Hurricanes

Question 1

Where do storm related deaths occur in Canada?

Answer 1

They occur in Newfoundland and Nova Scotia

Question 2

Impacts of Hurricanes

Answer 2

Rebuilding of damaged infrastructure

Impacts energy production
Ex. Offshore oil rigs need to be evacuated

Cost of severe coastal erosion

There are a lot of damages related to flooding

Question 3

What was significant about Hurricane Andrew?

Answer 3

It was a wake up call for the insurance industry

It passed through South Florida, and was one of the first heavy hurricanes to hit the U.S

It caused so much damage that it made some insurers go broke

It influenced the re-insurance industry, where insurers get insurance

People didn’t think much of the storm until damage assessments were carried out later on

Question 4

Definition of a Hurricane

Answer 4

Hurricane is a warm core, low pressure system, without any front attached.

Develops over tropical/subtropical waters

Organized circulation of winds at least 120km/hour

Different names depending on region
o Hurricanes Atlantic/Eastern Pacific Oceans
o Typhoons Western Pacific
o Cyclones Indian Ocean

Question 5

What is a warm core?

Answer 5

1. Warm moist air moves over the ocean
2. Water vapour rises into the atmosphere
3. As the water vapour rises, it cools and condenses into liquid droplets
4. Condensation releases heat into the atmosphere making the air lighter
5. The warmed air continues to rise with the cold air from taking its place and thus creating more winds

Question 6

Subsidience

Answer 6

Another means of warming a hurricane’s center. As the air in the eye of the cyclone sinks, it warms due to compression.

Question 7

Life cycle of a hurricane

Answer 7

Tropical Depression
First appearance
Cloudiness disorganized, center of low is not certain
Tropical Storms
Manning
Hurricane begins to form
Hurricane
Bands of cloudiness (alternating weather)
Clear region in the middle is the eye, the eyewall has the most severe weather

Question 8

Where do hurricanes occur?

Answer 8

Not much activity in South America because coastal weather is too cold

Particularly along eastern coasts because of warm currents

Lack of hurricane activity near the equator because it does not provide an environment conducive to rotation

Indonesia area because ocean temperatures are warmer

Question 9

When do hurricanes occur?

Answer 9

June 1st to November 30th is the official hurricane season, some outliers

Question 10

6 Important points about the worldwide occurrence of hurricanes

Answer 10

1. About 66% occur in Northern Hemisphere
2. Never originate within 5 degrees of equator
3. Rarely ever originate poleward of 25 degrees (North or South) (ocean temperatures too cold)
4. Of the 80 tropical storms that develop annually around the globe, between 50-70% develop into hurricanes
5. The western Pacific in the Northern Hemisphere produces the largest number of tropical cyclones (winter and summer)
6. Hurricanes form over all tropical oceans except the south Atlantic and the southeast Pacific oceans

Question 11

Conditions necessary for a hurricane

Answer 11

1. Enough coriolis force to develop a low pressure center
2. Sufficiently warm sea surface temperatures around 27 degrees C and at least 60m deep (if not deep enough cold water easily churned up by wind)
3. Low vertical wind shear

These conditions are necessary, but not sufficient

Question 12

What is the Coriolis force?

Answer 12

Deflection force that occurs in a rotating system

In the Northern hemisphere clouds are deflected to the right , in the southern hemisphere to the left
○ Because of rotation
○ Low level convergence
○ Deflected air vessels
Creates a sense of rotation along the low pressure system

Question 13

Why do hurricanes need warm sea surface temperatures?

Answer 13

Direct relationship between the intensity (central pressure) of the most intense hurricanes and the temperature of the sea-surface over which the storms are moving

Water vapour is the fuel for the hurricane

We need a deep warm layer of water to prevent cold water from reaching the surface

Question 14

Why do hurricanes require weak wind shear?

Answer 14

During high wind shear, winds are likely to tear hurricanes apart

Difference in wind speed as we change elevation

There needs to be the same amount of winds in the atmosphere for hurricanes to occur

El Nino causes high wind shear, which decreases the chance of a hurricane

Question 15

Hurricane Triggers

Answer 15

1. Intertropical convergence zone
   It migrates northward from the equator into areas with high coriolis force
2. Easterly waves
   Thunderstorms forming on the convergent side (to the east) have the potential to organize into hurricanes
3. Middle latitude cold fronts extending into the tropics
   Common in autumn months

Question 16

Hurricane Structure

Answer 16

The eye
Hurricane’s center is relatively calm, clear area of sinking air and light winds, usually dies over land
Eyewall
Ring of tall thunderstorms that produce heavy rains and strongest winds
Rainbands
Curved bands of clouds and thunderstorms that trail away from the eye wall in a spiral fashion

Hurricane Size: Typically 300 miles wide but can vary considerably

Question 17

Hurricane Hazards

Answer 17

Storm surge

Wind damage

Heavy rains (flooding)

Associated tornados

Question 18

What is storm surge?

Answer 18

8-160km wide dome of water that sweeps over the coastline during landfall

strong onshore winds and relatively low air pressure are responsible for a storm surge

surge is superimposed on the normal tidal oscillation, so that the danger is greatest at high tide