Severe Thunderstorms
Hot, humid, unsettled weather conditions. An approaching cold front or trough. The ideal conditions for severe thunderstorms, and their progeny of flash flooding, large hail, destructive wind gusts, and even tornadoes.
Severe Thunderstorm - A thunderstorm that goes from the mature stage to the severe stage before dissipating. Severe thunderstorms are most efficient "machines" because the updraft remains strong for a long time.
Severe Thunderstorm - a thunderstorm with wind gusts of 50 knots (58 mph) or greater, hail at least three-quarters of an inch in diameter, and/or a tornado or funnel cloud
Shear - see wind shear ...
Severe Thunderstorm Warning- Issued when large hail of damaging wind is actually occurring or imminent. Severe thunderstorms can produce tornadoes with little or no advance warning.
Severe Thunderstorm-Any one of the three conditions must be met. 1) Tornadoes 2) Hailstones larger than 3/4" 3) Wind gusts greater than 58 miles per hours.
Severe Thunderstorm Warning
This is issued when either a severe thunderstorm is indicated by the WSR-88D radar or a spotter reports a thunderstorm producing hail 3/4 inch or larger in diameter and/or winds equal or exceed 58 miles an hour; ...
Severe thunderstorm
A thunderstorm which produces any or several of the following:
Hail 2 cm in diameter or larger.
Flash flooding
Wind gusts in excess of 48 knots (96 km/h)
Tornado ...
Severe Thunderstorm A thunderstorm that produces either of the following: winds of 50 kts (58 mph) or greater (these speeds can result in structural or tree damage), hail ¾" in diameter or larger, or a tornado.
SEVERE THUNDERSTORM
A thunderstorm with winds measuring 50 knots (58 mph) or greater, 3/4 inch hail or larger, or tornadoes. Severe thunderstorms may also produce torrential rain and frequent lightning.
SEVERE THUNDERSTORM: A strong thunderstorm with wind gusts in excess of 58 mph (50 knots) and/or hail with a diameter of 3/4" or more. A thunderstorm with winds greater than 39 mph and/or hail greater than " inch is defined as approaching severe.
Severe Thunderstorm - A thunderstorm which produces tornadoes, large hail, or winds of 50 knots (80 kph) or more. Structural wind damage may imply the occurrence of a severe thunderstorm.
Severe Thunderstorm Warning
Indicates that severe thunderstorms have been sighted or indicated on radar.
Severe thunderstorms Intense thunderstorms capable of producing heavy showers, flash floods, hail, strong and gusty surface winds, and tornadoes.
SEVERE THUNDERSTORM - A thunderstorm with winds of 58 mph or more or hail 3/4-inch diameter or larger. Structural wind damage may imply the occurrence of a severe thunderstorm.
Severe thunderstorm Thunderstorms accompanied by locally damaging surface winds, frequently lightning, or large hail.
Severe Thunderstorm Watch- Issued when conditions are favorable for the development of severe thunderstorms in and close to a defined area.
Shallow fog- Fog in which the visibility at 6 feet above ground level is 5/8ths of a mile or more.
Severe Thunderstorm Warning - Issued to warn the public, emergency management and other cooperating agencies when a severe thunderstorm is forecast to occur or is occurring.
Very Severe Thunderstorm Warning: It is issued for sustained winds over 75 mph in the 7-county Minneapolis/St. Paul area.
Very Windy: 30 to 40 mph winds ...
SEVERE THUNDERSTORM: A thunderstorm with wind gusts in excess of 58 mph (50 knots), frequent lightning and hail with a diameter of 3/4" or larger.
SHOWER: Liquid precipitation with frequent changes in intensity or sudden stops or starts.
Severe thunderstorm: a thunderstorm that produces heavy precipitation, frequent lightning, strong, gusty surface winds or hail. A severe thunderstorm can cause flash flooding and wind and hail damage and may spawn tornadoes.
Severe thunderstorm due to:
surface winds greater than or equal to 50 knots
hail at the surface greater than or equal to 3/4" in diameter,
tornadoes,
Embedded thunderstorms,
Line of thunderstorms, or ...
SEVERE THUNDERSTORM - A thunderstorm which produces winds gusting at or above 58 MPH, hail at or exceeding 3/4", or where tornadoes develop. Either of these events, some, or all of them constitute a severe thunderstorm.
A Severe Thunderstorm Watch is issued by the Storm Prediction Center in Norman, Oklahoma.
6. Severe Thunderstorm Probability Charts.
7. Cloud Cover U.S. A.
8. Snow Depth U.S.A.
Generally, severe thunderstorm winds (58 miles per hour and higher) are needed to generate gustnadoes. Damaging gustnadoes most often form in straight-line wind events and are more prevalent in thunderstorms with winds in excess of 100 miles per hour.
HIGH RISK (of severe thunderstorms)
Severe weather is expected to affect more than 10 percent of the area. A high risk is rare, and implies an unusually dangerous situation and usually the possibility of a major severe weather outbreak.
Pulse Severe ThunderstormsSingle cell thunderstorms which produce brief periods of severe weather (3/4 inch hail, wind gusts in the excess of 58 miles an hour, or a tornado).
With respect to severe thunderstorms, a local region of clearing skies or reduced cloud cover, indicating an intrusion of drier air; often seen as a bright area with higher cloud bases on the west or southwest side of a wall cloud.
These conditions often favor the development of strong to severe thunderstorms.Transverse RollsElongated low-level clouds, arranged in parallel bands and aligned parallel to the low-level winds but perpendicular to the mid-level flow.
Watch Box(or simply "Box") - slang for a Severe Thunderstorm Watch or Tornado Watch issued by the SPC.
This product lets the NWFO know of the status of the current severe weather watch (Tornado or Severe Thunderstorm). During the severe weather watch, the Storm Prediction Center (SPC) will issue these reports periodically.
flare echo"A weak radar echo in the form of a tapered radial extension beyond the far edge of a severe thunderstorm, associated with the presence of large hydrometeors, especially hail, in the storm.
An option used by the SPC in tornado and severe thunderstorm watches when the potential for strong/violent tornadoes, or unusually widespread damaging straight-line winds, is high.
ENHANCED-V- An enhanced-V is a V-shaped region over and downwind from strong to severe thunderstorms on infrared imagery. The V signature is seen best on color enhanced infrared satellite images. The cold cloud tops and anvil form a V-shape.
This image shows some severe thunderstorm cells in western Illinois and eastern Missouri on April 19, 1996.
Moderate Risk (of severe thunderstorms) - Severe thunderstorms are expected to affect between 5 and 10 percent of the area. A moderate risk indicates the possibility of a significant severe weather episode.
For the latest news on severe thunderstorm events, tornadoes, waterspouts etc., a visit to the web site of the Tornado and Storm Research Organisation is essential.
Downbursts occur in regions of a severe thunderstorm where the air is accelerated downward by exceptionally strong evaporative cooling occurs (a dry downburst) or by very heavy rain which drags dry air down with it (a wet downburst).
More violent severe thunderstorms form in areas with a strong vertical wind shear that forces the updraft into the mature stage, the most intense stage of the thunderstorm.
A radar echo signature often associated with severe thunderstorms, especially those that produce wind damage. It is bent outward in a "bow" shape.
BOYLE'S LAW ...
A strong localized downdraft less than 4 km wide that occurs beneath severe thunderstorms. A strong downdraft greater than 4 km across is called a downburst.
Microclimate(6)
The climate structure of the air space near the surface of the earth.
Downbursts A severe localized downdraft that can be experienced beneath a severe thunderstorm. (Compare Microburst)
Downdraft Downward moving air, usually within a thunderstorm cell.
WATCH A forecast issued well in advance of a severe weather event to alert the public of the possibility of a particular hazard, such as tornadoes, severe thunderstorms, flash and river floods, winter storms, or heavy snows.
Values in excess of 2500 show enough energy to produce strong thunderstorms and may be used as a justification for the National Severe Storms Forecast Center (NSSFC) in Norman, OK to issue a severe thunderstorm watch.
 See also: Thunderstorm, Thunder, Storm, Weather, Cloud
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