Green flash - A brilliant green color that can appear on the upper limb of the sun as it rises or sets. It is believed that it occurs due to atmospheric refraction and is most commonly seen at sunset. On rare occasions it has been seen as a green ray of light briefly shooting up from the sun as it rises or sets.

Isobars - Isobars are lines on a weather map joining points that have the same air pressure at a given altitude. Isobars are typically drawn in for surface plots. When isobars are tightly packed, windy conditions can be expected.

Downburst - A strong wind that is the result of a strong downdraft that occurs beneath a severe thunderstorm. Downdrafts are pockets of air that accelerate downward from a thunderstorm, and then spread horizontally when they reach the ground. The resultant strong winds that are experienced at the surface is the downburst.

Twilight - Before sunrise and again after sunset there are intervals of time during which there is enough natural light provided by the upper atmosphere, which does receive direct sunlight and reflects part of it toward the Earth's surface. Some outdoor activities may be conducted without artificial illumination during these intervals of twilight. It is useful to have some means to set limits beyond which a certain activity should be assisted by artificial lighting.

Shelf Cloud - Also known as a roll cloud. A low, horizontal, sometimes wedge-shaped cloud formation associated with the leading edge of a thunderstorm's outflow winds or gust front. Shelf clouds normally stretch across the entire horizon as an organized line of storms approaches. When a shelf cloud is observed, prepare for a quick increase in winds. A severe line of storms can produce shelf clouds that indicate incoming straight-line winds of over 60 mph.

GFS (Global Forecast System) - One of the American operational forecast models run at the National Centers for Environmental Prediction. GFS stands for Global Forecast System. The GFS model is run 4 times a day and it covers the entire globe. GFS forecast output can extend up to 384 hours from when it is run.

Super-Typhoon - A tropical cyclone in the western Pacific basin that has one minute sustained wind speeds of a last 150 mph. This corresponds to what would be a category 4 or greater hurricane if the tropical cyclone were in the Atlantic or eastern Pacific.