Meteorology or Weather Terms +

A glass-like piece of rock formed when lightning strikes dry sand.

Some fulgurites measure up to 10 feet (3 meters) in length.

A rotating extension of a cloud that touches, or does not touch the ground; usually, associated with clouds that have the potential to form tornadoes or waterspouts.

A wind with a velocity that ranges from 32 to 63 miles (51 to 101 kilometers) per hour.

The colorful, circular halo seen when looking down at an object's shadow which is caused by diffraction of sunlight.

It is often observed when the shadow of a flying aircraft is seen on a cloud.

Fog that forms when the ground cools.

It rises less than about 200 feet (61 meters).

A sudden, brief increase in wind speed; usually, associated with fast=moving high pressure systems, squalls and thunderstorms.

Pellets of ice that range in size from less than a half inch to several inches, or more, in diameter; usually, formed in the tops of cumulonimbus clouds when water droplets freeze.

1. A dry, dusty wind from the northeast or east that blows from the Sahara across western Africa; especially, from late November until about mid-March.

It originates in the Sahara as a desert wind and extends southward to about 5°N in January and 18°N in July. In the humid lands along the Gulf of Guinea, its dryness is considered to be refreshing.

The harmattan is extremely dry and often reaches hurricane force which transports large amounts of dust and sand to the Atlantic Ocean.

It is associated with the high pressure area that lies over the northwest Sahara in the winter and the adjoining part of the Atlantic during other seasons.

During the summer, the cooler on-shore southwest monsoon undercuts it, but the harmattan continues to blow at a height of about two kilometers (3000–6000 feet) and sometimes deposits dust on ships that are at sea and this conflict of winds causes the so-called "West African tornadoes".

2. Also defined as a wind of western Africa, a north-east trade wind between 0 ° and about 20 ° latitude North, appearing primarily in the dry season and in winter (November till possibly March), and followed by the southwest monsoon (rainy season).

Cloud-to-cloud lightning, common in the summer, which occurs behind a cloud or below the horizon but lights up the surrounding clouds.

Usually no thunder is heard because of the distance from the observer.

The upper portion of the atmosphere approximating the region of the thermosphere and the ionosphere.

The heterosphere includes the layers of the thermospere and the exosphere.

The lower portion of the atmosphere which includes the layers (from the bottom up) troposphere, stratosphere, and mesophere.

Water vapor content of the air, usually expressed as relative humidity.

The condition when the air on the ground is cooler than the air at a higher latitude.

Inversions are usually associated with stable, but stagnant, air conditions.

Lines connecting areas of equal pressure on weather maps.

Winds that occur in a valley as the air cools and flow down the slope; usually, after sunset.