Example image showing definitions of windward (upwind) and leeward (downwind).
is the direction from which the wind is blowing at the time in question. The side of a
ship that is towards the
windward is the
weather side. If the vessel is heeling under the pressure of the wind, this will be the "higher side".
Leeward is the direction downwind from the point of reference. The side of a ship that is towards the
leeward is its
lee side. If the vessel is heeling under the pressure of the wind, this will be the "lower side".
Pronunciation
The traditional nautical pronunciations are the
elided forms and . However, nowadays these are sometimes regarded as old-fashioned, and the more literal and are common. The pronunciation for the
Leeward and
Windward Islands and the
Leeward Antilles is normally the latter form.
Meteorological significance
The terms "leeward" and "windward" refer respectively to what a
game stalker would call
downwind and
upwind. The terms are used by seamen in relation to their ships but also in reference to islands in an
archipelago and to the different sides of a single island. In the latter case, the windward side is that side of an island subject to the
prevailing wind, and is thus the wetter side (see
orographic precipitation). The leeward side is the side protected by the elevation of the island from the prevailing wind, and is typically the drier side of an island. Thus, leeward or windward siting is an important
weather and
climate factor on oceanic islands.
In the case of an
archipelago, "windward islands" are upwind and "leeward islands" are the downwind ones.
Significance
In aviation, "downwind" refers to a portion of an aircraft's
landing pattern, the long side parallel to the runway but flown in the opposite direction is called the downwind leg.
On land, "downwind" is often used to refer to a situation where a
point source of
air pollution or a scent moves from a point upwind; from the direction of the wind to the point of the observer.
"Downwind" has specific connotations in industrial cities in the English North, where less desirable or expensive housing was often situated to the leeward of steelworks, blast furnaces, mills or other sources of intense pollution. Hence in some cities it is used as a generic, slang, pejorative and discriminatory term for less wealthy areas or their inhabitants.
Nautical and naval
Windward and leeward directions are important factors to consider when
sailing a
sailing ship - see
points of sail. Other terms with broadly the same meaning are widely used, particularly "upwind" and "downwind", and many variations using the metaphor of height ("come up", "drop down", "we're pointing higher than them", "head below that mark", and so on).
The windward vessel is normally the more maneuverable vessel. For this reason, rule 12 of the
International Regulations for Preventing Collisions at Sea stipulate that the leeward vessel has right of way over the windward vessel. Similarly, a
square rigged warship would often try to enter battle from the windward direction (or "hold the weather gauge"), thus gaining an important tactical advantage over the opposing warship – the warship to windward could choose when to engage and when to withdraw. The opposing warship to leeward could often do little but comply without exposing itself unduly. This was particularly important once
artillery was introduced to naval warfare. The ships heeled away from the wind so that the leeward vessel was exposing part of her bottom to shot. If damaged between wind and water, she was consequently in danger of sinking when on the other tack. See
Spanish Armada.
The term "lee" derives from Old English hleo, "shelter", and was in use at least as early as 900 C.E.
See also
