As wind blows across the many different levels of the atmosphere, there are changes in wind speed and direction. These changes in speed and direction over a relatively short distance in the atmosphere are known as wind shear. Wind shear is most prevalent in the high latitudes as well as close to the jet stream; however, this shear plays a crucial role in the tropics as well. One critical factor in determining tropical cyclone development is calculating the shear of the environment over which the tropical cyclone will be above.
Through research and observation, two of the primary reasons that ordinary disturbances in the tropics can acquire tropical characteristics are due to the presence of warm sea surface temperatures as well as low values of wind shear. As a tropical cyclone is developing, heavy thunderstorms will build up near the center. Given a favorable environment, the whole system from sea level up to around 50,000 feet in the atmosphere will eventually begin to turn counter-clockwise (or cyclonically). Without wind shear, the turning within the tropical system will be uniform, or vertically aligned, which helps to keep the storm intact and likely strengthening. If, however, strong wind shear is present, then a system's structure will be vertically tilted toward the direction that the wind shear is blowing. A vertically tilted system is inefficient at drawing in warm and moist air from the ocean necessary for intensification; therefore, the storm never fully develops tropical characteristics.
If a well-defined hurricane moves from a region of low wind shear into an area of high wind shear, the vertically aligned center of the storm will become tilted in the direction of the wind shear and likely cause weakening or "tearing apart" of the center of the storm.
It is essential for meteorologists to determine and monitor wind shear across any tropical basin in order to forecast a tropical system's intensity as accurately as possible.
Why can different types of precipitation be seen on Earth while temperatures remain constant?
Dangerous flash flooding is captured as an arroyo becomes filled with water in Carson Valley, Nevada.
The RealFeel Temperature uses an equation to determine how it actually feels outside.
Knowing what the different advisories, watches, and warnings mean will lead to more informed decision making when a winter storm threatens a particular area.
How can you determine if and when the ice is thick enough for safely going out on?
Seeking shelter in the event of a tornado could save your life, but is there really any safe place to hide?
Driving on a 90-degree angle away from the tornado is a good strategy to follow in order to distance yourself from the tornado.
Supercell thunderstorms have been responsible for major tornadoes that have demolished parts of the U.S.
After a cold, clear winter night without much wind, the ground and nearby tree branches may be covered by tiny, white ice crystals.
A major cause of post-snow flooding are ice jams in waterways.
Greatest natural disaster for Arizona. Rains in central Arizona caused rivers to rise 5-10 feet per hour, sweeping cars and buildings 30-40 feet downstream. Twenty-three lives were claimed by the floodwaters. This rain came from Tropical Storm Norma.
Los Angeles, CA (1988)
110 degrees -- all-time September record.
Washington, DC (1939)
"Once in a hundred-year rainstorm" 4.40 inches in 2 hours at the Washington Zoo.