1. SevereThunderstormsElizabeth Wilkins 2. Severe Thunderstorms What are they? The National Weather Service (NWS) says that inorder for a thunderstorm to be classified assevere it must have the following characteristics: Hail Wind (and/or) lightning (and/or) tornadoes 3. Characteristics Hail It must be at least 0.75 inches in diameter Wind It must be at least 58 mph (50 knots) (and/or) lightning Not necessary to categorize a thunderstorm assevere because then every storm would beclassified as such. (and/or) tornadoes Giant hail is an indication for possibly a tornado 4. The Aftermath Severe thunderstorms can cause excessiverainfall which can result in flash flooding Strong winds and hail can damage cropsamongst other things Fires can also be produced Lightning usually kills approximately 80 people inthe United States per year On average, more people die in the UnitedStates from floods and flash floods than lighting ortornadoes 5. Precautions If you are caught outside during a severethunderstorm, try and seek safety in a building. Automobiles with metal frames and trucks are safe too Stay away from electrical appliances, cordedphones, and the shower AVOID: elevated places and isolated trees Lightning is more likely to strike there If you are on ground level then try to stay low, butdo not completely lie down. A surface current from lightning could travel throughyour body and injure/kill you Keep minimum contact to the ground 6. Ruthven, AustraliaStorm chaser David Ellem captured this picture of a severe thunderstorm onDecember 10th 2008 near the upper north coast of the New South Walesnear Ruthven. 7. Watch vs. Warning A watch means that there is potential for athunderstorm to occur Possibility that large hail and damaging winds mayoccur A warning means that the thunderstorm isoccurring or is impending based on Dopplerradar Stayed tuned in on the National Weather Servicereport for updates and possible warnings Take precautions and move inside to a safeplace!