Memorial Day Tornado of 1995

Radar Images (click to view full image)

Violent (F4 and F5) tornadoes are relatively rare in the northeast United States, but they do occur. The most recent occurred last Memorial Day when an F2 tornado ripped across Columbia County, New York. The tornado lifted as it approached the Massachusetts border. A short while later, an F3 to F4 tornado caused major damage across southern Berkshire County, Massachusetts.

The deadliest tornado in the Northeast, an F4, killed 94 people in Worcester, Massachusetts, in June 1953. In August, 1973, another F4 tornado struck Stockbridge, Massachusetts, killing 4. More recently in July, 1989, an F3 tornado moved across Schoharie County New York. The same thunderstorm complex that produced the Schoharie County tornado, later generated an F4 tornado in Hamden, Connecticut.

In addition to studying the meteorological conditions that produce violent tornadoes, meteorologists are studying the role that topography plays in their formation and intensity. New York and western New England possess complex topography. We have the Catskills, the Adirondacks and the mountains of western New England. The mountain ranges are separated by the Hudson and Mohawk River Valleys. To the west, Lake Ontario is the source of lake breezes that can help initiate summertime convection.

The State University of New York at Albany (SUNYA) has joined the NWS in a Cooperative Program for Operational Meteorology, Education and Training (COMET) project to study the Memorial Day 1995 tornado. In particular, we will be looking at the hypothesis that terrain channeling, by the Hudson Valley can on occasion create unusually favorable conditions for severe weather. In the Memorial Day Storm, it appears the Hudson Valley played a key role in the storm's intensification.

At about 330 pm EDT on May 29, 1995, a thunderstorm developed over central New York, a little northwest of Binghamton. The storm moved to the east during the next few hours crossing the Catskills and reaching the Hudson Valley just before 630 pm EDT. During the 3 hours the storm produced isolated reports of severe weather. When the storm reached the Hudson Valley it encountered air that was especially favorable for severe thunderstorm and tornado development. Very moist air (dewpoints in the mid to upper 60s F) flowing northeast from New Jersey and eastern Pennsylvania was funneled northward up the Hudson Valley. The added moisture made the air very unstable.

The wind flow in the lower atmosphere that day was from the southwest. However, since the Hudson Valley is oriented north to south, low level winds in the valley were more southerly. Turning the winds near the ground from southwest to south, increased the clockwise turning of the wind in the lower atmosphere. This increased turning of the wind and added instability, caused rapid strengthening of the thunderstorm as it reached the Hudson Valley. A tornado touched down in Columbia County at 640 pm EDT.

The National Weather Service's WSR-88D (Doppler radar) provided information on wind movement in the storm. Archived radar data was used to calculate the change in wind (shear) across the thunderstorm. As this shear value increases the strength of the storm's rotation increases. As the storm moved from central New York through the Catskills there was little change in the observed shear. However, when the storm reached the Hudson Valley there was a large increase in shear, indicating rapid intensification.

The first tornado lifted at 700 pm EDT. There was a large drop in the shear, shortly before the tornado dissipated. It appears that the area of high terrain in the southwest corner of Massachusetts, may have cut off the inflow of warm, moist air into the storm. Once the storm emerged into the valley to the east (where Great Barrington is located), it once again intensified and produced an F4 tornado.