`Meteorologists see perfection in strange things," writes Sebastian Junger in The Perfect Storm, , the book on which the current film of that name is based. "And the meshing of three completely independent weather systems to form a hundred-year event is one of them."
But Junger himself, it must be said, sees strange things in meteorology. He describes, for example, the forecasters of the National Weather Service as the storm approaches as being - need I say implausibly - "most of them seated at heavy blue consoles, staring resolutely at columns of numbers - barometric pressure, dewpoint, visibility - scrolling down computer screens".
He also tells us, with an accuracy which is at once unverifiable and irrefutable, that "the air above one square foot of equatorial water contains enough latent energy to drive a car two miles". But never mind all that. Junger's central thesis more than compensates, and he provides us with a gripping narrative well laced with a wealth of serendipitous weather information.
The "perfect" storm is the so-called "Halloween Storm" that ravaged the east coast of the United States for five days in late October and early November 1991. The story concerns one of the casualties, a fishing boat, the Andrea Gail.
And the "three completely independent weather systems" were an anticyclone over southeast Canada, a depression moving north-eastwards along its southern flank across New England, and the remnants of a dying hurricane called Grace.
The first two of these on their own would have been sufficient to produce a storm of great severity. In late October great masses of cold air surge southwards over western Canada to meet the warmer air still lying over the Atlantic, and the temperature contrast fuels fast-developing depressions. A stubborn "blocking high", strategically placed, enhances the gradient of pressure, and thereby strengthens winds.
But the third ingredient was crucial to explosive deepening. Long after the winds of a Caribbean hurricane have died away, a pocket of unusually warm and very moist air frequently survives to be carried northwards in the upper atmosphere. If this warm, humid air is absorbed into the circulation of an "ordinary" depression, it may add enough energy to cause a dramatic intensification of the low.
It happened here when "Hurricane" Debbie arrived in Ireland in September 1961. Likewise, the extinct hurricanes Isodore and Gustav contributed their residual energy to violent Irish storms in September 1990. And, of course, most of us remember "Hurricane" Charley in August 1986.
It was a similar rejuvenation of a very ordinary depression by hurricane Grace in late October 1991 that produced The Perfect Storm. .