Comprehensive Study Guide to Caribbean Tropical Cyclones and Emergency Preparedness

Characteristics and Formation of Tropical Cyclones

• Definition of a Tropical Cyclone:

  • A tropical cyclone is defined as a large, rotating storm system.

  • These systems form over warm ocean waters specifically in tropical regions, such as the Caribbean.

• Required Conditions for Formation:

  • Warm Water: The ocean surface temperature must be at least $26^\circ\text{C}$.

  • Atmospheric Pressure: These systems feature low pressure at their center.

  • Associated Weather: They produce strong winds, heavy rainfall, and thunderstorms.

  • Motion: The system rotates in a circular motion.

Classification of Tropical Cyclones by Wind Speed

Tropical cyclones are categorized into three primary stages based on their maximum sustained wind speeds:

• Tropical Depression:

  • Wind Speed: Less than $63\,\text{km/h}$.

  • Characteristics: This is the weakest stage of a tropical cyclone. Clouds begin to organize, and the system produces light to moderate rainfall.

  • Impact: Usually causes little or no damage but holds the potential to develop into a stronger system.

• Tropical Storm:

  • Wind Speed: Between $63\,\text{km/h}$ and $118\,\text{km/h}$.

  • Characteristics: Winds become stronger and rainfall becomes heavier. The system becomes more organized and is officially assigned a name at this stage.

  • Impacts: Can cause flooding and damage to trees and weak structures.

• Hurricane:

  • Wind Speed: $119\,\text{km/h}$ and above.

  • Characteristics: These are very powerful and dangerous systems. They are well-organized with a clear, calm center known as the "eye."

  • Impacts: Can cause severe flooding, destruction of homes, and significant loss of lives and property.

Differentiating Between a Weather Watch and a Warning

• Watch:

  • Definition: Indicates that the specific weather conditions are possible in the area.

  • Timing: Usually issued $24-48\,\text{hours}$ before the storm is expected to arrive.

  • Recommended Action: People should prepare their supplies and stay alert to further updates.

  • Example: A notification stating a hurricane may affect Jamaica.

• Warning:

  • Definition: Indicates that the weather conditions are expected or are already occurring.

  • Timing: Usually issued within $36\,\text{hours}$ or less of the expected impact.

  • Recommended Action: People must take immediate action to protect life and property.

Analysis of Watch and Warning Scenarios

Based on meteorological criteria, the following situations illustrate the difference between a watch and a warning:

1. Scenario: A storm in the Atlantic Ocean is moving toward Jamaica and may affect the island in 2 days. (Watch)

2. Scenario: A hurricane is expected to reach Jamaica within the next 12 hours. (Warning)

3. Scenario: Meteorologists say weather conditions are favourable for a storm to develop. (Watch)

4. Scenario: A tropical storm has formed and could pass near the island soon, but its path is uncertain. (Watch)

5. Scenario: Emergency shelters are being opened because a hurricane is definitely approaching within 24 hours. (Warning)

6. Scenario: Satellite images show a storm strengthening, and it is likely to affect the island in $36-48\,\text{hours}$. (Watch)

7. Scenario: The government announces that a hurricane will make landfall tonight. (Warning)

8. Scenario: A storm is far away, but experts say it might change direction and affect the Caribbean. (Watch)

9. Scenario: Flooding has begun in coastal communities and dangerous conditions are expected to worsen soon. (Warning)

10. Scenario: Satellite images show a storm strengthening, and it is likely to affect the island in $36-48\,\text{hours}$. (Watch)

Comparative Definitions: Natural Events, Hazards, and Disasters

• Natural Event:

  • Definition: Any occurrence in nature caused by the natural processes of the Earth, atmosphere, or oceans.

  • Impact: Can be harmless or even beneficial; it does not always result in damage.

  • Examples: Rainfall, gentle earthquakes, volcanic eruptions, river flow, and hurricanes forming over the open ocean.

• Natural Hazard:

  • Definition: A natural event that has the potential to cause harm to people, property, the environment, or the economy.

  • Examples: Earthquakes occurring near populated areas, hurricanes approaching land, droughts, floods, landslides, and volcanic eruptions near settlements.

• Natural Disaster:

  • Definition: Occurs when a natural hazard actually causes serious damage, loss of life, destruction, or disruption to a community that is unable to cope using its own resources.

  • Examples: A hurricane destroying homes in Jamaica, an earthquake causing buildings to collapse, or severe flooding forcing entire communities to evacuate.

The Saffir-Simpson Hurricane Wind Scale

Meteorologists use the Saffir-Simpson Hurricane Wind Scale to measure hurricane strength based primarily on maximum sustained wind speeds. The scale consists of five categories:

• Category 1:

  • Wind Speed (km/h): $119-153\,\text{km/h}$.

  • Wind Speed (mph): $74-95\,\text{mph}$.

  • Damage Level: Some damage. Strong winds can break tree branches, damage roofs, tear shingles from buildings, and cause minor coastal flooding. Power line damage may cause electricity outages.

• Category 2:

  • Wind Speed (mph): $96-110\,\text{mph}$.

  • Damage Level: Extensive damage.

• Category 3 (Major Hurricane):

  • Wind Speed (km/h): $178-208\,\text{km/h}$.

  • Wind Speed (mph): $111-129\,\text{mph}$.

  • Damage Level: Devastating damage. Buildings may lose roofs, weak houses may collapse, and coastal flooding becomes dangerous.

• Category 4:

  • Wind Speed (km/h): $209-251\,\text{km/h}$.

  • Wind Speed (mph): $130-156\,\text{mph}$.

  • Damage Level: Catastrophic destruction. Most trees will be snapped or uprooted, many homes will be severely damaged, and flooding can cover large areas.

• Category 5:

  • Wind Speed (km/h): $252\,\text{km/h}$ and above.

  • Wind Speed (mph): $157+\,\text{mph}$.

  • Damage Level: Catastrophic destruction. Can destroy homes, flatten buildings, destroy roads and bridges, and leave areas uninhabitable for weeks or months.

Water Vapour and Flooding Potential

• The Process of Evaporation and Condensation:

  • Air contains invisible moisture called water vapour, formed when water from oceans, rivers, lakes, and land surfaces evaporates into the atmosphere.

  • Warm tropical oceans, like the Caribbean Sea and the Atlantic Ocean, provide massive amounts of water vapour for developing storms.

  • As storms move over these warm waters, they absorb moisture. This moisture rises, cools, condenses into clouds, and eventually falls as heavy rain.

• Consequences of High Water Vapour Content:

  • Increased risk of flash flooding.

  • Heavy rain may persist for many hours or days.

  • Rivers may burst their banks.

  • Roads may become impassable.

  • Farms may be inundated.

  • Risks specifically increase for homes located in valleys and flood plains.

• Local Factors Increasing Flooding in Jamaica and the Caribbean:

  • Low-lying land.

  • Proximity to rivers.

  • Poor drainage systems.

  • Steep hillsides that cause rapid runoff.

  • Saturated soil (already full of water).

  • Man-made buildings that block natural drainage paths.

Tracking Tropical Cyclones: Forecast Cones

• Definition of a Forecast Cone:

  • Also known as the "cone of uncertainty," this is the cone-shaped area on weather maps surrounding a storm's projected path.

  • The Misconception: People often think the cone represents the physical size of the storm.

  • The Reality: The cone shows the possible path of the storm's center (the eye).

• Predictive Challenges:

  • Meteorologists cannot predict exact paths because storms change direction based on:

    • Wind currents.

    • Air pressure changes.

    • Ocean temperatures.

    • Interaction with land masses.

• Impact Outside the Cone:

  • A country outside the cone of uncertainty can still experience heavy rain, strong winds, flooding, and storm surges.

• Case Study: Tropical Storm Melissa Path:

  • Data Source: AccuWeather Exclusive Forecast.

  • Timestamp: $09:16:22$ on $27\text{-OCT-2025}$.

  • Path Timeline (All times EDT):

    • $8\,\text{PM MON}$: Located south of Hispaniola.

    • $7\,\text{AM TUE}$: Moving northwest toward Cuba.

    • $8\,\text{PM TUE}$: Positioned over eastern Cuba.

    • $11\,\text{AM WED}$: Moving north toward the Bahamas.

    • $8\,\text{PM WED}$: Eye path projected north of the Bahamas.

Emergency Preparedness Activity

Students are required to form groups of 5 or 6 to create a detailed action plan for preparing for, responding to, and recovering from tropical cyclones:

• Group 1 & 2: Tasked with creating a Home Plan.

• Group 3 & 4: Tasked with creating a School Plan.

• Group 5 & 6: Tasked with creating a Community Plan.