<P> The following are terms used to describe local or regional weather events . </P> <Ul> <Li> Santa Ana winds: Santa Anas are hot, high winds that blow from the eastern mountains and deserts towards coastal southern California, usually in the spring and fall . They are the result of air pressure buildup between the Sierra Nevada and the Rocky Mountains . This air mass spills out, is pulled by gravity, and circulates clockwise around the high pressure area, bringing winds from the east and northeast; as the air descends in elevation, it heats up and the humidity plummets to less than 15 percent . It is often said that the air is heated and dried as it passes through the nearby deserts, but according to meteorologists this is a popular misconception (it is actually due to adiabatic compression as the air flows from the higher elevations down to sea level); during Santa Ana conditions, it is typically hotter along the coast than in the deserts . As the Santa Ana winds are channeled through the mountain passes they can approach hurricane force . The combination of speed, heat, and dryness turns the chaparral into explosive fuel for wildfires . </Li> <Li> Pineapple Express: A complex combination of events, bringing high levels of torrential precipitation to California . The Pineapple Express occurs when the jet stream dips across California, and warm, humid air from the mid-Pacific (from the vicinity of Hawaii--hence, the name) is drawn towards California . The resulting combination can cause extraordinarily heavy rains . A January 2005 Pineapple Express dropped nearly 25 inches (63.5 cm) of rain in Santa Barbara County . </Li> <Li> Tule fog: A thick ground fog that settles in the San Joaquin Valley and Sacramento Valley areas of the California Central Valley . Tule fog forms during the mid fall, winter to early spring after the first significant rainfall . This phenomenon is named after the tule grass wetlands of the Central Valley . Tule fog can extend from Bakersfield to Chico . Accidents caused by the tule fog are the leading cause of weather - related deaths in California; visibility is usually less than an eighth of a mile (about 600 feet or 183--200 m), but can be less than 10 feet (3 m). </Li> <Li> May Gray / June Gloom: A characteristic weather pattern of late spring (May and June) in which a combination of inland heat, off - shore cool water, and prevailing wind patterns bring foggy and overcast weather to coastal regions . From Point Conception northwards the gloom continues until early autumn . (See also: Catalina eddy) </Li> <Li> Marine layer: The cool, moist layer of air coming in from the ocean which typically includes fog . A standard weather phenomenon along the northern and central California coast from late spring to early fall . </Li> <Li> "Earthquake weather:" Any unseasonal, uncomfortable weather, typically hot and more humid than usual, and often associated with high and mid-level clouds, is spoken of (usually jokingly) as "earthquake weather ." </Li> </Ul> <Li> Santa Ana winds: Santa Anas are hot, high winds that blow from the eastern mountains and deserts towards coastal southern California, usually in the spring and fall . They are the result of air pressure buildup between the Sierra Nevada and the Rocky Mountains . This air mass spills out, is pulled by gravity, and circulates clockwise around the high pressure area, bringing winds from the east and northeast; as the air descends in elevation, it heats up and the humidity plummets to less than 15 percent . It is often said that the air is heated and dried as it passes through the nearby deserts, but according to meteorologists this is a popular misconception (it is actually due to adiabatic compression as the air flows from the higher elevations down to sea level); during Santa Ana conditions, it is typically hotter along the coast than in the deserts . As the Santa Ana winds are channeled through the mountain passes they can approach hurricane force . The combination of speed, heat, and dryness turns the chaparral into explosive fuel for wildfires . </Li> <Li> Pineapple Express: A complex combination of events, bringing high levels of torrential precipitation to California . The Pineapple Express occurs when the jet stream dips across California, and warm, humid air from the mid-Pacific (from the vicinity of Hawaii--hence, the name) is drawn towards California . The resulting combination can cause extraordinarily heavy rains . A January 2005 Pineapple Express dropped nearly 25 inches (63.5 cm) of rain in Santa Barbara County . </Li>

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