1. Warmup Wednesday 9/30
As you go up into the atmosphere, is it hotter or colder (in general)
Does the air around us have a weight?
EXTRA: What is a “barometer?”… anybody know?

2. Key Concepts today Convection Low & High pressure in the atmosphere
Hurricane formation
Classification and power of hurricanes

3. Basic “convection” Heat goes up, cold goes down…
Increasing heat makes things expand, makes density less and thus it rises if it can
Taking away heat makes things contract, thus MORE dense and sink

4. Hurricanes – the largest & strongest storms on this planet!

5. How do they form?
First – you need to understand how convection works, and
Then a little more about high pressure and low pressure in the atmosphere.
And then we can tackle how a hurricane forms

6. The air on us has “pressure”… why don’t we feel it?

7. Barometers measure air pressure
Original barometers used Mercury – how much mercury would the air hold up in a vacuum tube
Modern barometers use an enclosed cell that expands or contracts and moves a lever

8. Air tries to move from ________ to __________
Low and High pressure
Air tries to move from ________ to __________

9. How does a “low pressure” form?
CONVECTION!!!!!!!!!! As the air is heated, rises…. Leaving a “hole”
Air will be pulled in to replace it
HOT
warm
warm
Equator

10. As warm humid air rises, it cools and the water vapor eventually will condense back into water to form a cloud and eventually rain RELEASING LOTS OF ENERGY AS IT DOES

11. Low pressure sucks, highs blow
If hot air rising creates “low” pressure,
What might cause a “high” pressure?

12. So, the center of a hurricane is a “super low” , sucking in all the hot humid air around it… but Why do hurricanes to spin counterclockwise

13. Anything in the north hemisphere moving will turn to the right
Anything in the north hemisphere moving will turn to the right! (Coriolis effect)

14. South:Left North:right

15. Pause, then back to hurricanes: Lets detail “Coriolis”
Coreolis is simple… yet very very confusing
Because we are on a spinning ball, even something going straight appears to curve over a long distance
This effect gets magnified by everything else turning!
(no, this has nothing to do with toilet water spinning and no toilets don’t spin the other way in the southern hemisphere)

16. The Coriolis Effect
An object moving across a rotating surface keeps the same direction and speed, but looks seems it curves if you are on the rotating surface.
In the fixed frame of reference, the black ball moves in a straight line.
However, the observer (red dot) standing in the rotating frame of reference sees the object as following a curved path.

17. This turning to the right, causes hurricanes to spiral counter clockwise in the north
In the southern hemisphere they spin clockwise

18. Hurricanes really “suck”
Base of the eye is a hot area of low pressure
Surrounding warm humid air moves toward the low, spiraling, getting warmer and rising up, losing moisture

19. Warmup: 10/1 Thursday
Over long distances, moving things in the atmosphere will turn to the ________ in the northern hemisphere
The force that causes them to turn is the __________ effect
________________ causes an area of low pressure.

20. Anatomy of a hurricane
Winds are breezy at the edge of the storm and increase to a maximum in the eyewall. Winds are relatively light in the ‘eye’ itself.

21. Or another view

22. OK, so far
Still hot humid air rises (Convection) causing low pressure “hole”
Air moving in to fill the low will turn to the right & it is FULL OF WATER VAPOR!!!!!!!
Air spirals and rises, ALL THE WATER CONDENSES – FORMING HUGE THICK CLOUDS & RELEASING LOTS OF ENERGY

23. If the “low” is just temporary and small.. = thunderstorm
Still hot humid air rises (Convection) causing low pressure “hole”
Air moving in to fill the low will turn to the right & it is FULL OF WATER VAPOR!!!!!!!
Air spirals and rises, ALL THE WATER CONDENSES – FORMING HUGE THICK CLOUDS & RELEASING LOTS OF ENERGY

24. If the “low” is long lasting, very hot and a large area…. = Cyclone!
Still hot humid air rises (Convection) causing low pressure “hole”
Air moving in to fill the low will turn to the right & it is FULL OF WATER VAPOR!!!!!!!
Air spirals and rises, ALL THE WATER CONDENSES – FORMING HUGE THICK CLOUDS & RELEASING LOTS OF ENERGY

25. Tropical Cyclones go by different names… (why do they all go west?

26. Ingredients for a hurricane:
Ocean is very warm and the warm is deep (80 degrees down to 150ft)
Everything is calm (low winds), so air heats up
Air rises quickly and creates a “super low” pressure area
HOT, humid, water carrying air zooms into the “super low” pressure carrying crazy amounts of water and heat energy into the storm
As it spirals up the eye it loses all it moisture and we get massive condensation (rain clouds)!

27. Storm Surge – the most deadly part of the hurricane!!!!!
The “LOW” pressure sucks in more than just air. It actually pulls the ocean surface up! Add this to the huge waves caused by wind…

28. Categories
Pressure (normally above 1000)
Winds
mph
Storm
surge ft
Damage ….
Tropical storm
>993
<74
1-3
Flood large areas H1
74-95
4-5
Take out trees H2
96-110
6-8
Rip roof off H3
9-12
Knock small buildings down H4
13-18
Destroy even large buildings H5
<920
155+
19+
Extreme damage

29. Before and after pictures