Tag Archives: wind

A Summer Sea Breeze

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While spending a weekend at the beach recently, I was reminded how pleasant a sea breeze can feel on a hot summer afternoon.

A sea breeze is a localized, daytime wind driven by the temperature difference between land and a large body of water. Since land is able to absorb the sun’s energy more quickly than water, it warms faster. As a result, air over the ground heats and rises, creating an area of low pressure. Cooler air is then drawn from the zone of higher-pressure above the ocean to fill the void, forming an onshore breeze.

These winds typically start flowing around mid-day and last throughout the afternoon.  They are valued for their moderating influence on local temperatures, keeping coastal areas cooler than their inland neighbors during the warmest months of the year.

Image Credit: physicalgeography.net

Flag Trees

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Objects that indicate the direction of the wind are known as weather vanes.  Not all, however, are man made.

Flag trees, for example, are living weather vanes.  They show the direction of the prevailing wind in a particular location.  On mountain ridges, where trees are constantly exposed to strong winds, the windward facing branches of a tree are often stunted or killed. On the leeward side, the trunk shelters the branches.  This allows them to grow to normal size.  As a result, the tree is sculpted to the shape of the wind and resembles a flag waving in a breeze.

These deformed trees are common features in the windswept sub-alpine landscape, but are not limited to that terrain.  Flag trees can also be seen in the tropics, where the strong, sustained trade winds contort trees in a similar fashion near the equator.

Flag Trees

Photo Credit: jmu.edu

Strong Santa Ana Winds

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Earlier this week, the southwestern region of the US experienced one of its worst wind storms in over a decade.  The winds that swept through the area were not a typical Santa Ana event.

The Santa Anas are robust easterly winds that blow dry air across southern California in the late fall.  It is formed by a large pressure difference that builds up between the inland Mojave Desert and the LA Basin. The steep pressure gradient between the two areas funnels air downhill through the canyons and passes of the San Gabriel and San Bernardino mountains toward the Pacific. Winds speeds generally reach somewhere between 40 and 60 mph.

This week’s event was unusual, because it followed a cold front and had a powerful northerly wind component with exceptionally strong gusts.  The NWS is reported to have measured wind gusts up to 140 mph along the Sierra Crest mountain ridge.  This fierce wind storm uprooted trees and knocked out power to over 300,000 people across the Los Angeles area.  Even LAX lost power and had to shut down briefly.

Another unusual aspect of this epic wind event was its wide reach across the region. Damage has been reported across the west from California to Colorado.  Some places in Utah experienced wind gusts over 100 mph and saw tractor-trailers flipped over like toys.

The tight pressure gradient that caused the storm has now weakened and the winds have subsided.  The forecast, however, is calling for blustery conditions to return to the southwest in the next few days.

Dust Up In Texas

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Earlier this week, a massive dust storm darkened the skies of Lubbock, Texas.  Wind gusts reached 70-mph and the cloud of dust climbed 8,000 feet into the air.

This type of intense dust storm is called a haboob. They are usually seen in arid climates when the strong downdraft of a thunderstorm reaches the ground and blows the dry loose sand up into the air.  We have seen a few of these in Arizona recently.   The Texas haboob, however, had different origins.  It was caused by the fast moving winds of the leading edge of an approaching cold front.

The Lubbock dust storm was a by-product of the extreme drought that has been plaguing most of Texas.  Without rain, crops have dried up and large tracts of land have been left barren. Lacking the stabilizing roots of natural prairie grasses and commercial crops, the dry soil is highly subject to wind erosion.

The images of this huge dust storm and the drought that caused it are reminiscent of the Dust Bowl storms of the Great Depression.  Throughout the early 1930’s, a severe drought in Kansas, Oklahoma, and Texas caused huge dust storms that damaged both the ecology and agricultural industry of the great plains.

Unfortunately, there is no end in sight for the current drought in Texas.  As a result, we could see more dust storms in that state.

Dust Bowl Storm, 1935

Photo Credit: ksu.edu