Matt’s World of Weather: Sea Breeze Circulation

A couple times a week we are witness to a very simple, yet very delicate atmospheric circulation. It can cloud up your sunny afternoon at the beach, shift wildfire smoke to a different area and also provide your neighbor's flowers with a free drink while you are forced to move the sprinkler. A meteorologists will talk about the "sea breeze" and "sea breeze showers", but how can a breeze help create rainfall?

A good question that will take a little bit more than a 2 minute video...

The circulation is relatively simple, but a bit more complex than what I described in the video. Rather than being based solely on temperature differences, the circulation responds to pressure changes based off the temperature differences.

Now for the good stuff...

Air tends to enjoy moving, but it especially enjoys moving from High pressure to Low pressure. In fact, this little "rule" is something from Meteorology 101. Like my first experience with a fork and a light socket, it's a lesson you learn early on and never forget. With the sea breeze, the sun heats the land and the air above responds by becoming less dense. As It rises not only does it begin our circulation but it does this by leaving behind a small area of low pressure. Since the ocean can't heat up as quickly as the land the ocean, by comparison, now has "higher" pressure. We complete the first half of the sea breeze circulation as air is now willing to move from the ocean to land or high to low pressure.

The second half of the circulation is where we get cloud development and thunderstorm activity. As warm air is forced up and over the pushy cooler air at the surface, clouds will begin to form on the leading edge of the sea breeze boundary. Early on cumulus clouds will form on the edge, but eventually the upper level winds will slowly push the clouds (and any thunderstorms) back towards the ocean. This is why on sea breeze days, we can have bright blue skies on the western side of the boundary, and a cobble stone cloud pattern east of the boundary. Eventually cooler air will sink back over the ocean and the whole process will repeat!

Everything falls apart with our delicate circulation when we start to cool from the hottest part of the day. No more temperature contrast, no more low/high pressure, no more moving air....and no more circulation. Pretty cool!

The Big Picture
Like different clouds, a sea breeze helps tell the "weather story" for a certain day. If you notice, it's very rare to even hear the phrase when a larger system is set to move into the area. Like most small circulations, a sea breeze is delicate and usually is found on calm, sunny summer afternoons. A sea breeze tells us that high pressure is probably hanging around and in control of our weather.

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