DRRR | Hazards

• Hydrometeorogical hazards


  Hazards related to the atmosphere and water
• Typhoon


  A tropical cyclone that forms in the western Pacific or northern Indian Ocean

  
• Effects of Tropical Cyclones

  • Strong winds
  • Storm surge
  • Heavy rains

  
• Storm Surge


  An abnormal rise of water generated by a storm, over and above the predicted astronomical tide

  
• Lightning


  A sudden electrostatic discharge that occurs during a thunderstorm
• Five Ways Lightning Strikes People

  • Direct strike
  • Side flash
  • Ground current
  • Conduction
  • Streamers
• El Niño Southern Oscillation (ENSO) Cycle


  A periodic fluctuation in sea surface temperatures and air pressure in the tropical Pacific Ocean
• El Niño


  A warming of the ocean surface, or above-average sea surface temperatures, in the central and eastern tropical Pacific Ocean
• La Niña


  A cooling of the ocean surface, or below-average sea surface temperatures, in the central and eastern tropical Pacific Ocean
• Southern Oscillation


  The irregular fluctuations in air pressure between the western and eastern tropical Pacific, coupled with the El Niño and La Niña conditions
• Typhoon


  • A severe weather disturbance characterized by strong winds and heavy rains which revolve around a central low pressure area.
  • Most powerful type of tropical cyclone that forms in the northwestern Pacific Ocean.
• Typhoon is most likely derived from the Chinese term "Tai

  Fung." (Ta = big, fung = wind)
• Typhoon is locally known as bagyo.

  It is coined after Baguio City where the wettest known tropical cyclone way back in 1911 hit and dropped approximately 2200 mm of rainfall for about three days.
• Tropical Cyclones 4 types:

  Tropical depression: 62 kph

  Tropical storm: 63-118 kph

  Typhoon: Greater than 118 kph

  Super typhoon : Greater than 220 kph
• Eye - area of lowest atmospheric pressure In this area, winds are weak, the temperature is warm, and the sky is clear.

  Eye wall - brings the strongest wins, heavy rains, and turbulence shortly after the passage of the eye

  Rain bands - spiraling strips of clouds in the fridges of tropical cyclones which are associated with rainfalls
• Tropical cyclones form because of the atmosphere's natural tendency to redistribute heat through wind from the equatorial regions to the polar regions.
• Strong winds

  Causes the most obvious damage

  PAGASA monitors where the eye will make landfall because of the strong winds in the eye wall
• Storm surge

  Localized unusual increase of sea water level way above the predicted astronomical tide level, happens due to intense winds and tropical cyclones.
• Heavy Rains

  Results in flooding and happens in tropical cyclones low intensity
• Storm Surge

  Localized unusual increase of sea water level beyond the predicted astronomical tide level primarily due to intense winds and lowered atmospheric pressure during the passage of an intense tropical cyclone from the sea to the land.
• Storm Intensity (Wind speed)


  • Storm surges are wind driven
  • The stronger the winds, the higher the storm surge
• Pressure effect


  • Lower atmosphere pressure results in a higher storm surge level
• Size


  • The larger the storm, the larger the area of ocean affected by its winds, thereby producing higher surge
• Storm forward speed


  • A tropical cyclone travelling with a higher velocity will produce a higher surge along an open coast
• Angle of approach to coast


  • When a tropical cyclone hits the coast perpendicularly, it will more likely form a higher storm surge
• Rainfall effect


  • Strong rainfall brought about by a storm can cause river waters to rise
  • When this water flows downriver and reaches the coast, it contributes to the water level rise there
• Bathymetry


  • The appearance of the ocean or sea bottom resulting from the variation in depth in different portions
  • Surges are worse when the slopes are gentle
• Shape of the coastline


  • Storm surge level is higher when a tropical cyclone hits a concave coastline
• Man-made and natural local features


  • Sea walls, breakwaters, mangroves, coral reefs, and other may weaken a storm surge
• Thunderstorms

  A violent, transient type of weather disturbance associated with thousands of meters tall cumulonimbus clouds and which usually involves lightning and thunder, strong winds, intense rainfall, and occasionally tornadoes and hail.
• Requirements for the Formation of Thunderstorms

  1. Moisture (water vapor) which must be readily available in the lower atmosphere to produce clouds and precipitation during storm formation;
  2. An unstable, rapidly rising mass of warm air;
  3. A strong upward current of air (updraft) to force moisture to higher, colder levels of the atmosphere.
• What Type of Stage in terms of the Thunderstorm Life cycle?

  Developing Stage
• What stage of the Thunderstorm Cycle is this?

  Mature stage

  
• What stage of the Thunderstorm Cycle is this?

  Dissipating Stage

  
• Lightning

  This is the abrupt, natural, visible high-voltage electrical discharge which takes place when positive and negative charges join within a cloud, between clouds, or between a cloud and the ground.
• Electrical charges within the thunderstorm cloud separate during its development, with the positive charges gathering at the top and the negative charges at the bottom.

  On the ground, positive charges begin to gather.
• Direct Strike


  A person struck directly by lightning becomes a part of the main lightning discharge channel. Most often, direct strikes occur to victims who are in open areas.
• Side Flash


  A side flash (also called a side splash) occurs when lightning strikes a taller object near the victim and a portion of the current jumps from taller object to the victim.
• Ground Current


  When lightning strikes a tree or other object, much of the energy travels outward from the strike in and along the ground surface. This is known as the ground current.
• Conduction


  Lightning can travel long distances in wires or other metal surfaces. Metal does not attract lightning, but it provides a path for the lightning to follow. Whether inside or outside, anyone in contact with anything connected to metal wires, plumbing, or metal surfaces that extend outside is at risk.