Changing Coastal Environments » Tropical Storm Distribution and Impacts

What you'll learn this session

Study time: 30 minutes

The global distribution of tropical storms
How tropical storms form and develop
Primary and secondary impacts of tropical storms
Case studies of major tropical storms and their effects
How communities prepare for and respond to tropical storms
The influence of climate change on tropical storm patterns

Tropical Storms: Nature's Power Unleashed

Tropical storms are among the most powerful and destructive natural hazards on our planet. These massive weather systems form over warm ocean waters and can cause devastating impacts when they make landfall. Understanding their distribution, formation and impacts is crucial for coastal communities worldwide.

Key Definitions:

Tropical Storm: A rotating, organised system of clouds and thunderstorms that originates over tropical or subtropical waters with a closed low-level circulation and maximum sustained winds of 39-73 mph (63-118 km/h).
Hurricane/Typhoon/Cyclone: Regional names for tropical storms that reach sustained wind speeds of 74 mph (119 km/h) or higher.
Storm Surge: An abnormal rise in sea level accompanying a tropical storm, measured as the height of the water above the normal predicted astronomical tide.

Global Distribution of Tropical Storms

Tropical storms form in specific regions around the world, primarily between the Tropics of Cancer and Capricorn (23.5° north and south of the equator). However, they rarely form directly at the equator due to the weak Coriolis effect there.

🌊 Where Tropical Storms Form

Tropical storms develop over warm ocean waters (at least 27°C) in six main basins around the world:

North Atlantic Basin: Hurricanes form in the Caribbean Sea, Gulf of Mexico and Atlantic Ocean
Northeast Pacific Basin: Hurricanes form off the west coast of Mexico
Northwest Pacific Basin: Typhoons form east of the Philippines (most active basin)
North Indian Basin: Cyclones form in the Bay of Bengal and Arabian Sea
Southwest Indian Basin: Cyclones form east of Madagascar
Southeast Indian/Australian Basin: Cyclones form near Australia

📅 Tropical Storm Seasons

Tropical storms have distinct seasonal patterns:

Northern Hemisphere: June to November (peak in August-September)
Southern Hemisphere: November to April (peak in January-February)
These seasons coincide with when ocean temperatures are warmest in each hemisphere
Climate change may be extending these traditional seasons

Formation and Structure of Tropical Storms

Tropical storms develop through a series of stages and have a distinctive structure that contributes to their power and destructive potential.

🌡️ Necessary Conditions

For a tropical storm to form, several conditions must be met:

Warm ocean water (at least 27°C)
Sufficient Coriolis force (at least 5° from equator)
Moist atmosphere
Little vertical wind shear
Pre-existing weather disturbance

🌪️ Structure

Tropical storms have a distinctive structure:

Eye: Calm, clear centre (8-50km wide)
Eyewall: Ring of intense thunderstorms with strongest winds
Rain bands: Spiral bands of clouds and thunderstorms extending outward
Counter-clockwise rotation in Northern Hemisphere, clockwise in Southern Hemisphere

📈 Development Stages

Tropical storms develop through these stages:

Tropical disturbance: Organised thunderstorms
Tropical depression: Winds up to 38 mph
Tropical storm: Winds 39-73 mph
Hurricane/Typhoon/Cyclone: Winds 74+ mph
Categorised using the Saffir-Simpson scale (Category 1-5)

Impacts of Tropical Storms

Tropical storms can cause devastating impacts on coastal environments and communities. These impacts are typically categorised as primary (direct) and secondary (indirect or longer-term) effects.

💥 Primary Impacts

Immediate effects during and immediately after the storm:

Strong winds: Damage to buildings, infrastructure and vegetation
Heavy rainfall: Flooding, landslides and soil erosion
Storm surge: Coastal flooding and erosion
Large waves: Damage to coastal structures and beaches
Deaths and injuries: From flying debris, flooding, building collapse

⏳ Secondary Impacts

Longer-term effects that occur after the storm:

Water contamination: From sewage overflow and chemical spills
Disease outbreaks: From contaminated water and poor sanitation
Food shortages: From crop damage and disrupted supply chains
Economic losses: Business disruption, tourism decline, reconstruction costs
Psychological trauma: Mental health impacts on affected populations
Environmental changes: Altered coastal landscapes and ecosystems

Case Study: Hurricane Katrina (2005)

Hurricane Katrina struck the Gulf Coast of the United States in August 2005, becoming one of the most devastating tropical storms in US history.

Key Facts:

Category 5 hurricane that weakened to Category 3 before landfall
Affected areas: Louisiana (especially New Orleans), Mississippi, Alabama
Storm surge up to 8 metres high
80% of New Orleans flooded when levees failed
Over 1,800 deaths
$125 billion in damage
1 million people displaced

Impacts:

Primary: Massive flooding, wind damage, storm surge destruction
Secondary: Oil spills (8 million gallons), disease outbreaks, long-term displacement, economic decline, environmental damage to wetlands

Response and Recovery:

Criticised emergency response by FEMA and government agencies
$14.5 billion spent on improved flood defences
New building codes and evacuation plans
Some areas never fully recovered; population of New Orleans still below pre-Katrina levels

Preparing for and Responding to Tropical Storms

Communities in tropical storm-prone regions have developed various strategies to prepare for, respond to and recover from these destructive events.

🛡️ Preparation and Mitigation

Long-term strategies to reduce vulnerability:

Early warning systems: Satellite monitoring, weather stations, public alerts
Building regulations: Hurricane-resistant construction standards
Coastal defences: Sea walls, flood barriers, beach nourishment
Land-use planning: Restricting development in high-risk areas
Education: Public awareness campaigns about evacuation procedures
Insurance schemes: Financial protection for property owners

🚑 Response and Recovery

Actions taken during and after a tropical storm:

Emergency evacuation: Moving people to safer locations
Search and rescue: Finding and helping victims
Emergency shelter: Providing temporary housing
Aid distribution: Food, water, medicine and other essentials
Infrastructure repair: Restoring power, water and transportation
Rebuilding: Long-term reconstruction of damaged areas

Case Study: Typhoon Haiyan (2013)

Typhoon Haiyan (locally known as Yolanda) struck the Philippines in November 2013 and was one of the strongest tropical cyclones ever recorded.

Key Facts:

Sustained winds of 315 km/h (195 mph)
Storm surge up to 5-7 metres high
Over 6,300 deaths
More than 4 million people displaced
$2.2 billion in damage

Impacts:

Primary: Catastrophic wind damage, massive storm surge, coastal destruction
Secondary: Water contamination, disease outbreaks, food shortages, economic losses in agriculture and fishing industries

Response and Recovery:

Major international humanitarian response ($763 million in aid)
Improved early warning systems and evacuation procedures
"Build Back Better" programme to create more resilient communities
New no-build zones established in high-risk coastal areas
Enhanced disaster preparedness training for communities

Climate Change and Tropical Storms

Scientific research suggests that climate change is affecting tropical storm patterns, though there remains some uncertainty about specific impacts.

🌡️ Potential Changes

Scientists predict several changes to tropical storms due to climate change:

Intensity: Likely increase in the proportion of high-intensity storms (Categories 4-5)
Rainfall: Increased precipitation during storms due to warmer air holding more moisture
Storm surge: Higher storm surges due to sea level rise
Range: Possible expansion of tropical storm regions poleward
Frequency: Less certainty about overall number of storms

🔍 Evidence and Implications

Current observations and future concerns:

Recent decades have seen more Category 4-5 hurricanes in some basins
Storms may be intensifying more rapidly ("rapid intensification")
Hurricane seasons may be getting longer
Storms may be moving more slowly, increasing rainfall and flooding
Communities need to adapt planning and preparation for changing storm patterns

Summary: Key Points to Remember

Tropical storms form over warm ocean waters (27°C+) between 5-30° latitude
They're called hurricanes in the Atlantic/Eastern Pacific, typhoons in the Northwest Pacific and cyclones in the Indian Ocean/South Pacific
Primary impacts include strong winds, heavy rainfall, storm surge and direct casualties
Secondary impacts include water contamination, disease, economic losses and long-term displacement
Preparation strategies include early warning systems, building regulations and coastal defences
Climate change is likely making tropical storms more intense and increasing their rainfall
Case studies like Hurricane Katrina and Typhoon Haiyan demonstrate the devastating potential of these storms

Understanding tropical storms is essential for coastal communities to develop effective strategies for reducing vulnerability and building resilience to these powerful natural hazards.

🧠 Test Your Knowledge!