Nacreous Clouds - Nacreous clouds are rare and are rarely found too far south of the poles. They form at an impressive elevation between 68,000 to 100,000 ft where temperatures are at or below -108F. They appear as large thin discs which tend to reflect vivid colors. Due to their high elevations, they can only be seen when the sun is just below the horizon.

Brontophobia - This phobia is defined as the irrational fear of thunder. For those who suffer, it creates high anxiety even though the thunder may pose no real threat to them.

Nautical Twilight - Is defined to begin in the morning, and to end in the evening, when the center of the sun is geometrically 12 degrees below the horizon. At the beginning or end of nautical twilight, under good atmospheric conditions and in the absence of other illumination, general outlines of ground objects may be distinguishable, but detailed outdoor activities are not possible. During nautical twilight the illumination level is such that the horizon is still visible, even on a Moonless night, thereby allowing mariners the ability to take reliable star sights for navigational purposes.

Doppler Effect - The shift in frequency that occurs when an object goes from moving towards an observer to away from an observer. Everyone has heard this when a police car drives by. As the police car is approaching, the siren will have a high pitch. Then when the police car begins moving away from you the pitch of the siren lowers. This effect is what weather radars use to calculate velocity.

Skew-T - A Thermodynamic Diagram on which temperature, dew point, and winds are plotted for the various levels in the atmosphere. Meteorologists receive the data needed to construct a skew-t diagram from weather balloon launches. Skew-t charts are a great way to diagnose how stable or unstable the atmosphere is on a given day.

St. Elmo's fire - A bright electric discharge that is projected from objects when they are in a strong electric field, such as occurs during a thunderstorm. This discharge can cause a ship's mast or airplane wings to have a greenish or bluish glow.

Air Mass Thunderstorm - Generally, a thunderstorm not associated with a front or other type of synoptic-scale forcing mechanism. Air mass thunderstorms typically are associated with warm, humid air in the summer months; they develop during the afternoon in response to solar heating, and typically have a short lifespan. They are less likely to be severe than other types of thunderstorms, but they are still capable of producing gusty winds, brief heavy rain, and (in extreme cases) hail over 3/4 inch in diameter.