The normal level of high-tide, used as a baseline for measuring height or depth.
Seeder-Feeder:
The process of orographic rainfall by which high-level clouds 'seed' rain clouds at a lower level.
Seeding:
The process by which condensation nuclei are artificially released in the atmosphere to encourage precipitation.
SIGWX:
The abbreviation for Significant Weather Effects - weather that affects flying conditions.
Smog:
Dirty fog produced by air pollution in cities, and often occurring beneath a temperature inversion. The action of sunlight can produce photo-chemical smog.
Snow:
Ice crystals that fall from clouds and which may stick together to form snowflakes.
Snowline:
The vertical limit of snow lying on mountain sides throughout the year.
Snowpack:
Snow lying on the ground for any significant period of time.
Solstice:
The time of the year when the Sun appears to be directly overhead at either the Tropic of Cancer or the Tropic of Capricorn.
Stratosphere:
The layer of the Earth's atmosphere above the troposphere.
Streamline:
A line used on some weather maps to indicate wind flow.
Synoptic Chart:
A map showing the weather in an area at a given moment.
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Sea-Level: