Mediterranean Sea 'heat wave'

[jack.h...@gmail.com]

https://www.bbc.co.uk/news/articles/c4g2v1l7j6yo

Good article.

Could cyclones (hurricanes) be spawned in the Med?

Jack

[Nick Gardner]

This is a very dubious article and veering into the realm of hyperbole. There are two SST temperature bouys near here (West Bay & Dawlish). Frequently they can give temperatures of up 24°C due to warm surface water pooling that affects just the top metre or so as the water stratifies under intense insolation. But are from from representative of the SST in general. As I have said, SST can be highly variable. Varying several degrees in just an hour as tidal/wind effects cause stilling/mixing. The map shows the current SST and they are nothing out of the ordinary (if a little below normal in the French Riviera). Mid-July normal SST in the Med usually go from 24°C in the western approaches around Gibralter up to 30°C south east of Cyprus. There will always be surface warm and cool pools that you can pick on to push whatever narrative you like.

 

 

[Graham Easterling]

I agree. It's surprising how much the temperature at wave bouys can vary over short timescales for the reasons you mention. Offshore/onshore winds make a big difference for some miles offshore.

This graph shows the Penzance wave bouy up until 10am today. Iif you draw a straight line from Mousehole to St. Michael's Mount, it's half way along. 

It's been averaging around 19C lately, but as well as tides & sunshine, it's highly dependent on wind direction. Highest in a S wind, lowest in a NE which causes an upwelling of cold water. Likely not to hit yesterday's values today, as the wind is tending to back more easterly and increase a touch. I've even seen Sevenstone bouy, well out in the Atlantic, hit 23C at slack water with no swell under sunshine, as a warm pool forms and drifts across. I'm very wary of sites which show snapshot SSTs, they really need to be averaged over a few days.

Anyway, it was warm in the sea this morning! MetO forecast temperatures for Penzance are excellent these days. BBC is complete rubbish in comparison. Current Penzance max temperature forecasts for today:- MetO 27C, BBC 22C. I rest my case! 

Graham

Penzance

[Graham Easterling]

I've just noted from your map that the mid English Channel summer 'cool pool' is now in place. I've often wondered why, possibly due to the mixing of 2 tides (double high tide) and slightly different salinity of the tide via the North Sea? Also SST lower off NW Iberia than Cornwall & Devon, not that exceptional in summer.

Graham

On Saturday, 12 July 2025 at 11:15:15 UTC+1 Nick Gardner wrote:

[Keith (Southend)]

Aren't the SST's derrived from satellite data?

Keith (Southend)

[Graham Easterling]

Yes, certainly as far as offshore north Atlantic data is concerned. Like the wave bouys, they can change quickly with a change in weather. It doesn't really matter where the data comes from, it's just easier to demonstrate rapid changes with the bouy data.

A big weakness in the article quoted is it's reliance on peak temperature bouy data during a sunny hot spell. In calm seas and hot sun they can give vaguely ridiculous figures at times as warm pools drift across. 

Graham

Penzance

[jack.h...@gmail.com]

This was the purpose of my original post:

[Nick Gardner]

Yes but with caveats.

They are mostly weaker than their oceanic counterparts. Intense localised rainfall is what often presents the most problems rather than the wind from these storms. 

Medicane Lanos near Greece, 17th September 2020.