Turn On It, Tune Out, Drop In

NW WIND 10 TO 15 KT.
WIND WAVES 2 FT.
W SWELL 7 FT AT 13 SECONDS.
TONIGHT NW WIND 10 KT...BACKING TO SW AFTER MIDNIGHT.
WIND WAVES 2 FT.
W SWELL 8 FT AT 13 SECONDS.

When the boar comes, the stream does not swell by degrees, as at other times, but rolls in with a head...foaming and roaring as though it were enraged by the opposition which it encounter

~Thomas Harrel 1824

Edited (stolen) from the "Severn Bore Page"...

The Severn Bore is one of Britain's few truly spectacular natural phenomena. A large surge wave that can be seen in the estuary of the River Severn, where the tidal range is the 2nd highest in the world, being as much as 50 feet (approx. 15.4m).

As many as 60 bores occur throughout the world where the river estuary is the right shape and the tidal conditions are such that the wave is able to form. The Severn Bore (one of 8 in the UK) is one of the biggest in the world, but bores also occur on the Seine and Gironde in France, on the Indus in India, on the Amazon in Brazil, and on the Knik Arm bore at the head of Cook Inlet, Alaska. The biggest bore in the World is the Ch'ient'ang'kian (Hang-chou-fe) in China. Spring tide waves can attain heights of up to 25 ft (7.5 m) and speeds of 13-15 knots (24-27 km/h). It is heard advancing at a range of 14 miles (22 km).

The shape of the Severn estuary is such that the water is funnelled into an increasingly narrow channel as the tide rises, thus forming the large wave. The river's course takes it past Avonmouth where it is approximately 5 miles wide, then past Chepstow and Aust, then Lydney and Sharpness where it is approximately 1 mile wide, and soon the river is down to a width of a few hundred yards. By the time the river reaches Minsterworth it is less than a hundred yards across, maintaining this width all the way to Gloucester.

As well as the width of the river decreasing rapidly, then so does the depth of the river also change rapidly, thereby forming a funnel shape. Therefore as the incoming tide travels up the estuary, it is routed into an ever decreasing channel. Consequently the surge wave or bore is formed.

A bore Blog...

Local Report:

[It] was on but the sets were spaced out...opted for the thumping close out barrels further south.

...first wave was a left. Quick bottom turn...started to pitch. ...actually got time to view the green curtain for a second or two before being hammered into the sandbar.

...prime view of Smith taking off on a super solid left. He stood tall on the drop and the thing began to throw...there were a good few seconds when the lip was pitching right over his head. He then released and shot out to the shoulder and went up to smack a backhand off the lip and came down with the close out.

...caught a fun right that actually allowed for a full cutback instead of closing out and drilling me.

~foulpete

...outside lefts...screaming through...holding shape...to the beach. Fun peaky drops followed by a petering mid section finishing up with a steep pitching inside run...

~bison