What Causes Hurricanes?
Pre-Conditions for Hurricanes There are perhaps seven atmospheric conditions which, if met, could cause a hurricane to form. A pre-existing disturbance, warm ocean water, low atmospheric stability, sufficient Coriolis force, moist mid-atmosphere, and upper atmosphere divergence are all important factors for hurricane formation. How 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.
Tropical cyclones that strengthen to Category 2 status and make landfall are capable of causing severe damage to human lives and infrastructure. As ofa total of 84 hurricanes have peaked at Category 2 intensity within the Northeast Pacific tropical cyclone basinwhich is defined as the region of the Pacific Ocean north of the equator and east of the International Date Line. Collectively, 1, people have been killed as a result of Category 2 Pacific hurricanes. Storms that also attained Category 3, 4, or 5 status on the scale are not included.
There is a plethora of factors that influence tropical cyclogenesisti formation of tropical cyclones, in the Northeastern Pacific. The How to set up led tv for best picture Pacific High and Aleutian Lowwhich occur from December to April, produce strong upper-level winds which prevents the formation of tropical cyclones.
During the summer and early autumn months, sea surface temperatures are generally warm enough to support tropical cyclone development hugricanes the Northeast Pacific, and perhaps even hurrianes intensification. There is also a cauwe risk of injury or death to humans and animals due to flying debris. The Northeast Pacific tropical cyclone basin is the area of the Pacific Ocean north of the equator and east of the International Date Line.
The basin is further divided into the east and central Pacific sub-basins. The east Pacific is located between the western coast of North America and the th meridian west.
The central Pacific is located between the th meridian west and the International Date Line. In the east Pacific and central Pacific sub-basins, hurricane season begins on May 15 and June 1, respectively, with both concluding on November Only one has occurred in the off-season: Hurricane Pali ofwhich developed on January 7, and marks the earliest formation of a tropical cyclone in the Northeastern Pacific basin on record. The majority of tropical cyclones form and organize in areas of warm sea surface temperaturesusually of at least When a pre-existing tropical disturbance — usually a tropical wave or a disturbance originating in the Intertropical Convergence Zone — enters an area where the aforementioned conditions are present, the disturbance can develop into a tropical cyclone, provided it is far enough from the equator to experience a sufficiently strong Coriolis forcewhich causes the counterclockwise rotation of hurricanes in the Northern Hemisphere.
Also, the presence of a semi-permanent high-pressure area known as the North Pacific High in the eastern Pacific greatly reduces tropical cyclone development in the winter months, as the North Pacific High results in vertical wind shear that causes environmental conditions to be unconducive to tropical cyclone formation. Another factor preventing tropical cyclones from forming during cquse winter is the presence of a semi-permanent low-pressure area called the Aleutian Low between January and April.
Its effects in the central Pacific near the th meridian west cause tropical waves that form in the area to move northward into the Gulf of Alaska. As the disturbances travel northward, they dissipate or transition into an extratropical cyclone.
The Aleutian Low's retreat in late-April allows the warmth of the Pacific High to meander in, bringing its powerful clockwise wind circulation with it. During the month of May, the Intertropical Convergence Zone migrates southward while vertical shear over the tropics decreases. As a result, the earliest tropical waves begin to form,  coinciding with the start of the eastern Pacific hurricane season on May This allows for tropical cyclones developing during that time to strengthen significantly, perhaps for rapidly.
Within the Northeast Pacific, the easterly trade winds cause tropical cyclones to generally move westward out into the open Pacific Ocean. Only rarely do tropical cyclones forming during the peak months of the season make landfall. Closer to the end of what part of the sky is the meteor shower season, the subtropical ridge steers some storms northwards or northeastwards.
Storms influenced by this ridge may bring impacts to the western coasts of Mexico and occasionally even Central America. In the central Pacific basin, the North Pacific High keeps tropical cyclones away from the Hawaiian Islands by forcing them southwards.
Out of the 83 Category 2 hurricanes in the east and central Pacific, 22 have made landfall as a tropical cyclone, collectively resulting in 27 landfalls. As tropical cyclones tend to weaken before landfall due to the effects of land interaction, only seven Category 2 hurricanes actually made landfall while still at Category 2 strength. Five storms made landfall twice each, namely IrahPaulAdolphCalvinand Marty ; Paul made both landfalls at Category 2 strength. No Category 2 Pacific hurricane to date has made whaf more than twice.
Multiple Category 2 how to make a birthday made landfall only in 2 years:with two systems Agatha and Bridget making landfall, andwith three systems Ignacio, Marty, and Nora making landfall.
From Wikipedia, the free encyclopedia. Wikipedia list article. Storm made landfall, see below for further information. Tropical cyclones portal Weather portal. Miami, Hurgicanes : National Hurricane Center. Archived PDF from the original on December 13, Retrieved May 24, How does it relate to gusts in tropical cyclones?
Atlantic Oceanographic and Meteorological Laboratory. Archived from the original on October 9, Archived from the original on November 13, Retrieved July 21, Central Pacific Hurricane Center. Archived from the original on September 22, Climate Prediction Center. May 27, Archived from the original on May 19, Archived from the original on July 28, Retrieved June 14, Retrieved 1 October A guide on how to read the database is available here.
Archived from the original on May 5, Retrieved July 24, Archived from the fofm on August 27, Retrieved August 18, Encyclopedia of hurricanes, typhoons, and cyclones 1st ed. Facts on File, Inc. ISBN Archived from the original on August 18, Earth Observatory. Archived from the original on May 6, The Weather Channel. Archived from the original on August 20, Retrieved August 20, Archived PDF from how to make games download faster on steam original on July 27, Retrieved July 27, Foreign Disaster Assistance August Archived PDF from the original on Retrieved March 25, Denney April Monthly Weather Review.
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California State University. Archived from the original PDF on October 20,
How climate change is making hurricanes more dangerous
Jul 08, · The criteria that conspire to form tropical cyclones are rather simple. It all starts with a small atmospheric disturbance located in or near a tropical ocean. If water temperatures are warm enough, generally more than 80 degrees Fahrenheit, and atmospheric conditions are supportive with moisture and uniform winds, a tropical system can evolve. Hurricanes can also spawn tornadoes, which increase their potential for destruction. Figure Saffir-Simpson Hurricane Scale Annually, more than one hundred tropical disturbances develop in the North Atlantic, but only about ten make it to a tropical storm status and five to six become hurricanes. The most widespread, damaging storms on earth are getting worse, and climate change is a big reason why. Here’s a look at what causes hurricanes and how to address the threat of a wetter.
Jump to navigation. Pounding rain, raging winds, and devastating storm surge. When hurricanes make landfall, they bring a trifecta of threats capable of leveling communities and destroying lives and livelihoods. Named after the ancient indigenous god Hurican the Carib god of evil , hurricanes are giant energy powerhouses. A hurricane is an intense low-pressure weather system of organized, swirling clouds and thunderstorms that gain energy from warm tropical waters.
To be classified as a hurricane, wind speeds must reach 74 miles per hour mph. With their distinctive buzz-saw shape when viewed from above, hurricanes spin around a low-pressure center known as the eye—an area of calm and sometimes even clear sky.
Journalist Edward R. Beyond the eye wall and extending for as much as hundreds of miles, slowly rotating rain bands bring their own intense thunderstorms, capable of producing fierce winds and tornadoes. The category of a hurricane reflects only the wind speed, not the overall potential for damage. In fact, the greatest risk comes from flooding associated with the storm surge or the intense rains the storms generate.
Consider Superstorm Sandy , which arrived in New Jersey with 80 mph winds barely over the category 1 minimum but still proved devastating. Sandy lacked the extreme winds of a major storm, but the massive swell of water it generated slammed into New Jersey and New York, obliterating beaches and boardwalks, filling subway tunnels, inundating neighborhoods, and destroying massive amounts of infrastructure.
Similarly, most of the damage caused by hurricanes Harvey and Florence were largely attributable to torrential rains, not wind or even storm surge in coastal areas. The Atlantic season peaks between mid-August and late October and produces an average of 6.
Hurricane season in the eastern Pacific, an area extending from the U. An average of 8. The central Pacific , which includes Hawaii, typically sees four to five hurricanes a year during its season—June through November—with most storms appearing in August and September.
Fewer than two hurricanes make landfall in the United States in a typical year, according to data from to , with an average of three major hurricanes pummeling the coastline every five years. About 40 percent of hurricanes make landfall in Florida, while nearly 90 percent of major hurricanes hit either Florida or Texas. Hurricane Michael in October was the first category 4 storm to strike the Florida Panhandle since record-keeping began in —and the strongest to make landfall the United States in more than 25 years.
The fact that hurricane , typhoon , and cyclone are all used for the same weather phenomena can be confusing. Typhoon A typhoon is tropical cyclone that occurs in the northwestern Pacific basin, covering eastern and southeastern Asia and Micronesia.
Tornado Although both storms are known for their spiraling, violently destructive winds, the similarity between tornadoes and hurricanes ends there. A hurricane forms over tropical waters and can span several hundred miles, last for days to weeks, and be predicted well in advance. A tornado, on the other hand, forms over land as a tall, rotating column of air that extends from the base of a thunderstorm including those produced by hurricanes to the ground.
The largest tornadoes are just over a quarter mile wide and typically last for no more than an hour, though they can pack a punch in terms of wind speed— as high as mph. Most hurricanes top out around mph. Advance warnings for tornadoes are typically less than 15 minutes. Monsoon Similar to a hurricane, a monsoon can produce torrential rains that lead to damaging floods, injury, and death.
But while a hurricane is basically a single weather event, a monsoon is a seasonal change in the prevailing winds that move from ocean to land—and vice versa—and can produce months of wet or even dry conditions.
Although most often associated with Southeast Asia, monsoon winds exist around the world, including the U. Hurricanes leave a trail of devastation in their wake, piling up costs in terms of lives and livelihood.
Here are some of the ways these storms impact communities and the surrounding environment. Hurricanes create a range of short- and long-term health and economic woes, with socially vulnerable populations often shouldering the greatest burden. In fact, flooding was the main cause of damage for many of the costliest hurricanes.
Economic loss Hurricanes are the costliest form of weather disaster, accounting for more than half of the total damages from billion-dollar U. That figure includes everything from wrecked homes and waterlogged hospitals to mangled material assets such as cars and boats. It also includes damage to public infrastructure such as roads, bridges, and power lines, along with lost wages and income-generating assets such as crops, livestock, and businesses.
It does not include health-related costs or values related to lost lives. Climate change is expected to further increase the tab, with potential future losses from hurricanes and other extreme weather events projected to as much as double by Health toll Hurricane Maria , which struck Puerto Rico in and is considered the deadliest hurricane in recent U. The second-most deadly storm in recent years, Hurricane Katrina struck the U.
Southeast in and claimed more than 1, lives. Flooding from rainfall is the second-gravest danger, resulting in about a quarter of immediate deaths. Drownings, either near shore or out at sea, account for 12 percent. Flood-induced sewage overflows from wastewater treatment plants can dump fecal bacteria into floodwaters and waterways, increasing the risk of skin, eye, ear, and gastrointestinal infections. Runoff from toxic waste sites and factory farms can expose nearby residents to hazardous waste.
After the storm has passed, flooded, water-damaged homes can harbor bacteria and mold, making the air unhealthy to breathe. Mold can be a particularly pervasive health hazard , since it starts growing immediately and can be hard to detect and remove. Who are the most vulnerable? Low-income communities, people of color, and the elderly are disproportionately exposed to storms. These populations often live in suboptimal housing situated in areas particularly vulnerable to storm threats—sometimes close to polluting industries that raise the risk of contamination via pipeline or facility leaks or chemically contaminated floodwaters.
Due to limited mobility, lack of funds, or insufficient storm-warning information, these communities often face greater challenges in escaping impending storms as well. Often they may be unable to bounce back as quickly after a hurricane has passed, facing challenges in accessing public disaster relief , job ass istance, and affordable housing. Ravaged homes and submerged streets are the images most often seen on the news after a hurricane strikes, but coastal ecosystems—both on land and at sea—experience their own forms of devastation as well.
When saltwater washes over land, it can harm or even kill bottomland forests and coastal trees unaccustomed to the uptick in salinity. The opposite can happen, as well: Heavy rains can cause freshwater to flood into coastal basins, decreasing the salinity of typically brackish waters and imperiling the species that depend on them. Meanwhile, floodwaters—from both storm surge and overflowing rivers and streams—can strand animals far from their natural territory.
Forest destruction Hurricane-force winds can uproot trees and bushes or strip them of their leaves, seeds, fruit, berries, and branches, damaging entire wooded ecosystems. This can not only create short-term food shortages for species, but also change the face of an entire area.
Once a forest canopy is damaged, a once cool, damp, and shady area may become a sun-filled, hot, and dry space—effectively creating new habitat for some invasive species while destroying ideal conditions for other, longer-term inhabitants. Wetland, dune, and beach loss Storm surge, waves, and winds can destroy wetlands and erode dunes and beaches, which provide critical habitat and important nesting grounds for a wide variety of wildlife species.
These areas provide a first line of defense from storm surge for us humans as well. Turbid waters Heavy rainfall and flooding can wash everything from soil and sediment to nutrient pollution to hazardous waste from wastewater treatment plants, refineries, and Superfund sites into marine, coastal, and freshwater environments.
The introduction of mud and debris can smother marine life, such as oysters, and damage grasses and agriculture; poisonous contaminants can accumulate in fish and shellfish and then be eaten by us ; and nutrient pollution can contribute to coral bleaching. The contrast in temperatures forms an area of strong high-altitude winds known as the African easterly jet, which moves from east to west.
Because of the difference in land temperatures over which it crosses, the jet wobbles from north to south, creating atmospheric troughs—basically V-shaped tropical waves—of low-pressure areas that get pushed along by the winds. These tropical waves, which can trigger clusters of thunderstorms, emerge near the Cape Verde Islands, just west of Africa hence the term Cape Verde hurricane and continue westward across the Atlantic Ocean. About 60 tropical waves typically track across the Atlantic Ocean each year, peaking in summer and early fall—around the same time that the ocean is at its warmest.
Like water going down a drain but inverted , moist air from surrounding areas rushes in to fill the atmospheric void, then evaporates as well, further fueling the formation of clouds and thunderstorms. As winds pick up and the energy-generating process continues, what was once a tropical disturbance can develop into a tropical depression and then a full-blown hurricane.
Since warm sea surface temperatures fuel hurricanes, a greater temperature increase means more energy, and that allows these storms to pack a bigger punch. Indeed, some weather analysts suggest a link between the intensity of Hurricane Florence—a Cape Verde storm that drowned the Carolinas with record-breaking rains —and warmer-than-normal Atlantic waters.
Rising air temperatures The burning of fossil fuels and other human activities have caused an estimated 1 degree Celsius 1. Since a hotter atmosphere can hold—and then dump—more water vapor, a continued rise in air temperature is expected to result in storms that are up to 15 percent wetter for every 3. Sea level rise As the ocean warms and expands and as terrestrial glaciers and ice sheets melt, sea levels are expected to continue to rise.
That increases the threat of storm surge —when powerful winds drive a wall of ocean water onto land—for coastal areas and low-lying nations. Longer-lasting storms Research suggests that global warming is weakening the atmospheric currents that keep weather systems like hurricanes moving, resulting in storms that linger longer.
Sluggish storms can prove disastrous—even without catastrophic winds—since they can heap tremendous amounts of rain on a region over a longer period of time. The stalling of Hurricane Harvey over Texas in , as well as the slow pace of Hurricane Florence, helped make them the storms with the greatest amount of rainfall in 70 years.
While there may seem to be a growing number of hurricanes snatching headlines each year, the Intergovernmental Panel on Climate Change IPCC does not see a general global trend toward increasing hurricane frequency over the past century. The exception is the North Atlantic, which the United Nations body notes has seen an increase in the frequency and intensity of its hurricanes—though as some researchers note , the uptick may be due in part to improvements in monitoring.
Looking forward, the IPCC projects that while there might be a slight decrease in hurricane frequency through , the storms that do make landfall are more likely to be intense—category 4 or 5—with more rain and wind. We may not be experiencing more storms, but we are riding out stronger ones, with heavier rainfall and more powerful winds hence all those news headlines.
Recent research , for example, estimates that Hurricane Harvey dumped as much as 38 percent more rain that it would have without climate change. Another Harvey analysis indicates that the likelihood of a storm of its size evolved from once per century at the end of the 20th century to once every years by —again, due to climate change.
Looking forward, the intensity of hurricanes that make landfall is expected to increase through the end of this century, with more category 4 and 5 storms. Of course, hurricanes are natural phenomena, and there is nothing we can do to halt any single storm in its path though some people may try. But getting there will require serious heavy lifting in the form of immediate, transformative global action, as the IPCC noted recently in a stark report drafted by some 91 climate scientists representing 40 countries.
It will mean slashing global carbon emissions by nearly half by , relative to levels, zeroing out emissions entirely by about , and meeting as much as 87 percent of global energy needs with renewable sources. Unfortunately, the Trump administration ignores the overwhelming evidence from climate scientists worldwide and has instead chosen to double down on fossil fuels and undermine policies designed to reduce carbon emissions and boost clean energy.
The administration has committed to withdraw from the Paris Agreement, ditch carbon-cutting policies such as the Clean Power Plan , weaken fuel efficiency standards for cars, and roll back wide-ranging environmental safeguards. But while the Trump administration is shirking its climate responsibilities, many American leaders—and much of the rest of the world— are pushing ahead. Mayors , governors , companies , and utilities are charting their own course, finding ways to tackle climate change.
As customers, we can support companies invested in meaningful climate action. And as global citizens, we can take myriad steps to slash carbon pollution from our own daily live s.
While we may not be able to prevent the next hurricane, there are ways to reduce the widespread destruction these storms leave in their wake. First, communities, cities, and states should work together to improve climate resiliency and ensure that public safety is a primary factor in determining where and what we build.