Arthur’s Winds and Your July 4th Beach Vacation

As we head into the July 4^th holiday weekend, many people escape to the seashore on the East Coast.  However, as many have heard, Tropical Storm Arthur was named yesterday and is expected to become a minimal hurricane as it moves northeast.  It’s expected to graze the Outer Banks of North Carolina bringing heavy rain, gusty winds as well as coastal flooding and beach erosion Thursday night and Friday.  Much of the east coast, though, will experience rip currents and higher than normal surf for most of the holiday weekend as Arthur heads out to sea by the end of the weekend.  So it will be important to heed the advice of meteorologists and local authorities depending on which seaside resort you’re planning to visit this weekend. 

Under typical weather conditions absent a tropical storm or hurricane, many people head to the beach during the summer months to cool off.  Temperature differences of 10 degrees or more are common between the shore and inland areas, despite equal amounts of sunshine and being on the same latitude.  Why is this so?  The primary factor that causes such temperature spreads is the cycle of sea and land breezes at the beach. 

Data from the University of Illinois shows that large bodies of water like a lake or ocean are able to absorb more energy from the sun without warming up as the land does.  We also know that warm air rises because it is lighter and less dense than cold air.  So, when the warm air over the beach rises, cooler air over the water rushes in to replace the void created by the rising air.  This rush of cooler air is what is commonly referred to as the sea breeze, which beachgoers can feel on their faces as it blows inland.  The sea breeze is an added benefit of the shore providing people with relief from the heat even before they get in the water.  We can enjoy the cooling effects of the ocean while we are still setting up our beach umbrellas!

In contrast, just a few miles inland from the beach – and away from the cooling effects of the sea breeze – it’s often unbearably hot.  At night the opposite is true, since the land cools off more quickly than the sea.  So, when the relatively warm air over the ocean rises, the cooler air over the beach rushes in to fill the void created over water.  Those who enjoy going for walks on the beach at night benefit from this land breeze blowing on their backs. 

Something else significant happens at the beach when the warm air rises.  If it rises high enough in the atmosphere, it leads to the formation of those puffy, fair weather clouds that meteorologists call cumulus clouds.  During the day, these cumulus clouds form just inland due to the sea breeze and just offshore at night because of the land breeze.  Under the right circumstances, these cumulus clouds can grow into cumulonimbus clouds and give rise to a thunderstorm.

Being a very small scale and localized weather event, sea and land breezes only occur during times of calm weather.  When a larger weather system such as a tropical storm or a front is in the vicinity, their associated weather supersedes the small scale phenomenon that’s exclusive to the beach.  So while enjoying your beach vacation over the holiday weekend and whenever you choose to go over the summer you can enjoy the cooling effects of the sea breeze while meteorologists keep you apprised of more urgent weather conditions should they arise.