Lecture 8 - Hurricanes Flashcards
Which way do winds in a cyclone blow in the northern and southern hemispheres?
North = counterclockwise South = clockwise
Tropical Cyclone?
Form over warm tropical or subtropical oceans
Extratropical Cyclone?
Develop over land or water in temperate regions (farther north)
What is the only difference between hurricanes/cylones/typhoons/nor’easters?
Their location
Hurricane?
Tropical cyclones in Atlantic and Eastern Pacific oceans
Typhoon?
Tropical cyclones in western Pacific Ocean and North of equator
Cyclone?
Tropical cyclones in the Indian Ocean and Pacific Ocean south of the equator
Nor’easter?
Extratropical cyclone moving northward along the east coast of NA
EXAM Q: what is the wind speed of a category 4 hurricane on the Saffir-Simpson scale?
210-249km/h
Who names the hurricanes?
The world meteoroloigcal organization names winds greater than 63 km/h from an alphabetical list of men and women’s names
Tropical disturbance?
An organized area of thunderstroms peristing for more than 24 hours
- associated with an elongated area of low pressure
Tropical depression?
A tropical disturbance with an increase in winds and faster spinning
Tropical storm?
Has winds of at lest 62km/h, gets a name.
Not as strong as a hurricane
Hurricane?
Winds of at least 119km/h
What are the necessary conditions for hurricane formation?
Warm water at least 26 degrees to a depth several tens of meters
Atmosphere cools quickly upward from the surface
Little vertical wind shear
Rain bands?
Areas of clouds and rain that spiral around a hurricane
- thunderstorms and surface winds increase in intensity toward the centre of the storm
Eyewall?
Innermost band of clouds and rain, most intense weatehr
Eye?
A circular area of calm conditions and broken clouds in the centre, most are smaller at the surface and widen upward
Upward rotation _____
- draws air from the eye, causing dry air to sink into the centre
- causes air to flow out the top of sthe storm, which is critical for survival of the hurricane (allows additional warm, moist air to converge inward at the lower level of the storm)
What controls hurricane movement?
- the coriolis effect
- steering winds
Which way do hurricanes track in the Northern Hemisphere?
Hurricanes track westward and then curve to the right
- Hurricane tracks are influenced by the size and location of the bermuda high in the north atlantic
How fast will a mature hurricane move?
19-27km/h
What are the necessary conditions for the formation of an extratropical cyclone?
- Strong temperature gradient in the air
- Strong winds in the upper troposphere (ex. jet stream)
What two jet streams exist in the Northern Hemisphere?
- Polar jet stream
- Subtropical jet stream
How does the polar jet stream shift?
From the northern US in the winter to southern canada in the summer
What causes jet streams to bend?
Large high-pressure ridges and low pressure troughs
What is often produced when a bend in the jet stream turns south?
Pineapple express - origin near hawaii, brings warm moist air out of the tropics
Nor’easters can form where?
In the merging of pola and subtropical jet streams off the southeast coast of the US
How do extratropical cyclones develop?
- Start: low pressure centre along a frontal boundary
- Cold front on the Southwest, Warm front on the Northeast
- Cold air circles counterclockwise, and rises on the southeast corner
- Cold front merges with warm front to produce an occluded front
- Warm air is trapped aloft
What kind of winds usually steer extratropical cyclones?
Winds in the middle of the troposphere
Which regions are at risk for hurricanes?
Atlantic coast of Canada/US, gulf coast of US
What is the atlantic hurricane season?
June 1st to November 30
Storm Surge?
Rapid local rise in water level that happens when hurricane winds push waster into a shoreline
What part of the hurricane produces the greatest storm surge and wind damage
Forward right quandrant
What two mechanisms cause a storm surge?
- larger the area over which the wind blows (fetch)
- the lower the atmospheric pressure
Overwash?
Sand eroded from the beach and deposited landward due to a storm surge
What happens to winds once they make landfall?
Tend to decrease speed
Rainfall from cyclones can cause _____
Inland flooding
How does climate change affect cyclones?
Sea levels rising increases their severity
What are some natural service functions of cyclones?
- Source of precipitation
- Equalize temperature of planet
- Benefit ecosystems; stir up nutrient rich waters, remove diseased trees, break apart corals
What are some methods of tracking/predicting hurricanes?
- Weather satellites
- Aircrafts flown into the storm
- Dopplar radar
- Weather buoys
EXAM Q: How many deaths resulted from the catagory 4 hurricane that hit Louisiana in 1866?
~400
