METEOROLOGY FLIGHT PLANNING
STANDING LENTICULAR CLOUD A more or less isolated cloud with sharp outlines that is
generally in the form of a smooth lens or almond. These clouds often form on the lee side of and
generally parallel to mountain ranges. Depending on their height above the surface, they may be
reported as stratocumulus standing lenticular cloud (SCSL), altocumulus standing lenticular
(ACSL), or cirrocumulus standing lenticular cloud (CCSL).
STATION ELEVATION The officially designated height above sea level to which station
pressure pertains. It is generally the same as field elevation at an airport station.
STATION IDENTIFIER A four-alphabetic character code group used to identify the observing
STATION PRESSURE Atmospheric pressure computed for the level of the station elevation.
SUMMATION LAYER AMOUNT A categorization of the amount of sky cover at and below
each reported layer of cloud.
SUMMATION PRINCIPLE This principle states that the sky cover at any level is equal to the
summation of the sky cover of the lowest layer, plus the additional sky cover present at all
successively higher layers up to and including the layer being considered.
SURFACE VISIBILITY The prevailing visibility determined from the usual point of
SYNOPTIC CHART A chart, such as the ordinary weather map, which shows the distribution
of meteorological conditions over an area at a given moment.
THUNDERSTORM A descriptor, TS, used to qualify precipitation produced by a
storm detected by lightning detection systems.
TIME OF OCCURRENCE A report of the time weather begins and ends.
TORNADIC ACTIVITY The occurrence or disappearance of tornadoes, funnel clouds, or
TORNADO A violent, rotating column of air touching the ground; funnel cloud touches the
ground (see funnel cloud and water spout).
TOWER VISIBILITY The prevailing visibility determined from the airport traffic control
tower when the surface visibility is determined from another location.
TOWERING CUMULUS A descriptive term for a cloud with generally sharp outlines and with
moderate to great vertical development, characterized by its cauliflower or tower appearance.