How Hurricanes FormHow Hurricanes FormStages of DevelopmentStages of Development

Gary ScholtensGary ScholtensWebster City Middle SchoolWebster City Middle School

Living in Iowa, usually our only experiences Living in Iowa, usually our only experiences with hurricanes are through the weather with hurricanes are through the weather

broadcasts.broadcasts.We don’t get to see them firsthand.We don’t get to see them firsthand.

Let’s see how they develop and work.Let’s see how they develop and work.

(Scholtens, 2011)

Hurricanes, as they are called in much of the Western Hemisphere (they are called Typhoons in the Western Pacific, Cyclones in the Indian Ocean, and in Australia), are tropical storms that form where the trade winds come together, and strengthen to have sustained wind speeds of 65 knots, or 74 mph, and even higher depending on how strong they become.- ("Hurricaneville," 2010)

(Jackson, 2009)

(Carson, 2010)

A hurricane is a huge storm! It can be up to 600 miles across and have strong winds spiraling inward and upward at speeds of 75 to 200 mph. Each hurricane usually lasts for over a week, moving 10-20 miles per hour over the open ocean. Hurricanes gather heat and energy through contact with warm ocean waters. Evaporation from the seawater increases their power. Hurricanes rotate in a counter-clockwise direction around an "eye." The center of the storm or "eye" is the calmest part. It has only light winds and fair weather. When they come onto land, the heavy rain, strong winds and large waves can damage buildings, trees and cars. - ("Weather WhizKids," 2010)

www.katrina.noaa.gov

Stages of a HurricaneStages of a HurricaneHurricanes just don't come out of nowhere to become what they are. Hurricanes just don't come out of nowhere to become what they are. They go through a They go through a process of developmentprocess of development that involves several different that involves several different stages. These stages can have different lengths just as in human stages. These stages can have different lengths just as in human development depending on certain development depending on certain environmental conditionsenvironmental conditions where it is where it is located at a particular time. If these conditions are right, a hurricane located at a particular time. If these conditions are right, a hurricane can develop rapidly, and go through these early stages very quickly. If can develop rapidly, and go through these early stages very quickly. If these conditions aren't right, then development can be slow, or these conditions aren't right, then development can be slow, or not at allnot at all. . Here are the various stages of development a hurricane goes through.Here are the various stages of development a hurricane goes through.

Tropical Tropical WaveWave

These are the most common of tropical disturbances with about 100 forming each season. They lack a closed circulation, which is when there are winds in every direction. Wind speeds are less than 20 knots, or 25 mph.

(Carson, 2010)

Tropical Tropical DepressioDepressionnA wave becomes a A wave becomes a depression when there is a depression when there is a presence of a closed presence of a closed circulation, and sustained circulation, and sustained winds are 20 knots, or 25 winds are 20 knots, or 25 mph. At this point, the mph. At this point, the system is still quite system is still quite disorganized.disorganized.

(Carson, 2010)

Tropical Tropical StormStormA depression becomes a tropical A depression becomes a tropical storm when shower and storm when shower and thunderstorm activity moves thunderstorm activity moves over the closed circulation, and over the closed circulation, and sustained winds reach at least sustained winds reach at least 35 knots, or 39 mph. At this 35 knots, or 39 mph. At this point, the system is capable of point, the system is capable of causing minimal damage.causing minimal damage.

(Doeden, 2008)

HurricaneHurricaneA tropical storm becomes a A tropical storm becomes a hurricane when the closed hurricane when the closed circulation becomes an eye, circulation becomes an eye, and sustained winds reach at and sustained winds reach at least 65 knots, or 74 mph. At least 65 knots, or 74 mph. At this point, the system is this point, the system is capable of causing capable of causing significant damage.significant damage. (Carson, 2010)

How Do Hurricanes FormHow Do Hurricanes Form• Hurricanes only form over really

warm ocean water of 80°F or warmer. The atmosphere (the air) must cool off very quickly the higher you go. Also, the wind must be blowing in the same direction and at the same speed to force air upward from the ocean surface. Winds flow outward above the storm allowing the air below to rise. Hurricanes typically form between 5 to 15 degrees latitude north and south of the equator. The Coriolis Force is needed to create the spin in the hurricane and it becomes too weak near the equator, so hurricanes can never form there. • - ("Weather WhizKids," 2010)

("Weather WhizKids," 2010)

Hurricane Hurricane StrengthsStrengthsAfter a hurricane goes through its After a hurricane goes through its stagesstages and matures, it still can and matures, it still can intensifyintensify to to certain sizes and strengths. Much like certain sizes and strengths. Much like that of humans once they're adults. This that of humans once they're adults. This all depends on the right environmental all depends on the right environmental factorsfactors and whether or not it is near land. and whether or not it is near land. The Saffir-Simpson Scale is a way to The Saffir-Simpson Scale is a way to indicate the strength of these storms by indicate the strength of these storms by their sustained wind speed, and central their sustained wind speed, and central barometric pressure.barometric pressure.

Category/ClassificationWinds (mph)

Pressure (in. of Hg)Damage

Category One74-95 mph

>=28.94 in. of Hg.minimal damage

Category Two96-110 mph

28.50-28.91 in. of Hgsignificant damage

Category Three111-130 mph

27.91-28.47 in. of Hgsevere damage

Category Four131-155 mph

27.17-27.88 in. of Hgextreme damage

Category Five>155 mph

<27.17 in.of Hgcatastrophic damage

Hurricane Hurricane ComponentsComponentsIt's time to take a look at what components, or features, It's time to take a look at what components, or features, make up a well-developed hurricane.make up a well-developed hurricane.Following, are the most common components of a Following, are the most common components of a hurricane.hurricane.

(Carson, 2010)

EyeEyeEye--Is the center of circulation, and area of lowest pressure within a hurricane. Within the eye of a hurricane, you will encounter clear skies and calm winds. However, don't let that fool you because once the eye passes your area, the other side of the storm will arrive, and the stormy weather will continue.

(Carson, 2010)

Eye WallEye WallEye Wall--Is the narrow area of intense thunderstorms that surround the eye of a hurricane. In this region, you will encounter the most ferocious portion of the storm with the highest winds it can muster. (Jackson, 2009)

Central Central Dense Dense OvercastOvercast

Central Dense Overcast--Or, CDO, as it is commonly known as, is the mass of embedded clouds that make up the inner portion of the hurricane. This contains the eye wall, and the eye itself. The classic hurricane contains a symmetrical CDO, which means that it is perfectly circular and round on all sides.

http://www.comet.ucar.edu/class/satmet/11_Apr19_1999/html/demariamn/sld039.htm

Central Central Dense Dense OvercastOvercast

http://www.wunderground.com/blog/JeffMasters/cohttp://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=1047mment.html?entrynum=1047

OutflowOutflowOutflow--This is the outer fringe of a hurricane that serves as a very important element in hurricane development. That is because the outflow represents all the energy being released by the hurricane. A powerful hurricane always has good outflow.

TextText

http://www.soest.hawaii.edu/MET/Faculty/businger/poster/hurricane/

OutflowOutflow

- - http://www.weather.com/blog/weather/8_22787.htmlhttp://www.weather.com/blog/weather/8_22787.html

Book CitationsBook Citations• Carson, M.K. (2010). Inside hurricanes. New York, NY: Sterling Publishing Co.

• Carson, M.K. (2010). Inside Hurricanes. New Carson, M.K. (2010). Inside Hurricanes. New York, NY: Sterling Publishing Co.York, NY: Sterling Publishing Co.

• Doeden, M. (2008). Hurricanes. Mineapolis, Doeden, M. (2008). Hurricanes. Mineapolis, MN: Lerner Publications Co.MN: Lerner Publications Co.

• Jackson, D. M. (2009). Extreme scientists. New Jackson, D. M. (2009). Extreme scientists. New York, NY: Houghton Mifflin Harcourt Publishing York, NY: Houghton Mifflin Harcourt Publishing Co.Co.

Web CitationsWeb Citations• Google images. (n.d.). Retrieved from Google images. (n.d.). Retrieved from

http://www.google.com/search?client=safari&rls=ehttp://www.google.com/search?client=safari&rls=en&qn&q

• Hurricanes 101: the basics. (n.d.). Retrieved from Hurricanes 101: the basics. (n.d.). Retrieved from http://www.hurricaneville.com/stages.htmlhttp://www.hurricaneville.com/stages.html

• The Weather Channel. (n.d.). Retrieved from The Weather Channel. (n.d.). Retrieved from http://www.weather.com/ready/tropical/stages.htmlhttp://www.weather.com/ready/tropical/stages.html

• University of illinois: Atmospheric Sciences. (n.d.). University of illinois: Atmospheric Sciences. (n.d.). Retrieved from Retrieved from http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/hurhttp://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/hurr/stages/home.rxmlr/stages/home.rxml

Web CitationsWeb Citations• Weather Underground. (2010). Retrieved from Weather Underground. (2010). Retrieved from

http://www.wunderground.com/blog/JeffMastershttp://www.wunderground.com/blog/JeffMasters• Weather Whizkids. (2010). Retrieved from Weather Whizkids. (2010). Retrieved from

http://www.weatherwizkids.com/weather-http://www.weatherwizkids.com/weather-hurricane.htmhurricane.htm