A multiscale examination of the 31 May 1998 Mechanicville, New York, tornado

On 31 May 1998, an F3 tornado struck Mechanicville, New York, injuring 68 people and causing $71 million dollars in damage. The tornado was part of a widespread, severe weather outbreak across the Northeast United States. The synoptic conditions that spawned the outbreak and the mesoscale and storm-scale environments that produced the Mechanicville tornado will be examined.

The coupling of two strong upper-level jets and a very strong low-level jet in association with an unseasonably strong surface cyclone, created a synoptic scale environment favorable for severe weather. The upper-level jets created strong atmospheric forcing, while the low-level jet provided the mechanism to transport rapidly, a very warm, moist air mass into the Northeast, and increased the vertical shear in the lower troposphere. Additionally, terrain channeling of the low-level southerly flow up the Hudson Valley may have created a mesoscale environment that was especially favorable for tornadic supercell development. A line of locally severe thunderstorms moved eastward across New York several hours prior to the tornado. The storm that produced the Mechanicville tornado developed over central New York ahead of this line of storms. Just prior to the tornado formation, outflow from the line to the west merged with the lead storm, suggesting that a boundary interaction may have contributed to supercell intensification and tornadogenesis.