The term "weather" refers to the changes within the atmosphere that we experience on the surface of the Earth from day to day. It includes the weather systems that produce gales, torrential rain, dust storms, hail, tornadoes, thunderstorms, lightning, and hurricanes. Weather causes climate changes as well as erosional processes, such as flooding, landslides, mudslides, and slope failure. Click on the individual photos to enlarge for better quality viewing.
Cumulonimbus clouds are towering vertical masses that are very tall, dense, and involve thunderstorms and inclement weather. They are the result of atmospheric instability. If the water droplets within the cloud freezes, then it can become charged with static electricity, and if the difference in charge becomes great enough, giant sparks leap from the cloud as lightning. The intense heating of the air around these explosive flashes generates thunder. Cumulonimbus clouds first start as cumulus clouds. Such smaller clouds are typically characterized by a flat base and a fluffy appearance.
A cyclone is low-pressure area of winds that spiral inwards. They occur counterclockwise in the northern hemisphere and clockwise in the southern hemisphere. Cyclones are actually fairly common and they drive much of the Earth's weather. Cyclones include hurricanes, typhoons, tropical depressions, and tropical storms. Hurricanes can spawn tornadoes which are smaller cyclonic storms that bring about more damage. The average life of most cyclones is one week. Cyclones are given names to meet the need for a unique identifier in issuing forecasts and warnings. During the last 200 years, cyclones have been responsible for the deaths of approximately 1.9 million people worldwide.
A dirty thunderstorm is a weather phenomenon that occurs when lightning is produced by a volcanic plume. Scientists who study volcanoes indicate that particles, such as rock and ash are a part of the ingredients that make up dirty thunder-storms. As the particles collide with each other, they form static electricity, which in turn, creates lightning. Scientists also report that in some instances, smaller lightning bolts have been observed bursting out of the mouth of a volcanic craters as the gases and ash explode. While dirty thunderstorms can be quite fascinating and incredible to watch, they can be very dangerous.
Dry Lightning Storms:
Dry lightning is lightning that strikes without any accompanying rain. It is important to know that, in any case, lightning is not particularly "wet". The western region of the United States is famous for its dry lightning, which sparks hundreds of wildfires each year. It is estimated that some 10,000 such fires are started across the United States in an average year. In a normal thunderstorm, lightning often strikes the ground while rain falls from the storm clouds. The rain, which comes down with the lightning, puts the fire out before it has a chance to spread. In a dry lightning storm, however, rain is produced but never reaches the ground. High winds only make such conditions worse for fires.
A dust devil is a strong, well-formed and relatively long lived whirlwind that can range in size, but most are about three feet in diameter. Their maximum wind speed is about 45 miles per hour and they often dissipate less than a minute after forming. The largest dust devils can grow up to 300 feet in diameter and travel at 60 miles per hour. Larger dust devils generally take about 20 minutes to dissipate. The primary vertical motion is upward, just the opposite of a twister or tornado. They are usually harmless, but can on rare occasions grow large enough to pose threat to people and cause property damage. Dust devils form as a swirly updraft of dust and dust particles under sunny conditions during "fair weather" and are very common in the southwestern United States. They usually take form over flat, barren and desert terrains. Dust devils, even small ones, can produce radio noise and electrical fields greater than 10,000 volts per meter.
Dust storms are meteorological phenomenons that are common in arid and semi-arid regions. Such storms arise when a gust front or strong wind lifts up fine-grained dust and dirt from a dry surface. Particles are known to be transported and deposited by suspension and saltation. The term sandstorm is used most often in the context of desert sand where the particles being transported and deposited are that of sand grains. A dust storm usually arrives suddenly in the form of an advancing wall of dust and debris that may be miles long and several thousands of feet high. They strike with little warning and make driving conditions for motorists quite hazardous.
El Nino and La Nina:
Variations in normal weather patterns, such as El Nino and La Nina, bring about some vast and extreme weather events. These involve unusual sea temperatures, changes to ocean currents, and effects on pressure systems. This weather pattern involves interaction between the ocean and atmosphere. The equatorial Pacific regularly experiences a much more extensive warming at irregular periods of between two and seven years, and this significant large-scale event is known as El Nino. These seasonal anomalies range from increased droughts to substantially wetter, stormy conditions. La Nina develops with a similar frequency to El Nino though in reverse.
Flooding is associated with widespread and continuous heavy rainfall. When the rivers and streams reach their limit for capacity, they overflow and spill over the banks. This can then lead to devastating floods. The amount of flooding is usually a function of the amount of precipitation in an area, the amount of time it takes for rainfall to accumulate, previous saturation of local soils, and the terrain around the river system. Flash floods often bring walls of water 10 to 20 feet high, and 95% of those that try to "outrun" the waters along their path rather than climbing rocks or going up-hill to higher ground end their lives with disaster. It looks like this "momma" pig and her two young ones had the right idea.
Freezing rain is the name given to rain that falls when surface temperatures are below freezing. Such conditions occur during the winter months under special conditions when rain produced in a warm air mass falls through a shallow cold air mass below it, freezing on contact with the ground (at least 32 degrees F). The rain will freeze once it makes contact with any surface, such as roads or sidewalks, leading to hazardous conditions. If more than about 1/2 inch of ice accumulates, then tree limbs, branches, and power lines begin to snap and break. The resulting damage can cost millions of dollars, and it may be days or even weeks before "downed" power lines can be fixed.
Hail is a shower of round or irregularly shaped pieces of ice known as hailstones. Hail is formed inside cumulonimbus clouds. They originate as small ice particles of frozen raindrops that are caught in the updraft of air inside a cloud. As they ascend, they get larger by gathering water on their surface. How big they grow depends on how strong and extensive the updraft is and how much water is in the cloud. Eventually, the droplets become too heavy to be supported by the updraft and they start to descend as hail.
Hurricanes form over warm waters of the ocean when there are large pressure and temperature differences between the warm water and the clouds. The "eye" is in the center of the hurricane and can measure up to 20 miles across. The region around the "eye" is the "eye wall" where wind will rotate around the "eye" at a faster pace resulting in the appearance of a snake rolling over. Clouds that form outside the hurricane are called "cloud chains". Such clouds are responsible for making the hurricane grow larger and more intense. Hurricanes can grow up to 400 to 500 miles across. Temperature and humidity are the two main ingredients for hurricanes, thus they generally form in tropical regions.
Cumulus clouds can grow in height to become cumulonimbus clouds, and when they do, the water droplets freeze. The frozen water droplets can become charged with electricity. If the difference in charge becomes great enough, giant sparks leap from the cloud as lightning. It is the intense heating of the air around these explosive flashes that generates thunder. Sometimes, you can feel the electricity in the air, but just how close is lightning? Here's a simple way determine the closeness of lightning. Step 1: Watch the sky for a flash of lightning. Step 2: Count the number of seconds before you hear the thunder. Step 3: Every five seconds equals one mile, so if you count fifteen seconds, then the lightning is three miles away.
These unique drooping, bulbous clouds usually form on the underside of cumulonimbus clouds and are indicative of a severe thunderstorm or possible tornado formation. They form in saturated, sinking air that is cooler than its surroundings. Mammatus clouds may appear as smooth, ragged, or lumpy lobes and may be opaque or translucent. They are usually composed of ice, but also can be a mixture of ice and liquid water or be composed of almost entirely liquid water. A lobe can last an average of 10 minutes, but a whole cluster of them can range from 15 minutes to a couple of hours. Here, their unusual shape is strikingly illuminated by the Sun as it is low in the sky.
Monsoons are an annually recurring weather phenomenon, triggered by the Earth's tilt in relation to the Sun. Most individuals promptly say that Monsoons are the bringers of rainy season, but in reality, they are responsible for very strong winds. Monsoons always blow from cold to warm places. The most well-known monsoons occur in Asia where the high elevations of the Tibetan Plateau enhance the temperature difference between land and water. The Asian monsoon influences a large percentage of Asia, but varies regionally and is therefore described as two separate sub-systems: Indian Summer Monsoon and East Asian Monsoon.
Sleet is a form of wintry precipitation that falls as ice pellets. In the atmosphere, snow falling aloft goes through a warm layer where it then melts into rain. After exiting this warm layer, the raindrops then refreeze into pellets of ice as they fall into a deep and/or very cold layer of sub-freezing air near and just above the surface of the Earth. Sleet, in the sense of wet snow, is unpleasant as it is wet, like rain, and also very cold, but it does not usually pose a substantial hazard. Freezing rain mixed with sleet are two components of an ice storm, and as you know, snow may slow things down, but sleet and freezing rain can be quite destructive.
Snow forms when tiny ice crystals in clouds stick together to become snowflakes. Deep snow and blowing snow are both very dangerous, causing serious and prolonged disruption. Frontal depressions are the most common source of widespread snow. Although most parts of the world experience nonthreatening amounts of precipitation, some extreme weather patterns involving rain or snow can lead to serious problems. In such cases, as in heavy snowfall, not only do businesses and schools have to close, but several roof tops have the potential to cave in due to the weight of the snow above.
Supercell thunderstorms are characterized by the presence of mesocyclones which involves deep, continuous rotating updrafts. Such phenomenon is sometimes called rotating thunderstorms. Supercells are the least common but the most potentially dangerous of all other types of thunderstorms. These unusual cells can dominate local weather up to 20 miles away. Supercells can occur anywhere but are most common in the Great Plains of the United States, which is also known as the "Tornado Alley". The storms are extremely dangerous because they not only produce strong winds, thunder and lightning but also tornadoes. This giant supercell easily dwarfs the car driving down the road.
Thunderstorms are the result of rapid upward movement of warm, moist air. They can produce a wide range of violent weather. They are the source of hail, thunder, lightning, torrential rain, strong-gusty winds, and tornadoes. Thunder-storms can start life as small cumulus clouds that can reach monstrous proportions in less than an hour. The possible rapid formation means that meteorologists must keep a very sharp and continuous eye on information from radar and other data sources to keep up with developments. Thunderstorms can also include snow, sleet, and hail or no precipitation at all.
Tornadoes are rotating columns of air extending from a thundercloud to the ground. Among the most violent of all weather systems in the United States, with wind speeds up to 300 mph, they can cause widespread destruction. Typically 165 to 330 feet wide, tornadoes are generally short-lived with average track lengths of 1 to 2 miles. Damage occurs not only due to the high wind speed of the funnel cloud but also because of the rapidly moving debris whipped up by it. Some tornadoes are strong enough to pick up vehicles and large farm animals, and sometimes survivors, including humans, will be carried a few miles and dropped off with minor injuries.