JPATS Weather - NETC

JPATS AVIATION WEATHER BOOKLET
APPENDIX A
GLOSSARY OF SELECTED METEOROLOGICAL TERMS
ACTUAL TIME OF OBSERVATION – For METAR reports, it is the time the last element of
the report is observed or evaluated. For SPECI reports, it is the time that the criteria for a SPECI
were met or noted.
ADIABATIC – The word applied in the science of thermodynamics to a process during which
no heat is communicated to or withdrawn from the body or system concerned. Adiabatic changes
of atmospheric temperatures are those that occur only in consequence of compression or
expansion accompanying an increase or a decrease of atmospheric pressure.
AIRCRAFT MISHAP – An inclusive term to denote the occurrence of an aircraft accident or
incident.
ALTIMETER SETTING – Pressure of the reporting station converted in order to produce a
reading on altimeters of field elevation at 10 feet above the runway (normal installation height of
the altimeter). Altimeter settings are given in inches of mercury and represent sea level pressure.
ATMOSPHERIC PRESSURE – The force exerted by the weight of the atmosphere from the
level of measurement to its outer limits.
AUGMENTED REPORT – A meteorological report prepared by an automated surface weather
observing system for transmission with certified weather observers signed on to the system to
add information to the report.
AUTOMATED REPORT – A meteorological report prepared by an automated surface weather
observing system for transmission, and with no certified weather observers signed on to the
system.
BLOWING DUST – Dust raised by the wind to moderate heights above the ground and
restricting horizontal visibility to less than 7 miles. If visibility reduced to between 5/8 and 5/16
then a Duststorm; if less than 5/16, a severe Duststorm.
BLOWING SAND – Sand raised by the wind to moderate heights above the ground and
restricting horizontal visibility to less than 7 miles. If visibility reduced to between 5/8 and 5/16
then a Sandstorm; if less than 5/16, a severe Sandstorm.
BLOWING SNOW – Snow particles raised and stirred violently by the wind to moderate or
great heights. Visibility is poor (6 miles or less) and the sky may become obscured when the
particles are raised to great heights.
BLOWING SPRAY – Spray raised in such quantities as to reduce the visibility at eye level (6
feet on shore, 33 feet at sea) to 6 miles or less.
BROKEN LAYER – A cloud layer covering whose summation amount of sky cover is 5/8
through 7/8.
CALM – A condition when no motion of the air is detected.
CEILING – The height above the earth's surface (field elevation or ground elevation) of the
lowest non-surface based layer that is reported as broken or overcast, or the vertical visibility
into an indefinite ceiling.
Version 3.2/Dec 08 A-1