Hydrometeorogical Hazards

• Cyclone

  A kind of hazard that forms in the northern hemisphere due to a phenomenon characterized by very low pressure. It is characterized by its "eye" or the spiral winds which flow counterclockwise toward its center.
• Cyclone

  • Tropical cyclones produce moderate to heavy rainfalls that can result to flash floods, mudflows, landslides, and storm surges in different areas affected by its movement
• Three classifications of tropical cyclone

  • Tropical depression
  • Tropical storm
  • Typhoon
• Tropical depression

  Moves from 35 kph to 65 kph
• Tropical storm

  Moves from 64 kph to 118 kph
• Typhoon

  Exceeds the wind movement of 118 kph
• Typhoon

  A low-pressure area or a tropical cyclone that is large and violent. It rotates counterclockwise with warm air rising above the warm water of the Western Pacific Ocean.
• Hurricane/Wily-wily


  Terms also used for tropical cyclone
• Tropical cyclone


  The typical term for non-frontal synoptic scale low pressure system over tropical or sub-tropical waters with organized convections such as thunderstorms and wind reaction.
• Three categories of tropical cyclone

  • Tropical depression (max sustained winds <17 m/s or 34 kt, 39 mph)
  • Tropical Storm (winds >=17 m/s or 34 kt, 39 mph)
  • Typhoons or Hurricane (winds >=33 m/s or 64 kt, 74 mph)
• Thunderstorm


  A weather condition generally characterized by heavy in thunder, lightning, and possibly a tornado. A typical thunderstorm occurs when the sun heats a large body of moist air near the ground.
• Thunderstorm formation

  1. Moist air rises and is cooled by expansion, condensing water vapor and forming cumulus clouds

  2. Turbulent air inside the cloud produces raindrops and strong electrical charges that result in lightning
• Thunderstorms

  • Can occur at night due to cooling of upper air layers by radiation
  • Can be caused by approaching cold air masses forcing warmer air to rise
  • Can be deadly and cause damage to property
• Flood

  The running and overlaying of water on land that is not ordinarily covered by it. The rise of water from a stream, water drainages, enclosed bodies, water, and rivers that is overflowing on adjacent lands; the overflowing a result of continuous heavy rainfall due to weather conditions such monsoons, tropical cyclones, and intertropical convergence zones.
• Floods

  • Hydrological phenomena that sometimes result from storm surges and tsunamis in coastal areas
  • Can be attributed to human activities like cutting of trees and urbanization that change the hydrological regime
• Factors contributing to floods

  • Rate of rain intensity
  • Duration of rainfall
• Storm surge

  The "masses of water that are driven toward the shore by meteorological forces". An escalating of seawater above the normal sea level.
• Storm surge formation

  1. Sea level is raised and driven towards the coast

  2. Where the depth is shallow and the sea bed slope is gradual, the water flow is delayed by friction

  3. As more water moves from the sea to the coast, excess water piles up on the shoreline
• Storm surges

  • Can be massively destructive, drowning people and animals, and affecting entire communities
  • Can result in long-term impairment of livelihoods and activities