Severe Weather Awareness
Thunderstorms
Damaging winds occur, on average, 19 days per year, in the area of Georgia north of Atlanta. These events have taken place in every month of the year, but tend to be most frequent during the spring and summer months. The peak month is July during which more than 500 events were reported over the past 40 years. During the favored months, the most likely time of day for wind damage is mid afternoon through early evening.
Large hail pelts the area on average seven days per year. April is the month of peak occurrence, but many episodes have also been reported in the other spring and summer months. During this active period, the most likely time of occurrence is from mid afternoon through early evening.
The average number of tornado days is six per year. While tornadoes have been reported in all months of the year, most occur in the March-April-May time frame. During this "tornado season" the most likely time of occurrence is from mid afternoon through early evening.
Tornado intensities of F2 or greater are involved in 37 percent of the events when the data is broken down into a county-by-county basis. These strong tornadoes are more likely to occur during the month of April than in any other month. During the period 1950-1993, 72 people lost their lives in tornadoes. Almost 1,700 were injured.
In Georgia, the biggest threat from severe thunderstorms is damaging straight line winds and large hail. Straight line winds can reach speeds excess of 100 mph and produce damage similar to a tornado.
Mp>The factors used by the National Weather Service to determine if a thunderstorm is severe are winds greater than 57 mph and hail greater than three-fourths inch in diameter or about the size of a penny. Typically, a severe thunderstorm lasts about 30 minutes and occurs in the afternoon and evening hours during the Spring and Summer months. However, severe weather is possible any time of the day and any time of the year. A special class of severe thunderstorms called "Supercells" are particularly violent and can last for several hours. Tornadoes are often produced from these supercell thunderstorms.
So what can you do to protect yourself and your family?
The best thing to do is to have a plan of action in place before threatening weather develops. Know what the difference between a watch and warning are. A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms to develop, but there is not an imminent threat. A Severe Thunderstorm Warning means a severe thunderstorm has been detected and an imminent threat to life and property has developed.
Know your area so you can track storms, listen to a weather radio, local TV or radio reports. Make sure you have battery backup. Monitor any forecasts if threatening weather is possible and you are planning outdoor activities.
If severe weather is imminent, and you are inside, move to shelter such as a basement or an interior room on the lowest floor of the building. Remember, it's best to put as many walls between you and the outside as possible.
If you are caught outside, try to seek shelter in a sturdy structure.
Remember, severe thunderstorms can produce tornadoes with little or no warning!!
Hail Size Estimates, Diameter in inches
Pea: ¼ inch
Penny: ¾ inch
Golf ball: 1¾ inch
Quarter: 1 inch
Half Dollar: 1¼ inch
Tennis Ball: 2½ inch
Baseball: 2¾ inch
Grapefruit: 4 inches
Wind Speed Estimates, Speed (MPH): Effects
25-31: Large branches in motion; whistling in telephone wires
32-38: Whole trees in motion
39-54: Twigs Break off of trees; wind impedes walking
55-72: Damage to chimneys and TV antennas; pushes over shallow rooted trees
73-112: Peels surface off roofs; windows broken; trailer homes overturned
113+: Roofs torn off houses weak buildings and trailer homes destroyed; large trees uprooted
Tornadoes
Considered nature's most violent storm, a tornado is a violently
rotating column of air extending from the base of the thunderstorm and in
contact with the ground (when it is not in contact with the ground, it is
called a funnel cloud). Tornado winds average 100 mph, but can exceed
300 mph.
The strongest tornadoes develop from severe thunderstorms in
atmospheric conditions with a wind profile that varies with height. Severe thunderstorms and tornadoes occur most often in the Mid-South in March, April and May. A secondary season occurs in the Fall, typically November and December.
Most tornadoes occur in the afternoon and evening. However, tornadoes have occurred in every hour of the day and night and every month of the year. No time of day or year is immune to tornado
occurrences.
Your Safety will improve if you stay alert to the risk of tornadoes from
thunderstorms that approach. This is especially true if a tornado watch
is in effect. Conditions should be carefully monitored when severe
thunderstorms are occurring, or are expected to occur.
Severe thunderstorms can produce tornadoes with little or no warning.
Know the difference between a TORNADO WATCH and a TORNADO WARNING.
- A tornado watch means tornadoes may develop; so keep an eye to
the sky for thunderstorms and the dangers they pose. Listen to NOAA
Weather Radio, commercial radio, or TV for weather statements or warnings.
A watch allows time to plan what to do if a tornado approaches. A watch
usually spans several thousand square miles, and can cover parts of more
than one state.
- A tornado warning means a tornado has been sighted, or is
indicated on weather radar. Persons in the path of the tornado should seek
shelter immediately.
Information taken from National Weather Service materials.
