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Dropsondes Measure Important Atmospheric Conditions
As our Hurricane Hunter Scientists make passes through the storm, they release small sensor packages on parachutes called dropsondes. These instruments provide measurements of temperature, pressure, humidity and wind as they descend through the storm. See more of our videos on YouTube.
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Frequently Asked Questions about Hurricanes
Why Don't Nuclear Weapons Destroy Hurricanes?
Radioactive fallout from such an operation would far outweigh the benefits and may not alter the storm. Additionally, the amount of energy that a storm produces far outweighs the energy produced by one nuclear weapon.
How Much Energy is Released from a Hurricane?
The energy released from a hurricane can be explained in two ways: the total amount of energy released by the condensation of water droplets (latent heat), or the amount of kinetic energy generated to maintain the strong, swirling winds of a hurricane. The vast majority of the latent heat released is used to drive the convection of a storm, but the total energy released from condensation is 200 times the world-wide electrical generating capacity, or 6.0 x 1014 watts per day. If you measure the total kinetic energy instead, it comes out to about 1.5 x 1012 watts per day, or ½ of the world-wide electrical generating capacity. It would seem that although wind energy seems the most obvious energetic process, it is actually the latent release of heat that feeds a hurricane’s momentum.
What Causes Tropical Cyclones?
In addition to hurricane-favorable conditions such as temperature and humidity, many repeating atmospheric phenomenon contribute to causing and intensifying tropical cyclones. For example, African Easterly Waves are winds in the lower troposphere (ocean surface to 3 miles above) that travel from Africa at speeds of about 3mph westward as a result of the African Easterly Jet. These winds are seen from April until November. About 85% of intense hurricanes and about 60% of smaller storms have their origin in African Easterly waves.
The Saharan Air Layer is another significant seeding phenomenon for tropical storms. It is a mass of dry, mineral-rich, dusty air that forms over the Sahara from late spring to early fall and moves over the tropical North Atlantic every 3-5 days at speeds of 22-55mph (10-25 meters per second). The air mass is 1-2 miles deep, exists in the lower troposphere, and can be as wide as the continental US. These air masses have significant moderating impacts on tropical cyclone intensity and formation because the dry, intense air can both deprive the storm of moisture and interfere with its convection by increasing the wind shear.
Many tropical cyclones form due to these larger scale atmospheric factors. Hurricanes that form fairly close in our basin are called Cape Verde hurricanes, named for the location where they are formed. Cape Verde origin hurricanes can be up to five per year, with an average of around two.
Why are Tropical Cyclones Always Worse on the Right Side?
If a hurricane is moving to the west, the right side would be to the north of the storm, if it is heading north, then the right side would be to the east of the storm. The movement of a hurricane can be broken into two parts- the spiral movement and its forward movement. If the hurricane is moving forward, the side of the spiral with winds parallel and facing forward in the direction of movement will go faster, because you are adding two velocities together. The side of the spiral parallel to the movement, but going in the opposite direction will be slower, because you must subtract the velocity moving away (backwards) from the forward velocity.
For example, a hurricane with 90mph winds moving at 10mph would have a 100mph wind speed on the right (forward-moving) side and 80 mph on the side with the backward motion.
How are Hurricanes Named?
During the 19th century, hurricane names were inspired by everything from saints to wives to unpopular politicians. In 1978, it was agreed that the National Hurricane Center would use alternating men and women’s names following the practice adopted by Australia’s bureau of Meteorology three years earlier in 1975.
Today, a list of potential names is published by the United Nations World Meteorological Organization for the Atlantic basin. These names extend into 2023, and the list repeats every seventh year. If a particularly damaging storm occurs, the name of that storm is retired. Storms retired in 2017 include Harvey, Irma, Maria, and Nate. If there are more storms than names on the list in a given season, the National Hurricane Center will name them using the Greek alphabet. Lastly, if a storm happens to move across basins, it keeps the original name. The only time it is renamed if it dissipates to a tropical disturbance and reforms.