The Perfect Storm, which portrays the real-life struggle of a fishing boat and its crew against enormous winds and waves, rocked movie theaters around the country. How did the weather conditions make this actual storm so "perfect"?

The movie The Perfect Storm, the book by Sebastian Junger that preceded it, and the actual event that inspired both works share the same name. That name came from meteorologist Bob Case, who helped forecast this once-in-a-lifetime storm in 1991. He was working as the deputy meteorologist in the Boston, Massachusetts, office of the National Weather Service (NWS).

"We had a pretty good idea that something big was in the offing on Sunday afternoon, October 27," Case remembers. "There was an electricity that ran through the office. Many meteorologists are in the field because it is an excitement and a passion. Anytime something like this is forecast, there is going to be that excitement."

What Case and his NWS colleagues were observing was a seldom seen meeting of natural forces 1,000 miles to the east, in the Atlantic Ocean. The storm forming there off the coast of Nova Scotia, Canada, was nothing remarkable in itself. It was following the typical pattern of a "northeaster," a weather system that often affects the eastern coast of the United States and Canada during the fall and winter.

But the enormous high pressure system and unusually cold Canadian air pushing down behind the storm front was setting the stage for a rare event. For starters, the high pressure kept the developing storm far away from any coastline that could diminish its power.

Meanwhile, to the south and east, Hurricane Grace had been collecting large quantities of energy—in the form of moisture and warm air—as it spun past the island of Bermuda. While Hurricane Grace's behavior was typical for the fall hurricane season, what was not typical was its collision with the northeaster off of Nova Scotia and the cold air behind it.

When that collision took place on Tuesday, October 29, the dwindling hurricane donated its massive supply of prepackaged energy to the other storm. "The storm off of Nova Scotia would have been strong in itself," Case observes, "but adding the remnants of Hurricane Grace was like throwing gasoline onto a fire. Every one of these factors fell into place in time and space. Had any of the factors not occurred, the end result would not have occurred."

That end result was a storm that grew vastly in its power and duration. Instead of dying out or moving on after 12 hours, as a hurricane might, this unnamed storm exploded and continued to churn for more than 3 days. The clash of the high pressure system with Hurricane Grace's exceptionally low pressure created severe winds.

"The greater the change in pressure, the stronger the winds," Case notes. And while the wind speed did not get much higher than 70 miles per hour, the effect of the wind on the Atlantic Ocean was remarkable:

By now, if you haven't seen the movie, you've probably caught the commercial for The Perfect Storm. As the rain falls torrentially and the wind roars ceaselessly, the ill-fated swordfishing boat Andrea Gail struggles at the bottom of an enormous wave about to crash down. This scene was created for the screen by the advanced technology of George Lucas's Industrial Light and Magic company. (Learn more about Industrial Light and Magic in the Riverdeep Today article, "Making the Most of Visual Effects.")

But in the case of the 1991 storm, the forces of nature matched anything a Hollywood studio could create. According to Case, one ship reported a 78-foot wave. "The storm created an abnormal wave system," he explains. "The period between each wave—the space between one peak and the next—became shorter and shorter. If you take that distance from peak to peak and cut it in half, that makes conditions extremely difficult for ships. Unfortunately, the Andrea Gail could not have been in a worse place at a worse time."

This storm may have been centered 1,000 miles out to sea, but its effects reached the East Coast:

• Winds along North Carolina reached 45 mph for 5 consecutive days.
  

• Waves 30 feet high hit the beaches from North Carolina all the way north to Nova Scotia, Canada.
  

• A wind gust of 74 mph was recorded on Cape Cod, Massachusetts, where the relentless pounding of the sea eroded more of the beach than at almost any other time in the past century.
  

• Coastal flooding extended all the way south to the islands of Puerto Rico and the Bahamas.

More Links

• The National Climatic Data Service has created its own site examining the events of "The Perfect Storm."

Related Resources

• Get Sebastian Junger's best-selling book, The Perfect Storm.