By midnight, a cluster of fasting-moving thunderstorms which meteorologists would describe as a Derecho had developed ahead of that front along the Niagara frontier. That cluster swept east through Rochester and Syracuse, then on into the Mohawk River Valley during the early morning hours of Monday, September 7. The Derecho continued into southern sections of Vermont and New Hampshire.
Significant thunderstorm wind damage was reported from Rochester and Syracuse east through Gloversville and Charlton. Nickel sized hail was reproted in several towns from Old Forge east through the southern Adirondacks. Winds of 80 to 90 mph were measured as the storms passed. The Derecho began its damage path on the Niagara frontier around 11:30 PM and reached western New England by 4 AM.
On Labor Day afternoon, a much anticipated intense squall line traversed the New York City Metropolitan Area including Long Island. The north to south oriented line was spawned by the same strong cold front which caused the upstate damage earlier in the day. Temperatures were near 90 when the squall line moved in from New Jersey. The storms moved from New Jersey east into Staten Island at first, with winds recorded as high as 80 mph. The storms quickly enveloped the remainder of the New York City region as they propagated eastward at 40 to 50 mph.
The damage resulting from the storms has been classified as primarily straight-line wind damage by the National Weather Service. There was one confirmed tornado in the Lynbrook area of Nassau County that resulted in an enhanced path of damage in that region.
The National Weather Service provided outstanding service to the public during this event that potentially resulted in the savings of many lives. The National Weather Service had advertised that severe weather was likely for Monday for more than 24 hours. Outlooks issued in the wee hours of Monday told the public and the media exactly what to expect. A severe weather watch was issued one and a half to three hours in advance of first reports of damage with warnings being issued on average 15 to 20 minutes before.
Map of Storm Damage and Hail Reports