Penzance Weather Report & Big swell

[Graham Easterling]

Day of sunny spells & showers yesterday, though the morning was mainly dry. Maximum of 11.6C.

Minimum of 7.4C last night. Rainfall to 09:00 4.9mm.

A big swell arrived overnight. Sevenstones

You may spot the period shown on wave buoys is normally short, sometimes way less than a site like Magic Seaweed shows. Wave period is far more important than the height, a 5ft 15sec period wave has far more power than a 10ft 10sec period wave, so getting it right is important.

Sevenstones may show 11secs, but dig a bit deeper and at Perranporth buoy this morning you can see the 11sec wave that Sevenstones is reporting as a minor energy peak, but there is a 5 times more powerful wave with a 16 sec period. This is the period Magic seaweed shows as the dominant one, and certainly what the EA should be looking at as regard coastal issues.  That's a very powerful wave.

The wave period shown for buoys such as Sevenstones is a crude averaging, has severe limitations, and for most purposes is very misleading. For anyone interested, bit more here. 

http://surfforecasting.magicseaweed.com/?p=647

Graham

Penzance