Think about the most recent storm you have witnessed. What was it like? Was the wind howling? Was the rain falling so hard that it pounded the roof? Was lightning flashing all around?

Storms are weather events. Unlike less energetic changes in the air, storms are violent disturbances. Sometimes, they appear with little or no warning. When they strike, they are accompanied by strong winds, intense precipitation, and other extreme conditions.

Weather describes the state of the atmosphere. We often describe weather as measured values of wind speed, temperature, air pressure, precipitation, and humidity. Weather conditions at any location change over time. Typically, these changes are gradual and predictable. However, when the change is sudden and energetic, beware! You’re probably experiencing a storm.

Suppose that heavy rain and wind gusts powerful enough to knock over trash barrels should suddenly occur. No doubt you’d consider that a storm. But suppose that the wind were powerful enough to knock down a building. Now, that’s a monster storm!

There are all sorts of monster storms. Hurricanes are among the largest of these powerful disturbances. Hurricanes are highly organized storms that can generate ocean waves of about 30 m (98 ft) and deadly storm surges over 9 m (30 ft).

When atmospheric conditions are right, a thunderstorm can grow into a supercell, which can spawn a tornado or even several tornadoes. Although more compact in size than hurricanes, tornadoes pack a powerful and deadly punch. With wind speeds that can exceed 322 km/hr (200 mph), twisters can toss cars and flip mobile homes as if they were toys. 
 

Tornado touchdown near Alfalfa, Oklahoma.

 

Lightning is an awesome electrical discharge that often accompanies hurricanes and tornadoes. A storm need not be a monster, however, to generate intense lightning. As long as weather conditions produce clouds having an unstable distribution of positive and negative charges, lightning can form.

 

Hailstones the size of baseballs have occasionally accompanied tornadic storms.

Strong wind circulation may also produce a shower of irregular pieces of ice called hail. Although hail seldom grows larger than pea-sized, monster hailstones larger than baseballs have been recorded striking people and property!

 

When the temperature falls, the scene may be set for a different type of monster storm—a blizzard. A blizzard is a severe snowstorm with winds in excess of 56 km/h (35 mph) and visibilities of 0.4 km (0.25 mi) or less for an extended period of time. Unlike those of a typical winter storm, the blizzard’s strong winds and heavy snow produce blinding conditions. In a blizzard’s most extreme form, snow-laden winds create a complete whiteout. During such an intense period, so much snow fills the air that an observer cannot tell the sky from the ground. 
 
Not all extreme weather arrives as a sudden or an intense disturbance, however. Extreme weather can develop slowly and gradually. Although such incremental change may lack the forceful onset of a tornado or hurricane, the effects of gradual change can have long-lasting consequences.

Have you ever experienced a drought? If so, you know that a drought is a prolonged period of below-normal rainfall. Over time, a drought will produce severe effects that range from crop loss to frequent wildfires. Droughts can cause a community to change the ways it uses and conserves water. In a state of emergency, communities will enforce laws that strictly regulate the use of the endangered water supply.

Now imagine a period of greater-than-normal rainfall. Over-abundant rainfall, even when it’s not part of the drenching from a monster storm, can produce dangerous floods. As the ground becomes inundated, it can no longer absorb water. This runoff then collects in low-lying areas. In cities, streets and highways may become flooded and impassable. In rural regions, if enough precipitation accumulates, streams and rivers will spill over their banks and submerge surrounding areas.

Prolonged periods of excessively hot or cold weather can also be extreme. A heat wave is a period of above-average temperatures. During summer months, heat waves can be deadly to humans, pets, livestock, and crops. Demands for air conditioning may strain electrical power grids and result in blackouts or partial power outages called brownouts.

Drops in temperature can be just as deadly. During winter months, extended periods of below-freezing temperatures produce life-threatening situations. Heating systems fail. Cars refuse to start. Water pipes freeze and burst. These circumstances only add to the dangers of extreme cold.

Forecasters collect measurements on atmospheric conditions, then predict each day’s weather. Each measurement provides a clue to what the weather is doing and how it might change within a few hours. Experienced forecasters can be very accurate in predicting the weather several days out from the data collected.

Researchers use many tools and instruments to piece together the big picture. With more research and better instruments, scientists hope to increase the accuracy of weather forecasts. When lives and property are on the line, accurate forecasting is critical.