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Thunderstorms
Lightning Links
NWS Lightning safety
What is a Thunderstorm?
A thunderstorm is formed from a combination of moisture, rapidly rising warm air and a force capable of lifting air such as a warm and cold front, a sea breeze or a mountain. All thunderstorms contain lightning. Thunderstorms may occur singly, in clusters or in lines. Thus, it is possible for several thunderstorms to affect one location in the course of a few hours. Some of the most severe weather occurs when a single thunderstorm affects one location for an extended time.
What is Lightning?
Lightning is an electrical discharge that results from the buildup of positive and negative charges within a thunderstorm. When the buildup becomes strong enough, lightning appears as a "bolt." This flash of light usually occurs within the clouds or between the clouds and the ground. A bolt of lightning reaches a temperature approaching 50,000 degrees Fahrenheit in a split second. The rapid heating and cooling of air near the lightning causes thunder.
Tornado
Be Aware, Be Prepared
Did you know …
- Tornadoes can generate wind speeds of more than 250 mph.
- A tornado's damage path can be more than a mile wide and 50 miles in length.
- Tornadoes are most likely to occur between 3:00 p.m. to 9:00 p.m.
What to Do
- Monitor radio, NOAA Weather Radio or television for the latest updates and EAS messages.
- If a warning is issued or a tornado is imminent, move to a shelter such as a basement or interior hallway.
- If outside, seek shelter in a safe building, ditch or low area.
- Do not remain in, or take shelter in, mobile homes.
- Do not try to outrun a tornado in a vehicle or remain in a vehicle during a tornado – take shelter in a ditch or low area.
Tornado Watches and Warnings
It is important to be aware of the severe weather advisories that are issued by the National Weather Service, including tornado watches and warnings. Severe thunderstorm advisories are also important because those storms can generate tornadoes. Remain alert to signs of an approaching tornado and seek shelter if threatening conditions exist.
TORNADO WATCH: Tornadoes are possible in your area. Remain alert for approaching storms.
TORNADO WARNING: A tornado has been sighted or indicated by weather radar. If a tornado warning is issued for your area and the sky becomes threatening, move to your predesignated place of safety.
SEVERE THUNDERSTORM WATCH: Severe thunderstorms are possible in your area.
SEVERE THUNDERSTORM WARNING: Severe thunderstorms are occurring.
Tornadoes: An Overview
Georgia is vulnerable to a range of severe and potentially life-threatening weather, including tornadoes. Over the past 50 years, a total of 1,220 tornadoes were reported in Georgia, including 33 in the year 2000. While tornadoes have occurred in every month of the year in Georgia, the months of March through May are the most active period of tornado activity in the state.
Our experience in Georgia is not unique, however, and is similar to that of many other states. Although tornadoes occur in many parts of the world, these powerful and destructive forces of nature are found most frequently in the eastern two-thirds of the Unites States. While they mainly occur during the spring and summer months, usually between the hours of 3:00 p.m. and 9:00 p.m., they can, in fact, occur at any time of the day at any time of year. In an average year, 800 tornadoes are reported nationwide, resulting in 80 deaths and more than 1,500 injuries.
A tornado is a violently rotating column of air extending from a thunderstorm to the ground. The most violent tornadoes are capable of tremendous destruction with wind speeds of 250 mph or more. Damage paths can be in excess of one mile wide and 50 miles long. Tornadoes typically move from southwest to northeast at an average forward speed of 30 mph, but they can sometimes be dangerously unpredictable and move in any direction. This underscores the importance of closely monitoring severe weather advisories and knowing what you would do and where you would take shelter in the event that a tornado threatens.
Tornadoes are generally produced by thunderstorms, which develop in warm, moist air in advance of eastward-moving cold fronts. These thunderstorms can be dangerous, producing heavy rains, damaging straight-line winds and hail. The most treacherous ones can generate tornadoes. Occasionally, large outbreaks of multiple tornadoes can develop from these systems. Tornadoes can also be generated hundreds of miles inland by hurricanes and tropical storms, for up to a day after they make landfall.
Advances in technology, such as Doppler radar, have steadily improved tornado forecasting over the years, and the warning time has improved. But radar has its limitations and the terrain in many parts of Georgia, particularly the northern part of the state, also makes it difficult to clearly identify a developing tornado and issue a timely warning.
Contrary to what is often reported, tornadoes do not “skip.” In order to be classified as a tornado, the rotating vortex must be in contact with both the cloud base and the ground. Funnel clouds, which appear to skip, are technically separate tornadoes. Many reports of skipping tornadoes are often the result of weak storms that do not leave a continuous path of visible damage or so multiple tornadoes with only a brief separation.
The size or shape of a tornado has no relationship to its intensity or capacity to cause damage. Some of the smallest tornadoes on record have been classified as F-4 or F-5 and have caused catastrophic destruction. Some large tornadoes, on the other hand, have caused virtually no damage.
Far too many people tend to think of the Wizard of Oz or the movie “Twister” when they picture a tornado, but this conjures up an image that is not always accurate. A tornado does not necessarily have a well-defined funnel. A tornado’s funnel cloud is often obscured by debris, heavy rain or a low cloud. The appearance of a tornado can also vary depending on the direction from which it is being viewed or where it is surrounded by heavy precipitation. Georgia and southern tornadoes differ from their Midwestern cousins in that they do not stay on the ground as long, their funnels are not as clearly defined, and they are harder to distinguish because of the rolling terrain.
During tornado “season,” it is important to pay close attention to severe weather advisories. But there are other signs that a tornado may be approaching including the onset of large hail, a noticeable wall cloud, a loud roar, or a sickly greenish colored sky.
Although heavy wind damage is commonly associated with tornadoes, not all windstorms are actually tornadoes. Damage destruction is often caused by straight-line winds.
Winter Weather
Be Aware, Be Prepared
Did you know...
- Winter storms are considered “deceptive killers” because most deaths are indirectly related to the storm.
- Seventy percent of fatalities related to ice and snow occur in automobiles, and approximately 25 percent of all winter-related fatalities are people caught off-guard in the storm.
- Prolonged exposure to extreme cold can cause frostbit or hypothermia.
- Powerful winter storms can also have thunderstorms associated with them. These storms can dump as much as three inches of snow or one inch of ice in an hour.
What to Do During a Winter Storm
- Monitor radio/TV or NOAA Weather Radio.
- Stay inside. Long exposure to cold increases the risk of frostbite or hypothermia.
- If you must go out, dress in layers.
- If you suspect frostbite or hypothermia, begin warming the person slowly and seek immediate medical assistance. Arms and legs should be warmed last because stimulation of the limbs can drive cold blood toward the heart and lead to heart failure. Put the person in dry clothing and wrap their entire body in a blanket. Never give a frostbite or hypothermia victim alcohol or caffeine.
- Avoid overexertion. The strain from the cold may cause a heart attack and sweating could lead to a chill and hypothermia.
- Keep your gas tank at least half full.
- Drive with caution and carry a disaster supplies kit in your trunk.
- Have an alternative emergency heating source, such as a fireplace or wood stove. Use appropriate safeguards and have proper ventilation.
- Make sure your home is properly insulated.
- To keep pipes from freezing, wrap pipes in insulation or layers of old newspapers, cover the newspapers with plastic to keep out moisture, let faucets drip a little to avoid freezing, and know how to shut off water valves.
Winter Storms - Terms to Know
Sleet: Rain: drops that freeze into ice pellets before reaching the ground. Sleet can accumulate but does not stick.
Freezing Rain: Defined as rain occurring when the surface temperatures are below freezing (32 degrees Fahrenheit, 0 degrees Celsius). The moisture falls in liquid form, but freezes upon impact, resulting in a coating of ice glaze on exposed objects.
Freezing Rain Advisory: This product is issued by the National Weather Service when freezing rain or freezing drizzle causes significant inconveniences, but does not meet warning criteria (normally an ice accumulation of 1/4 inch or greater) and if caution is not exercised, it could lead to life-threatening situations.
Ice Storm Warning: This product is issued by the National Weather Service when freezing rain produces a significant and possibly damaging accumulation of ice. The criteria for this warning vary from state to state.
Winter Weather Advisory: This product is issued by the National Weather Service when a low pressure system produces a combination of winter weather (snow, freezing rain, sleet, etc.) that present a hazard, but does not meet warning criteria. In this case, snowfall does not have to reach Snow Advisory Criteria. The criteria for this advisory can vary from place to place.
Winter Storm Watch: This product is issued by the National Weather Service when there is a potential of very heavy snow. The criteria for this watch can vary from place to place.
Winter Storm Warning: This product is issued by the National Weather Service when a winter storm is producing very heavy snow. The criteria for this warning can vary from place to place.
Snow Advisory: This product is issued by the National Weather Service when a low pressure system produces snow that may cause significant inconveniences but do not meet warning criteria and if caution is not exercised could lead to life threatening situations. The advisory criterion varies from area to area. In Michigan, the criteria for its issuance is a snow event that is forecasted to produce snow (average of forecast range) greater than 3 inches, but less than warning criteria (6 inches in Lower Michigan and 8 inches in Upper Michigan) in 12 hours. If the forecaster feels that it is warranted, he or she can issued it for amounts less than the minimum criteria. For example, it may be issued for the first snow of the season or when snow has not fallen in long while
Frostbite: A severe reaction to cold exposure that can cause permanent harm. A loss of feeling and a white or pale appearance in fingers, toes, nose or earlobes are symptoms of frostbite.
Hypothermia: A condition brought on when the body temperature drops to less than 95°F. Symptoms of hypothermia include uncontrollable shivering, slow speech, memory lapses, frequent stumbling, drowsiness, and exhaustion. Hypothermia is not always fatal, but for those who survive there are likely to be lasting kidney, liver and pancreas problems.
Winter Weather Links
National Weather Service
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