Presentation on theme: "Where Hurricanes Occur"— Presentation transcript:
1 Where Hurricanes Occur Gulf Of Mexico--This is a very favorable region for hurricane development since water temperatures range from 85 to 90 degrees during the course of the hurricane season.Western Caribbean--While the Eastern and Central Caribbean are usually not favorable areas for development since upper level winds are usually hostile, the Western Caribbean is more favorable since these same winds lessen.Cape Verde Islands--This is probably the most common area for the development of many of the classic and powerful hurricanes. This region usually doesn't become favorable for development until August when water temperatures become warm enough to support tropical formation.
2 How They DevelopHigh winds spiraling inward through bands of thunderstorms. These spiral bands are commonly known as the outflow, outer bands.These gusty winds stir up ocean moisture, which create thunderstorm clouds, which rise to the upper portion of the stratosphere and cool.The storm grows as it uses the ocean moisture as additional energy. Rising air near the center of the storm condenses, creating heavy downpours and releasing tremendous amounts of heat and energy, which is why these storms have such cold cloud tops.This in turn, forces the barometric pressure in the center of the circulation, or the eye to drop at the surface, pulling in more air and strengthening the storm as the air rises to about 50,000 feet where most of it is propelled outward, making room for more rising air.Some air sinks back into the center, warming it and creating the nearly cloud-free eye. The hurricane engine is now complete, and now the storm is mature and begins to grow into a dangerous threat.
3 what causes them to develop What causes hurricanes? There are approximately 100 tropical waves that travel westward from the West Coast of Africa through the Atlantic every year. So, how do these waves become one of the ten or so tropical storms, and hurricanes that occur each season. There are several key factors that come together to develop tropical storms and hurricanes: warm sea surface temperatures, light winds aloft, and rotation or spin. If any one of these factors is unavailable, then the tropical storm or hurricane can weaken or decay.Warm sea surface temperatures--This is a key ingredient because it serves as the fuel source for hurricanes. Sea surface, or ocean temperatures need to be at least 80 degrees Fahrenheit (27 degrees Celsius) where the system is located in order for it to develop into a tropical storm or hurricane.Light winds aloft--Hurricanes and tropical storms travel east to west so they are supported by an easterly wind flow. They are also vertical systems in that they have thunderstorms that build vertically in the atmosphere. These two conditions make hurricanes quite different from the storms that usually bring us our weather, and make it essential to have light westerly winds aloft so that there is no shearing, or tearing apart of thunderstorms.
4 weaken.What causes hurricanes to decay and dissipate? Hurricanes can become very powerful, but they're not immortal. Tropical cyclones such as tropical storms and hurricanes have a finite life span and their share of enemies such as cooler sea surface temperatures, hostile upper level winds, land, and sinking air that all inhibit further strengthening, or even dissipate them altogether.Colder sea surface temperatures--Warm water is the engine of all tropical cyclones. Sea surface temperatures must be at or above 80 degrees Fahrenheit in order for a tropical storm or hurricane to flourish. Anything colder than that will cause the storm to weaken or even dissipate.Shearing winds aloft--Tropical storms and hurricanes are "vertically stacked systems." That means that clouds in the hurricane engine build vertically to great heights in the troposphere and lower stratosphere. In order for this to happen, these storms must have light winds aloft. Hostile upper level wind conditions produce shearing, which blow off the high cloud tops of these storms, and causes them to become disorganized.Sinking air--Sinking air, or subsidence from high pressure such as the subtropical ridge can also inhibit development. Again, hurricanes are vertically stacked systems so they need to have air rise from the surface to the upper levels. Sinking air from high pressure hinders thunderstorm development, which is a critical element in hurricane strengthening.Land, of course--The ultimate hindering factor to hurricanes is of course land. When hurricanes or tropical storms make landfall, the friction caused by a large land mass, and their terrain cuts off the hurricane's circulation, and squeezes out the storm's moisture. In some cases rugged terrain such as mountains can squeeze out tons of moisture, which in turn produces heavy rainfall and flooding.
5 how strong they becomeHurricanes just don't come out of nowhere to become what they are. They go through a process of development that involves several different stages. These stages can have different lengths just as in human development depending on certain environmental conditions where it is located at a particular time. If these conditions are right, a hurricane can develop rapidly, and go through these early stages very quickly. If these conditions aren't right, then development can be slow, or not at all. Here are the various stages of development a hurricane goes through.Tropical Wave--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.Tropical Depression--A wave becomes a depression when there is a presence of a closed circulation, and sustained winds are 20 knots, or 25 mph. At this point, the system is still quite disorganized.Tropical Storm--A depression becomes a tropical storm when shower and thunderstorm activity moves over the closed circulation, and sustained winds reach at least 35 knots, or 39 mph. At this point, the system is capable of causing minimal damage.Hurricane--A tropical storm becomes a hurricane when the closed circulation becomes an eye, and sustained winds reach at least 65 knots, or 74 mph. At this point, the system is capable of causing significant damage. Note: Once arriving at hurricane status, these storms continue to intensify, and their intensity is classified by Categories according to the Saffir-Simpson Scale. This scale was created by a meteorologist, and a structural engineer to give people a sense of how powerful hurricanes can be at certain surface pressures and wind speeds.
6 componentsNow, that we've discussed the basics on hurricanes, where they form, their stages of development, and what factors influence their development or decay, it's time to take a look at what components or features make up a well developed hurricane. Below, are the most common components of a hurricane.Eye--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.Eye 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.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.Outflow--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 as good outflow.
7 effectsHurricanes are very fascinating to track and to view on satellite, but beyond the fascination there is some harsh reality to these storms. Hurricanes are among the most powerful and deadliest forces in nature, which bring various kinds of effects to the area it makes landfall over. Some of these effects such as copious amounts of rain can be beneficial during a drought, but most of the time these effects are unwanted. Below, are some of the common effects from a hurricane.Storm surge and tidal flooding--This is the most devastating and notable effect from a hurricane. Storm surge is the rising wall of water the comes ashore with a landfalling hurricane, and is responsible for 90 percent of all hurricane related deaths.High Winds--This is the most important effect of a hurricane since it determines how powerful the storm is, and how much storm surge and damage 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, but they do occur. Tornadoes occur in a hurricane as a result of the tremendous energy and instability created when a hurricane makes landfall. Most tornadoes that occur in hurricanes are only minimal in strength.Heavy rain and flooding--This is the effect of a hurricane that is completely taken for granted. After hurricanes make landfall, and their winds abate, the tremendous amounts of rainfall become a major factor, and can cause significant flooding as with Hurricane Floyd last year.
8 What time of year?Hurricanes usually occur during the summer and fall months of the year. As a matter of fact, the Atlantic Hurricane Season lasts from June 1st to November 30th each year. However, there have been instances where tropical storms and hurricanes have formed in May and December