Chapter 11: Hurricanes

Hurricanes are

• Large tropical cyclones

• Heat engines

• High speed winds

• Heavy rains, dangerous floods far inland

• Tornadoes spawned

Requirements for hurricane formation

• Seawater temp > 27 degrees C in upper 60 m

• Air warm, humid and unstable

• Coriolis effect get jet system spinning

• Weak upper-level winds (wind direction same as storm direction)

Hurricanes begin with

Tropical disturbance

Coriolis effect creates

Tropical depression

_ sends warm, moist air into stratosphere

Core

Condensation releases _

Latent heat

Tropical storm wind speeds

> 63 kph

Hurricane wind speeds

> 119 kph

Strength of hurricane depends on

Efficiency of energy transfer (no wind shear aloft)

Inward-flowing air rotates faster closer to

Core

When speed can no longer increase,

Converging winds rise sharply upward

Eye wall is a

Cylinder-shaped area of spiralling upward thunderstorms around eye with heaviest rainfall and highest wind storms

Clear core

Aloft cool air sinks into eye, warms adiabatically and absorbs moisture

• forming eye into atmosphere

Tornadoes within hurricanes form predominately from outer rain bands in hurricanes that are

• large, intense, strongly curving

• Moving as a system at 12 to 30 kph

• Interacting with old, weakened fronts

• Over land

What hurricane in 2004 spun out and killed 7 people

Hurricane Ivan

Hurricane energy release

• Transfer heat: tropical seas to hurricane core

• Huge amounts of latent heat released as air rises

• Cloud formation and rain release huge amounts of energy

Difference from

high-latitude storms

Main energy source is

Latent heat released by water vapor condensation

Weaker high altitude winds results in

Stronger hurricane

Hurricanes not associated with

Fronts

Hurricanes weaken rapidly when moves onto

Land

Hurricane winds weaken with

height

Different names in different parts of the world

• Indian Ocean: cyclones

• Western Pacific Ocean: typhoons

Hurricanes from on _ of oceans where warm water is concentrated

West sides

Hurricanes from between what degrees of latitude

5 - 20

Hurricanes do not form along the

Equator

• Coriolis effect is zero

Once formed hurricanes cannot cross

The equator

• lose rotation

Typhoons of Pacific about 3 times as common and hit

Japan, China, and the Philippines

Saffir-Simpson scale for damage categories

1: some wind damage

2: some trees, roofs, mobile homes blown down

3: larger trees down, destroy mobile homes

4: sings, windows, roofs damages; inland flooding

5: severe building damages

North Atlantic Hurricanes are

Large, mobile, and long lasting (4 to 28 per year)

Most hurricanes form in

Late summer when sea surface temps are warmest

Northern Atlantic hurricanes usually begin as

Easterly waves moving west away from Africa

North Atlantic Ocean hurricanes: _ with trade winds gaining energy over great distances of warm sewater

Blown westward

North Atlantic Ocean Hurricanes: movement curves northward due to

Coriolis effect

Atlantic hurricane paths are

Difficult to track

Bermuda high

High pressure zone commonly sits above North Atlantic OCean

North Atlantic basin tropical storms and hurricanes given names alternating

Male and female

If more than 21 storms, names start over using the

Greek alphabet

Hurricane deaths are down in recent decades due to

Better advanced warning

Hurricane damages are up due to

• More people living on coastline

• larger, more expensive homes

• Damage calculated in constant dollars suggests the future will be even more costly

Most hurricane deaths associated with

Sea surges

Rise in sea level under storm due to

• Winds push water ashore to pile up above normal levels, blown inland on right of eyewall, out from land on left of eye

• Low atmospheric pressure causes water to mound up under eye of hurricane

After moving on land no more water vapor is absorbed into hurricane therefore it

Loses its strength

What causes massive flooding

Precipitation of massive volume of water in dissipitating hurricane

What hurricane cost almost $200 billion in damages due to flooding

Harvey

Katrina came ashore east of

New Orleans

katrina is the deadliest natural disaster since

Okeechobee hurricane

Hurricanes like Katrina was

Anticipated for years

What hurricane hit Lee County Florida in October 2022

Ian

What hurricane led to tougher building codes being enacted

Andrew

How do you prevent lift off of roofs

• Elimination or strengthening of eaves

• Strap roofs to walls

• Ban stapled asphalt roofing sheets on plywood

Seven of world’s nine most deadly weather events in 20th century were cyclones hitting where

Bangladesh