Catabatic wind is a dense, cold air flow descending down slopes under the influence of gravity. In simpler terms, when air at elevations (mountains, plateaus, glaciers) cools significantly, it becomes heavier and begins to "slide" downward into valleys or towards the coast. Such wind is sometimes called a falling wind or drainage wind. It most often occurs at night when the land cools and chills the adjacent air. The cold air at the slope's peak is denser than the warmer air below, causing it to rush down the terrain. Unlike foehn (dry westerlies) or shamal winds, which warm up as they descend, catabatic winds retain their low temperature and carry cold.
Catabatic winds vary in scale. They can range from a light nighttime breeze from the shore (essentially a small drainage of cold air) to a genuine storm air flow from the mountains reaching hurricane strength. For sailors, yachting courses are important because they can suddenly surge in certain areas, although this is not always apparent in general weather forecasts. Let's take a closer look at how and why catabatic winds arise, where they are encountered, and why they are dangerous for seafarers.
How Does a Catabatic Wind Arise?
A catabatic wind (blue arrow) forms when cold, heavy air rushes downward from an elevation under the influence of gravity. The diagram shows a flow of cold air from the Antarctic ice plateau towards the ocean.
The main reason for the formation of a catabatic wind is the difference in air density over the slope. This usually occurs when the air cools at elevation. For example, at night, the ground and mountain slopes rapidly lose heat (especially if the sky is clear and the wind is weak), causing the air near the surface to cool. The cold air becomes denser and heavier than the warm air and begins to flow downward — this is the catabatic flow. Gravity "pulls" the cold air mass down the slope into the valley or towards the sea.
Sometimes, the catabatic wind is intensified by a large reserve of cold at the peaks. This happens on glaciers and snow-covered plateaus: the air above them is constantly cooled by the icy surface. Such a glacial wind can blow continuously, day and night. In Antarctica, for example, cold air flows from the interior ice shield towards the continent's edges, forming constant strong flows. The wind accelerates as more cold air "flows" into the stream while descending. In narrow mountain valleys, the effect is amplified — the air accelerates like in an aerodynamic tube in the gorges and at their exits.
It is important to note that not every wind from the mountains is catabatic. If the descending air warms up (over land, due to compression under falling pressure), such wind is called a foehn (for example, a warm dry wind from the mountains on the leeward side). A catabatic wind, on the other hand, initially has a source of cold — cooling at altitude. Thus, the key conditions for a catabatic wind are: the presence of an elevation (mountains, plateaus), sharp cooling of the air above (at night, in winter, or over ice), and the ability for this air to flow downward (weak background wind, open valley or slope towards lowlands).
Where and When Are Catabatic Winds Encountered?
Catabatic winds are a local phenomenon but widespread worldwide. In any region where there are mountains or elevations near lowlands or the sea, under suitable conditions, such descending flows can arise. They are usually observed during the cold part of the day or year — at night, early morning, winter, when cooling is strongest. Here are a few typical situations and places where catabatic winds occur:
- Mountain Valleys – at night, mountain slopes cool, and cold air flows into the valley. Many sailors, staying overnight on the shores of fjords or under a mountainous coast, note that by dawn a cool wind blows from the shore — this is a classic nighttime land-to-sea breeze, catabatic by nature. During the day, the sun warms the slope, and the wind changes to an anabatic (rising up the slope) wind, but at night, the cold flow from the mountains descends again.
- Winter in Continental Areas – over plateaus or plains, a cold anticyclone sets up, and air flows from the elevation towards the warmer coast. Often, strong catabatic winds occur in coastal zones of temperate latitudes: cold air from the mainland rushes towards the relatively warm sea. For example, in Northern Europe during winter, cold air can flow down from the Norwegian or Scottish highlands towards fjords and the coast, causing strong gusts on the shore.
- Polar Regions – the most powerful and persistent catabatic winds are observed in Antarctica and Greenland. The enormous ice caps of these regions act as "refrigerators," from which air flows to the edges. In Antarctica, winds at coastal stations with speeds of 50–100 m/s (up to 200–300 km/h) are not uncommon during strong catabatic storms. In Greenland, the catabatic wind is known as pitaraak — it originates on the ice plateau and rushes down to the eastern coast.
A NASA satellite image (MODIS) shows a powerful air flow off the eastern coast of Greenland (a blurred gray strip over the dark sea surface) — this is the cold storm wind pitaraak descending from the glacier. Such winds can reach hurricane strength and carry snow and ice far into the ocean.
As seen in the Greenland example, the catabatic wind is especially strong when the following conditions are combined: clear weather (the atmosphere loses heat through radiation), the presence of a cold highland (glacier), and proximity to the sea or lowlands where the air flows. Pitaraaks in Greenland often occur when a high-pressure area stands over the ice shield, and a cyclone approaches the coast. The cold air accumulated over the ice rapidly "breaks" downward to the low-pressure zone at the shore. Locals are very wary of pitaraaks — the word piteraq in Greenlandic means "that which attacks." Meteorological services in Greenland and Denmark (DMI) even issue special storm warnings for pitaraaks.
In addition to polar regions, catabatic winds are also known in warmer latitudes — in areas of the Mediterranean Sea, North America, Asia. They usually have local names. Below we will consider the most famous catabatic winds in the world and their features.
Famous Catabatic Winds of the World
Mistral
The mistral drives dust and foamy surf on the coast of Marseille (southern France). A mountain range from the north and the Rhône Valley act like a "pipe," accelerating this wind towards the Mediterranean Sea.
The mistral is a strong cold northwesterly wind blowing in the Provence region (southern France) through the Rhône Valley towards the Mediterranean Sea. It occurs when a high-pressure area sets over central France, and a low-pressure area is over the western Mediterranean (the so-called "Genoese depression"). Air rushes from north to south and, breaking through the mountain passes of the Central Massif and the Rhône Valley, accelerates to storm levels. The average daytime speed of the mistral can reach ~50 km/h (≈27 knots), with gusts over 90 km/h (up to 25 m/s, ≈49 knots). The wind is especially strong in winter and spring, after cold fronts pass, and can blow for several days in a row. The sky is usually clear during the mistral, the air is transparent and dry — but the sea has high, short waves.
For sailors, the mistral is one of the most formidable winds of the Mediterranean. It starts suddenly after calm or a light breeze, while the weather remains sunny, which can mislead inexperienced seafarers. Literally within hours, the strongest wind and 2–4-meter waves rise in the Gulf of Lion (the area between the French coast and Corsica). There are many cases when the mistral damaged yacht masts and sails, tore poorly secured boats from anchors. Therefore, when planning crossings in Provence and Liguria, skippers need to carefully monitor the forecast: if a mistral is expected, it's better to wait it out in a reliable marina or shelter. If caught out at sea — it's necessary to quickly furl the sails (or at least set minimal reefing) and seek shelter on the leeward (eastern) side of islands or bays.
Bora
A Sentinel-2 satellite image shows the effect of the bora: parallel lines of foam on the surface of the Adriatic Sea off the coast of Croatia. On the day of the image, bora gusts exceeded 100 km/h, the wind blew from the mainland (top right) through the mountains to the island of Pag and then into the sea.
The bora is a gusty north or northeast wind on the Adriatic Sea coast (Croatia, Slovenia, Montenegro, northeast Italy). It is also categorized as catabatic: cold air from the Balkan Peninsula flows through the mountain passes of the Dinaric Alps towards the sea. The bora is most characteristic in winter when a cold anticyclone stands over Eastern Europe, and a low-pressure area is over the Adriatic. The wind blows in bursts, with individual gusts being incredibly strong. In the zone from Trieste to northern Dalmatia, bora gusts are among the strongest in the world — speeds exceeding 200 km/h have been recorded during the most powerful jets (equivalent to >100 knots). More common values are 80–150 km/h in turbulent gusts along the coast and in straits. In open sea, the bora noticeably weakens, although it can still maintain a strong storm wind there.
The bora is dangerous due to its suddenness and destructive power. It often arrives after relative calm in clear, cold weather. In the Croatian mountains, the appearance of special "cap" clouds over the Velebit ridge is a reliable sign of an approaching bora: cold air is already "spilling" over the crest. For sailors, the bora is a serious challenge. This wind surges down the mountains in gusts, so even with moderate average wind, gusts can greatly exceed it. There are known cases when the bora overturned small boats in port and tore yachts from moorings. In the Kvarner Gulf, bora gusts knocked people off their feet on the promenades. When sailing in the Adriatic, every captain must consider the bora: if a bora is forecast, it's better to stay in a sheltered marina or a reliable bay protected from the northeast. The southern sides of large islands are well protected (wind shadow). When anchored, give a large extra length of chain (5–7 scopes) and check the bowline, or better yet, set two anchors. In a marina — double the moorings. If the bora catches you on the way, urgently furl the sails and, if possible, drift or move to shelter under engine power. Remember that a bora often lasts more than a day, with short "attacks" repeating for several days.
Other Known Catabatic Winds
In addition to the mistral and bora, there are many local catabatic winds around the world with their own names. Here are a few examples:
- Pitaraak (Greenland) – we already discussed it above. A glacial storm wind that rushes down from Greenland's ice shield to the eastern coast. The name translates to "attacking wind," reflecting its dangerous nature. Pitaraaks usually occur in winter; when they appear, the air temperature can drop sharply, the sky remains clear, and the wind reaches hurricane strength, causing destruction in coastal settlements.
Dust plumes stretch over the Pacific Ocean from the coast of Southern California under the influence of Santa Ana winds. NASA satellite image, February 2002.
- Santa Ana (California) – a dry, hot wind blowing from the mountains and deserts of inland Southern California towards the Pacific coast. Despite its warm nature, the Santa Ana has a catabatic nature: high plateaus and deserts east of the coast cool down at night, and air rushes down through mountain passes (Canyon, San Gorgonio, etc.) to sea level. Santa Ana winds usually blow in autumn and early winter when a high-pressure area forms over the Great Basin (Nevada, Utah). The wind flows through canyons to Los Angeles and San Diego, accelerating on the descents. Santa Ana gusts often reach 40–60 knots (20–30 m/s), especially in gorges. This wind is also known for bringing severe drought and dust: the sky can be obscured by a haze of dust and smoke from wildfires, which the wind carries far into the ocean. For sailors off the coast of California, Santa Ana is dangerous primarily near the shore — sudden offshore gusts can catch you off guard when leaving the harbor or during coastal sailing. However, in the open ocean, the influence of Santa Ana usually weakens. Nonetheless, mariners planning crossings along the Southern California coast should consider periodic warnings from the US National Weather Service about strong Santa Ana winds (especially in autumn).
- Meltemi (Aegean Sea) – a seasonal north wind in the eastern Mediterranean. In summer, a strong high-pressure area sets over the Balkans, and a low-pressure area forms over the scorched Anatolian plain, causing the etesian winds (also known as meltemi in Greece) to blow from the north for several months. Strictly speaking, meltemi is not a classic catabatic wind (the air is not sufficiently cold), but during nighttime hours, it strengthens due to the drainage of cool air from the mountains of Greece and Turkey. Meltemi is famous for consistently blowing 20–30 knots of northern wind almost every summer afternoon in the Aegean Sea, sometimes with gusts up to 40 knots. For vacationers, it is a relief from the heat, but for sailors — a serious challenge: sailing against the meltemi is difficult, with short and sharp waves. Experienced skippers in Greece plan routes considering shelter from the meltemi and prefer to set sail early in the morning while the wind is calming. By evening, meltemi usually picks up again.
Of course, this is far from a complete list. Strong catabatic winds have other names: fön Marmi ("black blizzard") in Altai, villivau in Alaska, orog in Japan, northeast in Novorossiysk, etc. Knowledge of local winds comes with experience and studying the sailing area. The main thing is to understand their nature of occurrence and consider them in navigation.
How to Identify a Catabatic Wind in Forecasts?
Catabatic winds are challenging to predict because they are very local and depend on the terrain and time of day. Large-scale weather models (such as GFS, ECMWF, etc.) often have insufficient resolution to account for narrow mountain valleys and sharp nighttime cooling. Therefore, in a regular large-area forecast, a catabatic wind may be averaged out and not stand out as a separate phenomenon. For example, the forecast may show a "calm" or light wind around a bay, while in reality, a strong gusty flow will surge down the adjacent slopes at night.
To detect the threat in time, it's worth paying attention to weather forecasts and specialized models. In meteorology, high-resolution models exist that can simulate wind considering terrain details. An example is the French AROME model from Météo-France with a ~1.3 km grid, designed specifically to forecast dangerous local phenomena. It can predict, for example, mistral jets along the Rhône Valley or bora winds in specific mountain passes, which a global model might not show. However, such models provide forecasts only 1–2 days ahead and do not cover the entire planet. On services like Windy, regional models are available: experienced skippers in the Mediterranean use AROME for short-term forecasts over 24–36 hours, comparing it with the global ECMWF. This way, if locally a model like AROME "draws" a narrow strip of 30–40 knots wind amid a general calm — it's likely a catabatic wind.
Besides AROME, there are other local models: for example, ICON-D2 for the Alpine region, HIRLAM for Scandinavia, HRRR for the USA, etc. On Windy or similar platforms, switch to these models in areas known for their catabatic winds. Also, read local meteorological warnings: national agencies often separately mention strong mountain winds. For example, Meteo-France issues storm bulletins for the mistral and tramontane, Croatian DHMZ — bora warnings, and the American NWS — Santa Ana wind warnings.
Finally, pay attention to signs in nature and forecast details: a sharp cooling of the air (low nighttime minima in the mountains), clear sky, high pressure over land and lower pressure over the sea — all are indicators of a possible catabatic wind. If a model implicitly shows wind strengthening at night from the shore (even if the "land-sea" direction does not dominate during the day) — stay alert. It's better to be safe than to miss a sudden squall. Remember that such winds significantly affect navigation: gusts of bora, for example, can stop a vessel's progress or force it to change course. High-accuracy forecasts (like Copernicus Marine services) now integrate data on local winds, helping sailors plot a safe route. Use these features when planning.
How to Prepare Your Yacht for a Catabatic Wind?
If you suspect that a catabatic wind may occur in your anchoring or sailing area, it's important to prepare in advance. Here are some recommendations for novice sailors and skippers:
- Study the Area and Forecast. Before setting sail, find out which local winds are characteristic for your route. Check high-resolution model forecasts or special warnings. If the forecast indicates the possibility of a strong gusty wind from the shore (especially at night or morning), plan accordingly.
- Choose a Safe Anchorage. Avoid anchorages and marinas open to the possible wind direction. For example, in the Adriatic, when a bora is threatened, it is not advisable to stay overnight on the northeast coast of an island — better move to the leeward side. Look for bays sheltered by mountains from the wind drainage direction. If this is not possible, ensure that the anchoring a yacht and moorings can withstand strong loads.
- Check Rigging and Equipment. Before a catabatic wind sets in, furl or securely fasten sails. This is especially important for genoas and spinnakers — it's better to stow them away entirely. Remove tarps, biminis, and anything that can catch the wind. Ensure that dinghies, boards, jerry cans, and other items on deck are securely tied down — a gust can easily throw them overboard.
- Strengthen Anchor and Moorings. If anchored, increase the deployed length of the anchor chain (more than usual, up to 5–7 scopes or even more in storm conditions). If possible, set a second anchor (e.g., in a bow or stern configuration) for backup. In a marina, add extra mooring lines, place more fenders between the boat and the dock — a catabatic wind can push or pull the yacht with gusts.
- Be Ready to Maneuver. Keep the engine ready in case the anchor starts to drift or moorings fail — you may need to go out to sea and keep the bow into the wind under engine power. While underway with an expected gusty wind, immediately set a minimal sail (a heavily reefed ketch or a storm jib) or motor under one engine to avoid risking sails. Always use life jackets and safety tethers in storms.
- Monitor Weather Changes. Catabatic winds often give clues: a sudden sharp drop in air temperature, calm before the wind's arrival, characteristic clouds over mountains (e.g., lenticular or "cap" clouds on peaks) — all these are signs of incoming drainage air. If you notice them, immediately finish all preparations and stay alert.
By following these recommendations, you significantly increase sailing safety. A friendly tip: do not hesitate to ask local seafarers about local winds. Experienced captains and fishermen are happy to share knowledge about where "the wind starts to blow by morning" and where you can wait it out. The catabatic wind is a formidable phenomenon, but by being aware of it and preparing properly, you can ride it out without adventures. Ultimately, respect for the forces of nature and thorough planning are the keys to successful and safe yachting for captains of any level. Seven feet under the keel!