Glossary

/Glossary/

Cap

A layer of relatively warm air aloft, usually several thousand feet above the ground, which suppresses or delays the development of thunderstorms. Air parcels rising into this layer become cooler than the surrounding air, which inhibits their ability to rise further and produce thunderstorms. Sometimes called the lid.

Clear Slot

A local region of clearing skies or reduced cloud cover, indicating an intrusion of drier air on a severe thunderstorm; often seen as a bright area with higher cloud bases on the west or southwest side of a wall cloud. A clear slot is believed to be a visual indication of a rear flank downdraft (RFD).

By | January 30th, 2017|Uncategorized|0 Comments

Climate

The generally prevailing weather conditions of a region over a period of years.   Some elements of climate include average high temperatures for a particular day or normal precipitation for a month or season.

By | January 15th, 2016||0 Comments

Convection

The transport of heat and moisture by the movement of a fluid; In meteorology, the term is used specifically to describe vertical transport of heat and moisture in the atmosphere, especially by updrafts and downdrafts in an unstable atmosphere.  Cumulonimbus, towering cumulus clouds and alto-cumulus castellanus clouds are all visible forms of convection. Convection is [...]

By | January 15th, 2016|, |0 Comments

Convective Outlook

A forecast containing the area(s) of expected thunderstorm occurrence and expected severity over the contiguous United States, issued several times daily by the SPC. The terms marginal, slight risk, enhanced risk, moderate risk, and high risk are used to describe severe thunderstorm potential. Local versions sometimes are prepared by local NWS offices.

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Convergence

Tending to move toward one point or to approach each other. Convergence in a horizontal wind field indicates that more air is entering a given area than is leaving at that level.  Convergence at low levels may result in upward forcing; at higher levels convergence may result in downward forcing.  When other factors such as [...]

By | January 27th, 2016|, |0 Comments