Hydrometeorological Hazards

Hydrometeorological Hazards

  • Definition: Processes or phenomena of atmospheric, hydrological, or oceanographic nature that can cause loss of life, injury, property damage, loss of livelihoods and services, social and economic disruptions, or environmental damage.

  • Examples: Tropical cyclones, thunderstorms, hailstorms, tornados, blizzards, heavy snowfall, avalanches, coastal storm surges, flood (flash flood), drought, heat waves, and cold spells

*Tropical cyclones - non-frontal, synoptic-scale cyclones developing over tropical and sub-tropical waters at any level and having an organized circulation. In other parts of the world, these are called hurricanes, typhoons, or simply tropical cyclones, depending on the region.

Types of Hydrometeorological Hazards

  1. Typhoons

    • Tropical cyclones classified based on wind speed and location.

    • In the West Pacific, referred to as typhoons (e.g., Typhoon Ompong/Mangkhut).

    • Form in tropical regions with warm water and low pressure conditions.

  2. Storm Surges

    • Abnormal rise of water due to storm impacting coastlines.

    • Distinct from storm tides (combination of storm surge and astronomical tides).

  3. Thunderstorms

    • Characterized by lightning, thunder, intense rainfall, and sometimes hail or tornadoes.

    • Require moisture, unstable air, and a lifting mechanism for formation.

  4. Flooding

    • Overflow of water onto normally dry land.

    • Types include:

      • Inland flooding

      • Flash floods (rapid onset due to heavy rain)

      • River flooding

      • Coastal flooding

      • Urban flooding (poor drainage)

  5. El Niño-Southern Oscillation (ENSO)

    • Periodic fluctuations affecting climate variability across the Pacific.

    • El Niño: warmer temperatures and potential for droughts in certain regions.

    • La Niña: cooler temperatures, often generating more rainfall.

Typhoon Characteristics

  • Formation: Occurs in tropical/subtropical waters with temperatures above 26°C, enhanced by warm water evaporation and the Coriolis effect.

  • Regions by Name:

    • Hurricanes: North Atlantic and Eastern North Pacific.

    • Cyclones: Indian Ocean.

  • Structure:

    • Eye: The calm center surrounded by the eyewall.

    • Eyewall: Ring of tall thunderstorms producing the strongest winds.

    • Rain Bands: Spiraling bands of clouds and storms circulating outwards from the eye.

Factors Affecting Typhoons

  • Wind Speed: Stronger winds lead to higher storm surges.

  • Pressure: Lower pressure raises water levels.

  • Size and Forward Speed: Larger cyclones affect a broader area; faster storms raise surge levels on coasts.

  • Angle of Approach: Perpendicular hits increase surge height.

Impact of Tropical Cyclones

  • Winds: Can exceed 240 km/h, producing destructive gusts.

  • Rainfall: Beneficial for some but can lead to significant flooding.

Safety Measures and Risk Mitigation

  • Early Warning Systems: Monitoring and predicting typhoon tracks for timely evacuations.

  • National Disaster Risk Reduction and Management Council (NDRRMC): Coordinates local disaster response.

  • Public Awareness: Community education on risks and responses to typhoons.

Storm Surge Details

  • Definition: Abnormal rise of water generated by storms, posing threats to coastal areas.

  • Differences from Tsunamis and Tidal Waves:

    • Tsunamis: Result from seismic activity, with high heights and long wavelengths.

    • Tidal Waves: Caused by gravitational forces from the moon and sun.

  • Influencing Factors:

    • Storm intensity, pressure, size, forward speed, angle of coast approach, and coastal bathymetry/topography.

Flash Floods and Flood Risks

  • Cause: Sudden intense rainfall or rapid water releases.

  • Response: Identify high ground; pre-evacuate; stay informed through local alerts.

El Niño and La Niña

  • ENSO Impacts:

    • Affect global weather patterns, rainfall distribution, and health concerns.

    • Create conditions for diseases like malaria, depending on climate variability.

  • La Niña Characteristics:

    • Below-average sea temperatures with effects opposite to El Niño (increased rainfall).

Thunderstorm Formation and Safety

  • Ingredients: Moisture, rising unstable air, and lifting mechanisms.

  • Safety Tips:

    • Stay indoors during thunderstorms.

    • Avoid water and metal structures.

    • Use counting seconds between lightning and thunder to assess distance.

In conclusion, understanding the characteristics and impacts of hydrometeorological hazards is crucial for preparedness and risk management in affected areas such as the Philippines, which is frequently hit by multiple storm events each year.