This topic submitted by Karen Kosiba, Jess Downing on 3/20/02 .
Atlantic Basin Hurricanes: Policy and Threats
This is Hurricane Andrew from 1992
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 (also known as a tropical cyclone) development and intensification. Research
has shown a slight increase in hurricane activity has occurred in the last 111 years. Positive relationships or correlations,
although tentative, have been established between an increase the in the mean surface sea temperatures (SST), increased levels
of atmospheric carbon dioxide, non-El Nino Years, increased monsoonal activity and increased hurricane activity in the
Northern Atlantic Basin.
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 (Elsner and Kara, Hurricane of the North Atlantic, Chapter 10, 1999).
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. Furthermore we will investigate the correlation between hurricane-spawned tornadoes
and El Nino years as well as the correlation between hurricane-spawned tornadoes and coastal SST. We will look at data from
hurricane/tornado 1951-2001 in the Northern Atlantic Basin.
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
1951-2001 time frame.
Ia. Research Question
This study of hurricanes will be two fold, consisting of a social aspect as well as hurricane dynamics. First, the question of
hurricane preparedness and mitigation will be assessed by making reference to how it has changed over the years, as a result of
increasing hurriane destruction. We will also touch on what sort of policies have been put forth by those mitigation entities in
order to ensure that safety remains top priority in times of such natural disasters.
Second we are going to investigate if correlations exist between the following variables:
1. Intensity (maximum wind speed/minimum pressure) and the number and intensity of hurricane-spawned tornadoes;
2. Coastal SST and the number and intensity of hurricane-spawned tornadoes and
3. El Nino years and the number and intensity of hurricane-spawned tornadoes.
Hurricanes are perhaps natures most destructive storms. For people living along the coastal regions of the Gulf of Mexico as
well as the Atlantic Coast, hurricanes have the possibility of destroying homes, taking lives, and even stopping daily activity.
Hurricanes are not a storm to be taken lightly.
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
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
A tropical cyclone is a non-frontal vortex that develops in the tropical latitudes. The pressure gradient force acting inward and
the Coriolis and centrifugal forces acting outwards balance air circulating around a low-pressure center.
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 (1981) 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 (DeMaria and Kaplan, 1994).
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 1920s. 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. The USGS offers a great comparison, of the last century, between property damage and loss of life, and how they
have both oscillated over time. 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 peopleÍs lives in danger by drastically slowing down the evacuation process. As the director
of FEMA, James Lee Witt appropriately said "..the increase in infrastructure has not kept up with the increase in population.."
and publicly called for the re-evaluationof the programs current policies relating to hurricane preparation and mitigation.
Another major player in aiding in hurricane preparation and mitigation for the United States is the American Meteorological
Society and their Atmospheric Policy Program, and they also recognized the importance of changing their policies after
Hurricane Floyd, which resulted in the largest peacetime evacuation, resulting in completely chaotic traffic and numerous deaths
to flooding and other events which could have been avoided. The director of the APP was quoted saying that ñour current
systems-for forecasting these major storms, getting the word to those in harms way, and getting them out of danger-are
inadequate to handle such a disaster.î
Because of this, FEMA has came up with their Disasters Mitigation Act of 2000, which they claimed 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 ñthe US would provide aid, through an intermediary nation, if it
was requested, only for the Cuban people, not for Castros regime.î 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 1951-2001 due to the
fluctuation in hurricane intensity throughout that period.
Hurricane data is to be downloaded from the National Hurricane Center and UNISYS. Tornado data will be downloaded from
the Storm Prediction Center. We will categorize hurricane intensities using the Saffir-Simpson Scale (Maximum Wind
Speed/Minimum Pressure) and tabulate the number of tornadoes and their F-Scale Rating that occurred for a given hurricane of
a particular intensity. We will also record the coastal SST and whether or not the year was an ESNO year. We will perform a
correlation analysis on the data to see if there is a statistically significant effect on hurricane intensity, coastal SST, ESNO and
tornado production and intensity.
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 have PDFs for most articles. We still are waiting for the rest. As soon as they are available, we will
post them as a response.**
1. Henderson-Sellers, H. et. al., 1998:
Tropical cyclones and global climate change: a post-IPCC assessment, 79, Bulletin of the American Meteorological Society.
2. Merrill, R. T., 1988: Environmental influences on hurricane intensification, 45, Journal of the Atmospheric Sciences.
3. Evans, J. L., 1993: Sensitivity of tropical cyclone intensity to sea surface temperature, 6, Journal of Climate.
----, B. F. Ryan, and J. L. McGregor, 1994: A numerical exploration of the sensitivity of tropical cyclone rainfall intensity to sea
surface temperature. J Climate., 7, 616-623.
4. DeMaria, M., J. Kaplan, 1994: Sea surface temperature and the maximum intensity of Atlantic tropical
cyclones , 7, Journal of Climate.
5. Emanual, K. A., 1987: The dependence of hurricane intensity on climate, 326, Nature.
----, 1991: The theory of hurricanes. Annu. Rev. Fluid. Mech., 23, 179-196.
----, 1997: Some aspects of hurricane inner-core dynamics and energetics. J. Atmos. Sci.,52, 3969-3976.
6. Knutson, T. R., et. al, 1998: Simulated increase of hurricane intensities in a CO2-warmed climate, 279, Science.
7. Chan, J. C. L., 1985: Tropical cyclone activity in the northwest Pacific in relation to the El Nino/Southern Oscillation
phenomenon. Mon. Weather Rev., 113, 599-606.
8. Gray, W. M., 1984a: Atlantic seasonal hurricane frequency. Part I: El Nino and 30 mb quasi-biennial oscillation influences.
Mon. Wea. Rev., 112, 1649-1668.
9. Lander, M. A., 1994: An exploratory analysis of the relationship between tropical storm formation in the western North
Pacific ESNO. Mon. Wea. Rev., 122, 636-651.
10. Landsea, C. W., 1993: A climatology of intense (or major) Altantic hurricanes. Mon. Wea Rev., 121, 636-651.
----, N. Nicholls, W. M. Gray, and L. A. Avila, 1996: Downward trends in the frequency of intense Atlantic hurricanes during
the past five decades. Geophys. Res. Lett., 23, 1697-1700.
11. Lighthill, J., et. al., 1994: Global Climate Change and tropical cyclones. Bull. Amer. Meteor. Soc., 75, 2147-2157.
12. Revell, C. G., and S. W. Goulter, 1986: South Pacific cyclones and the Southern Oscillation. Mon. Wea. Rev., 114,
13. Mayo, N., 1994: A Hurricane Model for physics students. The Physics Teacher, 34.
1.FEMA, Mitigation Policies.
4.Some great basic hurricane information.
5.Here are the guys who know all about how mean hurricanes can be, the Hurricane Hunters!
6.FEMAÍs newest Disaster Mitigation Act of 2000.
7.FAQ: Typhoons, Tropical Cyclones and Hurricanes Contains much general information as well as relevant links on hurricanes.
8.The Tropical Meteorology Project
9.The National Hurricane Prediction Center
10.Atlantic Oceanographic and Meteorological Laboratory
11.CISMM Tropical Cyclones
12.GFDL Hurricane Dynamics
13.Storm Prediction Center Climatological Data
14.Need for Change in Hurricane Mitigation and Preparation Policies
15.A nice USGS analysis of current hurricane trends
1. Elsner, J. B. and Kara A. B. Hurricanes of the North Atlantic. Oxford University Press, New York. (c) 1999.
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