Each fall, weather across North America typically goes through a transition that signals the end to autumn's often summer-like warmth and the beginning of winter's months of icy chill. Canadian high pressure sweeps increasingly cool air across the northern USA. But, off the East Coast, the Atlantic Ocean, heated for months by the summer sun remains warm. Cool winds blowing over the warm water clash to produce major coastal storms. Mix in a late-season hurricane and the ingredients are there for a stormy brew.

Here's how it happened, creating an extreme nor'easter, in 1991.

The making of a 'perfect storm'

On Oct. 27, 1991, Hurricane Grace formed over the warm Atlantic Ocean southwest of Bermuda. The hurricane continued to grow over the warm waters of the Atlantic. By late on Oct. 28, the storm's 95 mph winds pushed 10 - 15 foot swells towards the coast of the Southeast USA.

Meanwhile, along the East Coast, the weather on Oct. 28 began to show improvement as high pressure moved in behind a cold front that moved off the coast earlier in the day. Along the eastward marching cold front, a new area of spinning low pressure developed just east of Nova Scotia.

On Oct. 29, Grace moved north along the front toward the stalling low-pressure area. Drawing Grace into its large circulation, the low-pressure system exploded into a major storm as it fed off the temperature difference provided by cold, dry air to its northwest clashing with the warmth and humidity from the remnants of Grace.

But it wasn't until this intense low-pressure area moved west toward the USA and then south and east to a point midway between Bermuda and New Jersey that it reached its maximum intensity. At this point on Oct. 30, sustained winds in the storm reached 70 mph, churning the Atlantic into a maelstrom of 40- to 80-foot waves, as reported by a weather buoy east of Long Island, N.Y. Other unsubstantiated observations reported winds and waves considerably higher, including a 101 foot wave measured by a buoy south of Nova Scotia, Canada.

During Oct. 30 - 31, the storm, still churning over the Atlantic, pounded much of eastern North America from North Carolina to Nova Scotia with waves 10 to 30 feet high. High tides along the coast were three to seven feet above normal, exacerbating the storm's effects. Heavy surf and extreme coastal flooding caused extensive damage along the New England and mid-Atlantic coast. Damage estimates in Massachusetts alone reached $100 million. Federal disaster areas were declared for seven counties in Massachusetts, five in Maine, and one in New Hampshire. Coastal flooding and raging seas raked places from Jamaica to Newfoundland, Canada.

The storm continued to churn the Atlantic for another two days before making landfall along the Nova Scotia coast November 2, 1991. As if its tumultuous life was not already enough, the immense mid-latitude storm evolved into a hurricane again when its center moved over the warm waters of the Gulf Stream Nov. 1. Hurricane hunters dispatched to the storm confirmed the transition. But the National Hurricane Center decided not to name the hurricane for fear it would unnecessarily alarm coastal residents that had just weathered a major northeaster, as well as confuse people into thinking it might mean another major storm.

Source: USA Today

The color-enhanced infrared image above taken at 1200 UTC October 30, 1991 depicts a monster storm off the Eastern Seaboard, which was described by the National Weather Service as the "perfect storm." In this image, the storm was at its peak intensity. The storm became subtropical thirty hours later, just before the inner core of the storm developed into a topical storm and later an unnamed hurricane.

Labeled the "perfect storm" by the National Weather Service, the storm sank the sword fishing boat Andrea Gail.

The Andrea Gail

Visit The Perfect Storm Foundation
for more information about the
real Andrea Gail