The world鈥檚 great seasonal winds have names and international reputations. Think of the chinook, the mistral, the bora. But the UK鈥檚 only wind with a name is little known and strangely exclusive. Called 鈥渢he helm鈥�, it blastsjust one strip of land in north-west England 鈥� desiccating crops, knockingsheep off theirfeetand drivingfarmingfamilies into depression. The deafening roar alone is maddening, but what鈥檚 worse is not knowing when it will stop. It comes out of the blue and can rageforthree hours, three days orthree weeks. If the British have a peculiar outlook on the weather, this eccentric wind must surely be partly to blame. In the1930s, geographer Gordon Manley sought an explanation forthis weird manifestation of a 鈥渢urbulent Nature鈥�.
WHEN the helm wind blows, always from the east, it plummets with devastating force down what was once known as the Fiend鈥檚 Fell 鈥� the highest ridge of the Pennine hills of northern England. Some say its modern name, Cross Fell, dates from a bishop鈥檚 bid to lessen the wind鈥檚 demonic powers by erecting a cross on the summit. If so, the intervention must have been an embarrassing PR disaster for the church. Today no one even attempts to predict the wind鈥檚 arrival, let alone soften its force. But at least there is an explanation for this strange phenomenon, thanks to the courage and curiosity of English geographer Gordon Manley.
So unexpected and powerful is the wind that when the local police force launched its pre-Christmas blitz on crime last year, they dubbed it Operation Helm Wind. Speeding up as it descends the leeward slope of the fell, the wind can reach hurricane speeds during the spring or autumn, forcing walkers to their knees. Breathlessness followed by utter exhaustion soon strikes anyone who tries to defy it. Those in the know steer clear when they see the distinctive 鈥渉elm cloud鈥� appear on the summit of Cross Fell; this helmet-shaped cloud probably gave the wind its name.
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As the wind reaches the valley bottom, it begins to slacken 鈥� but only to turn into severe and damaging gusts. Then, at last, a few kilometres to the west and just short of the river Eden there is a sudden end to the wind鈥檚 violence. Beneath a curious sausage-shaped cloud known as the 鈥渉elm bar鈥�, an eerie calm descends.
Locals say the helm wind never crosses the river. Such lore is often discounted, but Manley took it seriously. For him, local weather knowledge lay at the very foundations of modern science. He suspected that Britons derive both 鈥渕ental stimulation and keenness of perception from their variable climate鈥�. It certainly did the trick for him.
Born in 1902, Manley grew up in the cold and wet north-west of England. Accustomed to in-your-face weather, he took a precocious interest in recording local meteorological conditions. Later, when he delved into the history of his subject, he couldn鈥檛 help noticing the preponderance of eminent scientists and inventors 鈥渂red among the cloudy hills鈥�, and he stuck to his belief that there was something special about folk nurtured in the north-west. Not least, he surmised, 鈥渨ind plays an increasing part in their consciousness鈥�.
Manley discovered geography as a postgraduate at the University of Cambridge, where his interest in bleak, cold places was fostered by Frank Debenham, a geologist who had been to the Antarctic with Captain Scott. Soon, however, he moved back north to Durham, where he set to work on research that would revolutionise our understanding of the peculiarities of the British weather. In his long career, he was also to pioneer the study of climate change.
鈥淲hen the local police force launched its blitz on crime, they dubbed it Operation Helm Wind鈥�
In 1931, newly married and appointed curator of the University of Durham鈥檚 weather observatory, Manley began work on standardising almost a century of temperature records for the city. Long before computers, he laboriously calculated corrections for variations in technique 鈥� a drunken observer of 1854-55 was a particular bugbear. At the same time, he wanted to know what was happening in the hills, so he set up a weather station 鈥� by far the highest in England 鈥� at Moor House, a shooting lodge on the northern Pennines.
In 1937, he decided to tackle the helm wind. He erected a small wooden hut directly in its path, at 848 metres on Great Dun Fell, just south-east of Cross Fell. He visited his extreme shed every few days, a round trip of 193 kilometres by car from Durham and another 13 kilometres on foot across the fells. Over two years, he made more than a hundred visits.
Even in the severest winter weather he stayed on the summit for days at a time. Ice build-up on the equipment was a particular problem, and occasionally the hut itself was completely encased in ice. To this day his observations remain the longest unbroken record of mountain weather conditions, in what proved to be the coldest place in England.
Throughout, the helm wind was irritatingly quixotic, often choosing to blow just when Manley had to be in town. But finally he got the data he needed to understand it. For a start, the prevailing wind must be blowing from the north-north-east or east at a strength of at least force 4 (25 kilometres per hour). And there must also be an inversion 鈥� a layer of warmer air above the hill crest 鈥� to concentrate and speed the flow of cold air beneath it.
Manley likened the airflow down the fells to a stream of water passing over a submerged weir. The result is a standing wave, with the air sinking and rising in the valley, creating a 鈥渞otor cloud鈥� 鈥� the helm bar. Beneath this rotating cloud, the violent easterly helm wind abruptly stops blowing.
In the early summer of 1939 intrepid members of the Newcastle Gliding Club confirmed his findings, exploiting the lift provided by the uprush of air in the standing wave. One pilot, Noel Maclean, reached 11,140 feet (3395 metres), breaking the British altitude record.
In essence, Manley explained, the secret of the helm wind lies in the unique ramp-shape of the Pennine ridge: a gentle upward sloping approach on the east, a solid, unbroken ridge crest and a steep but very long, smooth descent on the western, lee side. Once the air has passed over the ridge, it becomes warmer, drier and faster. With no obstacles to slow its progress on the downward slope, the wind acquires tremendous force. One way to stop it, or at least lessen its impact, would be to plant trees on the leeward slope, suggested Manley.
Today, the western slopes of Cross Fell remain treeless. Manley鈥檚 hut is gone, supplanted by an automated radar station. The hunting lodge at Moor House is dismantled too, replaced by an automatic weather station that transmits data to the UK Environmental Change Network. The helm wind persists, however, and is still a very challenging thing to predict, says Robin Thwaytes, a forecaster at the UK鈥檚 Met Office. Manley, for all his scientific instincts, would probably be pleased. He took particular delight in demonstrating that the UK has some of the most erratic weather in the world.
Yet if the unpredictability of the UK鈥檚 weather entranced Manley, so did its long-term patterns. When he died in 1980 he had just re-analysed decades of data from Moor House to standardise his early records in line with observations collected later. Recently, Joe Holden of the University of Leeds and John Adamson, who manages the Moor House station, used the standardised data to pick up the first signs of climate change in the Pennines from a temperature record that now spans more than 70 years. In the past decade, winter months in particular have grown significantly warmer, with less frequent frosts and fewer days with snow lying. This trend may seem trivial, yet Manley showed that major climatic shifts can be caused by small changes that persist.
Manley knew better than anyone that the climate of his beloved Pennines had radically altered many times before. Ancient tree stumps found in the peat at 830 metres testify to a forest on the flanks of Cross Fell some 4000 years ago. If the climate today continues to warm, the upland ecosystem will be transformed again, with far-reaching consequences for flora, fauna and the entire region鈥檚 water supply. Trees could even return to the Pennines鈥� leeward slopes and perhaps eventually make it to the summit. If nothing else, that event at least might bring relief to the local people by stopping the helm wind in its tracks.
