If there is too strong a tailwind (synoptic-scale easterlies along the east coast of Florida, for example), the sea-breeze front races inland and is quickly loses its identity to heating and mixing. If this headwind is too strong, the sea-breeze can't advance inland, and the mesoscale boundary that marks the leading edge of the sea breeze, called the sea-breeze front, blows out to sea. In a nutshell, the strength of the "headwind" associated with synoptic-scale winds blowing offshore is crucial to the formation of the sea breeze. For a visual, check out this schematic showing the size-scale of the mesoscale circulation of air associated with a sea breeze.įor a mesoscale sea-breeze circulation to develop, the "background" synoptic-scale pressure pattern must be relatively weak, because relatively strong synoptic-scale pressure gradients will overwhelm sea-breeze circulations. Note that the onshore wind speeds associated with the passage of the sea-breeze front typically fall between 5 and 10 meters per second (10 to 20 knots, approximately).
Sea breeze wind series#
In reality, the facets of the mesoscale circulation you see here develop simultaneously, but I presented the sea-breeze circulation as a series of steps to help you better understand this process.įor the record, the typical depth of the sea-breeze circulation ranges from 500 meters to one kilometer.
The resulting mesoscale pressure gradient near the earth's surface now drives cooler maritime air toward land, creating the faithful sea breeze (Step #4). Air aloft moving away from land eventually converges over the sea, causing surface pressure to increase over coastal waters (Step #3). With higher heights (higher pressure) aloft, air flows toward the sea at higher altitudes, creating weak divergence that helps to lower the surface pressure over the land (Step #2). In response to this differential heating, the heights of constant pressure surfaces rise near 925 mb rise (see Step #1 on the idealized schematic below). As the land heats up after sunrise, the overlying air becomes considerably warmer than the lowest layer of air over coastal waters. Coast from spring to autumn (essentially the warm season). Climatologically speaking, sea breezes typically develop along the U.S. Let's start to build our conceptual model of a sea breeze.
As a general rule, the greater the temperature difference between land and sea, the stronger the sea breeze. That's because relatively strong synoptic-scale winds disrupt the development of sea breezes. Based on empirical studies, the daytime temperature difference between land and water must be at least six degrees Fahrenheit in order for sea breezes to develop, assuming that the background synoptic-scale pressure gradient is weak.
The Meteorology of Sea Breezesįor the record, a sea breeze is a mesoscale, onshore wind system that develops near the coast in response to the differential heating of a land mass and the adjacent, relatively large body of water. That aside, how do such huge temperature contrasts develop over California in the summer? The answer is the "sea breeze." While the interior of California bakes under the summer sun, coastal locations routinely stay in the 50s or 60s as cool sea breezes blow inland from chilly offshore waters. "The clash of warm air and cold air" is really a rather poor explanation of the cause of thunderstorms, but I bet you've heard it before (or will now, if you listen for it). Think about that next time you hear a weathercaster explain severe thunderstorms as a result of the "clash of warm air and cold air." If that was really the case, we'd get thunderstorms all the time in southern California during the summer (which doesn't happen). Note on the surface analysis above that temperatures were more than 100 degrees over California's Central Valley, while readings near the coast were in the 50s and 60s! Over distances of roughly 100 miles, temperatures varied by some 50 degrees! Even with such huge temperature contrasts in place, there was nary a thunderstorm to be found in the region (which is often the case during the summertime in southern California). As it turns out, such a wide range in temperatures over relatively short distances in California isn't all that crazy (although I admit that the forecast above could be clarified a bit more).
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