Land and Sea Breezes
Sea breezes are a type of mesoscale coastal wind caused by thermal circulation.
In the day, the land heats more quickly than the adjacent water causing
a shallow thermal low over the land. The air over the water remains relatively
cooler giving rise to a shallow thermal high pressure region. The strongest
pressure gradients exist at the land-sea boundary and that is where the
strongest winds form.
At night, the land cools more quickly than the water causing a high
pressure area over the land and a relatively lower pressure area over the
water. With the higher pressure over land, the wind blows from the land
out over the water, producing a land breeze.
Due to the presence of the Gulf of Mexico, land and sea breezes are
a major factor in surface winds in summer months. Considering a no-force
gradient, when the land warms to 7-10 degrees F above local bay and gulf
temperatures, a sea breeze will develop in any season, but is more pronounced
in the summer months June to early September.
During an average summer day (24 hours), the following usually occurs:
Between midnight and 0800-0900 local, the land is cooler then
water and a land breeze sets up as winds drain from the NNW-NE 3-5 knots.
When the land warms to above the bay temperatures (generally
0930-1030 local) the wind shifts to the SE, 120-160 degrees, at 5-8 knots.
By early afternoon (1300 local) the true sea breeze veers
and sets in from the SSW (220) at 8-12 knots, increasing to 15-20 knots
at max land heating (1400-1600 local). The SW flow continues as the
winds gradually decrease as evening cooling occurs. As the land slowly cools to below the surrounding water, the
winds initially become light and variable, then calm by 2200 local.
By midnight, the air has cooled enough for the land breeze
to set up again.
In August, when the Bermuda High has moved to its northern-most position
over the central North Atlantic, the sea breeze maintains a SE component
throughout the day. During August and early September, the SSW sea breeze
does not normally occur.