Geography 101



Forces Motion Global Local

Local Winds

What are land and also sea breezes and what reasons them? What areas of the Islands most frequently endure sea breezes? Describe some of the topographic impacts on wind. What are some examples of topographically induced winds and also clouds in Hawai"i?

Global winds take a trip hundreds, even thousands, of miles. Within these vast prevailing wind belts, many type of, many kind of smaller wind systems intrude, many of them moved by regional heating and cooling of the surchallenge.

You are watching: Why do clouds tend to form over land with a sea breeze and over water with a land breeze?

Consider the diagrams listed below. During the daytime, the sunlight heats the land surchallenge. Remember that water surfaces tfinish to continue to be about the very same temperature both day and also night. So, during the daytime, land also becomes warmer than the adjacent water surchallenge. This reasons a reasonably low pressure mechanism through climbing air to develop over land also and also via greater pressure and also sinking air over water setting in movement a small version of the planetary Hadley cell. The regional wind blows from the greater press over the ocean toward lower push over land also. Because this surface wind blows from the sea, it is referred to as a sea breeze. In basic, these circulations are as well tiny to be affected significantly by Coriolis.

Daytime Sea Breeze (onshore) Nighttime Land Breeze (offshore)

The opposite occurs at night. Land also cools to a reduced temperature than the ocean surconfront, creating relatively greater press, and also the circulation reverses. The nighttime wind blows away from land, creating a land also breeze. This reversal of land and sea breezes occurs virtually eincredibly day in some areas, wbelow it have the right to dominate the local wind pattern.


Consider the image of the Big Island also, taken on a calm day. The southern (Ka"u district) and also western (Kona district) flanks of Mauna Loa in the foreground have actually clouds developing on mountain slopes under a occurring sea breeze. Anyone who has been to Kona has actually checked out clouds creating over the inland slopes in late morning as the sea breeze gains strength. Notice the clouds execute not rise to the height of the mountain, but are capped at the invariation level of around 1800 to 2400 meters (6000 to 8000 feet) elevation.

The sea breeze/land breeze circulation cycles everyday on the leeward slopes of the Big Island. It commonly forms on the leeward slopes of other islands too, particularly on calm days. When the profession winds are absent or light, clouds might darken the skies of central O"ahu in late afternoon, sometimes also producing thunder, as sea breezes from north and also southern shores converge. Windward slopes likewise endure these thermal winds. In Hilo, for instance, a cool land also breeze blows out to sea essentially eexceptionally night of the year.

Topographic Variations

Anvarious other resource of neighborhood wind patterns vital in Hawai"i is the shape of the Islands themselves. Wind funneling via networks between islands is one of the a lot of obvious impacts. Look at the photo listed below. The Big Island also creates a vast "bow wave" (1) cloud as it blocks the prevailing tradewind airflow. (See the semi-circular cloud pattern?) As air streams around the Big Island, it funnels in between Maui and Hawai"i, accelerating in rate, and creating the inrenowned rough conditions of the "Alenuihaha ("great billows smashing") channel. Many kind of locations in Hawai"i are listed for high winds brought about by topographic acceleration, such as the Pali Lookout and also Kahuku Point on O"ahu, and of course, at South Point, Big Island wbelow powerful winds are so consistent that tree crowns thrive downwind of their trunks, as displayed in the photo listed below.


Other topography-induced wind features are apparent in the image. See the line of clouds stretching downwind from southwest ridge of Haleakala, East Maui (2)? This cloud street develops as air relocating north and also south of the hill converges on the leeward side, producing sufficient lift to reason clouds to form. A comparable cloud street regularly creates downwind of the East Moloka"i mountains. Another neighborhood wind function of leeward Haleakala (not visible in the image) is the Maui vortex. This is simply a circular eddy that occasionally produces a ring of clouds close to the tvery own of Pukalani ("hole in the sky").

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Also, look at the sharp edge of the clouds over the Kohala hills (3), especially in the saddle close to the tvery own of Waimea. Here, the air stream, under normal trade winds, reverses its cloud-creating, upslope activity and begins traveling downhill towards Kawaihae and the leeward shore. Under particular atmospheric conditions, this downslope wind might acceleprice, developing incredibly high gusts at the coast. These katabatic winds have the right to be believed of as a sort of dry, upside-dvery own thunderstorm.

Finally, additionally notification the S-shaped band also of sea breeze clouds developing as air moves inland also throughout daytime heating of the Big Island"s leeward slopes (4).