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Technically Speaking: The Beaufort Scale

On a perfect wreck-diving day of infinite clear skies and mirror calm seas, there's nothing better than a smooth run out to site, an easy dive, a beautiful wreck and current-free deco; before finning gleefully back to the boat to leisurely peel out of your gear and relish the sunshine.

We've all had those dream runs where the sea is glass, the vis like mountain air and the only waves are the repercussions of melting ice as you raid the esky. On magic days like this, it's hard to imagine it being any different. In fact, it can be so complacency-inspiring and blissfully, reassuringly calm that it can be nigh impossible to even imagine storms, meteorological or other ocean ferocities that were perhaps responsible for sinking the wreck in the first place...

But first, a refresher on the Beaufort Scale: that interminable 200+ year old grading system used to rate wind speed against observed conditions at sea. The scale was designed in 1805 by one Admiral Sir Francis Beaufort, who saw a need to standardise some otherwise subjective descriptions of weather conditions (were mariners of the early 1800's prone to a little creative embellishment, perhaps??).

It was targeted at the sail ship Captains of the time, who would systematically draw in their sails during incremental weather, but describe the conditions in any variety of adjectives and intensity. The scale worked via a very basic rule of thumb: Subtract from '13' however many sails you still had up, and that is your rating. Nice and simple. So if you had the usual 13 sails, and all 13 were still up, then "13-13 = 0" (ie; those dream conditions described earlier). But if the winds were whipping and you'd taken in all but one sail to protect them during extreme conditions, then "13-1 = 12", and you'd better be hanging on tight to something.....this '12' ranking is categorised by 64+ knot winds (118km/h), huge 46ft (14m) seas and earns itself a "Category One" on the Saffir-Simpson Hurricane Scale.

The scale was adapted over the years to account for the decline in sail ships and the onset of steam, engine and fuel technology; then extended out from 0-12 to 0-17, with those scary later ranges addressing similarly scary tropical cyclones and typhoons. Put "Beaufort Scale" into your favourite search engine and you'll get a whole array of charts and illustrations to get a better idea of the sequence of deteriorating conditions.

So now back to how this relates to wreck diving and diver's imagination....

During the recent library-time stage of some on-going shipwreck research, it was reported in the archives that during the afternoon in the area the ship 'went down in a storm', conditions were "9-10 on the Beaufort Scale". They might not sound like big numbers, but then depending which version of the Beaufort Scale you're reading, all the descriptions are along the lines of;

"....Strong Gale to Storm Force Winds of 41-55 knots (78-107km/hr)... seldom experienced inland.... the surface of the sea takes on a white appearance...wave heights of 23-41ft (7-12m)...."

Most people's idea of a storm these days is completely passive - we close the windows and wait out the rain with a DVD and a hot dinner, all from the warmth and safety of home. But suddenly, a ship just going 'down in a storm' takes on a new level of significance when you can try to picture real waves and racing winds, and what that actually means the unfortunate crew were trying to survive. If you are reading this during a surface interval or run to/from a site from the sunny safety of a dive boat on a dreamy "Beaufort 0" day, try for a moment to imagine being at the other end of the scale. Try to imagine being a deckie or an engineer, on-board a merchant vessel out at sea, and suddenly caught out in those nightmarish "Beaufort 9" conditions as reported for the ill-fated crew mentioned earlier. Imagine those smooth blue seas raging white at heights taller than your house, and winds so fast and violent as to whip away even the sound of the alarm to abandon ship. Imagine the fury and ferocity of a storm so powerful that all the tools and technology we use to convince ourselves that we are safe and powerful are suddenly worthless and heading to the ocean floor in futility.

Many of the wrecks we dive met their fate long before improvements in technology for weather prediction and communication systems. Mariners have always been at the mercy of the elements - the sea can be as wild as it can calm, and we should be under no complacent illusion that we have any sort of control or even ability to accurately predict constantly changing conditions. It's this untameable power of the ocean which makes it so mesmerising for most of us in the first place, and many wrecks serve as testament to the consequences of being at sea when the forces of the ocean lash up the Beaufort Scale.

The sailors and crews of the ships we now dive for fun and recreation went through anything but that as their vessel was swallowed up by the sea in conditions of almost unimaginable terror. So next time you're diving a wreck that fell to a storm, spare a thought for the crew and what was actually going on during the intense conditions in those eternal final hours - they were surely not the serenely peaceful resting place you're seeing now.

Revere the sea, and as always, respect the wreck.

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