Hurricanes aqa revision


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Hurricanes aqa revision

  1. 1. Caribbean Sea China Sea Hurricanes Typhoons Bay of Bengal Cyclones Northern Australia Willy willies
  2. 2. 1.Warm, humid surface air and an unstable atmosphere Latent heat release during condensation is the driving energy for tropical storm intensification.2. Warm ocean surface waters (Temperature > 26.5°C [80°F]). This is the "fuel" for hurricanes.Depth of warm water > 60 m (200 ft) As cyclone develops, winds churn up water, bringing up water from below the ocean surface. If this water is too cold, hurricanes cannot develop.3. Pre-existing large-scale surface convergence and/or upper-level divergence Created by a convection thunderstorm which developed over west Africa and moving out over the Atlantic.4. Must be further than 4° Latitude away from the Equator In order to get winds to rotate counterclockwise around an area of low pressure, there must be a Coriolis effect. The Coriolis force at the equator is zero and gets larger as one moves toward the poles.5. Absence of strong vertical wind shear Wind shear inhibits deep convection, essentially ripping tropical storms apart. Generally, tropical storms are best able to strengthen when the rising warm air near the center of the storm goes straight up. Wind shear can cause the updrafts to bend over, which is not favorable for the storm to strengthen.
  3. 3. Parts of a HurricaneOnce a hurricane forms, it hasthree main parts:Eye - the low pressure, calmcenter of circulationEye wall - area around the eyewith the fastest, most violent windsRain bands - bands ofthunderstorms circulating outwardfrom the eye that are part of theevaporation/condensation cyclethat feeds the storm
  4. 4. Below, are the most common components of a hurricane.Eye--Is the center of circulation, and area of lowest pressure within a hurricane. Withinthe eye of a hurricane, you will encounter clear skies and calm winds. However, dont letthat fool you because once the eye passes your area, the other side of the storm willarrive, and the stormy weather will continue.Eye Wall--Is the narrow area of intense thunderstorms that surround the eye of ahurricane. In this region, you will encounter the most ferocious portion of the storm withthe highest winds it can muster.Central Dense Overcast--Or, CDO, as it is commonly known as, is the mass ofembedded clouds that make up the inner portion of the hurricane. This contains the eyewall, and the eye itself. The classic hurricane contains a symmetrical CDO, which meansthat it is perfectly circular and round on all sides.Outflow--This is the outer fringe of a hurricane that serves as a very important elementin hurricane development. That is because the outflow represents all the energy beingreleased by the hurricane. A powerful hurricane always as good outflow
  5. 5. It can take anywhere from hours to several days for a thunderstorm todevelop into a hurricane.Although the whole process of hurricane formation is not entirelyunderstood, three events must happen for hurricanes to form:A continuing evaporation-condensation cycle of warm, humid oceanair.A patterns of wind characterized by converging winds at thesurface,resulting from air pulled in to replace warm rising air.A strong, uniform-speed winds at higher altitudes, allowing air to riseand not sheared off.
  6. 6. Warm, moist air from the ocean surface begins to rise rapidly.As this warm air rises, its water vapor condenses to form storm cloudsand droplets of rain.The condensation releases heat called latent heat of condensation.This latent heat warms the cool air aloft, thereby causing it to rise.This rising air is replaced by more warm, humid air from the oceanbelow.This cycle continues, drawing more warm, moist air into the developingstorm and continuously moving heat from the surface to the atmosphere.This exchange of heat from the surface creates a pattern of wind thatcirculates around a center.This circulation is similar to that of water going down a drain.
  7. 7. The air in the eye of the hurricaneis at low pressure, and is calm. Asthe eye passes over, the windsmay drop altogether, and a smallcircle of clear sky may be visibleoverhead for a short period of time.This lull ends when torrential rainsfall around the eye, and ragingwinds, drawn in from hot air spiralup the wall of the eye. These hotrising winds circulate at speeds of50 km/h (30 mph). The strongestwinds, with gusts of up to 360 km/h(225 mph) are found beneath theeye wall, immediately outside theeye.
  8. 8. Below, are some of the common effects from a hurricane.Storm surge and tidal flooding--This is the most devastating and notableeffect from a hurricane. Storm surge is the rising wall of water the comesashore with a landfalling hurricane, and is responsible for 90 percent of allhurricane related deaths.High Winds--This is the most important effect of a hurricane since itdetermines how powerful the storm is, and how much storm surge anddamage it can cause. Winds in a hurricane can reach up to 200 mph.Tornadoes--This is probably the least thought of effect of a hurricane, butthey do occur. Tornadoes occur in a hurricane as a result of the tremendousenergy and instability created when a hurricane makes landfall. Mosttornadoes that occur in hurricanes are only minimal in strength.Heavy rain and flooding--This is the effect of a hurricane that is completelytaken for granted. After hurricanes make landfall, and their winds abate, thetremendous amounts of rainfall become a major factor, and can causesignificant flooding as with Hurricane Floyd last year.
  9. 9. •Hurricanes bring with them huge amounts of rain. A big hurricane candump dozens of inches of rain in just a day or two, much of it inland.That amount of rain can create inland flooding that can totallydevastate a large area around the hurricanes center. Many communities and small towns in eastern North Carolina found themselves afloat following Hurricane Floyds massive rainfall and the ensuing floods. Streams and waterways were already swollen from Hurricane Dennis, which struck eastern North Carolina (twice) just weeks before Hurricane Floyd.
  10. 10. High sustained winds causestructural damage. These winds canalso roll cars, blow over trees anderode beaches (both by blowing sandand by blowing the waves into thebeach).The prevailing winds of a hurricanepush a wall of water, called a stormsurge, in front of it. If the storm surgehappens to synchronize with ahigh tide, it causes beach erosion andsignificant inland flooding. Hurricanes often cause severe structural damage. This building, in the U.S. Virgin Islands, was leveled.
  11. 11. Storm SurgeA storm surge is a rise in the ocean as the result of strong winds from a hurricaneor other intense storm. This ocean water crashes onto the land in a powerfulsurge. The storm surge combined with the heavy rain that comes with thehurricane can cause dangerous flooding in low-lying coastal areas, especiallywhen a storm surge coincides with a high tide. This flooding can be the mostdangerous part of a hurricane, potentially causing many deaths.The height of the storm surge is the difference between the level of the oceanand the level that would have occurred normally. A storm surge is usuallyestimated by subtracting the regular high tide level from the observed storm tide -it can be 15 feet tall or more in a very strong storm. For example, in 1985,Hurricane Opal (a Category 3 storm) caused storm surges up to 24 feet, causingflood damage along the Florida coastline near Fort Walton Beach.
  12. 12. Ocean-front property is particularly susceptible to damage fromhurricane storm surges, when ocean waves are very high andstrong because of the strength of the hurricanes winds
  13. 13. Once a hurricane forms, it is rated on the Saffir-Simpson Hurricane Scale. There are five categories in this rating system.
  14. 14. The National Weather Service has many tools to watch hurricanes. Satellites, ships and buoys, airplanes radiosondes, and radar are to name a few. They also have a computer model to help forecast a storms strength. Satellites collect information about the land, biosphere, atmosphere and the oceans. Human activity are speed up changes by increasing the carbon dioxide levels. Scientists are still trying to decide the cause and effect of the changes to the climate conditions. A warning is more important than aForecasters can estimate watch.Location The aftermath of Hurricane Camille.Size Large ships were no match for Camille.Movement Gulfport, Mississippi (1969)Intensity of the storm Satellites can measure:tell about its surrounding environment Reflected radiationTwo types of warnings Cloud picturesHurricane Watch-will hit in the next 36 Land surface temperaturehours Sea surface temperatureHurricane Warning- will hit into he next 24 Winds from cloud motionshours Size of cloudsA warning is more important than a watch. Rainfall
  15. 15. Usually people know that a hurricane is coming so they have time toprepare for it. Here are some tips to try:Keep listening to the weather reportsMake a planMake a first aid supply kitStore water and foodProtect windowsRemove outside antennasShut off all water, electricity and gasStay indoors during the storm
  16. 16. The Hurricane Hunters are members of the53rd Weather ReconnaissanceSquadron/403rd Wing, based at Keesler AirForce Base in Biloxi, Mississippi. Since1944, the U.S. Department of Defense(which oversees the U.S. military) has beenthe only organization to fly into tropicalstorms and hurricanes. Since 1965, theHurricane Hunters team has used the C-130Hercules, a very sturdy turboprop plane.The only difference between this plane andthe cargo version is the specialized, highlysensitive weather equipment installed on theWC-130. The team can cover up to fivestorm missions per day, anywhere from themid-Atlantic to Hawaii.
  17. 17. Efforts in storm modification go as far back as the late 1940s when Dr. IrwinLangmuir began exploring the idea of using ice crystals to weaken storms suchas hurricanes. In 1947, he organized a team of scientists from General Electric,and brought his idea to fruition with Project Cirrus.The highlight of this effort occurred on October 13, 1947 when Langmuir and histeam had a Navy plane fly into a hurricane off the coast of Georgia, and drop apayload of dry ice into it.The hope of using dry ice was to release energy from the storms inner core.and thus weaken the hurricane itself. It was originally considered a success.After the cloud seeding had taken place, the hurricane suddenly changeddirection, and made landfall near the coastal city of Savannah, Georgia.However, about a decade later, a scientist named Mook recognized that thestorms sudden change in direction was not caused by the seeding, but ratherthe upper level steering winds in the vicinity of the hurricane.