Katabatic Winds

This is the second of the strange weather phenomenon series – just as gravity waves this is one we generally don’t hear about in the weather reports.


A katabatic wind (is the technical name for a drainage wind, a wind that carries high-density air from a higher elevation down a slope under the force of gravity. Such winds are sometimes also called fall winds; the spelling catabatic winds is also used. Katabatic winds can rush down elevated slopes at hurricane speeds, but most are not as intense as that, and many are 10 knots (18 km/h) or less.

Not all downslope winds are katabatic. For instance, winds such as the föhn and chinook are rain shadow winds where air driven upslope on the windward side of a mountain range drops its moisture and descends leeward drier and warmer. Examples of true katabatic winds include the bora (or bura) in the Adriatic, the Bohemian Wind or Böhmwind in the Ore Mountains, the Santa Ana in southern California, the piteraq winds of Greenland, and the oroshi in Japan. Another example is “the Barber”, an enhanced katabatic wind that blows over the town of Greymouth in New Zealand when there is a southeast flow over the South Island. “The Barber” has a local reputation for its coldness.

Katabatic winds are most commonly found blowing out from the large and elevated ice sheets of Antarctica and Greenland. The buildup of high density cold air over the ice sheets and the elevation of the ice sheets brings into play enormous gravitational energy. Where these winds are concentrated into restricted areas in the coastal valleys, the winds blow well over hurricane force, reaching around 300 km/h (190 mph). In Greenland these winds are called piteraq and are most intense whenever a low pressure area approaches the coast.

In a few regions of continental Antarctica the snow is scoured away by the force of the katabatic winds, leading to “dry valleys” (or “Antarctic oases”) such as the McMurdo Dry Valleys. Since the katabatic winds are descending, they tend to have a low relative humidity, which desiccates the region. Other regions may have a similar but lesser effect, leading to “blue ice” areas where the snow is removed and the surface ice sublimates, but is replenished by glacier flow from upstream.

In the Fuegian Archipelago (Tierra del Fuego) in South America as well as in Alaska, a wind known as a williwaw is a particular danger to harboring vessels. Williwaws originate in the snow and ice fields of the coastal mountains, and they can be faster than 120 knots (140 mph; 220 km/h)


We continue with our ‘blah’ weather pattern today and through the rest of the week.  Thursday will be our warmest day with highs breaking 50° – other than that the clouds will be in place for the most part with patchy fog and drizzle and heavier rain moving in on Thursday – our best chances of seeing the sun again will be Saturday.


 

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Barry in Zeeland
Barry in Zeeland

Never heard of those kinds of winds! 190 mph winds off the ice sheets? That sounds like something from another planet!

Mookie
Mookie

Sure feels warm out lately with the snow melting and rain and 50’s upcoming. This “week of winter” we experienced has been similar to other recent years where we get a big winter blast followed by nothing for weeks.

Slim

Very interesting information on katabasis winds. With wind speeds that high just think of what the wind chill factor must be. I know the winds will warm as they are forced down but still it mush be a cold wind,
Slim

Rocky (Rockford)
Rocky (Rockford)

Our current to date November snowfall is 100% above the November normal! Wow!

Slim

So far GR has had 6.5″ of snow this month average by this date is 2.8″
Slim

Rocky (Rockford)
Rocky (Rockford)

Funny how people were saying it felt warm yesterday, yet it was another in a string of below normal temp days! What a pattern!

Slim

I did not think it felt all that warm yesterday but then again I went for a long walk outside and will do the same today.
Slim

Rocky (Rockford)
Rocky (Rockford)

Our below normal temp pattern continues and the long term below normal temp pattern keeps rocking! Get ready for a wild winter! Incredible!

Mookie
Mookie

Mainly 40’s and 50’s on the long-term and rain. CPC shows no big arctic outbreaks until at least mid December. I love it!