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Cool Breeze
Posted: Friday, November 10, 2017 2:42 PM
Joined: 19/08/2014
Posts: 67

Well into a successful charter season, M/Y Downdraft’s captain made it his mission to discover the dramatic coastline’s untouched anchorages in the first few weeks. In doing so, he now had an in-depth knowledge of the most picturesque spots to wow charter guests. The crew were getting better every week at dropping the hook in challenging spots close to the shore and taking a very big yacht into some extremely tight spots. With steep sided terrain, it made for some impressive anchorages for the guests.
The conditions since the season’s beginning had been almost perfect — light winds building around 11 in the morning and dropping off around four or five in the evening. The schedule each day involved cruising to a new spot for swimming and lunch, then moving to another new spot to drop the hook for the night or occasionally docking in a marina. Impressed by the captain’s little black book of anchorages most perfect, the guests’ own itineraries were going out the window in favor of off-the-beaten track locations and a wilderness they didn’t know existed.
Halfway through a weeklong charter, M/Y Downdraft dropped anchor in the most impressive location yet — a high-sided valley on the remote southwestern coast of a mountainous island. Sheltered and completely deserted, the guests swam and went ashore in the tender to take pictures of the yacht in its most scenic location yet. Planning to stay just for lunch, the captain was surprised when the guests announced they wanted to stay overnight. Anchoring in such a narrow inlet was perfectly safe in calm conditions, but involved lines tied ashore and left little room for error. Staying overnight would be fine, but if the weather was to change, life would become quite difficult for the crew. He reviewed the forecast and with a high pressure in place, nothing was obvious to create concern; besides, it was just for that one night.
Later that afternoon, M/Y Downdraft suddenly found itself in 50 knots of offshore wind in the space of 10 minutes. Doing everything they could to pack up the toys and escape what was certainly no longer an ideal spot, the wind was bitingly cold and came rushing down the valley on top of them.
“Katabatic winds are known for catching people out, but are often misunderstood,” says Stokey Woodall, an International Ocean Services meteorologist and experienced instructor. “They can be the product of very fair weather, i.e., a particularly warm, sunny day, combining with very cold air on land at the top of a mountainous region. The cold air is then drawn down the slope at high speed, accelerating even more in valleys, and reaching very high speeds as it goes across the water, often in gusts.”
M/Y Downdraft dropped her shorelines and brought the anchor aboard as quickly as possible, working her way out of the anchorage into a choppy sea state. The guests looked relieved, and it was obvious to all on board that they had been lucky to escape such a tight spot without doing any damage to the yacht or crew.
“The telltale signs of a katabatic wind coming are few and far between. Avoiding one is about recognizing the conditions [that] make them possible,” explains Jim Dale, owner and senior meteorologist at British Weather Services, a professional forecasting and routing service. “If you are anchored at the foot of a valley and a katabatic wind flows down through it, the effect will be amplified further. What you’re likely to feel is a rush of sudden cold air, seemingly from nowhere.”
Formerly a Royal Navy meteorologist, Dale describes his own experience of a katabatic wind anchored off the Falkland Islands. “We anchored in very clear conditions, under a full moon, with high pressure, and a seemingly stable night ahead. What we woke up to was the ship swinging right round its anchor [with] winds in excess of seventy miles per hour; something that lasted around thirty to forty minutes before abating very suddenly. The captain was woken up, and we had to react fast; it’s an experience that really sticks in my mind,” Dale says. “In those very clear conditions, it’s something always worth considering might be possible if you have a mountainous landmass near to you. In the case of that ship, we were at the foot of a very cold glacial slope; another catalyst to even stronger katabatic winds due to the bigger than usual temperature differential.”
“Katabatic winds [are] experienced in lots of places,” adds Stokey. “In some places, like the Canary Islands, they are common and predictable, but it’s where they are possible, but not so common, that the effect can be lethal and catch people out. The true katabatic winds generally involve extremes — big differences in pressure between the top of the land and at sea level [or] a big difference in temperature [with] topographical factors added in to further amplify the effect. If you head out to sea the same distance as the height over land from which the wind originates, you’ll no longer feel the effect.”

Once out at sea, the conditions soon started to abate and the fair weather returned very quickly. However, the guests, captain, and crew were no longer so keen on ambitious anchorages, despite clear conditions. It was a lucky escape from their first katabatic encounter and an education in an unusual weather phenomenon.