Tropical Storms

Mr. T. Tonna

Index• What are Tropical Storms?• How and Where do they form?• Main Features of a Tropical Storm.• Recent Tropical Storms• Case Study: Hurricane Katrina, 2005.• Destructiveness of Tropical Storms• Summary

Mr. T. Tonna

What are Tropical Storms?

• Tropical storms are areas of intense low pressure. • They produce violent weather with high winds (The

average speed is 120 km/h. Although it may vary from 32 km/h to 200 km/h or more. At times it reaches 400 km/h also), thick cloud and torrential rain.

• Depending on where they are in the world they can also be called:– Hurricanes– Cyclones– Typhoons

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How and Where do they Form?

• There are three main criteria needed for a tropical storm to develop:

- Warm Tropical Oceans (Temperature of 26°C or more)- Late Summer early Autumn where sea temperature is

optimum.- In Certain Latitudes: 5°-20°

North and South.

Mr. T. Tonna

Mr. T. Tonna

Mr. T. Tonna

Mr. T. Tonna

Main Features of Tropical Storms

Mr. T. Tonna

Mr. T. Tonna

• Warm air and water vapour is ‘sucked’ up from the oceans in the centre of the storm cell.

• This air then cools and as it condenses it forms clouds and then releases its huge energy that powers the storm.

• Once the storm makes landfall the source of heat (the ocean) is lost and the storm decreases in strength.

• Tropical storms tend to move westwards when over seas and polarly once they have hit land.

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• Tropical Storms are at their most powerful either when at sea or at landfall due to the presence of thermal energy.

• Due to the high winds present, storm surges are common and these increased depending on the category of the storm.

• Tropical Storms are categorised according to the Saffir-Simpson Hurricane Scale based on their wind Speeds and resulting damage.

Mr. T. Tonna

Mr. T. Tonna

Mr. T. Tonna

Mr. T. Tonna

Recent Powerful Tropical Storms

• Typhoon Haiyan, Philippines- November 2013• Hurricane Sandy, North-East USA, October 2012• Hurricane Katrina, South-East USA, August 2005• Hurricane Ivan, South-East/East USA, September

2004.

Mr. T. Tonna

Case Study: Hurricane Katrina

• Hurricane Katrina formed as Tropical Depression over the south-eastern Bahamas on August 23, 2005.

• The tropical storm moved towards Florida, and became a hurricane only two hours before it made landfall on August 25.

• It weakened over land but soon ended up in the Gulf of Mexico where it regained it’s Strength, going from category 3 to 5 in 9 hours.

Mr. T. Tonna

Mr. T. Tonna

Below: The Course of Hurricane Katrina, 2005

Left: The Saffir-Simpson Hurricane Wind Scale used to measure the Category of Hurricanes.

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Hurricane Katrina Over New Orleans

• New Orleans is the largest city in the state of Louisiana. • It is located 2-6m below sea level which is why Hurricane

Katrina was so devastating.• Over New Orleans Katrina had:– Wind Gusts over 175miles per hour (over 280km/h)– Levees protecting the city from flooding collapsed due to the

wind and storm surge (7 Feet High) produced by Katrina– An estimated 80 percent of New Orleans was under water, up to

20 feet deep in places.– The centre eye had extremely low pressure: 920 mbar.

Mr. T. Tonna

Mr. T. Tonna

Mr. T. Tonna

Destructive Results of Katrina

• Despite an evacuation order, many of the poorest people remained in the city.

• People sought refuge in the Super Dome stadium. Conditions were unhygienic

• shortage of food and water. • Looting was commonplace throughout the city. • The final death toll was at 1,836: Louisiana (1,577) /Mississippi (238) • 1 million people homes destroyed $81 billion in damages.• Oil facilities were damaged and as a result petrol prices rose in the UK

and USA.• Total Estimated Damages exceeded $150 billion in Louisiana and

Mississippi alone.

Mr. T. Tonna

Mr. T. Tonna

Mr. T. Tonna

Summary

• Tropical Storms can only be found in the Lower latitudes between 5°-20° North and South where sea temperature exceeds 27°C.

• They usually occur between late summer and early Autumn.

• Hurricane Katrina was one of the most destructive Tropical storms ever to hit Mainland USA.

• It is a pure example of how quickly a ‘contained’ storm can change into a cataclysmic event.

• The storm showed just how costly Tropical storms could be, with an estimated damage cost exceeding $150billion.Mr. T. Tonna