cover the severe weather threat with this derecho as it raced through Canada and moved into New York.
8 am surface analysis - Intense low pressure with central pressure down to 992 mb (very strong for late May) was tracking north of the region dragging the convectively active warm front across the region.
11 am surface analysis - showing the eastward progress of the strong warm front through eastern New York. The Michigan derecho was in the process of moving into western New York at this time.
With western and northern New York under an early morning meteorological gun with strong and severe thunderstorms, sunshine was simultaneously breaking out across eastern New York and western New England with dewpoint temperatures rising quickly with the passage of the warm front. By early Sunday afternoon the dewpoint temperatures had reached sultry levels in the upper 60s and air temperatures had climbed into the 70s and low 80s. CAPE values (convective available potential energy) were in the process of climbing to a range of 2000 to 4000J/kg with a notable elevated mixed layer moving into the region behind the warm front. (An elevated mixed layer (EML) is a layer of warm dry air aloft which acts to cap or prevent thunderstorm development until a combination of upper level cooling and surface warming erodes the cap allowing for explosive development to occur. EML's are often a necessary ingredient for widespread violent severe weather outbreaks.
At the surface, winds increased from the south-southeast up to 30 mph in response to the strong low passing to the region's north. Upper air winds increased from the west to between 40 and 80 mph between the 5000' to 20,000' levels. The dramatic change in wind direction and speed with height created a highly wind sheared environment favorable for developing violent supercell thunderstorms (storms with rotating updrafts.)
Adding further to the favorable environment for violent thunderstorms was the configuration of two jet stream segments at the 30,000' to 40,000' levels. A powerful 100 to 150 mph jet streak stretched from the Great Lakes into the Ohio and Tennessee valleys putting the Northeast in its left exit region, or a region of strong atmospheric lift. A second powerful jet streak of 100 to 150 mph arched from NW to SE from Quebec to Maine, putting the Northeast in its right entrance region, also an area of strong lift. The combined effects of the diffluent flow aloft from this jet configuration over the capped highly unstable and strongly wind sheared environment set the stage for the widespread outbreak of tornadic thunderstorms. All that was needed was the trigger to set it all off.
By 1 pm the initial line of severe thunderstorms (the Michigan derecho) was weakening, but still producing damaging straight line wind, as it moved into the western Adirondacks. The main tornado event triggered along the derecho's outflow boundary (a zone of rain cooled air, almost a mini cold front) which sagged south into the Mohawk valley and Capital Region. The outflow zone acted as a convergence boundary which coupled with cooling aloft zipped open the cap and initiated the first round of violent afternoon storms and the supercell that went on to produce the Mechanicville-Stillwater tornado. A PDS (particularly dangerous situation) tornado watch was issued by 2:30 pm for all of eastern New York and western New England as the storms began erupting.
The first tornadic supercell formed on the outflow boundary in Montgomery County around 3:30 pm. This storm rapidly intensified near Amsterdam, getting a boost from increased low level wind shear due to local terrain effects, and moved east at 50 mph into Saratoga county producing the devastating tornado which moved through Mechanicville and Stillwater. A tornado warning for Saratoga County was issued by the Albany NWS at 3:43 pm. The tornado began doing damage on Usher's Road in Halfmoon at 4:20 pm, racing into Mechanicville and Stillwater at its peak intensity through 4:30 pm, then continued through Schaghticoke along Route 67 and into Bennington, VT finally dissipating over Shaftsbury, VT with the last of the damage occurring on Lower East Road at 5 pm.
By 4:30 pm, other rotating severe thunderstorms had explosively developed throughout the region with many areas being affected by frequent lightning, high wind, hail, and torrential rain. At 4:40 pm a second tornado (F-1 intensity) developed from a supercell at the Albany airport. A peak wind gust of 82 mph was recorded with the passage of that storm at 4:40 pm with damage into the town of Colonie. From 3:30 pm to 7:00 pm almost every county in the WRGB coverage area in New York and New England experienced severe weather in the form of large hail, damaging straight line winds or tornadoes.
The following series of base reflectivity Albany Doppler radar images show the storm shortly after it formed in Montgomery County, when it was over southwest Saratoga County, and after it was absorbed by a squall line over Mechanicville while producing the tornado. (These images are from video screen grabs from the television weather coverage that I did that day.)
Solitary supercell thunderstorm over eastern Montgomery County with a fast moving squall line across southern Herkimer and Otsego counties. This was around 3:30pm
The supercell at this time, roughly 4pm, was over far northern Schenectady and southwest Saratoga counties moving east at approximately 50 mph toward Mechanicville and Stillwater. Funnel clouds had been reported with the storm but no tornado touchdown through this time. A tornado warning was in effect for Saratoga County from the National Weather Service at the time.
This image was about the time the tornado was moving through Mechanicville, around 4:30pm. The supercell at this point had been absorbed by the squall line but the circulation remained in tact and powerful with the storm continuing on through northern Rensselaer and southern Bennington counties. The squall line continued to the New England coast through the afternoon producing widespread severe weather along its path.
ALB SP 2046 AO2A 1 SCT 21 SCT E33 OVC 1/2TORNADO TR 68/63/2712G71/958/ WND 25V32 FUNNEL CLOUD B45 PK WND 32071/2040 TSB17RAB17 PRESRR FRQ LTGCG OHD TS OHD MOV E PCPN 0040=
Decoded
ALB SP 2058 A02A 1 SCT E24 OVC 1TRF 64/63/2219G60/963/ FUNNEL CLOUD E57 WSHFT 2042 PRESRR PCPN 0000=
Decoded
Northeast radar composite around 6:30pm, May 31, 1998 showing the widespread coverage of severe thunderstorms, many of them supercells, across New York northern Pennsylvania, and New England with the outbreak continuing into the night.
The entire severe event finally ended locally by 10:30 pm with the passage of the cold front.
8 pm surface analysis - showing the advancing cold front and pre-frontal trough as well as an intense 988 mb low over SE Canada. The cold front moved east of the region by 11 pm ending the severe weather outbreak.
The Albany National Weather Service issued approximately forty six severe weather warnings for eastern New York and western New England, most of them tornado warnings, the most tornado warnings the Albany National Weather Service forecast office had issued for a single event to date. Doppler radar indicated rotation in most of the storms which formed and moved across the local area, certainly a very rare type of severe weather outbreak for this part of the country. What was even more rare was the initial "High Risk" severe weather outlook from the Storm Prediction Center. It was the first and only (to date) "High Risk" ever issued in the Northeast.
Tornado winds of up to 165 mph produced extensive damage to the Viall Hill section of Mechanicville and Stillwater on May 31, 1998. The photographs show the damage in the Viall Hill area as well as the Route 4/32 area. The roof and many interior walls were blown out of this home with the front lawn littered with debris from other homes
This structure was declared a complete loss with the roof and much of the second floor missing.
This home was in the direct path of the tornado and was completely destroyed. Meteorologist survey tornado damage to rank the intensity of the storm. Damage of the magnitude shown in this photograph indicates an F-3 borderline F-4 tornado on the Fujita tornado intensity scale.
Trees adjacent to this home were twisted apart and stripped of their foliage. An automobile was thrown through the air landing at the base of the trees in a pile of debris.
Only a shell remained of this structure with the roof gone and windows and walls blown out.
Winds of 165 mph stripped this home completely from its foundation reducing it and its contents to debris.
Considerable damage occurred to these buildings facing the Hudson river as the tornado moved towards Rensselaer county.
This Ford Taurus was lifted and thrown several hundred yards landing in this yard.
This small section of the Viall Hill neighborhood was ground zero with the complete destruction of trees and several homes.