How do hurricanes form ?Ingredients for hurricane formationHow do hurricanes form? Hurricanes usually form in the summer or early autumn when several key atmospheric ingredients come together. Contrary to common belief, many factors other than warm ocean water cause hurricanes to form. In fact, the water is always warm enough in the deep tropics for hurricanes to form all year long. During the winter and spring, upper air winds are hostile, and usually do not allow tropical cyclone development. So, what does it take for a hurricane to form?
- 1. Pre-existing Disturbance or low pressure area must have formed in the low levels of the atmosphere to start winds converging and uplift.
- 2. Warm Water to a sufficient depth to support the energy that a hurricane will need. The temperature needs to be about 26.5º Celsius or 80º Fahrenheit to a depth of about 50 meters or 150 feet deep.
- 3. Low Stability will allow deep convection or cumulonimbus clouds to build to great heights in the atmosphere. A stable air mass will inhibit cloud development and not allow for significant cloud growth to support the deep convection needed for a hurricane to develop.
- 4. Coriolis Force The disturbed area of weather needs to be at least 4-5º away from the equator. This is the approximate distance from the equator for the Coriolis force to achieve a gradient wind balance to sustain the low pressure area.
- 5. Moist Mid Level of the atmosphere. If there is dry air aloft it will weaken or choke off the updrafts in the cumulus clouds.
- 6. Low Vertical Wind Shear from the surface to upper troposphere. This allows for the thunderstorm clouds to build to great heights. If the wind speed increases or changes direction with height, the cumulonimbus clouds get deformed can not sustain the hurricane heat engine.
- 7. Divergence in the upper Atmosphere allows for the transport of mass away from the hurricane.
Hurricane FormationIf the conditions above are met sufficiently, showers and storms will start to gain organization as low level winds converge toward the center of the low pressure area. The cluster of convection will start to form bands. As the convection increases, the warm air near the surface rises and cools. As it cools the water vapor condenses. There is a tremendous amount of heat produced from the condensation of water vapor. Some of this heat warms the center region of the low. As the temperature of the air near the core rises it produces lower pressure. In response to this lower pressure, winds increase in intensity. A tropical storm forms when the surface winds reach sustained winds of 39-73 mph. A hurricane officially classified as the winds reach sustained values of 74 mph.
Even if all of the ingredients of a hurricane are in place, it does not guarantee that a hurricane will form. Many of the factors in hurricane formation exist in the tropics, especially in the heart of hurricane season. Despite this, very few disturbances actually develop into a hurricane.
NASA / NOAA GOES-13 satellite image showing earth on August 26, 2011 at 14:45 UTC (10:45 a.m. EDT). Hurricane Irene can been seen on the U.S. East Coast. Irene Almost 1/3 the Size of East Coast. Irene has become a major hurricane, and NASA satellite data shows its diameter is now about 510 miles -- roughly 1/3 the length of the U.S. Atlantic coastline. Hurricane watches are in effect for much of the East Coast. For up to date information related to Hurricane Irene go to: www.nasa.gov/mission_pages/hurricanes/main/index.html Credit: NOAA/NASA GOES Project Larger image
This is a video released by Nasa of Irene passing over New York:
This is Hurricane Irene's track, which was published in the NY Times
This week has been devastating to our already punished economy. Vast communities around 11 states have suffered the force and destruction of hurricane Irene. Broken trees and flooding have caused loss of power lines and destruction of homes and businesses. Towns in Puerto Rico, North Caroline, New York, New Jersey, Vermont, Connecticut and others have been reduced to a bundle of muddy remains...it is like nature released its force and spread a wrath of destruction at its pace. The contents of this article have shared information with many NY Times blogger articles and other webs to bring you the most accurate information I could gather. Here are some of the most striking news and information.
In southern Vermont, the National Guard airlifted food, water and other supplies on Tuesday to hundreds of people who were stranded in 13 towns that have been cut off by floodwater since Sunday. Mark Bosma, a spokesman for the Vermont Office of Emergency Management, said most of the isolated towns had no electricity and none had potable water because floodwaters had overwhelmed local sewage and water treatment plants.
More than 260 roads and 30 state bridges remained at least partly closed Tuesday because of the flooding, which in some areas remains a threat as larger rivers, like the Connecticut, are expected to continue rising until at least Wednesday as they gather runoff and flow from tributaries, officials said.
Hurricane Irene will most likely prove to be one of the 10 costliest catastrophes in the nation’s history, and analysts said that much of the damage might not be covered by insurance because it was caused not by winds but by flooding, which is excluded from many standard policies.
Industry estimates put the cost of the storm at $7 billion to $10 billion, largely because the hurricane pummeled an unusually wide area of the East Coast. Beyond deadly flooding that caused havoc in upstate New York and Vermont, the hurricane flooded cotton and tobacco crops in North Carolina, temporarily halted shellfish harvesting in Chesapeake Bay, sapped power and kept commuters from their jobs in the New York metropolitan area and pushed tourists off Atlantic beaches in the peak of summer.
While insurers have typically covered about half of the total losses in past storms, they might end up covering less than 40 percent of the costs associated with Hurricane Irene, according to an analysis by the Kinetic Analysis Corporation. That is partly because so much damage was caused by flooding, and it is unclear how many damaged homes have flood insurance, and partly because deductibles have risen steeply in coastal areas in recent years, requiring some homeowners to cover $4,000 worth of damages or more before insurers pick up the loss.
This could make it harder for many stricken homeowners to rebuild, and could dampen any short-term boost to the construction industry that typically accompanies major storms, Jan Vermeiren, the chief executive of Kinetic Analysis, said in an interview.
“Especially now that the economy is tight, and people don’t have money sitting around, local governments are broke, and maybe people can’t even get loans from the banks,” Mr. Vermeiren said.