High Wind Event (Curtis Lumber Yard
An early morning high wind event struck portions of eastern New York, from the Catskills and Schoharie valley east into the Capital Region and southern Vermont, and north into the Adirondacks. The first reports of high wind and damage were received at 5:30 am in the western Catskills, with the strong wind moving through the Capital Region between 6:15 am and 7:00 am, and finally into southern Vermont by 7:30am.
A strong cold front associated with high wind in the low and mid levels of the atmosphere was the primary culprit in developing showers and t-storms in the Ohio valley on the 20th which spread east, in much weakened form, to produce the local high wind early on the 21st.
Typically, the low levels of the atmosphere cool sufficiently at night, especially during the cooler months, to produce a temperature inversion. (Cool air near the ground, warmer air aloft.) When a temperature inversion is present, the atmosphere is considered quite stable and not mixed. In cases when there are inversions, strong winds that may be present in the low or mid levels of the atmosphere cannot be transported down to the ground to form strong surface wind gusts. In this case, however, the atmosphere over New York and western New England remained warm, somewhat humid, and well mixed, due to southerly winds and cloud cover, preceding the cold front, through the night. Temperatures did not fall lower than the mid 60's, mild for late September. The lack of any substantial inversion present over the region during the morning set the stage for strong downbursts of wind that developed in the showers associated with the cold frontal passage.
The convection itself was not particularly impressive and in fact was weakening as it pushed into eastern New York early on the 21st. However, strong winds, of about 70 mph, existed very low in the atmosphere, at the 5000 to 6000 foot level. The updrafts and downdrafts in the showers interacted with the high momentum air just off the surface and very effectively mixed those strong winds down to the ground in the form of a strong gust front. That gust front whipped through the region with winds on average of 50 mph, for a ten to fifteen minute duration, downing trees and power lines in some communities. There was very little if any lightning and thunder with the showers, indicating that the vertical extent to the convection and strength of the updrafts were not particularly strong. Had the high wind, associated with the parent cold front, not existed just above the surface, these showers would have come through the area with very little fan fare.
An interesting micro severe weather event occurred within the larger wind area, that produced extensive damage, much more extreme than was witnessed in any other parts of the area, to the Curtis Lumber facility in Ballston Spa, Saratoga county. The cause of the extreme wind damage at this location was something called a gustnado. Essentially, the shower approaching Ballston Spa, at 6:20 am, produced a powerful microburst of wind that, due to some local effect, rotated as it hit the ground, forming a brief vortex that enhanced the wind and hence the damage in the lumber yard. Winds likely with this gustnado were in the 70 to 100 mph (F-0 on the Fujita tornado intensity scale) range for thirty to forty five seconds. A gustnado is a type of very small tornado, but formed very differently from a more classic tornado such as the type that moved through Mechanicville on Memorial Day, 1998. Gustnado's are formed on the leading edge of t-storm outflows and are part of the downburst. Tornado's of the type that occurred in Mechanicville are produced by rotating thunderstorms and have a deep layered circulation, quite evident on Doppler Radar. Gustnadoes occur very low in the atmosphere and are of such short duration that radar typically can not see them very well or at all making these events almost impossible to warn for.
The table below is a listing of National Weather Service as well as WeatherNet 6 wind and damage reports from this event.