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wximpact New Orleans

Page history last edited by dkowals2@... 12 years, 6 months ago







New Orleans Profile


Population mfalls2


New Orleans is the largest city in Louisiana and one of the major U.S. port cities. Before Hurricane Katrina hit the city the population stood at 484,674. After Hurricane Katrina hit New Orleans, the population was greatly reduced. In 2006, the population was just over 223,000 [1]. Recently, it has been recorded that the cities population is at 302,191. It is believed that with the numerous amount of people moving back to the city that by 2010 the population could reach 420,000 [1]. In 2006, when the population of the city was at 223,338, the city was 36.8% White, 58.8% Black, 0.2% Native American, 4.1% Hispanic, 2.8% Asian, and 0.8% other [1]. These numbers continue to change everyday though with the growing amount of people moving back to the city. [1,16]




Geography of New Orleans



The city of New Orleans occupies 181 of Louisiana’s 43,562 square miles[1]. It lies on the Mississippi River Delta in the southeast toe of the Louisiana boot stretching up to the southern coast of Lake Pontchartrain at 29° 58' North Latitude, 90° 05' West Longitude[2]. The Gulf of Mexico lies just over land to the south placing the city in a region always threatened by the dynamic weather the Gulf can throw at it.
New Orleans' Elevation ranges from minus 4 feet to 8.5 feet above sea level[3].
In 1805 the city was separated into 7 distinct wards and by 1880 expanded to 17 as it still stands today[4] as shown in this photo courtesy of http://www.mardigrasdigest.com/travel/new_orleans_districts_and_wards.htm.


Topography of New Orleans (ksharp2)





Ecology of New Orleans pojman



The Mississippi River Delta comprises a large portion of New Orleans' ecosystems and vegetation as well as a large portion of its economy. It is also a commercially significant region, supporting the economy of New Orleans with significant shipping traffic, providing 16 to 18 percent of the U.S. oil supply and providing 16 % of the U.S.'s fisheries harvest, including shrimp, crabs, and crayfish [11]. Landings from the rich grounds surrounding the river delta, referred to as the fertile fishery crescent by the late Gordon Gunter, account for 70-80% of the 1.8 billion-pound annual commercial catch from the Gulf of Mexico, second only to Alaska in the United States [12].



The ecology of New Orleans changed drastically after Hurricane Katrina. A swamp tour guide decribed the scene as, "The saltwater came in and killed all the vegetation — all of it, nothing was alive. It looked like someone dropped an atomic bomb." He also described how the saltwater that had been rushed in by Hurricane Katrina had killed all of the freshwater fish in the area. "You could see them a week after the storm, floating up and down the river, which left the water rancid for a couple of weeks." [20]



Many trees and vegetation were destroyed in Hurricane Katrina as can be seen by this uprooted tree.



Photo courtesy of MSNBC 21

Local wildlife also was harmed with some native species losing more than half of their populations.

Two of New Orleans long standing native animals are the alligator and the heron. The heron was harmed by Katrina because Katrina killed millions of freshwater crawfish. These happen to be a crucial part of the heron's diet. 24




Photos courtesy of Picasa Web Albums 22 and Bovits.com 23





Land Use


New Orleans is the largest city in the state of Louisiana, with a population estimated at 302,191. New Orleans is a densely populated city with a population average of 2,684.3 per square mile. The city covers 181 square miles of the states total 43,562 square miles [8]. According to the National Atlas, New Orleans uses less than 5 percent of their land for crops [9]. Due to the direct after effects of Hurricane Katrina, it was estimated that 248,000 people were left unemployed 10. In November of 2005 a panel of experts released a plan to rebuild New Orleans after hurricane Katrina. They held an open forum to discuss the ways in which the city of New Orleans should go about rebuilding itself. One of the key points that they laid out was the rebuilding of an adequate levee system and restoring the coastal wetlands while rebuilding those levees [11].



New Orleans is largely located between Lake Pontchartrain to the North and the Mississippi River to the South, with several canals running through the city connecting the two bodies of water. Much of the city sits below sea level, making the city vulnerable to flooding. To combat this threat, the shorelines of the river and the lake are bordered by levees 5 and the city has a large system of pumps to handle any flood waters. [6] However, the flood waters from Hurricane Katrina caused many of the levees and flood walls along the city's canals to fail, and many of the pumping stations were submerged and could not operate.[7]





Climate bwlezie2



In general, the average temperature in New Orleans is 68.8 degrees Farenheight. During the summer months, the daily average is usually in the low 80 Farenheight degrees while in the winter months, the daily average is in the mid 50 Farenheight degrees.14 July is typically the warmest month, and January is usually the coolest month. The record for the lowest temperature recorded was 7 degrees Farenheight, in February 1899. The highest temperature on record was 102 degrees Farenheight, in the summers of 1901, 1915, and 1980.



The normal precipitation for New Orleans is about 64 inches or rain in a year.[15] Usually, most of the precipitation occurs in July.[14] Snow is rare in New Orleans, but it can happen. The last time that there was a significant amount of snow was on December 22, 1989, when about 1-2 inches fell.16


Degree Days

On average, New Orleans has about 1417 normal heating degree days, 2773 normal cooling degree days [14] , and 6513 growing degree days



Climate chart for New Orleans
temperatures in °Fprecipitation totals in inches

source: Weather.com33




























Since most of the attractions and accommodations are within walking distance of each other in New Orleans, walking and mule-drawn carriages are the common modes of transportation. Costing only $1.25, the RTA bus service follows 28 lines and uses 61 buses during the weekday peak hours. Bus service to Kenner and Baton Rouge, and special service for the disabled is also available. The most famous mode of transportation in New Orleans is the streetcar system. The streetcars are historic olive-green Perley Thomas-type streetcars, which makes them inaccessible to the handicapped. Due to the proximity to water, riverboats, ferries and river shuttles are also popular transportation modes. Fare is collected on two ferries, the Gretna/Jackson Avenue and the Algiers/Canal Street. Driving in the city is possible, but drivers should be cautious. Intersections that do not have functioning traffic signals should be treated like four-way stops. Parking restriction, meters and no parking zones are enforced and cars can be towed until 7 p.m. Several bridges and major roadways, including the Crescent City Connection Bridge, Lake Ponchartrain Causeway, I-10 Slidell Twin Span Bridge and I-10 Lake Charles, are open to the public. The Louis Armstrong International Airport is only 15 miles from the Central Business District and French Quarter. The Union Terminal, which serves Greyhound Bus and AMTRAK train, is also conveniently located for travelers. Rental cars, taxis, limousines, and shuttle services are also available to tourists. [18]

New Orleans Riverboat

new orleans streetcar 28 27






Industry and Economic Base: Pre-Hurricane Katrina

New Orleans economy can be compared to a three-legged stool, with tourism, port operations, and education serving as the legs of the stool and thereby providing almost all of it finances. Although these are general categories many employment opportunities fall under them. New Orleans is widely recognized as being among the most visited cities in the United States, with attraction like Mardi Gras, the French Quarter and the annual Sugar Bowl game. People travel not only from all over the United States but around the world to take in the sites and sounds of the city. It has become a rising attraction for spring break goers as well as those planning to take a cruise. Each year tourism is a multi billion dollar industry. Along with tourism a less recognized but equally important part of the economy is the port industry. Through the course of the year approximately 5,000 ships from nearly 60 countries dock at the Port of New Orleans. The port as been a part of international trade since the 1700’s, it is also the only deep water port in the US. Coffee, steel, forest products, rubber, copper and containerized cargo are the primary commodities. In 2004 the port employed over 160,000 people and was responsible for approximately 8 billion dollars in earnings. Similarly to tourism the port also generated revenue through cruises. Carnival, Norwegian and Royal cruise lines sail out of the port weekly, and an estimated 700,000 people travel through the port annually. The third leg of the stool is higher education. The New Orleans area is home to 10 four-year universities, 2 medical schools, 2 junior colleges, 3 HBCU and a number of technical and vocational schools. It is easy to see how much of an impact higher education has on the economy. Some of the schools include LSU (Louisiana State University), Tulane University, the University of New Orleans, Loyola University New Orleans, Xavier University of New Orleans, Southern University of New Orleans and Dillard University. By 2000 the tourism industry increased in importance, it represented 16.0 percent of employment and 8.0 percent of the total wages generated in the city. Government was also on a rise it represented 20.8 percent of all jobs and 24.7 percent of total wages. In 2000, 1 out of 5 people working in New Orleans was employed by the government, 1 out of 6 in tourism, and 1 out of 10 in health care. Oil and gas extraction, water transportation, warehousing and storage, were also among the highest ranked industries in the city.[19]25 26








Industry and Economic Base: Post-Hurricane Kartrina

Although the hurricane devastated the people and the land of New Orleans not all areas or industries were affected the same. The complexity of the situation still affected areas that were able to avoid the blunt of the direct storm like the French Quarters. Although the French Quarters were not hit directly and sustained minimal damage the tourist rate for this area decreased drastically. In the first 10 months following the hurricane the city suffered an average loss of approximately 95,000 jobs. By November 2005 there were 105,300 fewer job and people employed then in November one year earlier. Lost wages over the 10-month period from September 2005 to June 2006 were about $2.9 billion, with 76 percent of the loss attributable to the private sector. Tourism experienced the largest job loss among all sectors as well as the largest potential loss based off the gains it would have experienced in employment. During the 10 month period following the storm the tourism industry lost approximately 22,900 jobs and 382.7 million dollars. The port industry lost approximately 136.1 millions dollars and 3,500 jobs. The professional and technical services sector was one of the bright spots in the New Orleans economy, returning to its pre-Katrina employment trend line by mid-2006. The construction sector has been the one industry showing an increase in jobs in the New Orleans economy. This increase can clearly be seen because of the need to rebuild. A large number of houses were damaged by the storm and soon after the rebuilding of the city began. In the months following the storm construction jobs increased by nearly 5,000 which added close to 2 million dollars worth of income. By May 2006, educational services had almost reached pre-Katrina employment levels unfortunately employment losses began again soon after possible due to the number of students who did not move back after they evacuated from the storm. Job losses for education reached close to 2,000 jobs and 66 million dollars. Other substantial loses were from the health care and social services fields. The combined for a total of over 13,000 lost job and 377.8 million dollars in lost wages. New Orleans is far from the status and level that it was three years ago but it is on the right track. Tourism is back on the rise with the help of things like the Jazz musical fest and the NBA all-star game which was held there this year. And New Orleans wouldn’t be itself without the largest Mardi Gras festival in the country. Although the city will always remember what happed, it will continue to rebuild and regain its reign as one of the greatest cities in the country. [19] 25 26







Weather In the Big EASY New Orleans, Louisiana



Floods: pojman



Floods tend to be quite frequent in New Orleans because the elevation level is actually below sea level for many parts of the city. It is very difficult to get rid of flood waters, therefore floods can last much longer and cause much more destruction than at a higher elevation level. The four characteristics needed for a hurricane to form are: weak wind shear, warm and deep ocean water,

sea-surface temperature (SST) of over 81 degrees, and a location more than 5 degrees away from the equator. These conditions are satisfied quite

frequently in New Orleans, which makes the city more prone to frequent hurricanes. Floods are generally more likely during hurricane season, which runs from June until November, when tropical storms can bring large amounts of rain very quickly. New Orleans also has the potential to flood in the spring when the Mississippi river begins to rise.



There are several different ways a flood can happen in New Orleans. Floods can be categorized according to their location as well as their strength and

duration. New Orleans is susceptible to many different types of floods. When a hurricane or strong tropical storm hits New Orleans and causes flooding it is a coastal flood, which may include intense flash flooding due to the heavy rain as well as damaged dams or levees. 53 The other frequent flood would be a

river flood that could occur if a heavy spring rain causes the water level in the Mississippi to rise beyond what the river can hold and overflow the banks. Photo1


Case Study: Hurricane Katrina pojman


Hurricane Katrina turned out to be the costliest natural disaster in the history of the United States as it cost over 80 billion in damages. The hurricane formed on August 23, 2005 and reached land in the United States on August 25, 2005 in Florida. The second and far more devastating time this storm hit land was on August 29, 2005 in Louisiana. Six hours after Hurricane Katrina had reached landfall, 1200 people had lost their lives and 200,000 homes were destroyed. The levee failure started with a miniscule leak at the Interstate 10 high-rise and concluded with the destruction of the floodwalls at the 17th street canal as well as the London Avenue canal. These canals along with the industrial canal accounted for the majority of the flooding. 54


One account claims that a massive wave came across Lake Pontchartrain and threw a steel barge through the industrial canal. This in turn caused a 500-foot breach in the levy that allowed flood waters to reach much of the city. This along with the other levee failures caused about 80 percent of New Orleans to flood in the aftermath of Hurricane Katrina. The extent of the flooding can be seen in the flood damage map below.55 Some parts of the city were under as much as 20 feet of water. This extent of flooding was not typical of the average hurricane, but the levees breaking caused the flooding to be much more severe. 56





The hurricane itself was very well forecast as there was a hurricane warning issued well before the hurricane made landfall in New Orleans. However, the flooding associated with the hurricane was not well forecasted at all, as many believed that the levees would remain strong. One of the reasons that the levees may have failed at such an alarming and unexpected rate could be due to the sinking land in New Orleans. Because the land is sinking, the levees are actually shorter than when they were designed. Therefore they may not have been able to withstand a category 2 or 3 hurricane and surely could not withstand a category 5. 57




One impact of the extensive flooding was the massive loss of life, as over 1,500 people lost their lives in Louisiana related to Hurricane Katrina. In addition to the loss of life, many additional people lost their homes in New Orleans and were forced to move elsewhere. Many cities in surrounding areas had drastic population surges due to all of the former residents of New Orleans not having a home to go back to.


There were also devestating environmental consequences of Hurricane Katrina. Hurricane's environmentally destructive forces include strong winds, inland flooding, storm surge, and tornadoes. All were present in the destruction of on August 29, 2005 in Hurricane Katrina. One environmental consequence was the loss of wetlands. Katrina turned 30 square miles of wetlands into open water in the Brenton Sound as a result of the storm. After the storm, much of the flood water was pumped into Lake Pontchartrain containing raw sewage, pesticides, toxic chemicals and 6.5 million gallons of oil. These flood waters are likely to kill much of the ecosystems that thrived at the lake before Katrina. Also the saltwater intrusion from the storm surge could kill many fish as well as lakeside habitat. 71




Another impact of the flooding was the costly repairs that needed to be completed in order to restore the city and prevent future catastrophes. Levees needed to be rebuilt in order to withstand the power of a strong hurricane. The cost of reparing all of the levees in order to pass insurance standards and be ready for future storms is estimated at almost 10 billion dollars.72 Roads needed to be repaired, as many were destroyed by the storm. New Orleans in reality will take a very long time to return to their pre-Katrina state, a process that has only just begun.



Ebony Jones



Hail Formation

Hail forms in thunderstorms with a strong updraft that is above the freezing level


Hail embryos form first; they are ice particles that are in the center of the hailstone. They function as the center of growth.


Graupel particles are soft ice particles, they form around the bounded weak echo region and are the initial particles that becomes hailstones


Hailstones are hard or spongy large ice spheres that fall to the earth


When a water droplet is picked up in the updraft it will freeze, if it goes back in the downdraft it may unthaw some but will be picked up again


The graupel may continue to be pick up in the updraft, each time it does so it moves back up into the freezing air and adds and additional layer of ice forming hail.5 22







Impact on New Orleans

Although hail is not one of the most frequently occurring sever weather events in New Orleans it does take place there. It is most common during the spring because of the increase in severe thunderstorms. Between 1950 and 1993 there were nearly 2,000 cases of hail in the city. The average size of the hailstones were 1.3 inches, the largest size of the hailstones were 2.75 inches which occurred multiple times. In New Orleans large hail can and has caused millions of dollars in damage because it is rare and the city does not have an emergency action plan in place. In New Orleans hails impact is not always immediately seen. There has been time when people didn’t know they had sustained damage to their property until there was another storm in which rain was coming through their roofs. Large hail can have a devastating impact on the city because of the percent of people who are living in poverty. Many of these people do not have the financial means to repair damage to their properties. 23


Case Study Hail

Ebony Jones



January 23, 2000 New Orleans experienced a hail storm that caused millions of dollars in damage. The size of the hailstones raged from approximately the size of a golf ball to nearly the size of a baseball. The average diameter was 1.75 inches. The wind gust reached upwards of 45 mph. A cold frontal boundary moved in from the north and the dew point was 20 degrees warmer north of the frontal line. There was a 125 kt jet core moving in from the west in the core was a 155 kt jet maximum. This provided enhanced lift and storm top divergence. From the northwest there was a cold pool moving into the area. This storm was not typical, especially for this time of the year. Most hail storms take place during the spring, and this one occurred in the winter. The sizes of the hailstones were above the average size typically experienced by the city. Even filing insurance claims were different for many people in the area. There were many residents who did not immediately file claims, particularly for damage to their roofs. Following the storm the city experienced a drought and many homeowners did not know for some time after the storm the extent of the damage their homes experienced. The five insurance companies that represent over 60 percent of the people in New Orleans have received over 42,000 claims for homes and 37,000 claims for automobiles. The total damage is around 500 million dollars. This event was forecast well, but the extent of the damage could not be avoided because of the size and the power of the wind that was pushing the hail.23 80




El Niño

El Niño, meaning the boy and referring to the Christ Child in Spanish, is a change in the water temperatures in the Pacific Ocean. El Niño occurs approximately every 2-3 years, usually followed by an episode of La Niño. El Niño is part of a larger phenomenon known as the Southern Oscillation. The Southern Oscillation is the oscillation in the intensity of the Walker Cell, which is a gigantic circulation cell that is created by the vertical motions of the from the major pressure centers in the tropical Pacific mixing with the westward surface winds creating return flow of air aloft from west to east. When this system weakens or breaks down El Niño occurs. When this happens the surface pressure systems weaken and the trade winds slow down in the Pacific Ocean. This causes the cold water that usually flows from east to west are slowed down and the water in the pacific to remains or becomes warmer. Over time, the water persists at a warmer than normal temperature along the pacific and begins to cause unusual atmospheric behavior. 4,5

The image below shows the differences in the Pacific Ocean during regular conditions and El Niño conditions.






El Niño effects all parts of the world in different ways. Most of the effects of El Niño occur during the winter months. The image below shows the differences in precipitation across the United States during the winter months of an El Niño season.In New Orleans, along with parts of the other Gulf States, El Niño typically results in heavy rainfall and flooding in addition to occasionally higher temperatures. 6,7




In 1982 and 1983 El Niño brought extremely heavy rains and flooding to New Orleans. Almost 75% of the city’s streets were underwater. There was an estimated cost of about $350 million for the damage that occurred as a result of this flooding in Mississippi and Louisiana. In addition to the large costs from the flooding, more than 100,000 poultry and 1,000 cattle died, and 17% of Mays cotton crop was lost as a result of the heavy rains caused by El Niño. 8

El Niño has also been able to help New Orleans through the prevention of hurricanes. As a result of El Niño, air sinks in the middle and upper atmosphere and wind sheer is increased to higher than normal levels. This creates conditions that are not good for hurricane formation and results in milder hurricane seasons. In 2006, New Orleans was able to greatly benefit from an El Niño formation that brought a mild hurricane season after the devastating previous hurricane season the year before. 9




(http://skyflashes.com/) (http://bestanimations.com/Nature/Storms/Storms3.html) (http://skyflashes.com/)



According to Encyclopedia Britannica, lightning is the visible discharge of electricity that occurs when a region of a cloud acquires an excess electrical charge, either positive or negative, that is sufficient to break down the resistance of air. It is most often associated with cumulonimbus clouds, or thunderclouds, but can also occur in strait form clouds, snowstorms, dust storms, and sometimes in the dust and gas from erupting volcanoes 10.



Lightning comes in three main types in nature including: 11

· Cloud-to-Ground -- The most damaging and dangerous type of lightning

· Intracloud -- The most common type of lightning that strikes within a single cloud

· Intercloud -- A less common type of lightning that strikes from one cloud to another


To compound these types of lightning can take on many forms which consist of: 11

· Forked Lightning

· Sheet Lightning

· Heat Lightning

· Ball Lightning

· St. Elmo’s Fire

· High-altitude Lightning (“red sprites,” “green elves,” “blue jets”)


On Average lightning strikes occur around the world an astonishing 100 times per second which translates to 8,640,000 strikes per day.12 In the U.S. alone an estimated 25 million flashes occur each year accounting for an average 62 fatalities each year. This figure ties the amount of deaths each year by tornadoes but seems to remain an underestimated hazard. 13


In the United States, the area most frequently affected by lightning is in the southeast in Florida, Louisiana and surrounding states. Louisiana ranks in the top 10 states in lightning based fatalities 14 falling right in this danger zone experiencing eight or more flashes per square kilometer per year as shown by the map below provided by the National Oceanic and Atmospheric Administration. 15


Many documented incidents of lightning strikes have been recorded in New Orleans ranging from a 180,000 gallon fuel tank outside the city in 2001, 16communications towers in 2007 creating radio problems for New Orleans emergency services, 17 the Hannah High School campus in 2008 closing classes for a day, 18 Jefferson Presbyterian Church in 2008 causing a devastating fire, and many others. Because of the ever present danger of thunderstorms producing lightning in the summer months in New Orleans, one week late in June is dubbed Lightning safety week to promote safe choices and actions when such weather is possible. Information on this week as well as links to lightning safety tips can be found at http://www.srh.noaa.gov/lix/html/lightningsafety.htm.







For a very interesting, frequently updated track of lightning activity in and around New Orleans visit http://www.qsl.net/w5hjs/Lighting%20Page.htm and see what’s happening in the area now!




Thunderstorms (ksharp2)



New Orleans averages around 70 days a year with thunderstorms, which is fairly typical for areas along the Gulf Coast.73


New Orleans' warm, humid summers often produce afternoon showers and airmass thunderstorms.19 The winds off of the Gulf of Mexico often act as the trigger mechanism for the thunderstorms. These seabreezes, as they are called, are caused by the differences in temperature between the air over land and over water. The cooler air from over the water displaces warmer air onshore, causing it to rise and form clouds and precipitation.69 A significant portion of New Orleans' rainfall comes from these airmass thunderstorms, with nearly 22 inches of its yearly rainfall coming from them.




New Orleans is far enough from the plains where Mesoscale Convective Systems usually form that it is not often affected by them. Less than 4% of New Orleans' percipitation comes from MCS events. MCS are most common during the month of April.70


Squall lines formed by cold fronts associated with extratropical cyclones that form east of the Rocky Mountains are also common in the fall, winter, and spring months.


Heavy precipitation from thunderstorms can often cause flash floods in New Orleans. Since New Orleans is below sea level, this heavy rainfall has nowhere to flow and gets trapped inside the city. Thus, New Orleans relies on a system of pumps in order to rid the city of floodwaters.



Thunderstorms which strike New Orleans are occasionally severe. Most recently, on Tuesday February 12, 2008, several supercell thunderstorms and a squall line associated with a strong extratropical cyclone caused strong winds and several tornadoes across Louisiana. New Orleans itself got strong winds and several reports of wind damage from this event.20 The strong winds forced the Lake Ponchartrain Causeway to close for 20 minutes.21


Radar image from the Slidell, LA doppler radar showing the squall line that brought high winds to New Orleans on February 12, 2008





I. Frequency and Timing of Hurricanes in New Orleans


Although hurricane season officially starts on June 1st, very few hurricanes occur in the Gulf Coast until the middle of August. If hurricanes do happen early in the season in the Gulf, they usually are not as strong because the water temperatures have not had as much time to warm 24. Hurricane frequency in New Orleans typically peaks in September 25. The hurricane season technically ends on November 30th, but hurricanes are much less frequent after September in the Gulf 24.


Statistically, no hurricanes have affected New Orleans in June and only 3 have hit in July over the last 150 years. Seventy-five percent of recorded hurricanes in New Orleans have occurred in late August or September 24. Overall, an average of 5.9 hurricanes form throughout the Atlantic Ocean every year 26.


II. Meteorological Development of Hurricanes


In order for a hurricane to develop, a cluster of thunderstorms must be present. Thunderstorms, in turn, can only occur if there is low-level convergence to lift air. This convergence can develop from cold fronts, waves in the easterly flow, and the Intertropical Convergence Zone, which represents the collision of Hadley cells north and south flows, if the Coriolis force is strong enough. If convergence and resulting thunderstorms are present, other conditions in the atmosphere must be met for a hurricane to develop. The temperature of the sea must be at or above 81 degrees Fahrenheit and the surface layer of warm water must be about 60 meters deep because hurricanes gain their energy from heat and moisture. Winds cannot change significantly with height because the required heat must be concentrated in order to form the characteristic hurricane cloud vortex. Finally, the thunderstorm clusters must be located at least 5 degrees north or south latitude from the Equator because the Coriolis force, which is zero at the Equator, is necessary for hurricane rotation.

If all of these conditions are met, heat will transfer from the ocean to the atmosphere and the air will move inward, descend, and warm, which forms a low-pressure center. The system will eventually begin to rotate due to the pressure gradient and Coriolis forces, and the updrafts during rotation will form the hurricane eyewall. Once a hurricane has developed, it usually moves northwest, but west winds eventually steer the hurricane back eastward 5 .


III. Unique Aspects of New Orleans Related to Hurricanes


The effects of hurricanes are greatly determined by a particular location’s proximity to an ocean coast and terrain. New Orleans is very near but still separated from the coast of the Gulf of Mexico. However, the Mississippi River, one of the greatest rivers in the world, flows directly through New Orleans. The river is particularly prone to flooding, so New Orleans constructed a 25 foot high river levee system to provide protection. There is also a 15 foot high levee specially designed to shield the city from hurricanes weaker than fast (less devastating) category 3 storms 25. The levees also protect the city from overflow from the city's large inland lake, Lake Pontchartrain30 . These levees can obviously guard against weaker hurricanes and floods, but they can be overtopped or broken, which would make the city much more vulnerable to hurricane-induced flooding by trapping water inside 27.


Another significant aspect of the land in New Orleans is that most of it is below sea level. On average, the land is 1.8 meters below sea level 25. These levels will not remain constant, however, as the land in New Orleans is actually sinking. The soil in New Orleans consists of soft sand, silt, and clay, which need to be replaced in order to avoid subsidence, which refers to a settling of the ground surface that causes it to sink. However, due to the flood control provided by the levees, the ground does not receive these nutrients and does undergo subsidence 29 . These low ground levels make New Orleans much more susceptible to hurricanes and the flooding that they produce.


New Orleans also contains significant amounts of wetlands. These wetlands slow hurricanes and limit their access to New Orleans 27 by restricting the availability of warm water and creating barriers to storm surge 28. However, wetlands are gradually disappearing because the levees in New Orleans keep wetlands from receiving the occasional floodwaters and mud that they need to survive 27. The importance of wetlands clearly illustrates the vital necessity of preserving the remaining wetlands and rebuilding destroyed wetlands.


http://www.pbs.org/journeytoplanetearth/images/1la2.jpg&usg=AFQjCNH8J6l8lJzPRAZQqrzmjyije4epvQ" />


The New Orleans Wetlands 60 New Orleans Topographical Map 61



IV. Lasting Impacts


Hurricanes are associated with numerous destructive forces. Storm surge is an abnormal rise in sea level that is responsible for a large percentage of structural damage and flooding. Hurricanes also bring heavy rains as they move over land that cause inland flooding, which is responsible for most of hurricane-related deaths. Although they do not cause as much structural damage as storm surge, high winds in hurricanes can have great impacts as well. Hurricanes may even have weak tornadoes embedded within them 5.


Hurricane Katrina, which occurred in August 2005, probably had the greatest impact of any hurricane ever to hit within the United States. As of December 2005, 1,833 deaths were

linked to Katrina, most of which were due to the flooding and storm surge in New Orleans. The flooding was also made worse by levee breaks, particularly the levees restraining Lake

Pontchartrain 30 . Thousands of homes and businesses were covered by floodwaters, and several buildings had their

windows and roofs blown out by high winds. Thousands of people no longer had their jobs, and the city lost millions of dollars in tax revenues. The total cost of Katrina is estimated to be

about $81 billion 31 .


Flooding in New Orleans after Katrina 62



Case Study: Hurricane Rita



I. Meteorology


Less than a month after Hurricane Katrina devastated New Orleans, Hurricane Rita began to develop and head toward the same area. It first appeared as a tropical depression late on September 17, 2005 just east of the Turks and Caicos Islands in the Atlantic Ocean. The following afternoon, the depression moved west and became a tropical storm. On September 19th, the storm continued traveling northwest through the central Bahamas. As it moved through the Florida Straits on September 20th, the storm intensified and reached a category 2 hurricane level. Over the course of the next 24 hours, Rita entered the Gulf of Mexico and became the most powerful type of hurricane, a category 5. Hurricane Rita reached its peak intensity on September 22nd. Early that day, the winds were 180 miles per hour and the pressure was at 895 millibars, which is the fourth lowest pressure ever recorded for a hurricane in the Atlantic Basin. By the end of the day, however, the hurricane began to weaken. As it approached land, Hurricane Rita produced storm surge and flooding in New Orleans. On September 23rd, it turned farther northwest and weakened to a category 3 hurricane. At 2:40am on September 24th, Hurricane Rita made landfall between Sabine Pass and Johnson’s Bayou just east of the Texas-Louisiana border. Once it reached northwest Louisiana late on September 24th, Hurricane Rita was no longer a tropical storm. It then turned northeast and merged with a frontal system 32 .


Most hurricanes travel northwest for the majority of their lives and then east, so this Hurricane Rita’s track was very typical 32. However, Rita’s rapid intensification from a category 2 to a category 5 was highly unusual, especially because most hurricanes do not even reach category 5 if they develop at a normal rate. Scientists have predicted that this intensification occurred because of the Loop Current, which separates the Gulf of Mexico from the Caribbean Sea but brings the warmer Caribbean waters into the Gulf about once every 9 months 33.


Hurricane Rita was also unusual because it experienced eyewall replacement. This process begins when winds moving toward the center of the hurricane form a new eyewall outside the original eyewall. This cuts off the center of the hurricane from an energy source, incoming winds, which eliminates the old eyewall. Replacement of the eyewall usually reduces the intensity of the storm, as Rita experienced right before its landfall, because the new eyewall is larger and winds must thus move more slowly around it 34.


Hurricane Rita's Track and Development 63


II. Implications


One of the most significant effects of Hurricane Katrina in New Orleans was flooding, much of which resulted from broken levees. Many of these levees were depending on unstable back-up levees or beginning to be repaired, at least temporarily, when Hurricane Rita arrived. The wind and rain power, as well as storm surges as high as 8 feet, from Rita re-broke or overtopped many of the levees in New Orleans 37. As a result, the entire city experienced more flooding. In particular, the Ninth Ward, the area of New Orleans that was hardest hit by Katrina’s floods, contained about 4 to 6 feet of standing water 38. Flooding also occurred due to the 3 to 5 inches of rain that fell. The flooding problem was made more difficult because flood pumps were still damaged from Katrina and only operating at 35% capacity 37. Due to accurate forecasting, however, people in New Orleans were much more prepared for Rita than they were for Katrina. Nearly everyone that was still in the city successfully evacuated, more systemic search methods were used after the storm, and more supplies and troops entered New Orleans before the storm 39. The effects of Rita itself were relatively moderate, but they were made more harmful because the city was already very weak from Katrina.


Flooding in Ninth Ward after Rita 64 Levee Breaks after Rita 65


III. Forecasting


Hurricane Rita was very well forecast. As soon as it became a tropical depression on September 17th, the National Hurricane Center (NHC) issued a hurricane watch for the Bahamas and warned the southern Florida Peninsula and Florida Keys to closely monitor the storm, all of which were eventually affected several days later. When Rita moved into the Gulf of Mexico, the NHC immediately warned people on the northwest coast of the Gulf to remain vigilant. Two days before Rita made landfall between Texas and Louisiana, the NHC accurately warned the entire coast areas of these states. They also began to warn inland states, such as Oklahoma, of great rainfall accumulation that could occur once Rita made landfall. They also specifically predicted large tides, rain accumulation of two to four inches, and flooding in New Orleans, all of which occurred 35.


In addition to these predictions from the National Hurricane Center, Hurricane Rita was also well predicted by a new advanced research weather model. The model was run by the National Center for Atmospheric Research. At the time, widely used hurricane forecasting models had coarse resolutions that required scientists to estimate cloud processes in order to forecast hurricanes. The new model, however, had a high-resolution grid with data points that were only 4 kilometers apart, which allowed scientists to more accurately and directly predict the location of rainbands, eyewall structures, and wind damage. They were also able to establish these positions farther in advance, usually about 72 hours before their occurrence. This model, although it was not being used by the National Hurricane Center at the time, was very successful with Rita and could definitely be used by the NHC in the future for improved hurricane predictions 36 .




Tornadoes bwlezie2



Although Louisiana is not in “tornado alley”, tornadoes occur fairly often. 5 On average from 1953 to 2004, there have been 27 tornadoes reported each year. 42 In Louisiana, the peak months for tornadoes to form are from March until May and in November.40 Usually they occur sometime between 3 PM and 9 PM; however, it’s possible for them to happen anytime. 41




How tornadoes develop meteorologically:

Tornadoes usually form within supercell thunderstorms; however, they can also develop in thunderstorms along squall lines, near the ends of thunderstorm bow echoes, and within hurricanes that have reached land. The life of a tornado typically happens in five stages. First, a funnel cloud usually appears from the wall cloud of the storm as the tornado is forming. Then, the rotation makes contact with the ground, which is when it is actually a tornado. This is the dust swirl stage. Next, the funnel cloud comes down to the ground and increases intensity during the organizing stage. The mature stage, where the tornado is at its maximum size and intensity of the vortex is at its highest, happens next. At this stage, the tornado is usually almost vertically erect. While most tornadoes stay small at this stage, some grow extremely large and can have diameters around 0.8 km (or 0.5 miles). The vortex then tilts over more in the shrinking stage and begins to look like a rope. Then finally, during the decay stage, tornadoes dissipate after stretching into rope-like formations. 5




Unique aspects of tornadoes to New Orleans:

The middle latitudes have very good conditions for tornado formation, especially between about 30 degrees and 50 degrees latitude. This is because here, cold, polar air comes up to the warmer, subtropical air. 59 New Orleans is right around 30 degrees latitude, so it is near this environment, however, other parts (north of New Orleans) are actually within this latitude, 58 and they have more tornadoes.43


Lasting impacts:

During a tornado in New Orleans on February 12, 2008, numerous river vessels came loose. A freighter that had been docked was pushed across the river and two vessels collided with it. Then the freighter was lodged on a bank right beside a levee. The levee did not appear to have any serious damage. Tornadoes present a danger of flooding, because they could damage the levees that help protect the city. 44 Another tornado in occurred in New Orleans that damaged several buildings, pushed trees over, and left as many as 29,000 customers of Entergy Corp. powerless. In neighborhoods that were still recovering from Hurricane Katrina, this tornado “further unnerves everybody” according to Mayer Ray Nagin. This tornado further hindered New Orleans. 45









Droughts are the number one killer worldwide. In 1998, there were 173 deaths due to extreme heat.52 They are the longest lasting weather related disaster. In the central and eastern United States, droughts occur most often in the spring and summer. In the western United States, droughts occur in the winter months. Droughts last until the area receives an adequate amount of precipitation.


Southern Louisiana endured a drought that lasted over a year. Climatologists say 12 out of 14 months, from April 2006 and before, had below-normal rainfall in Baton Rouge. The only two exceptions were August and September with hurricanes Katrina and Rita. La Nina is likely to be a culprit for the drought. Climatologists define La Nina by a region of cooler- than-normal waters extending thousands of miles across the central equatorial Pacific Ocean. This cold pool of Pacific waters causes changes in the atmospheric jet stream that flows above it. As the jet stream flows eastward, the La Nina effect is to divert winter and spring storm tracks northward over the United States. The common result is less rain over the Gulf Coast states. LSU research suggests that well-developed La Ninas lead to drier- than-normal winters and springs over south Louisiana in 80 percent of these events. The south Louisiana drought of 1998- 2000, which ranks among the most severe droughts of the 20th century for that region, was largely a function of a prolonged La Nina. 50

There are four different types of droughts:


-Meteorological drought is a long period of below normal precipitation. It is defined usually on the basis of the degree of dryness and the duration of the dry period. Some definitions of meteorological drought define periods of drought on the basis of the number of days with precipitation less than some specified threshold. Other definitions may relate actual precipitation departures to average amounts on monthly, seasonal, or annual time scales. 46


-Hydrological drought is a deficit in ground water and/or stream flow. It is associated with the effects of periods of precipitation (including snowfall) shortfalls on surface or subsurface water supply. It takes longer for precipitation deficiencies to show up in components of the hydrological system such as soil moisture, streamflow, and ground water and reservoir levels. 46


-Agricultural drought is a reduction in topsoil moisture. It focuses on precipitation shortages, differences between actual and potential evapotranspiration, soil water deficits, reduced ground water or reservoir levels, and so forth. 46


-Socioeconomic drought is when the water supply is reduced for human needs. Its definitions of drought associate the supply and demand of some economic good with elements of meteorological, hydrological, and agricultural drought and are different from the previous types of drought because its occurrence depends on the time and space processes of supply and demand to identify or classify droughts. 46


Drought has the potential to cause cracks to form in the levees in New Orleans, which makes drought particularly dangerous. The cracks can be 15-20 ft long and 3 ft deep. Engineers say that shrinkage cracks occur when extremely dry conditions cause the clay in levees to contract. If the levees receive rainfall or artificial watering, then the clay will expand and the cracks will disappear. The cracks can appear in the roadbed on top of the levees, which provides access for official vehicles, or in the levee system’s grassy slopes. All the cracks are monitored closely to make sure they do not get too deep or too wide. If the cracks do get too deep or wide, they can be filled and watered or excavated and repacked, but for now there are no cracks that large.

Another impact is that streets and highways begin to crack and buckle because the heat causes the asphalt to expand and break. Also, grass is grown on the dirt levees to help prevent erosion, but due to drought, grass sometimes cannot be established on the levees that were rebuilt or raised since Hurricane Katrina. The Levee District President said that his agency takes proactive steps to establish new grass, keep the existing grass alive and prevent new cracks from forming. 48



The shipping companies, the Coast Guard and the Army Corps of Engineers joined together to make sure that the bottlenecks, which is a narrow entrance or passageway 51, that idled Mississippi River shipping traffic during the summer drought will not recur. The shipping industry suffered an estimated $200 million loss, which is about 20 percent of its annual revenue, during the drought. In New Orleans, the river ran at about 130,000 cubic feet a second, which was an increase from the 114,000 cubic feet a second it was running at earlier in the year. At 130,000 cubic feet a year, the river was running at about 55 percent of the normal rate for that time of the year. Slow and steady improvement is better, because a sudden heavy flow of water down the Mississippi would dump more sand and sediment downriver, causing as many problems as it would solve.

Because the river was reduced by the drought, salt water from the Gulf of Mexico came up the river and turned the water from muddy and brown to blue-green, which threatened New Orleans’ water supply. The Army Corps built a $790,000 underwater dike, 15 to 25 feet high across the river bottom, about 30 miles south of New Orleans to stop the saltwater from creeping up the Mississippi River and fouling New Orleans’ water supply. They also supplied downriver communities with millions of gallons of freshwater by barge, with the count totaling over 52 million gallons of water. Because the Mississippi River flow increased, the number of bottlenecks that caused the idle traffic in June decreased, which led to restrictions on towboats being removed. 49









Although this picture of Louisiana does not show New Orleans in the drought, the surrounding areas are suffering from the drought. This makes it hard on New Orleans because they will have to help

provide water to the surrounding areas, which could lower their water supply.











There are usually only a few downbursts each year in the New Orleans area. The general season that downbursts occur in is late spring through summer and occasionally into early fall. 66 Downbursts are high winds that are created from thunderstorms and need evaporation to be taking place as well as drag force from the falling rain or hail. The downdraft wind speed of the thunderstorm must be very high to create a downburst. Other conditions must be met to create downbursts which include the high speed downdraft as well as the thunderstorm must have a boundary layer that is fairly dry, and there needs to be lots of precipitation. The damage caused by downbursts is sometimes mistaken for tornado damage. The difference is that downbursts cause damage outward from the point where the winds hit the ground. The damage that is seen is has a divergent pattern where tornadoes have a circular pattern.





Downbursts are a big problem for the airline industry and one caused a plane crash at New Orleans international airport. 67 Since this occurred they have now developed and put into affect a radar system at each airport. This is called the Terminal Doppler Weather Radar and it detects microbursts and wind shear. 5 Lasting effects from downbursts in New Orleans is only seen with the changes with the airports after the plane crash caused by a downburst.





Heat Waves



There is not technically a universal definition of a heat wave, but it is typically considered to be temperatures that are outside of the typical climate of a given area. 66. Heat waves occur when strong upper atmospheric high pressure systems become locked over a region for an extended period of time 67, causing the heat index. The heat index is defined is a number representing the effect of temperature and humidity by considering the "apparent" temperature 68. The chart below demonstrates the dangers associated with relevant temperature, humidity, and, in turn, heat index.

The National Oceanic and Atmospheric Administration derived the following standards to issue the appropriate heat-related products, according to the weather:
Excessive Heat Outlook: when the potential exists for an excessive heat event in the next 3 to 7 days. An outlook is used to indicate that a heat event may develop. It is intended to provide information to those who need considerable lead time to prepare for the event, such as public utilities, emergency management and public health officials.
Excessive Heat Watch: when conditions are favorable for an excessive heat event in the next 12 to 48 hours. A watch is used when the risk of a heat wave has increased, but its occurrence and timing is still uncertain. It is intended to provide enough lead time so those who need to set their plans in motion can do so, such as established individual city excessive heat event mitigation plans.
Excessive Heat Warning/Advisory: when an excessive heat event is expected in the next 36 hours. These products are issued when an excessive heat event is occurring, is imminent, or has a very high probability of occurrence. The warning is used for conditions posing a threat to life or property. An advisory is for less serious conditions that cause significant discomfort or inconvenience and, if caution is not taken, could lead to a threat to life and/or property.
Heat waves are the most deadly, and arguably dangerous, weather phenomenon in the United States today. More specifically, cities, particularly well-populated ones such as New Orleans, pose special hazards, as the stagnant atmospheric conditions of heat waves trap pollutants in such areas, creating a serious health problems 71. Considering that the typical weather in the summer months is already very warm and the relative humidity is significant in New Orleans, the danger of experiencing a deadly heat wave is fairly high. This is particularly true in July and August, which are New Orleans' hottest months with temperatures that range from 81 to 85 degrees with high humidity. From July through October, tropical winds can bring high tides and heavy rains to the area, which is not only dangerous, but the rains can increase the prevalence of heat waves with the higher humidity levels. The bordering Gulf of Mexico is the cause of most of the heat waves that New Orleans experiences. As for problems incurred with the occurrence of heat waves, the aforementioned high death totals is clearly number one. However, when it comes to prevention, the main concerns center around infants and children, individuals over the age of 65, people who are physically ill or overweight, and people that tend to overexert themselves 72.




1. http://www.classicalvalues.com/archives/002747.html



4. http://www.pmel.noaa.gov/tao/elnino/el-nino-story.html

5. Rauber, Robert M., John E. Walsh, and Donna J. Charlevoix. Severe and Hazardous Weather: An Introduction to High Impact meteorology.

6. http://www.pmel.noaa.gov/tao/elnino/impacts.html#part2

7. http://seawifs.gsfc.nasa.gov/OCEAN_PLANET/HTML/oceanography_el_nino.html

8. http://www.ncdc.noaa.gov/oa/climate/elnino/gulfcoast.html

9. http://www.ens-newswire.com/ens/dec2006/2006-12-01-06.asp

10. http://www.britannica.com/eb/article-9048228/lightning

11. http://www.centennialofflight.gov/2003FF/lightning/types.html

12. http://www.newton.dep.anl.gov/askasci/wea00/wea00239.htm

13. http://www.lightningsafety.noaa.gov/overview.htm

14. http://www.srh.noaa.gov/lix/html/lightningsafety.htm

15. http://www.lightningsafety.noaa.gov/lightning_map.htm


17. http://www.nola.com/news/t-p/frontpage/index.ssf?/base/news-7/117152537665700.xml&coll=1


19. http://www.srcc.lsu.edu/southernClimate/atlas/ladescription/view

20. http://www.srh.noaa.gov/lix/html/12feb08/index.htm

21. http://blog.nola.com/tpnorthshore/2008/02/photo_thunderstorm_moves_throu.html

22. http://www.islandnet.com/~see/weather/elements/hailform.htm

23. (Sara Strey Graduate assistant, Teaching assistant department of Atmospheric Sciencehttp://www.spc.noaa.gov/

24. http://www.nola.com/news/t-p/frontpage/index.ssf?/base/news-5/114914805686060.xml&coll=1

25. http://www.globalsecurity.org/security/ops/hurricane-risk-new-orleans.htm

26. http://www.nola.com/hurricane/?/washingaway

27. http://americanradioworks.publicradio.org/features/wetlands/hurricane3.html

28. http://www.teachersdomain.org/resources/ess05/sci/ess/earthsys/neworleans/index.html

29. http://www.asce.org/files/pdf/ERPreport.pdf

30. http://www.cnn.com/2005/WEATHER/08/30/katrina.neworleans/

31. http://www.nhc.noaa.gov/pdf/TCR-AL122005_Katrina.pdf

32. http://www.nhc.noaa.gov/archive/2005/tws/MIATWSAT_nov_final.shtml

33. .http://www.physorg.com/news67704617.html







40. http://www.nssl.noaa.gov/edu/safety/guideimg/pic12.jpg

41. http://www.nssl.noaa.gov/edu/safety/tornadoguide.html

42. http://lwf.ncdc.noaa.gov/img/climate/research/tornado/avgt5304.gif

43. http://lwf.ncdc.noaa.gov/img/climate/research/tornado/tornadoalley500.jpg

44. http://www.wdsu.com/news/15292386/detail.html

45. http://www.alertnet.org/thenews/newsdesk/N13190671.htm

46. http://www.drought.unl.edu/whatis/concept.htm

47. http://www.drought.unl.edu/dm/DM_state.htm?LA,S

48. http://www.nola.com/news/t-p/metro/index.ssf?/base/news-15/1151302171103220.sml&coll=1

49. http://query.nytimes.com/gst/fullpage.html?res=940DE5DD1431F935A3573AC0A96E948260&fta=y

50. http://findarticles.com/p/articles/mi_qn4200/is_20060419?pnum=3&opg=n16146106

51. http://dictionary.reference.com/browse/bottleneck

52. http://www.weather.gov/om/hazstats/sum98.pdf

53. http://library.thinkquest.org/03oct/02054/floodtype.htm

54. http://www.nola.com/katrina/t-p/index.ssf?/katrina/articles/citys_fate_sealed_in_hours.html

55. http://alexhessler.com/general/new-orleans-flood-damage-map.htm

56. http://archive.newsmax.com/archives/articles/2005/9/12/210912.shtml

57. http://www.nhc.noaa.gov/archive/2005/KATRINA.shtml

58. http://go.hrw.com/atlas/norm_map/usa.gif

59. http://lwf.ncdc.noaa.gov/oa/climate/severeweather/tornadoes.html

60. http://www.pbs.org/journeytoplanetearth/images/1la2.jpg

61. http://serc.carleton.edu/images/research_education/katrina/topography.jpg

62. http://www.katrina.noaa.gov/helicopter/images/katrina-new-orleans-flooding4-2005.jpg

63. http://cimss.ssec.wisc.edu/tropic/archive/montage/atlantic/2005/RITA-track.gif

64. http://media.npr.org/programs/totn/features/2005/10/ninth_ward_street.jpg

65. http://www.greatdreams.com/weather/rita-orleans2.jpg

66. http://www.weatherquestions.com/What_is_a_downburst.htm

67. http://www-frd.fsl.noaa.gov/mab/microbursts/micro_course.html

68. http://www.srh.noaa.gov/lix/swaw/swaw08.htm

69. http://www.islandnet.com/~see/weather/elements/seabrz.htm

70. http://ams.allenpress.com/archive/1520-0493/131/12/paf/il1520=0493-131-12-3003.pdf

71. http://assets.openas.com/rpts/RL33117_20051018.pdf

72. http://www.ens_newswire.com/ens/mar2006/2006-03-31-06.asp





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Although annually hail is only present in a small number of thunderstorms, it still is capable of causing a lot of damage. Hailstorms cause damage to both property and agriculture. On average the damage to agriculture is upwards of 1 billion dollars and the damage to property is approximately 1.5 billion dollars. Property damage is most common to window, siding, roofs and of course automobiles. These annual numbers are just for the United States and total much higher worldwide. Reported cases of severe storms have totaled upwards of 2 billion dollars for a single storm in one city. Although rare there have been some reported fatalities due to storms, more common are reported cases of injuries.5

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