What are the three criteria that the NWS uses to qualify thunderstorms as severe?
The NWS declares that a thunderstorm is severe if wind gusts reach 57.5 mph or faster, if hail is three quarters of an inch in diameter or bigger, or if the thunderstorm produces a tornado or tornadoes. Thunderstorms often produce frequent thunder and lightning as well as heavy rain.
What criteria characterize a severe thunderstorm?
A thunderstorm is classified as “severe” when it contains one or more of the following: hail one inch or greater, winds gusting in excess of 50 knots (57.5 mph), or a tornado. How many thunderstorms are there?
How is thunderstorm severity measured?
The scale ranks thunderstorms by a combination of their average rainfall rate, maximum wind gusts, hail size, peak tornado potential, lightning frequency and storm impact.
What are the five categories of potential severe weather?
The outlook includes five different categories – marginal, slight, enhanced, moderate, and high. Each category is tied to the possibility of a severe weather event withing 25 miles of a particular location.
Which of the following indicate a severe thunderstorm quizlet?
An overshooting top is a good visual indication of a severe thunderstorm.
How are thunderstorms categorized?
Although thunderstorms can vary in size and shape, we can classify them into four main groups: single cell, multi-cell clusters, multi-cell lines, and supercells.
Is there a scale to measure the intensity of a tornado?
Tornado strength is currently measured on what is called the Enhanced Fujita Scale (adapted from the simpler Fujita Scale in 2007), which gives the tornado a rating from 0 to 5 based on estimated wind speeds and the severity of the damage.
What scale is used to measure tornadoes?
The EF Scale
The EF Scale is the standard way to measure tornadoes based on wind damage. The original Fujita Scale (or F Scale) was developed by Dr. Theodore Fujita. All tornadoes, and other severe local windstorms, were assigned a number according to the most intense damage caused by the storm.
What is the K index for severe weather?
K index: 30 (35). K values will be lower if dry air is present at 700 mb, but severe weather or even heavy rain still can occur (see K index section).
What are the levels of severe weather?
Hazardous Weather Outlook: Definitions of Hazard Levels and Their Associated Triggers
| Hazard Level | 0 | 5 |
|---|---|---|
| Hail | Nil | > 3 inches |
| Wind (convective) | Nil | Derecho |
| Tornado | Nil | EF4-EF5 |
| Winter Weather | Nil | Paralyzing Winter Weather (ie., 1 inch or more ice or blizzard w/ heavy snow) |
What is a severe thunderstorm warning?
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 one inch or larger in diameter and/or winds equal or exceed 58 miles an hour; therefore, people in the affected area should seek safe shelter immediately.
What are the three criteria for a winter weather advisory?
Snow accumulations 1-3 inches; Any freezing rain accumulations less than ¼ inch; Any sleet accumulations less than ½ inch. Winter Weather Advisories are issued in any one of the three criteria are forecast to be met.
What is the frequency of Lightning for a severe thunderstorm warning?
Lightning frequency is not a criteria for issuing a severe thunderstorm warning. They are usually issued for a duration of one hour. They can be issued without a Severe Thunderstorm Watch being already in effect. Like a Tornado Warning, the Severe Thunderstorm Warning is issued by your National Weather Service Forecast Office (NWFO).
Can a severe thunderstorm be issued without a watch?
Severe thunderstorms can produce tornadoes with little or no advance warning. Lightning frequency is not a criteria for issuing a severe thunderstorm warning. They are usually issued for a duration of one hour. They can be issued without a Severe Thunderstorm Watch being already in effect.