lancingsc.org.uk

Mike Croker · Joined: 29 Jul 2004 Posts: 922 Location: Steyning

As we had our first sea breeze last Monday, I thought a quick note to outline how it works at Lancing might be useful to those new to coastal sailing. (For the full story, and much more, I suggest that you get hold of a copy of 'Wind Strategy' by David Houghton: pub. Fernhurst Books.)

1) Basic sea breeze (with little or no gradient wind): land near shore gets hot due to sunshine - the vital ingredient - heats air above land which rises, pulling cooler sea air in over the shoreline. Needs 2 to 3 degC difference in air temperature to work. Look for a line of fluffy clouds just inland of the coast. As time goes on the wind will veer (e.g. at Lancing, wind will go from just east of south when the breeze starts to WSW in late afternoon).

2) Sea breeze with a gradient wind of force 3 or less: what's the gradient direction? See diagram for 4 quadrants:
Quad.1: sea breeze will start near the shore and rapidly strengthen as it veers - can reach force 5 by mid afternoon!
Quad.2: sea breeze will start off-shore with a calm patch near the shore - can be very entertaining to sail in! Eventually the calm patch dissapears and a reasonable breeze will develop.
Quad.3: the gradient wind will be backed then reinforced - expect the wind to veer with time.
Quad.4: wind veers and weakens considerably / dies to flat calm - very frustrating!

Hope this helps Cool

Mike Croker · Joined: 29 Jul 2004 Posts: 922 Location: Steyning

Oh what fun the wind had today. Offshore, so nice 'n gusty, with just enough heat inland to generate a sea breeze - eventually!
Data from http://www.shorehamweather.info/mariners.html

Mike Croker · Joined: 29 Jul 2004 Posts: 922 Location: Steyning

If anyone doubted that a NW gradient wind in June was good sea breeze weather, take a look a this Shoreham record for 13 June 2005 Wink

(from http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=ISHOREHA1)

Karen McGrath · Joined: 26 Oct 2004 Posts: 43 Location: Worthing

OK so why no real sea breeze yesterday or today, but a good one on Tuesday?

Is it a) the land's now heated up sufficiently to prevent any real air flow

b) somehow connected to midday high tide

c) high atmospheric pressure preventing thermal breezes

All theories greatly appreciated

Mike Croker · Joined: 29 Jul 2004 Posts: 922 Location: Steyning

I was kind of wondering that too......
Here's Tuesday's and Wednesday's weather records from Shoreham to help our deliberations Laughing

Mike Croker · Joined: 29 Jul 2004 Posts: 922 Location: Steyning

And here are the forecast pressure maps from http://meteocentre.com/models/modelsukmet_eur_e.html
(I couldn't find the archive for the 00:00 analyses for each day, but these are the 18:00 forecast charts from the UK model run at 12:00 on each day.)
I think that there was a stronger NW wind on 21/6 (which helps recirculate the sea breeze out to sea) than on 22/6, where the high pressure had moved NE by evening...... Confused

Mike Croker · Joined: 29 Jul 2004 Posts: 922 Location: Steyning

The beer was nice though Laughing

Thanks Don Very Happy