Hurricane Rita

On September 18, 2005, less than a month later after Katrina had devastated the central Gulf Region, Hurricane Rita formed from a tropical depression that had formed the same day near the Turks and Caicos Islands. The storm increased intensity over the next two days, becoming category 1 on the 20^th. Later that afternoon, Rita grew to a category 2 as it passed near the Florida Keys and South Florida. It caused sustained tropical storm force winds on Key West with gusts of up to 76 mph.

Rapidly intensifying, Hurricane Rita tracked westward into the Gulf of Mexico. By the afternoon of the 21^st, Rita reached category 5 strength on the Saffir-Simpson scale, with winds of 165 mph. It became the second hurricane of the season to reach category 5 and first time in record that two hurricanes reached category 5 strength in the Gulf of Mexico in the same season.

Rita continued to intensify and reached wind speeds of 175 mph and the minimum central pressure of the storm reached to 897 mb. It became the third lowest on record for the Atlantic Basin, after Hurricane Gilbert (888 mb) and 1935 Labor Day Hurricane (892 mb).

During the afternoon of the 22^nd, Rita started to weaken due to an eye wall replacement cycle and perhaps some influence of slightly cooler sea surface temperatures. Hurricane Rita’s intensity dropped to a surface wind speed of 145 mph and continued to gradually weaken over the next 36 hours prior to landfall. Rita tracked west northwest on the 23^rd and made landfall at the Texas Louisiana border early on the 24^th at a category 3. Hurricane force winds were sustained more than 150 miles inland.

http://www.ncdc.noaa.gov/special-reports/rita.html



El Niño

El Niño is the name given to a change in the flow of water currents in the Pacific Ocean near the equator. El Niño in Spanish means the child. It was given that name because if often occurs around Christmas. Although El Niño takes place in a small portion of the Pacific, it can affect the weather in large parts of Asia, Africa, Indonesia, and North and South America.

The rotation of Earth and the exchange of heat between the atmosphere and the oceans create wind and ocean currents. At the equator, trade winds blow westward over the Pacific, pushing surface water away from South America toward Australia and Indonesia. These strong trade winds bring life giving monsoons to eastern Asia. As warm surface water moves west, cold water from the deep in the ocean rises to replace it.

Every three to five years, the trade winds slacken or reverse direction allowing winds from the west to push warm surface water eastward toward South America. This change is called the Southern Oscillation and is caused by a shifting pattern of air pressure between the eastern and western ends of the Pacific Ocean. The warm, moist air that slams into South America coast brings heavy rains and storms. At the same time, countries on the western Pacific, such as Australia, Indonesia, and the Philippines, have dry weather.

Another type of weather that follows El Niño is La Niña which in Spanish means the girl. La Niña and El Niño are opposite. El Niño is a warming trend that raises the water temperature as much as 5.6 degrees Celsius above normal and La Niña is a cooling of the waters that drops the temperature of the water as much as 8 degrees Celsius below normal.

http://www.scienceclarified.com/El-Ex/El-Ni-o.html

What is a Thunderstorm?

     A thunderstorm is millions of droplets of water vapor in the atmosphere that produce lightning, rainfall, winds, hail, and thunder. Thunderstorms form when instability in the atmosphere cause cumulonimbus clouds to form. Towards the tops of the thunderstorm water droplets become supercooled and is a region know as the anvil. This is where the thunderstorm can’t go any higher because the stratosphere is stable. The cloud starts to spread out along the bottom of the stratosphere. Dust is sucked into the cloud when growing so the supercooled water droplets come in contact with it and turn into to ice.

     If enough ice particles collide and clump together, a small hailstone will form. Forced by gravity, the hailstone falls toward the earth. If the updrafts are strong enough, the hailstone will be sucked back to the top of the storm and get bigger. This process continues until the hailstone is too large and the updraft can’t support it anymore. This causes it to fall to the earth.

     Lightning occurs when the ice particles in the cloud rub each other and cause friction which in turn charges the water droplets. Once enough charge builds between the ice particles rubbing against each other and the ground, the stage is set for lightning. A single lightning can heat the air around it to 30,000 degrees Celsius. This intense heating occurs so rapidly that air density cannot respond. The rapid rise in air temperature is accompanied by an increase in air pressure that generates a shock wave. The shock wave goes outward and produces thunder. This explains why it’s called thunderstorm.

http://michael.bsch.au.com/whatisstorm.html

Cumulus Congestus Clouds

Cumulus congestus clouds are thick fluffy clouds. Basically, water vapor starts condensing at a particular altitude, and as it rises further, it tends to drift upwards in the Earth's atmosphere. These factors play a significant role in giving the clouds its fluffy appearance. A congestus cloud has the ability to cover a significant vertical distance, which gives it a gigantic appearance. Cumulus congestus clouds are characteristics of areas of the atmosphere that are undergoing convection. They are often characterized by sharp outlines and great vertical development. Because cumulus congestus is produced by strong updrafts, it is typically taller than it is wide, and don’t reach higher than the lower troposphere.

It is the largest of the four possible species of Cumulus. Congestus can develop from the smaller humilis and mediocris species when the atmospheric conditions are unstable. This means that the way the air temperature changes with latitude tends to encourage the rising column of warm, moist air at the centre of the cloud to keep lifting higher and higher. Such convection makes the cloud swell to dreadful proportions.

Cumulus congestus clouds are also called towering cumulus. The tops of them look like cauliflower and sometimes light rain can fall from them. Congestus clouds are in the last stage of development. This stage of Cumulus is when it is at the point of maturing into a Cumulonimbus cloud. Once the top of the cloud begins to glaciate, its droplets freezing into ice crystals, the crisp edges of it soften and become more blurred. This is the point at which the cloud has officially turned into a Cumulonimbus cloud and thunderstorms with rain, hail, thunder and lightning can occur.

http://amsglossary.allenpress.com/glossary/search?id=cumulus-congestus1