Sea Breeze Along the Coasts

During the late spring and summer along the Gulf Coast there's a shift in wind just about every afternoon. It's known as the Sea Breeze. The sea breeze is defined as A coastal wind that blows from sea to land, caused by temperature difference when the sea is colder than the adjacent land. Along the sea breeze, ordinary thunderstorms are common, especially in the afternoon. Often, these thunderstorms can produce locally heavy rainfall, frequent lightning, and even waterspouts before moving onshore.

1. Hot air rises over land due to heating by the sun.
2. The rising air leaves less air in one spot, low pressure forms.
3. Generally, from 3,000 to 5,000 feet, the air cools, high pressure develops.
4. Meanwhile, over the cooler water, air sinks, leaving less air aloft.
5. More air piles up at the surface of the water, high pressure forms.
6. Air moves from high pressure to low pressure.
7. The sea breeze generally forms during the afternoon. This creates a mini cold front that helps lift air upward to create thunderstorms.

Sea Breeze Process Details:
During the day, when the air rises as temperatures warm, cumulus clouds form. Unequal heating between the land and water leads to a difference in air pressure. (Think of an inflated balloon, and one that is deflated.) Warm air over the land rises and expands as temperatures soar during the afternoon (a full balloon). Since there is less air at the surface while heating is taking place (because the air rose), an area of low pressure develops in place of the missing air (a balloon with less air). High pressure (the full balloon) then develops 7,000 feet above the ground.

By the late afternoon, the temperature differences between the water and land are at the highest level. With low pressure now in place over the land (the deflated balloon), air from the water (called the sea breeze front), replaces the missing air (trying to blow up the balloon). This is why the sea breeze moves from the water to land. With the passing of the sea breeze front, especially along the beaches, winds start to strengthen, air temperatures drop, moisture increases, and then the sky often clears after the front passes.

As the sea breeze front moves over land, air parcels will continue to rise and cool. By the afternoon, thunderstorms develop. Where the thunderstorms occurs changes daily due to the timing of the sea breeze front, and the shape of the coastline. When you look at the sea breeze and coastline interaction from a side view, you see the air circulates, and that's why it's also known as a sea breeze circulation

Basic Facts of Water and Land:
More heat is needed to warm up water than land, so land heats and cools faster than water, and the daily temperature of land varies more than water. (This is why the warmest water temperatures along the Gulf Coast occur in September and October, while the warmest land temperatures occur in July and August. Also, this explains why the sea breeze is stronger during late spring and early summer, with the large temperature difference).

Another Circulation Begins:
As the sun sets, the heating weakens, and the land starts cooling faster than the water. The thunderstorms dissipate. The sea breeze reverses itself to form another circulation called the land breeze.

The definition of land breeze is similar to the sea breeze, with the two main differences in wind and temperatures: A coastal breeze blowing from the land to sea, caused by the temperature difference when the sea is warmer than the adjacent land.

At night, the temperature over land cools fast while the water stays warm.

Cooler air is heavier than warm air, so the air over land at night cools and sinks to form high pressure at the surface. Less air is left in the atmosphere, and a region of low pressure develops above the ground.

Keeping in mind that air moves from high pressure to low pressure the land breeze circulation begins.

In the early morning hours along the Gulf Coast, cumulus clouds and thunderstorms are often over the Gulf waters, but quickly they dissipate. These offshore thunderstorms are a response to the land breeze. The land breeze is generally weaker than the sea breeze circulation since the land and water temperature difference at night tends to be smaller than the temperature difference during the day.