ST L6: Hurricanes/ How Hurricanes Manipulate the Energy

Question 1

What are hurricanes made up of?

Answer 1

thunderstorms

Question 2

What is the eye wall?

Answer 2

It is a ring of thunderstorms around the relatively calm eye of the hurricane.

Question 3

What are spiral bands?

Answer 3

Additional bands of thunderstorms that spiral outward from the eye wall.

Question 4

Describe pressure and wind speeds around and in the eye of the hurricane.

Answer 4

In the eye of the hurricane there is low pressure near the surface. Low-altitude winds (boundary-layer) blow counterclockwise (in Northern Hemisphere) around the hurricane eye and spiral inwards. Wind speeds increase as the air gets closer to the eye wall, eventually exceeding the hurricane-criterion speed of 33 m/s.

Question 5

What scale gives hurricane intensity?

Answer 5

the Saffir-Simpson Hurricane Scale. It categorizes hurricanes based on wind speed, although some tables also show typical eye pressure and storm surge levels. Faster winds mean stronger hurricanes. From Category 1 to 5, 5 being the worst (250 km/h+ winds)

Question 6

What exception to dying can happen to thunderstorms?

Answer 6

When the ambient atmosphere happens to have the right amount of wind shear to continurally advect fresh fuel into the storm. It can also move thunderstorms to new regions where there is still boundary-layer fuel. Supercell thunderstorms work in this way.

Question 7

How are hurricanes more advanced than thunderstorms?

Answer 7

Instead of relying of serendipitous environmental wind to maintain long-lasting fuel supply, the hurricane MANIPULATES the environment to continually create fuel needed by its bands of thunderstorms by tapping into the heat stored in the ocean.

Question 8

How does the hurricane suck boundary layer air?

Answer 8

Low pressure in the eye. As the air gets closer to the eye, it moves faster and faster. Faster winds create larger waves on the ocean surface. Evaporation from the ocean surface, along with wave spray, adds significant moisture into the boundary layer air. By the time the boundary-layer air reaches the base of the eye wall, it is warm and exceptionally humid, and contains tremendous amounts of sensible and latent-heat fuel needed by the eye-wall thunderstorms.

Question 9

In order for the hurricane to be fueled by the ocean, what must be a criteria?

Answer 9

The ocean surface temperatures must be warmer than 26 degrees C, and be roughly 60m or more in depth so that the turbulent mixing within the ocean caused by surface waves doesn’t mix with the colder waters. These deep warm layers often form in the tropics during the summer, when max. heating of the sun occurs.

Question 10

When do hurricanes typically occur?

Answer 10

Late summer and early Fall. Max. extent and depth of warm waters.

Question 11

The constant supply of thunderstorm fuel (boundary-layer air) continues only as long as:

Answer 11

there is low pressure in the hurricane eye to suck in the air to create large ocean waves

the hurricane remains over the warm ocean.

Question 12

What maintains the low pressure of the hurricane eye?

Answer 12

the thunderstorms that make up the hurricane

Question 13

If the hurricane moves either over ____water or over ____, then it cannot generate sufficient warm, humid air to serve as fuel, and the hurricane weakens and dies

Answer 13

colder; land

Question 14

What is the Coriolis effect? Where is it 0? How does it increase?

Answer 14

Hurricanes needing to extract rotation from the Earth’s rotation. It is 0 at the equator. Hurricanes cannot form and cannot cross the equator. The effect increases moving away from the equator.

Question 15

Where are hurricanes most likely to form?

Answer 15

Most likely to form between latitudes of 10 and 30 degrees, where there is both warm sea-surface temperature (at least 26 degrees C) and non-zero Coriolis force.

Question 16

What is the Bermuda High?

Answer 16

Semi-permanent region where winds blow around, and form hurricanes over the Atlantic Ocean. Large Bermuda High circulation turns the storms more northward near the East Coast of North America. As a result, hurricanes strike the Gulf Coast States and SE Coastal states.

Question 17

Describe the eye of the hurricane.

Answer 17

Relatively clear, conical shaped opening in the clouds. Inside the eye, the air is gently descending. Surrounding the eye is a wall of thunderstorms called the eye wall.

Question 18

The removal of air from the hurricane eye and eye wall occurs where?

Answer 18

At the top of the hurricane in a large outflow region. Outflow is visible from weather satellites as a clockwise-turning, outward moving spiral of ice crystals in the tops of the thunderstorm anvil clouds.

Question 19

What is a warm core?

Answer 19

The net result that the eye and eye wall, together known as the core of the storm, are warmer than the surrounding air.

Question 20

Pressure decreases more ____ with altitude in the warm core of the hurricane than outside. This results in a relative ____ pressure at the ____ of the hurricane core, which causes ____ at the top of the hurricane, and helps keep the surface pressure __ in the core.

Answer 20

slowly; high; top; outflow; low

Question 21

Why can hurricanes last for weeks, in spite of all the air molecules continually being blown into the core?

Answer 21

Heavy condensation and precipitation from thunderstorms in the eye wall cause the hurricane core (eye + eye wall) to become very warm (lots of energy!) relative to its surroundings.

Question 22

What is the Ekman transport?

Answer 22

ocean currents moving outward from the eye caused by ocean current dragged by the strong hurricane winds.

Question 23

What is a storm surge?

Answer 23

Sea-level rise along coastlines, caused by outward moving water from the Ekman transport. It is most significant hazard of hurricanes near coastal regions.

Question 24

Why was Hurricane Juan (reached Nova Scotia in 2003) able to maintain hurricane strength?

Answer 24

the cold coastal waters were unusually narrow that week, and that it translated so quickly northward that it didn’t have time to diminish to Category 1.

Question 25

Hurricanes consist of ____ bands of thunderstorms around an eye of ___ pressure. Hurricanes do more than CONSUME fuel (sensible and latent heat in air) to power their violent motions – they CREATE new fuel within the _____ air that is drawn ____ while over ____, deep ocean waters in the tropics.

To maintain this circulation, latent heating in the eye wall is so intense, it creates a warm core within the storm. This warm core produces a ___ pressure at the ____ ____ of the storm that removes air aloft __ ____ __ it comes in from below.

Thus, hurricanes can exist for roughly ____, until they move over ____ waters or ____, where they no longer have their fuel supply. On land, the greatest threat to life and property is the _____ _____ associated with the storm surge.

Answer 25

spiral; thunderstorms; low; boundary-layer; inward; warm; latent; warm; high; top; center; as fast as; a week; colder; land; sea-level rise

Question 26

Why does simply knowing past hurricane conditions and their tracks not the best predictor?

Answer 26

Computer models also depend on current atmospheric and sea surface conditions to make forecasts. Various models still end up conflicting with forecasts, especially for predictions that extend beyond the predictive capability of the models (beyond average 48 hour period). There will always be uncertainty in extreme weather prediction.

Question 27

What can you do to keep safe from hurricanes?

Answer 27

Do not buy or build houses on or near the beach in Southeastern USA.
Plan in advance for evacuation, do not think you can “ride out the storm”.