token breakfast he checked a couple of addresses in his notebook, then went into the town. When he arrived back at the Imperiale to pick up Julie he was very thoughtful and inclined to be absent-minded, so there was little conversation as they drove to Cap Sarrat in the car he had hired. They were halted briefly at the gates of the Base, but a telephone call from the guardroom soon released them, and a marine led them to Wyatt’s office.
Julie looked curiously at the charts on the walls and at the battered desk and the scuffed chairs. ‘You don’t go in for frills.’
‘This is a working office,’ said Wyatt. ‘Please sit down.’
Causton examined a wall chart with some misgivings. ‘I’m always baffled by boffins,’ he complained. ‘They usually make the simplest things sound hellishly complicated. Have mercy on us poor laymen.’
Wyatt laughed, but spoke seriously. ‘It’s the other way round, you know. Our job is to try to define simply what are really very complex phenomena.’
‘Try to stick to words of one syllable,’ pleaded Causton. ‘I hear you went to look at a hurricane at first hand the other day. It was more than a thousand miles from here – how did you know it was there?’
‘That’s simple to explain. In the old days we didn’t know a hurricane had formed until it was reported by a ship or from an island – but these days we’re catching them earlier.’ Wyatt spread some photographs on the desk. ‘We get photographs from satellites – either from the latest of the Tiros series or from the newer Nimbus polar orbit satellites.’
Julie looked at the photographs uncomprehendingly and Wyatt interpreted. ‘This tells us all we need to know. It gives us the time the photograph was taken – here, in this corner. This scale down the edge gives the size of what we’re looking at – this particular hurricane is about three hundred miles across. And these marks indicate latitude and longitude – so we know exactly where it is. It’s simple, really.’
Causton flicked the photograph. ‘Is this the hurricane you’re concerned with now?’
‘That’s right,’ said Wyatt. ‘That’s Mabel. I’ve just finished working out her present position and her course. She’s a little less than six hundred miles south-east of here, moving north-west on a course that agrees with theory at a little more than ten miles an hour.’
‘I thought hurricanes were faster than that,’ said Julie in surprise.
‘Oh, that’s not the wind-speed; that’s the speed at which the hurricane as a whole is moving over the earth’s surface. The wind-speeds inside this hurricane are particularly high – in excess of 170 miles an hour.’
Causton had been thinking deeply. ‘I don’t think I like the sound of this. You say this hurricane is south-east of here, and it’s moving north-west. That sounds as though it’s heading directly for us.’
‘It is,’ said Wyatt. ‘But fortunately hurricanes don’t move in straight lines; they move in curves.’ He paused, then took a large flat book from a near-by table. ‘We plot the paths of all hurricanes, of course, and try to make sense of them. Sometimes we succeed. Let me see – 1955 gives an interesting variety.’
He opened the book, turned the leaves, then stopped at a chart of the Western Atlantic. ‘Here’s 1955. Flora and Edith are textbook examples – they come in from the southeast then curve to the north-east in a parabola. This path is dictated by several things. In the early stages the hurricane is really trying to go due north but is forced west because of the earth’s rotation. In the latter stages it is forced back east again because it comes under the influence of the North Atlantic wind system.’
Causton looked closely at the chart. ‘What about this one?’
Wyatt grinned. ‘I thought you’d spot Alice. She went south and ended up in North Brazil – we still don’t know why. Then there’s Janet and Hilda – they didn’t curve back according to theory and went clear across the Yucatan and into North Mexico and Texas. They killed a lot of people.’
Causton grunted. ‘It seems to me there’s something wrong with your theory. What about this wiggly one?’
‘Ione? I was talking about her only yesterday. It’s true she wriggled like a snake, but if you smooth her course you’ll see that she fits the theoretical pattern. But we still don’t know exactly what makes a hurricane change course sharply like that. I have an idea it may be because it’s influenced in some way by a high-altitude jet stream, but that’s difficult to tie in because a hurricane is very shallow – it doesn’t extend more than a few thousand feet up. That’s why contact with land destroys it – it will batter itself to death against a ridge, but it does a lot of damage in the process.’
Julie looked at the lines crawling across the chart. ‘They’re like big animals, aren’t they? You’d swear that Ione wanted to destroy Cape Hatteras, then turned away because she didn’t like the land.’
‘I wish they were intelligent,’ said Wyatt. ‘Then we might have a bit of luck in predicting what they’re going to do next.’
Causton had his notebook out. ‘Next thing – what causes hurricanes?’
Wyatt leaned back in his chair. ‘You need a warm sea and still air, and you will find those conditions in the doldrums in the late summer. The warm air rises, heavy and humid, full of water vapour. Its place is taken by air rushing in from the sides, and, because of the earth’s rotation, this moving air is given a twist so that the whole system begins to revolve.’
He sketched it on a scrap pad. ‘The warm air that is rising meets cooler air and releases its water vapour in the form of rain. Now, it has taken a lot of energy for the air to have lifted that water vapour in the first place, and this energy is now released as heat. This increases the rate of ascent of the air – the whole thing becomes a kind of vicious circle. More water is released and thus more heat, and the whole thing goes faster and faster and becomes much bigger. As much as a million tons of air may be rising each second.’
He drew arrows on the scrap pad, spiralling inwards. ‘Because the wind system is revolving, centrifugal force tends to throw the air outwards, and so the pressure in the centre becomes very low, thus forming the eye of the hurricane. But the pressure on the outside is very high and something must give somewhere. So the wind moves faster and faster in an attempt to fill that low pressure area, but the faster it moves the more the centrifugal force throws it outwards. And so we have these very fast circular winds and a fully fledged hurricane is born.’
He drew another arrow, this one moving in a straight line. ‘Once established, the hurricane begins to move forward, like a spinning top that moves along the ground. This brings it in contact with more warm sea and air and the process becomes self-sustaining. A hurricane is a vast heat engine, the biggest and most powerful dynamic system on earth.’ He nodded to the chart on the wall. ‘Mabel, there, has more power in her than a thousand hydrogen bombs.’
‘You sound as though you’ve fallen in love with hurricanes,’ said Julie softly.
‘Nonsense!’ Wyatt said sharply. ‘I hate them. All West Indians hate them.’
‘Have you had a hurricane here – in San Fernandez?’ asked Causton.
‘Not in my time.’ said Wyatt. ‘The last one to hit San Fernandez was in 1910. It flattened St Pierre and killed 6,000 people.’
‘One
