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Flashcards in Storm Hazards Deck (37):
1

What are tropical storms

huge spinning storms with STRONG WINDS and TORRENTIAL RAIN

2

How tropical storms develop

over warm water

WARM MOIST AIR rises + condenses
RELEASE ENERGY that INCREASES WIND SPEED

3

Tropical storm favourable conditions

27*C sea water temperature so that lots of water will evaporate
=continuous source of heat
=able to maintain rising air currents

something near the sea -surface that will disturb it and trigger the storm (low pressure area)
-ocean depth of atleast 70m = moisture provides latent heat + drive the system to keep on

a location AT LEAST 5* FROM THE EQUATOR
-north + south
-so the Coriolis effect can bring about MAXIMUM ROTATION OF THE AIR
^^^^^ weak at the equator
^^^^^ can stop a circular air flow from developing

A CONVERGENCE OF AIR in the LOWER ATMOSPHERIC SYSTEM (either along the boundary between warm + cold air masses or within the ITCZ)
= FORCES WARM AIR TO RISE
=wind shave to come together near the centre of low pressure zone

4

Where do tropical storms form

in the TROPICS
= because the water there is warm enough

usually develop on the western side of oceans as they lose inputs of energy

5

Where do tropical storms occur

Caribbean Sea, Gulf of Mexico, Atlantic Ocean (known as HURRICANES)
Bay of Bengal, Indian Ocean (known as CYCLONES)
China Sea + N. Australia, Pacific Ocean (known as TYPHOONS)

6

Tropical storm movement

Lose strength as they MOVE OVER LAND because the supply of warm, moist air is cut off
=lose Coriolis Effect that spins the air

First of all, they move WESTWARDS due to EASTERLY WINDS in the tropics

Move AWAY FROM THE EQUATOR because of the CORIOLIS EFFECT

Usually travel NORTH in their tracks due to the CONVECTION OF THE WIND pulling + spinning it up on their tracks

7

What are tropical revolving storms

(hurricanes, cyclones, typhoons, tropical storms)

INTENSE LOW PRESSURE WEATHER SYSTEMS - develop in the tropics

measure 200-700km in diameter

8

How do tropical revolving storms happen

begin with an area of low pressure
= as a result = surface heating (warm air is drawn into a spiralling manner)

rotating wind systems can cause enlarge from small-scale disturbances to TROPICAL DEPRESSIONS
- can continue to grow into a much more rapid and intense rotating system = THE TROPICAL REVOLVING STORM

9

How they're measured

on the Saffir-Simpson Scale
=based on wind speed

category 1 - (120-150 km/h) limited damage
category 2 -
category 3 -
category 4 -
category 5 - (over 250 km/h) catasrophic damage

10

What the Saffir-Simpson scale does

estimates how much DAMAGE a storm of a GIVEN MAGNITUDE will do

11

Storm Hazard frequency

around 1 hundred a year

not reaching land = NO development into a MAJOR HAZARD

frequent in N.Hemisphere = June-Nov
frequent in S.Hemisphere = Nov-April

12

hazards created by the storms pattern

LARGELY IRREGULAR

no clear spatial or temporal pattern

13

Why their PATH can be easily predicted

certain CLOUD FORMATIONS in tropical areas can be identified from SATELLITE IMAGERY
= used to tell when a tropical storm is forming

Can then be TRACKED using the SATELLITE IMAGERY
= scientists able to clock when and where it is likely to hit land

14

Storm hazards taking a number of forms

High Winds
Landslides
Coastal Flooding
River Flooding
Storm Surges

15

whats air pressure measured in

millibars (mb)

16

whats wind speed measured in

knots (kts)

17

High Winds

caused when winds MOVE THROUGH different air pressures

wind gusts and speeds 120km/h = 250km/h on record

-tear off roofs
-breaking windows
-damaging communication lines
-debris being whisked up in the wind
-damaged power lines
-potential fires
-transport disruption on roads

18

Storm Surges

a RAPID RISE IN SEA LEVEL during tropical storms where water is piled up against the coastline in EXCESS OF THE HIGH TIDE MARK
=as a result of a much lower air pressure so the SEA CAN RISE VERTICALLY and the powerful,driving surface winds
=due to the lower pressure
= surge of up to 3m in height

-loss of life
-flooding to low-lying areas
-polluting fresh water supplies
-destroying homes
-destroying infrastructure
-enhanced coastal erosion

(Hurricane Katrina - 7.6m surge = one of the largest on record)

ACCOUNT FOR APPROX. 90% OF TROPICAL STORM DEATHS

19

Landslides

the intense rainfall of the tropical storm increases PORE WATER PRESSURE
=weakens COHESION
=triggers slope failure
=weight of the water worsens the problem

-fast winds
-trigger mudflows
-rainfall of high volumes lasting a long time
-can trigger earthquakes in TECTONICALLY STRESSED REGIONS

(Hurricane Mitch - 1998 - triggered landslides killing 18,000 people)

20

Coastal Flooding

occur when a hurricane comes ashore and the strong winds push the water up the coast
=builds up so much until its able to flood onto the land

-washed up debris - risk to sea life/animals
-ports and fishing villages suffering
-enhanced coastal erosion
-flooding of land - loss of industry and agriculture
-potentially spoilt and salty land
-damaged ecosystems

(Tohuko earthquake + tsunami - 2011 - saw 319 ports close down)

21

River Flooding

occurs from TORRENTIAL RAIN
can last a week or longer (200m m in just a few hours)
^^^^^^ from the warm moist air

-can cause flash flooding at the coast
-overwhelm drainage systems in urbanised areas
-rapid overland flow - IMPERMEABLE SURFACES
-excessive uncopeable rainfall

(Hurricane Irene - 2011 - caused widespread river flooding in New Jersey - over one million evacuated)

22

Whats the Coriolis Effect

the curvature of everything that moves freely on earth - ocean currents, global winds
= due to the earth's rotation on its axis

influences wind direction

force that is used to predict the path of storms

23

why don't storms develop within 5* of the equator only 5* out from the equator

because of the Coriolis force/effect

24

What types of clouds form in the EYEWALL

Cumulonimbus

25

How tropical revolving storms are given their names

Alphabetically
Gendered

26

Why don't the UK have real hurricanes

There are different systems ie. the UK have depressions

27

Whats a tropical depression

forms when a low pressure area is ACCOMPANIED BY THUNDERSTORMS that produce A CIRCULAR WIND FLOW with maximum sustained winds BELOW 39 mph.

Most tropical depressions have maximum sustained winds between 25 and 35 mph.

Becomes a tropical cyclone when the cyclone circulation becomes more organised
with maximum sustained winds gust between 39 mph and 73 mph.

28

where do tropical revolving storms exist and how they mature

exist where there is a supply of LATENT HEAT and MOISTURE
=to provide ENERGY and LOW FRICTIONAL DRAG on the ocean's surface

once the system reaches MATURITY, the CENTRAL EYE develops
=area 10-15km in diameter
=calm conditions - clear skies, higher temperatures, descending air
=wind speeds of more than 300km/h recorded around the EYE

once the system reaches land/colder waters
=will decline
=source of heat + moisture is removed

29

Tropical Revolving Storm impact

Winds
-can often exceed 150km/h

Heavy Rainfall
-exceed 200-300mm
-bring about severe flooding, landslides, mudslides
^^^^^^^^^^^^^^ high relief near the coastal area = rainfall could increase to over 500mm/day

Storm Surges
-when the wind-driven waves pile up and the ocean heaves upwards = because of low atmospheric pressure
-devastating effect upon low-lying coastal areas (river deltas)
-soil contaminated by water

30

amount/intensity of storms link with global temperature increase?

NONE

last 2 decades - have been several years with lots of tropical storms = the pattern however, is more erratic
^^^^^^ 2006,2007,2009 recorded low numbers

ALSO no evidence that hurricanes are becoming more intense either (of a higher magnitude)

longer time period of study would be needed for scientists to see any long-term trends

warmer atmosphere able to hold more moisture HOWEVER there has been an increase in wind shear ACTS AS A NEGATIVE FEEDBACK LOOP to cancel out any tropical storm formation

31

tropical storm regularity

can be predicted:

-moistly restricted to the tropics
-do not occur close to the Equator
-mostly occur from late summer into autumn
^^^^^ peak from Aug-Oct

32

Whats NOAA

(US National Oceanographic and Atmospheric Administration) publishes a prediction to the hurricane activity for the upcoming season

uses sea surface temperatures, atmospheric conditions and short term climatic cycles (El Nino) to suggest how many storms will be expected to occur

2016 - predicted a near-normal hurricane season with 4-8 hurricanes (1-4 predicted to be major)

33

tropical storms following tracks

tend to follow similar tracks

each storm however, develops its own characteristics and responds uniquely to the atmospheric and oceanographic conditions

tropical storms will erratically follow tracks, some tracks can be very erratic and crazy
=demonstrates the dangers in attempting to make predictions to it all

34

Storm hazards :
Preparedness

awareness of the hazard

weather forecasting - predicting storm tracks

emergency supplies

evacuation routes and emergency centres

monitoring sea temperatures closely

35

Storm hazards :
Mitigation

hard engineering structures (Levees)

soft engineering schemes

emergency services

property having insurance for damage

disaster aid (short term emergency humanitarian aid) and (long term reconstruction aid)

improving building resilience to these hazards

environmentally managing coral reefs and mangroves

36

Storm hazards :
Prevention

cloud seeding

hard engineering structures

37

Storm hazards :
Adaptation

land use zoning

building alterations