Definitions

 

SEVERE THUNDERSTORM DEFINITION:A severe thunderstorm as defined by the National Weather Service is a storm with hail = or > than 3/4" in diameter or convective wind gusts = or > than 58 mph. Even if a storm is not severe, it still remains a potential killer. Lightning, flash flooding, wind blown hail (even small hail), and general thunderstorm wind gusts pose a threat to life and / or property. Severe thunderstorms also have the potential of producing a tornado with little or no advanced tornado warning.

NOAA WATCH AND WARNING DEFINITIONS:

SEVERE THUNDERSTORM WATCH- The conditions are favorable for the development of thunderstorms that will contain hail = or > than 3/4" in diameter or convective wind gusts = or > than 58 mph. Severe thunderstorms are also capable of producing a tornado.

TORNADO WATCH- The conditions are favorable for the development of tornado producing storms.

SEVERE THUNDERSTORM WARNING- A severe thunderstorm has been spotted by a valid storm spotter or there is strong evidence from radar data that a severe thunderstorm is occurring.

TORNADO WARNING- A tornado has been spotted by a valid storm spotter or there is strong evidence from radar data that a tornado is occurring.

A tornado -is a "violently rotating column of air in association with a cumulonimbus cloud that is in contact with the earth's surface".

FUNNEL CLOUD — A funnel shaped cloud, usually extending from a convective cloud, which is associated with a violently rotating column of air that is NOT in contact with the ground.

The Fujita Scale is the standard scale for rating the severity of a tornado as measured by the damage it causes. A tornado is usually accompanied by thunder, lightning, heavy rain, and a loud "freight train" noise. In comparison with a cyclone or hurricane, a tornado covers a much smaller area but can be more violent and destructive.

Hazard Mitigation -any action taken to reduce or eliminate the long-term risk to human life and property from natural hazards"

Natural Disaster - any condition affecting or threatening public health, welfare, safety or security including, but not limited to flood, tornado, earthquake, wind, storm, winter storm or other natural cause.

Manmade Disaster - shall mean incidents such as dam failure, power failure, structural fires, hazardous materials both fixed facility and transportation, radiological both fixed facility and transportation, transportation accidents such as air, rail, highway, water, and other incidents which are beyond the control of regular forces.

Winter Weather Definitions

 

Black Ice- thin, new ice that forms on fresh water or dew covered surfaces; it is common on roadways during the fall and early winter and appears "black" because of its transparency.

Outlook:
Issued when significant winter precipitation is possible in the next three to five days. An outlook does not guarantee the event will occur, but should be a "heads-up" to monitor later forecasts and information.

Watch:
Issued when significant winter precipitation is possible in the 24 to 48 hours. Again, a watch does not mean it’s a sure thing, but is designed to alert you to the fact that hazardous winter weather could occur. Watches are issued for winter storms, heavy snow or blizzards.

Warning:
Issued when winter precipitation that could lead to a threat to life or property is expected. A warning is the most serious of the winter weather messages and indicates that action should be taken immediately to get ready for the storm. Warnings are issued for winter storms, ice storms, heavy snow, blizzards and heavy sleet.

Advisory:
Issued for winter precipitation that is not expected to produce significant risks to life and/or property, but that could still impact travel or other activities. Advisories are issued for a variety of winter weather conditions.

Winter storm:
This term may refer to a combination of winter precipitation, including snow, sleet, freezing rain, etc.

Sleet:
Rain drops that freeze into pellets of ice before reaching the ground. Sleet usually bounces when hitting a surface and does not stick to objects. However, it can accumulate and cause dangerous driving conditions.

Freezing rain:
Rain that falls onto a surface where the temperature is below freezing. This causes the rain to freeze on contact with trees, power lines, cars and roads. This coating or glaze of ice causes serious travel problems, even with very small accumulations.

Ice storm:
A high impact event caused by excessive accumulations of freezing rain on trees and power lines. Generally, a quarter of an inch or more of ice is considered dangerous. However, this can vary depending on other factors.

Blizzard:
This life-threatening event is produced by a combination of falling or blowing snow, and high winds, typically 35 mph or more for a prolonged period of time. This combination can create potentially deadly travel conditions with impassable roads and zero visibilities.

Wind chill:
The combination of wind and temperature that serves as an estimate of how cold it actually feels to exposed human skin. Wind chill values below -19 degrees are considered dangerous

Flood: An overflow of water onto normally dry land. The inundation of a normally dry area caused by rising water in an existing waterway, such as a river, stream, or drainage ditch. Pond of water at or near the point where the rain fell. Flooding is a longer term event than flash flooding: it may last days or weeks.

Flash flood: A flood caused by heavy or excessive rainfall in a short period of time, generally less than 6 hours. Flash floods are usually characterized by raging torrents after heavy rains that rip through river beds, urban streets, or mountain canyons sweeping everything before them. They can occur within minutes or a few hours of excessive rainfall. They can also occur even if no rain has fallen, for instance after a levee or dam has failed, or after a sudden release of water by a debris or ice jam.

FLASH FLOOD WATCH — Issued to indicate current or developing hydrologic conditions that are favorable for flash flooding in and close to the watch area. When a watch is issued, be aware of any potential flood hazards. Those in the affected area are urged to be ready to take quick action if a Flash Flood Warning is issued or flooding is observed.

FLASH FLOOD WARNING — Issued when flash flooding is in progress, imminent, or highly likely. Those in the affected area should evacuate immediately or move to higher ground if possible. Information in this warning will include the locations in the flood and any areas which may be impacted. Flash Flood Warnings can be issued without a Flash Flood Watch in effect.

FLASH FLOOD STATEMENT — A product issued which provides follow-up information on any flooding which has occurred or is occurring, and what areas will be affected.