Mullion Cove is nice, but...

[Yngmar]

Lovely yesterday. Anchored a bit off the harbour in what looked like good shelter from the easterlies at the time. Rowed ashore and had a little wander around, but the café and chocolate shop were already closed and not much else around. Found a crack in the rocks inside the harbour that led through a cave to a beach accessible only at low tide - very nice.

Today not so nice though. Shelter from waves but not wind. It was blowing 27 knots with gusts in the low 40s, much the same as the airport weather station on the Lizard reported. Our anchor held nicely (although we'll see later when we pull it up whether that's because it's stuck on a rock). Top gust was 44 knots and during it this poor bastard dragged through some fishing gear but managed to get the engine on and not foul his prop, avoiding being smashed to bits on Mullion Island behind him. Hopefully he had a spare pair of trousers on board, that didn't look fun and I don't think I could've done much to help him, other than a radio call. He's anchored closer in now and things have calmed down a good bit.

 

[fisherman]

Yes I was hauling pots not far from you, gaff blew out of my hand. Katabatic winds here in E-lies. I have on occasion passed off Kynance 2 miles or so to the south, had gear blowing about the deck and water climbing the side of the boat, then get off the Lizard and it's a benign force 2-3. Max recorded at Seven stones was 24kts at 11am. Once we had several boats just off the point unable to get back to Falmouth, the boat seven miles off was in a flat calm.

 

[Jamesuk]

Been there a few times, it can be a rock and roll affair at any time.

 

[Yngmar]

Well, the anchor came up without problems and we've had a night sail complete with foggy arrival back in Falmouth. More photos on the blog: https://sdfjkl.org/blog/2017-07-20-scillies-not-really/

Oh, and apparently this happened just on the other side of the headland. We thought those big fat clouds where hovering in one place a long time, but we were just glad they didn't come over to us: https://www.theguardian.com/environ...k-floods-after-helicopter-rescues-in-cornwall

 

[johnalison]

You haven't told us what anchor you used.

For God's sake don't answer.

 

[AntarcticPilot]

Yes I was hauling pots not far from you, gaff blew out of my hand. Katabatic winds here in E-lies. I have on occasion passed off Kynance 2 miles or so to the south, had gear blowing about the deck and water climbing the side of the boat, then get off the Lizard and it's a benign force 2-3. Max recorded at Seven stones was 24kts at 11am. Once we had several boats just off the point unable to get back to Falmouth, the boat seven miles off was in a flat calm.

<pedantry>
They AREN'T katabatic winds! Rollers probably, but there are no places in the UK where katabatic winds are feasible.You need a high elevation at low temperatures (e.g. a glacier or ice field) and a continuous slope from the high elevation to sea-level to get katabatic wids - really only found in the Andes, Greenland and Antarctica (in the latter case, possibly resulting in sustained wind speeds of over 100 knots for several weeks!)
</pedantry>

 

[Yngmar]

You haven't told us what anchor you used.

For God's sake don't answer.

Intentionally! I've been here a while now

 

[fisherman]

<pedantry>
They AREN'T katabatic winds! Rollers probably, but there are no places in the UK where katabatic winds are feasible.You need a high elevation at low temperatures (e.g. a glacier or ice field) and a continuous slope from the high elevation to sea-level to get katabatic wids - really only found in the Andes, Greenland and Antarctica (in the latter case, possibly resulting in sustained wind speeds of over 100 knots for several weeks!)
</pedantry>

I bow to your superior knowledge. No rollers, just very strong wind along that shore in easterlies. Mullion is unfriendly because between there and the Lizard there are nine hours of very strong flood every tide, starting before LW and running until after HW Penzance. The slightest S in the wind means the seas come round the Lizard and get kicked up something alarming, running into Mullion, and it gets much worse as the wind shifts to the S if cyclonic. We one morning got as far as the Rill, no wind but main flood and seas the remnants of s wind overnight, it was heartstopping. We had to turn, when we could, come N a mile then head out W for two miles to round the shoals to get S and outside the Lizard.

 

[RichardS]

<pedantry>
They AREN'T katabatic winds! Rollers probably, but there are no places in the UK where katabatic winds are feasible.You need a high elevation at low temperatures (e.g. a glacier or ice field) and a continuous slope from the high elevation to sea-level to get katabatic wids - really only found in the Andes, Greenland and Antarctica (in the latter case, possibly resulting in sustained wind speeds of over 100 knots for several weeks!)
</pedantry>

My understanding is that the Bora / Bura wind which we regularly "enjoy" in Croatia is a genuine katabatic wind. Do you think it's not?

Richard

 

[Seajet]

I think the downwards blowing winds on the leeward side of hills are known as ' rotor's ' - ask glider pilots - they might as well be called Katabatic though as they have the same effect, including at Studland Bay.

 

[TiggerToo]

... one morning got as far as the Rill, no wind but main flood and seas the remnants of s wind overnight, it was heartstopping. We had to turn, when we could, come N a mile then head out W for two miles to round the shoals to get S and outside the Lizard.

Hi F,

where is "the Rill"? We might be heading out there in a couple of weeks, and I had not heard of this (yet)....

Cheers!

 

[RichardS]

I think the downwards blowing winds on the leeward side of hills are known as ' rotor's ' - ask glider pilots - they might as well be called Katabatic though as they have the same effect, including at Studland Bay.

My understanding, albeit based on miniscule knowledge, is that katabatic winds have to have their source in high mountains which slope down towards a flat plain like the sea. The very cold air at the top of the mountain starts to drop down the side of the mountain because it's heavier that the warmer air lower down. If the mountains are the right shape the cold air funnels down gathering speed as more cold air feeds in from the top and by the time it gets to the plain at the bottom it's going at 50 knots or more.

It all sounds rather unlikely to me ... but if that's what katabatic is then I think the bora is genuinely katabatic.

Richard

 

[AntarcticPilot]

My understanding, albeit based on miniscule knowledge, is that katabatic winds have to have their source in high mountains which slope down towards a flat plain like the sea. The very cold air at the top of the mountain starts to drop down the side of the mountain because it's heavier that the warmer air lower down. If the mountains are the right shape the cold air funnels down gathering speed as more cold air feeds in from the top and by the time it gets to the plain at the bottom it's going at 50 knots or more.

It all sounds rather unlikely to me ... but if that's what katabatic is then I think the bora is genuinely katabatic.

Richard

I don't know the topography of the bora winds, but given the proximity of high mountains in the Alps, katabatic winds are a possibility.

 

[jimi]

You can get katabatic wind at Lochranza with the wind falling down from Cioch na-h-oighe, similarly I'd have thought there's potential anywhere there is a mountainside or even a hillside where cold air can drain down it (usually warming up in the process as its pressure increases at the lower altitude). I'd suspect the Lizard creates a compression zone rather than a katabatic effect. Mullion is lovely but not where I'd choose to anchor except temporarily in very settled conditions.

 

[fisherman]

Hi F,

where is "the Rill"? We might be heading out there in a couple of weeks, and I had not heard of this (yet)....

Cheers!

South of Mullion, half nmile NW of Kynance. The flood piles up round it. Flood starts between Mullion and the Rill 2 hours before LW(PZ) and works along to the Lizard, where it meets the late ebb til 3 hours after. If you meet se wind there it's horrible. It only ebbs for two hours or so on the Rill.

https://www.google.co.uk/maps/@49.9768013,-5.240157,1183m/data=!3m1!1e3

 

[fisherman]

I suppose if you were looking for some help the flood along there would shove you along a bit, the SW rock off old Lizard head, the Mulvin, shows on google maps, once you pass that when you see the Black head (3 nm beyond Bass point) appear outside of Bass point, which has the white square Lloyd's signal station on it, keep the two together and you will hit the end rock S of the Lizard. You can go inside that one.........

 

[AntarcticPilot]

You can get katabatic wind at Lochranza with the wind falling down from Cioch na-h-oighe, similarly I'd have thought there's potential anywhere there is a mountainside or even a hillside where cold air can drain down it (usually warming up in the process as its pressure increases at the lower altitude). I'd suspect the Lizard creates a compression zone rather than a katabatic effect. Mullion is lovely but not where I'd choose to anchor except temporarily in very settled conditions.

Sorry - it's not a katabatic wind. Katabatic winds require a cold reservoir such as a glacier at the top of the mountain; the best we can do in the UK is one or two semi-permanent snow patches on Ben Nevis or Cairngorm. The point is that the air has to be cooled at higher altitude so that it becomes denser than the air mass it is embedded in; katabatic winds are density flows. A cold stream of air doesn't do the job; the necessary density differential can't arise. There's nowhere in the UK with the necessary cooling potential. The way you describe it sounds more like a foehn wind, where cold air passing over a mountain descends on the other side.

Be glad we don't get them - katabatic winds hit speeds of over 100 knots under the right conditions, and under ideal conditions for them (e.g. Cape Dennison in Antarctica), they can persist for weeks on end! A mountain gust in the UK isn't in the same league.

 

[jimi]

Sorry - it's not a katabatic wind. Katabatic winds require a cold reservoir such as a glacier at the top of the mountain; the best we can do in the UK is one or two semi-permanent snow patches on Ben Nevis or Cairngorm. The point is that the air has to be cooled at higher altitude so that it becomes denser than the air mass it is embedded in; katabatic winds are density flows. A cold stream of air doesn't do the job; the necessary density differential can't arise. There's nowhere in the UK with the necessary cooling potential. The way you describe it sounds more like a foehn wind, where cold air passing over a mountain descends on the other side.

Be glad we don't get them - katabatic winds hit speeds of over 100 knots under the right conditions, and under ideal conditions for them (e.g. Cape Dennison in Antarctica), they can persist for weeks on end! A mountain gust in the UK isn't in the same league.

Well we'll agree to differ. Your definition is of a specific type of katabatic wind, not a generic katabatic wind which is also quite common in Greece or Turkey where you can see the specific lump of air rolling down the hillside then flattening everything at the bottom!


edited: https://en.wikipedia.org/wiki/Catabatic_wind just looked up wikopedia .. for once it agrees with my understanding ;-)

 

[RichardS]

Well we'll agree to differ. Your definition is of a specific type of katabatic wind, not a generic katabatic wind which is also quite common in Greece or Turkey where you can see the specific lump of air rolling down the hillside then flattening everything at the bottom!


edited: https://en.wikipedia.org/wiki/Catabatic_wind just looked up wikopedia .. for once it agrees with my understanding ;-)

Your link also says "see also Bora".

Richard