Aeronautical Terms beginning with E

Echo

In radar, (1) the energy reflected or scattered by a target; (2) the radar scope presentation of the return from a target.

Eddy

A local irregularity of wind in a larger scale wind flow. Small scale eddies produce turbulent conditions.

En Route Flight Advisory Service (EFAS)

An en route weather-only AFSS service.

Estimated ceiling

A ceiling classification applied when the ceiling height has been estimated by the observer or has been determined by some other method; but, because of the specified limits of time, distance, or precipitation conditions, a more descriptive classification cannot be applied.

Evaporation

The change of liquid water to water vapor.

Extratropical low (sometimes called extratropical cyclone, extra

Any cyclone that is not a tropical cyclone, usually referring to the migratory frontal cyclones of middle and high latitudes.

Eye

The roughly circular area of calm or relatively light winds and comparatively fair weather at the center of a well-developed tropical cyclone. A wall cloud marks the outer boundary of the eye.