physic side of a hurricane

8/14/2019 Physic Side of a Hurricane

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Physic side:

Hurricanes


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Table of Contest:

Introduction:Physic side of a hurricane:

ACE

Intertropical Convergence Zone Storm Surge

Il Nio and La NiaAppendixSources


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Introduction:

In this paragraph I am going to explain about the physic side of hurricanes. A hurricane needs

some more ingredients to form and in this paragraph we are going to look at that. But these

subjects arent the only physic things of a hurricane, also in the main paragraph we are going

to look to some subjects how reflects to hurricanes, but also to tornadoes.


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Physic side of a Hurricane:

ACE


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Definition:Accumulated Cyclone Energy (ACE) is a number where you can look to the strength of a

season or hurricane/tropical storm system. With these numbers you can also look to the

activity of a hurricane season. The ACE number is only in use with the hurricane season of

the Atlantic Ocean and the Pacific Ocean.

As we concluded and give a short explanation about the ACE in one line, we can say: Howhigher the ACE number is in one season, how stronger the season was. Moreover, how higher

the ACE number is with a storm system (hurricane or tropical storm) how stronger the system

was!

Formula:ACE= (knots) ^2 / 10.000

Every 6 hours the NHC (National Hurricane Center) gives data about the wind speed in knots

of a hurricane or tropical storm how is active on the same time. If you calculate every ACE

number of every 6 hours and count these numbers together, from the moment that a storm

system reaches more than 34 knots till the moment he gets under that number, you have the

total ACE number of one system. If you count all the ACE numbers from a season, you get

the total ACE number which is very useful to look to the activity of a hurricane season.

Categories:You can put the ACE number is different categories. These categories only counts when you

look to the total activity of one season! In the next table we are going to look to these

categories and after that I will explain something more about these categories.

Category: ACE number:

Above normal (Hyperactive) > 103

Above normal > 103Normal All the other seasons

Below normal < 66

Also if a category is giving to a season, the scientist also looks to the number of storm system

that was produced in one season. So a season with an ACE number of 93 can be categorized

as a below normal season, because the season didnt produced many hurricanes or tropical

storm. It can be that there was one hurricane with a very high ACE number, as hurricane Ivan

(2004). Ivan had an ACE number of 70! That can be the total number of one normal season.

The season of 2004 was a hyperactive season with 14 tropical storms, 9 hurricanes and 6

major hurricanes.

Exceptions:Normally every storm system how reach a wind speed of 34 knots gets an ACE number. But

there are some exceptions. A subtropical storm system doesnt get an ACE number. But as we

look for example to subtropical storm Laura (season 2008). Laura got an ACE number, but

what happened. Laura first was a tropical storm. So the only used the numbers of the time

while she was active as a tropical storm.


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Example:On this page I will gave an example how the scientist calculate the ACE of one hurricane. I

used hurricane Ike. Ike was the strongest hurricane of the season 2008 and moreover, Ike had

the highest ACE number.

Date/time: Wind speed:(knots)


01 / 1200 35 Tropical Storm 0.1225

01 / 1800 45 Tropical Storm 0.2025

02 / 0000 45 Tropical Storm 0.2025

02 / 0600 45 Tropical Storm 0.2025

02 / 1200 50 Tropical Storm 0.25

02 / 1800 55 Tropical Storm 0.3025

03 / 0000 55 Tropical Storm 0.3025

03 / 0600 55 Tropical Storm 0.3025

03 / 1200 60 Tropical Storm 0.3603 / 1800 75 Hurricane category 1 0.5625

04 / 0000 105 Hurricane category 3 1.1025







05 / 1800 100 Hurricane category 3 1


06 / 0600 100 Hurricane category 3 106 / 1200 95 Hurricane category 2 0.9025









08 / 1800 75 Hurricane category 1 0.562509 / 0000 70 Hurricane category 1 0.49











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Date/time: Wind speed:

(knots)




12 / 0000 85 Hurricane category 2 0.722512 / 0600 90 Hurricane category 2 0.81






13 / 1800 50 Tropical Storm 0.25

14 / 0000 35 Tropical Storm 0.1225

14 / 0600 35 Tropical Storm 0.1225

14 / 1200 40 Extra tropical 0.1614 / 1800 50 Extra tropical 0.25

15 / 0000 50 Extra tropical 0.25

15 / 0600 40 Extra tropical 0.16

15 / 1200 35 Extra tropical 0.1225

Total: 39.87

If you look to the Wikipedia page with the ACE data of the hurricanes and tropical storms,

you can see that the wound up the number to 39. But you can explain that with the numbers of

the wind speed. The number of the ACE that the NHC gave is a number with more specific

wind speed data. Our numbers are wound up to speed with a difference of 5 knots. That is

why our ACE number is higher than that the National Hurricane Center gave.


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Psychic side of a hurricane:

Intertropical Convergence Zone


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Definition:

Intertropical convergence zone is the zone on earth near the equator. This zone is the zone

where the weather is the most unpredictable. The warmest air on earth is rising up there,

which can cause large low pressure areas, which can develop into a hurricane. The rising air

movement is caused by the fast amount of the condensation of the seawater.

As you can see in this picture the wind (the surface winds) is pulled to an Intertropical

Convergence Zone. (Low-pressure area in the neighbourhood of the equator) For the North

there are 2 different surface winds that come together. This causes heavy rainfall and tropical

storms. With these winds and the warm air there are enough elements to produce a heavy

hurricane. What you also see with hurricanes is that tropical waves from Africa help to

develop the hurricane even more.

Zenith point:

The Intertropical Convergencezone can be over land. When this

happens, the surface winds move

slowly back to the suns zenith

point. A zenith point is the place

where the distance to the sun is

the lowest. In our case this is the

equator. As you can see in this

picture, the man in the middle is

the equator and if you look you

can see that the spot right above

him is the zenith spot. The area

right above the equator is the

suns zenith.

The Intertropical convergence zone is never the same line. The line is not the equator but the

line is always different. But the line is always close to the equator.


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Convergence or Divergence:As you can see here on the right, is a

picture that shows how the

convergence zone between the

Caribbean Sea works. This is a typical

example of the working of the surfacewinds to hurricanes. What you can see

is that a hurricane (if it forms before it

comes in the waters of the Caribbean

Sea) can choose between 2 directions.

To the north (further on the Atlantic

Ocean) or to the south (in the

Caribbean Sea, or even later to the

Golf of Mexico). This choice is made

by the surface winds, that push the

hurricane into a direction. If a

hurricane is above the Lesser Islands, the chances are very high that the hurricane will movefurther on the Atlantic Ocean, but there is a small chance (25 to 50%) that it goes to the

Caribbean Sea, by moving over Cuba or Dominican Republic.

But if it is right above Puerto Rico, or just below Puerto Rico, the surface winds push the

hurricane into the Caribbean Sea.

This theory is very useful to predict

the path of a hurricane. If you know

where the hurricane is when he

passes the Lesser Islands, you know

where the hurricane is heading for.

The surface winds are the winds

that push the hurricanes into a

direction. Of course the hurricane

moves by itself, but the surface

winds are just like a wheel of a car.

In the picture on the left, you can

see how the surface winds move in

the Oceans. This means, this is the

direction where the low pressure

systems are pushed.


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Physic side of a hurricane:

Storm Surge


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Definition:A storm surge is a flood of water that threatens the coast area. This surge is most of the time

caused by a storm or in our case a hurricane. The wind pushes the seawater up, and this

causes a sort of flood. When the flood is near the shore, it will rise, by the withdrawing of the

seawater on the beach. This makes the storm surge even higher.

The picture on the right explains a little bit more about how a storm surge works.

Height:The height of a storm surge from a hurricane is different for each category of a hurricane. In a

table, I will show you the heights of a storm surge with a landfall of a hurricane with different

categories.

Category: Pressure: Storm Surge:

Tropical Depression >1010 None

Tropical Storm 990 till 1010 Above the normal high tide

Hurricane Category 1 980 till 989 1.2 till 1.6 meters




Hurricane Category 5 < 920 Above the 5.4 meters!


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Pressure compared to a storm surge:Pressure is an important thing to form a storm surge even if the wind is forming the storm

surge. The pressure is formed by the rapidly decreasing air from the storm system. If this

happens, there is a sort of pressure that arises. The faster the air is decreasing, the lower the

pressure in the centre of the storm is. This decreasing air is pressed to the seawater. This

seawater is pushed back, and a sort of flood arises by the decreasing air. The picture herebelow will show you this a little bit better. The air is dropping in the eye and pushes the

seawater back. Because of this a higher level and a lower level of the seawater arise. This

causes the storm surge.

Landfall:

On the right we see a picture of astorm surge from a hurricane making

landfall to United States. In this

picture we clearly see that before the

eye hits land, there is an amazing

storm surge between 8 and 9 feet. This

is an amount of 3 meters high. This is

definitely a hurricane with the strength

of category 3 on the scale from Saffir/

Simpson. The red spot in the centre

represents the highest waves. If you

look very well, you can see a blackline with a red spot at the end. This

represents the track of the eye of a

hurricane. The closer the hurricane is

getting to land, the higher the storm

surge will be.


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Physic side of a hurricane:

El NioLa Nia


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Definition:El Nio and La Nia are two different things how can affect the atmosphere and the seawater.

The La Nia causes warmer seawater and can cause more hurricanes. On the next two

pictures I will show you the different between an El Nio and a La Nia.

El Nio:

This picture shows how the El Nio affects the seawater and the weather in the colored area.

La Nia:


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I will first explain the colours in the picture, after that I will explain something more about the

El Nio and La Nia.

Colour: Meaning:

Cool air

Wet airDry and cool air

Warm and dry air

Cool and Wet air

Wet and Cool air

Warm air

Dry

Wet and Warm

As you can see if there is El Nio conditions, which affects the water in the Atlantic Ocean,

the seawater changes dramatic. The ocean atmosphere and also the seawater become colder

and even weather condition become wetter. So more rainfall in the Caribbean area.

The normal conditions for the Pacific Ocean are the warm water in the west and cold water in

the area of the South American coast line. That is the reason, why hurricanes cant approach

San Francisco in normal conditions of the seawater.

The El Nio conditions causes that the warmer water comes in the area of the South American

coast line. The normal conditions of the colder air do not take place and this cause for

increasing warmer air and seawater.

The La Nia causes only that the warmer water is further west than usually. These

phenomenon most have a magnitude 0.5 Celsius and most last long for more than 5 months to

name it a El Nio or La Nia episode (year). If this is not, but the magnitude is over the 0.5Celsius, than these ocean conditions called El Nio or La Nia conditions. One episode of an

El Nio or La Nia can last for 2 years with a break of 2-7 years.

Signs:El Nio:

Higher air pressure in the area of the Indian Ocean, Indonesia and Australia

Lower air pressure in the area of Tahiti and central and eastern Pacific Ocean

Trade winds weaken in the south Pacific Warmer air in Peru, with causes rainfall in the dessert of Peru

Decreased fishing activity in Peru Extensive drought in the West Pacific Ocean

Rainfall in dry areas of the East Pacific Ocean

La Nia:

Cold ocean temperatures in the East Pacific Ocean

Atlantic hurricane activity can be increased by the La Nia episode. This means, that

the hurricanes or tropical storms in the Atlantic Ocean, can be better developed and

also more dangerous than in a non La Nia year.


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Stages:El Nio:

Stage 1:The seawater is getting warmer

by the effects of the El Nio.

Stage 2:The seawater is still getting

warmer. The blue (colder) areas are

slowly disappearing.

Stage 3:The evolution of the El Nio is

almost done. The blue areas arealmost gone, only in the north

and the south. In these areas is

still colder seawater. As you look

to the equator, the seawater

around this area is very hot in

compare to the first stage.


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Stage 4:The evolution from the El Nio is

complete. The seawater on the

south coast of the Middle Americancontinent is very hot and all the

cooler seawater in this area is

almost gone. This is now a perfect

spot for hurricanes to develop.

These stages where made in the El Nio episode in 1997. Two years later after the El Nio a

La Nia episode reaches the Pacific Ocean.

La Nia:

Stage 1:The seawater in the south area of

the Pacific Ocean is showing

some cooling. But the Atlantic

Ocean and the Gulf of Mexico is

getting hotter.

Stage 2:The cooling is still in progress andthe warmer areas are slowly

disappearing to the west.


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Stage 3:The cooling process is almost

done. The warmer seawatermoved to the south and the west.

But on the Atlantic Ocean there

are still signs of the warmer

seawater, what can caused a

perfect spot for hurricanes to

develop!

Stage 4:The La Nia evolution is complete.

The colder water has taking place

for the warmer seawater. Moreover

the seawater in the Atlantic Ocean

is still warmer than normal.

These stages represent the La Nia event in 1999. Short after the El Nio episode two years

earlier.


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Appendix:

This paragraph contains a lot of information about hurricanes, but this isnt everything to

understand how a hurricane works. The time was too short to do research to that. But these

subjects are the most important to understand how this beautiful weather phenomena works. I

hope you can use this information to understand hurricanes and maybe some other weatherphenomenas.


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