Marine Glossary

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winds aloft

Wind speeds and directions at various higher levels beyond the domain of surface weather observations. Generally refers to steering winds above the 18,000 foot range, or in the vicinity of the jet stream winds, or in the domain of high clouds. These winds guide weather patterns around the globe along serpentine paths made up of Rossby waves. The path and speeds (some 30 to 80 knots) of the winds aloft are usually indicated on 500-mb maps, which show the contours of the 500 mb surface. From the surface, the direction and rough estimates of the speeds can be made from observations of patterns and shapes of cirrus clouds, as explained in G245.

A sample map of the winds aloft is shown in G401. The flow of winds aloft is illustrated schematically in G218.

Knowing the direction of the winds aloft is valuable because this is the direction surface weather patterns travel. We can think of surface winds as whirlpools in the river of winds aloft. Consequently, winds on the surface may be quite different in strength and direction from those aloft. Typically when we experience surface winds from the south, the entire pattern of southern winds is moving eastward (Benjamin Franklin was the first to recognize this fundamental aspect of weather).

There is also a correlation between the severity of storms on the surface and the speeds of the winds aloft.

See AM-602. See storm track and also crossed winds rule.