With the increase in the United States' coastal population as well as the concern for the affects of global warming, it is necessary to understand the parameters that affect hurricane development and intensification. Research has shown a slight increase in hurricane activity has occurred in the last 111 years. Positive relationships, although tentative, have been established for an increase the in the mean surface sea temperatures, increased levels of atmospheric carbon dioxide, non-El Nino Years and increased monsoonal activity.
Although global warming will increase the amount of energy in the atmosphere/ocean system, scientists are unsure as to how this energy change will manifest.
Through extensive literature review, it is apparent that a relationship between hurricane intensity and hurricane-spawned tornadoes has not yet been established. We will investigate if a relationship exists between intense hurricanes and hurricane-spawned tornado frequency. We will look at data from hurricane/tornado 1990-2001. This time frame is of particular interest because it encompasses because it contains a wide range of hurricane frequency. Furthermore, the beginning of the 1990s was categorized by relatively low hurricane activity whereas the latter half of the decade was characterized by high hurricane frequency.
It is also of paramount interest to investigate the policies that have been implemented to address storm preparedness as well as disaster relief in those coastal communities. This will be accomplished by extensive review of hurricanes that occurred in the 1990-2001 time frame.
As the coastal population in the United States increases, hurricanes become an increasing concern. With the potential to cause millions of dollars in property damage and a large death toll, it is important to understand policies and programs that have been implemented to protect those areas. Furthermore, it is necessary to understand the influence of climatological factors that affect hurricane development and intensification.
Hurricanes contain damaging winds, dangerous storm surges, torrential rains, inland flooding, and the potential to produce tornadoes. Hurricane-spawned tornadoes, although less violent than their frontal-spawned counterparts, account for up to 10% of all hurricane fatalities and 50% of all property damage. Therefore it is of paramount interest to investigate the frequency of hurricane-spawned tornadoes.
Due to the potentiality to disrupt economic functions both on a local and federal level, governmental and humane programs have been implemented to minimize these [possibly] detrimental effects that hurricanes and all the threats associated with them, might have on the immediate environment. These programs could be aimed at evacuating the people to ensure that everyone remains safe, or they could be programs in which the local community effectively analyzes its resources to put a price on them so that it is easier to collect damages after a destructive storm. Whether it is a storm preparation program or a disaster relief program, these packages, in light of the costly damages associated with such recent storms, have been ‘re-vamped’ in order to handle modern worries.
There are four stages of tropical cyclone development (listed in order of increasing intensity and organization): tropical disturbances, tropical depressions, tropical storms and hurricanes.
A hurricane is defined as a tropical cyclone with near surface (below 10 meters) winds in excess of 73 mph and a central pressure deficit of at least 60 mb. Hurricanes are categorized according to the Saffir-Simpson intensity scale , with a Category 1 hurricane as the weakest (central pressure > 980 mb, sustained wind speeds between 74-95 mph and a storm surge of 4-5 feet) and a Category 5 hurricane as the strongest (central pressure < 920 mb, sustained wind speeds in excess of 155 mph and a storm surge greater than 18 feet).
Hurricane intensity is defined by either the minimum sea level pressure (MSLP) or the maximum sustained low-level winds. Hurricane intensification is said to occur when either of the aforementioned parameters increases.
Hurricane frequency is defined as the number of hurricanes that occur within a given time interval. A hurricane makes landfall when part or its entire eye is over land.
IV. Hurricane Structure
Hurricanes are two-celled structures (contain both upward and downward air movement) that derive their energy from the release of latent heat due to condensation. Hurricanes contain a low-pressure, warm-core center known as the eye. The eye is a 16-70 km diameter column of subsiding air that is being warmed by compression. As the warm air sinks, it spreads out, rises and feeds the cumulonimbus towers surrounding the eye. The surrounding annular area of cumulonimbus towers is a region known as the eye wall. It is in the eye wall that the most intense vertical motions, the heaviest rain and the largest wind speeds occur. Surrounding the eye wall are spiral-like arms known as the feeder or spiral bands. These bands contain heavy rains and strong, gusty winds.
Va. Literature Review of Climate Factors
Hurricanes are complex dynamic structures influenced by a variety of atmospheric and oceanic factors.
Gray has identified six conditions that support the development of tropical cyclone development. They are:
1. Large values of low-level vorticity,
2. Coriolis parameter (development is favored several degrees poleward from the equator since the Coriolis parameter at the equator is zero),
3. Week vertical shear of horizontal winds,
4. High SSTs (in excess of 26 C) and a deep thermocline,
5. Conditional instability through a deep atmospheric layer, and
6. Large values of relative humidity in the lower and middle tropopause.
Although these conditions may contribute to hurricane development, they are not sufficient to predict hurricane development.
With the concern of global warming and its affects on the atmosphere and oceans, the scientists are interested on how the predicted effects will influence tropical cyclone activity. It is though with an increase in global warming, that the ocean temperatures will increase. Furthermore, it is thought that warm ocean water will migrate northward from their previously tropical locations. It has been shown that sea temperatures 26 C and upwards are favorable for the development of tropical cyclones. With an increase in sea temperatures, will hurricanes become more frequent or more intense? Research has indicated that although there is a correlation between SSTs and hurricane intensity, SSTs alone cannot predict whether or not a hurricane will intensify.
It has been found that there is a correlation between SST and hurricane intensity. SST alone, though, cannot predict whether a particular hurricane will intensify.
Studies have shown there to be a modest increase in hurricane development in the North Atlantic Basin from 1886-1996.
For the same time frame, there has also been a positive trend in baroclinic hurricanes and the mean latitude of occurrence.
As hurricanes make landfall, frictional dissipation of surface winds occur more readily then at higher elevations. This, along with other favorable environmental conditions, combine to produce tornadoes. Hurricane-spawned tornadoes are most frequent in the front right quadrant of the hurricane system. Most of the tornadoes produced are F2 or below.
Vb. Literature Review of Societal Aspects
For this reason, there have been countless governmental and insurance programs designed to keep those people, who live in the potential path of a hurricane, safe. As far as records go, there have been massive hurricanes dating back to the 1920’s. In fact, during those times, there were two extremely destructive hurricanes, which some analysts say were more economically destructive (with economic inflation taken into account) than the 1992 hurricane Andrew, because of lack of programs to keep people safe. Nowadays, there is the renowned FEMA, and Red Cross institutions, to name a couple, that are the primary players in hurricane preparedness and mitigation.
In recent times, FEMA was forced to re-evaluate its mitigation plans when the ordered evacuation of thousands of people led to mass amounts of traffic which put people’s lives in danger by drastically slowing down the evacuation process. Now, FEMA has come up with their Disaster’s Mitigation Act of 2000, which they claim, will aid in the process of preparing the affected regions for possible hurricane onslaught, as well as instigating some community-based preparation to better assess values of local resources (which can then be filed for damages in case of being destroyed).
Along with this new FEMA program, there are countless websites, insurance programs, and other humanitarian/governmental resources, which the public can access, in order to get up to the minute readings of the impending storm, as well as pamphlets on hurricane readiness, and even a Hurricane Disaster Supply Kit. There is no question that in current times, the vast majority of the coastal and inland communities (as even those far inland are eventually affected by the dying tropical storm, or depression), are at the very basic level, adequately prepared for any sort of tropical storm situation, and that there will be a very resourceful clean-up crew (and process) following the storm.
On this note, one area that I find worthy of investigating is the way that other nations in the Gulf are affected by these monstrous storms, and what sort of aid, if any, the US provides. One issue that I found off the CNN website, which peaked my interest, is that when Hurricane Michelle ravaged the nation of Cuba, the United States was very reluctant to offer any sort of humanitarian aid. The reply of the US interest section to this issue was that “the US would provide aid, through an intermediary nation, if it was requested, only for the Cuban people, not for Castro’s regime.” Hmm. Interesting how political factions go so deep, eh?
VI. Statement of the Problem
As is evident from the aforementioned discussion, hurricanes making landfall pose great threat to the population and economy. Therefore, it is our intent to analyze the policies adapted to address these concerns. As mentioned earlier, there is a significant amount of damage generated from landfall hurricanes that spawn tornadoes. It is also our intent, then, to look at the number and intensity of hurricane-spawned tornadoes for a given length of time. We have chosen the span from 1990-2001 due to the fluctuation in hurricane intensity throughout that decade.
Hurricane date is to be downloaded from the National Hurricane Center. Tornado data will be downloaded from the Storm Prediction Center. We will categorize hurricane intensities using the Saffir-Simpson Scale and tabulate the number of tornadoes that occurred for a given hurricane intensity. We will perform a correlation analysis on the data to see if there is a statistically significant affect on hurricane intensity and tornado production.
After extensive review of this data, we will look at the correlation between increased storm activity and new and existing government programs aimed at minimizing potential damage.
**At the present time, we are waiting for our articles to be put into pdf format at the library. As soon as they are available, we will post them as a response.**
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1. Hurricane Threats.
3. Some great basic hurricane information.
5. FEMA’s newest Disaster Mitigation Act of 2000.
7. The Tropical Meteorology Project
9.Atlantic Oceanographic and Meteorological Laboratory
11.GFDL Hurricane Dynamics
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