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28-676: Western Washington is known as having a far wetter climate than the eastern portion of the state, primarily due to the effects of the Cascades' rain shadow . The average location in Eastern Washington only receives an average of 46.87 centimetres (18.45 inches) of precipitation per year, whereas the average place in Western Washington receives 167.72 centimetres (66.03 inches). The average location in Western Washington gets 168 days of measurable precipitation per year. The place that receives

56-643: A land area of 24,742 square miles (64,080 km), for a population density of 244.03 people per square mile (94.22 people per square kilometer). Counties in Western Washington: Major cities in Western Washington: Rain shadow A rain shadow is an area of significantly reduced rainfall behind a mountainous region, on the side facing away from prevailing winds , known as its leeward side. Evaporated moisture from water bodies (such as oceans and large lakes )

84-404: Is carried by the prevailing onshore breezes towards the drier and hotter inland areas. When encountering elevated landforms , the moist air is driven upslope towards the peak , where it expands, cools, and its moisture condenses and starts to precipitate . If the landforms are tall and wide enough, most of the humidity will be lost to precipitation over the windward side (also known as

112-595: Is limited to precipitation that crosses over the Continental Divide . While many locations west of the Divide may receive as much as 1,000 millimetres (40 in) of precipitation per year, some places on the eastern side, notably the cities of Denver and Pueblo, Colorado , typically receive only about 12 to 19 inches. Thus, the Continental Divide acts as a barrier for precipitation. This effect applies only to storms traveling west-to-east. When low pressure systems skirt

140-473: The Rocky Mountains and approach from the south, they can generate high precipitation on the eastern side and little or none on the western slope. Further east: Westerlies The westerlies , anti-trades , or prevailing westerlies , are prevailing winds from the west toward the east in the middle latitudes between 30 and 60 degrees latitude . They originate from the high-pressure areas in

168-566: The high-pressure area caused by a system traversing the Westerlies, its general track around the high-pressure area is deflected significantly by winds moving towards the general low-pressure area to its north. When the cyclone track becomes strongly poleward with an easterly component, the cyclone has begun recurvature, entering the Westerlies. A typhoon moving through the Pacific Ocean towards Asia, for example, will recurve offshore of Japan to

196-542: The horse latitudes (about 30 degrees) and trend towards the poles and steer extratropical cyclones in this general manner. Tropical cyclones which cross the subtropical ridge axis into the westerlies recurve due to the increased westerly flow. The winds are predominantly from the southwest in the Northern Hemisphere and from the northwest in the Southern Hemisphere . The westerlies are strongest in

224-451: The rainward side) before ever making it past the top. As the air descends the leeward side of the landforms, it is compressed and heated, producing foehn winds that absorb moisture downslope and cast a broad "shadow" of dry climate region behind the mountain crests . This climate typically takes the form of shrub–steppe , xeric shrublands or even deserts . The condition exists because warm moist air rises by orographic lifting to

252-542: The trade winds is the zone between about 30° N and 30° S, blowing predominantly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere . The westerlies are the prevailing winds in the middle latitudes between 30 and 60 degrees latitude , blowing predominantly from the southwest in the Northern Hemisphere and from the northwest in the Southern Hemisphere. Some of

280-790: The Cordillera, in the direct lee of specific mountain ranges. This includes much of the Basin and Range Province in the United States and Mexico . The Pacific Coast Ranges create rain shadows near the West Coast: Most rain shadows in the western United States are due to the Sierra Nevada mountains in California and Cascade Mountains , mostly in Oregon and Washington . The Colorado Front Range

308-465: The Northern Hemisphere are weaker than those in the Southern Hemisphere due to the differences in strength between the westerlies of each hemisphere. The process of western intensification causes currents on the western boundary of an ocean basin to be stronger than those on the eastern boundary of an ocean. These western ocean currents transport warm, tropical water polewards toward the polar regions . Ships crossing both oceans have taken advantage of

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336-519: The Sun, solar heating would cause winds across the mid-latitudes to blow in a poleward direction, away from the subtropical ridge. However, the Coriolis effect caused by the rotation of Earth tends to deflect poleward winds eastward from north (to the right) in the Northern Hemisphere and eastward from south (to the left) in the Southern Hemisphere. This is why winds across the Northern Hemisphere tend to blow from

364-482: The current more north–south oriented, slowing the westerlies. The strongest westerly winds in the middle latitudes can come in the roaring forties , between 40 and 50 degrees south latitude. The westerlies play an important role in carrying the warm, equatorial waters and winds to the western coasts of continents, especially in the southern hemisphere because of its vast oceanic expanse. If the Earth were tidally locked to

392-718: The development of strong cyclones of all types at the base of the Westerlies, both within the atmosphere and within the ocean . The Kuroshio ( Japanese for "Black Tide") is a strong western boundary current in the western north Pacific Ocean , similar to the Gulf Stream, which has also contributed to the depth of ocean storms in that region. An extratropical cyclone is a synoptic scale low-pressure weather system that has neither tropical nor polar characteristics, being connected with fronts and horizontal gradients in temperature and dew point otherwise known as "baroclinic zones". The descriptor "extratropical" refers to

420-432: The fact that this type of cyclone generally occurs outside of the tropics, in the middle latitudes of the planet, where the Westerlies steer the system generally from west to east. These systems may also be described as "mid-latitude cyclones" due to their area of formation, or "post-tropical cyclones" where extratropical transition has occurred, and are often described as "depressions" or "lows" by weather forecasters and

448-467: The general public. These are the everyday phenomena which along with anticyclones , drive the weather over much of the Earth. Although extratropical cyclones are almost always classified as baroclinic since they form along zones of temperature and dewpoint gradient, they can sometimes become barotropic late in their life cycle when the temperature distribution around the cyclone becomes fairly uniform along

476-506: The impact of the westerlies is when dust plumes, originating in the Gobi Desert combine with pollutants and spread large distances downwind, or eastward, into North America . The westerlies can be particularly strong, especially in the Southern Hemisphere, where there is less land in the middle to cause the progression of west to east winds to slow down. In the Southern hemisphere, because of

504-492: The most recorded precipitation is Lake Quinault on the Olympic Peninsula , with an average of 332.92 centimetres (131.07 inches) per year. The Long Beach Experimental Station has the most days of measurable precipitation, averaging 215 each year. As of the 2020 census , Western Washington was home to 6,037,688 of the state's total 7,705,281 residents, making its population comparable to that of Missouri . The region has

532-463: The mountain. The air descends on the leeward side, but due to the precipitation it has lost much of its moisture. Typically, descending air also gets warmer because of adiabatic compression (as with foehn winds) down the leeward side of the mountain, which increases the amount of moisture that it can absorb and creates an arid region. There are regular patterns of prevailing winds found in bands round Earth's equatorial region. The zone designated

560-436: The north, and then to the northeast, if the typhoon encounters southwesterly winds (blowing northeastward) around a low-pressure system passing over China or Siberia . Many tropical cyclones are eventually forced toward the northeast by extratropical cyclones in this manner, which move from west to east to the north of the subtropical ridge. An example of a tropical cyclone in recurvature was Typhoon Ioke in 2006, which took

588-657: The ocean currents for centuries. The Antarctic Circumpolar Current (ACC), or the West Wind Drift, is an ocean current that flows from west to east around Antarctica . The ACC is the dominant circulation feature of the Southern Ocean and, at approximately 125 Sverdrups , the largest ocean current. In the northern hemisphere, the Gulf Stream , part of the North Atlantic Subtropical Gyre , has led to

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616-472: The poles, the flow is more meridional, blowing from the direction of the pole towards the Equator , which brings cold air into the mid-latitudes. Throughout the year, the westerlies vary in strength with the polar cyclone . As the cyclone reaches its maximum intensity in winter , the westerlies increase in strength. As the cyclone reaches its weakest intensity in summer , the Westerlies weaken. An example of

644-401: The radius from the center of low pressure. An extratropical cyclone can transform into a subtropical storm, and from there into a tropical cyclone, if it dwells over warm waters and develops central convection, which warms its core and causes temperature and dewpoint gradients near their centers to fade. When a tropical cyclone crosses the subtropical ridge axis, normally through a break in

672-466: The southwest, but they tend to be from the northwest in the Southern Hemisphere. When pressures are lower over the poles, the strength of the westerlies increases, which has the effect of warming the mid-latitudes. This occurs when the Arctic oscillation is positive, and during winter low pressure near the poles is stronger than it would be during the summer. When it is negative and pressures are higher over

700-453: The stormy and cloudy conditions, it is usual to refer to the westerlies as the roaring forties, furious fifties, or shrieking sixties according to the varying degrees of latitude. Due to persistent winds from west to east on the poleward sides of the subtropical ridges located in the Atlantic and Pacific oceans, ocean currents are driven in a similar manner in both hemispheres. The currents in

728-667: The strongest westerly winds in the middle latitudes can come in the Roaring Forties of the Southern Hemisphere, between 30 and 50 degrees latitude. Examples of notable rain shadowing include: On the largest scale, the entirety of the North American Interior Plains are shielded from the prevailing Westerlies carrying moist Pacific weather by the North American Cordillera . More pronounced effects are observed, however, in particular valley regions within

756-419: The top of a mountain range. As atmospheric pressure decreases with increasing altitude, the air has expanded and adiabatically cooled to the point that the air reaches its adiabatic dew point (which is not the same as its constant pressure dew point commonly reported in weather forecasts). At the adiabatic dew point, moisture condenses onto the mountain and it precipitates on the top and windward sides of

784-423: The winter hemisphere and times when the pressure is lower over the poles, while they are weakest in the summer hemisphere and when pressures are higher over the poles. The westerlies are particularly strong, especially in the Southern Hemisphere (called also 'Brave West winds' at striking Chile , Argentina , Tasmania and New Zealand ), in areas where land is absent, because land amplifies the flow pattern, making

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