Natural Phenomena


Rain, thunder and lightning:

We all enjoy cool soft breeze in summer evenings

 but when same breeze increases in speed and starts causing havoc we need to prepare for dangers. High winds are known to cause damage, depending upon their strength. Wind speeds as low as 23 knots (43 km/h) may lead to power outages when tree branches fall and disrupt power lines. Some species of trees are more vulnerable to winds. Trees with shallow roots are more prone to uproot, and brittle trees such are more prone to branch damage.

High speed Winds may cause poorly designed suspension bridges to sway. In worse cases it may even fail and fall.

Hurricane-force winds, caused by individual thunderstorms, thunderstorm complexes, tornadoes, extra tropical cyclones, or tropical cyclones can destroy mobile homes and structurally damage buildings with foundations. Winds of this strength due to down slope winds off terrain have been known to shatter windows and sandblast paint from cars.

Once winds exceed 135 knots (250 km/h) within strong tropical cyclones and tornadoes, homes completely collapse, and significant damage is done to larger buildings. Total destruction to man-made structures occurs when winds reach 175 knots (324 km/h). The Saffir–Simpson scale for cyclones and Enhanced Fujita scale (TORRO scale in Europe) for tornados were developed to help estimate wind speed from the damage they cause.

Heavy rainfall can lead to a number of hazards, most of which are floods or hazards resulting from floods. Flooding is the inundation of areas that are not normally under water. It is typically divided into three classes: River flooding, which relates to rivers rising outside their normal banks; flash flooding, which is the process where a landscape, often in urban and arid environments, is subjected to rapid floods; and coastal flooding, which can be caused by strong winds from tropical or non-tropical cyclones. Meteorologically, excessive rains occur within a plume of air with high amounts of moisture (also known as an atmospheric river) which is directed around an upper level cold-core low or a tropical cyclone. Flash flooding can frequently occur in slow-moving thunderstorms and are usually caused by the heavy liquid precipitation that accompanies it. Flash floods are most common in dense populated urban environments, where less plants and bodies of water are presented to absorb and contain the extra water. Flash flooding can be hazardous to small infrastructure, such as bridges, and weakly constructed buildings. Plants and crops in agricultural areas can be destroyed and devastated by the force of raging water. Automobiles parked within experiencing areas can also be displaced. Soil erosion can occur as well, exposing risks of landslide phenomena. Like all forms of flooding phenomenon, flash flooding can also spread and produce waterborne and insect-borne diseases cause by microorganisms. Flash flooding can be caused by extensive rainfall released by tropical cyclones of any strength or the sudden thawing effect of ice dams.


Potential consequences of heavy rainfall

Heavy rainfall can lead to numerous hazards, for example:

  • flooding, including risk to human life, damage to buildings and infrastructure, and loss of crops and livestock
  • Landslides, which can threaten human life, disrupt transport and communications, and cause damage to buildings and infrastructure.

Where heavy rainfall occurs with high winds, risk to forestry crops is high.

Hurricanes, Typhoons and Cyclones:

There is an old expression that a hurricane is Mother Nature’s way of telling us that she is angry. But of course hurricanes are not just a byproduct of nature’s ire.

Hurricanes — or more broadly, tropical cyclones — generally begin as clusters of thunderstorms over tropical ocean waters, taking anywhere from several hours to several days to become organized and graduate to hurricane status.

  • There has to be a perfect storm, so to speak, of conditions for a hurricane to form, including: Water that is at least 80 degrees Fahrenheit (26.6 Celsius)
  • Relatively moist air
  • Very warm surface temperatures
  • A continuous evaporation and condensation cycle
  • Wind patterns of varying directions that collide (converging winds)
  • A difference in air pressure between the surface and high altitude

Tropical cyclones form all around the world, generally about 300 miles (480 kilometers) north or south of the equator. When they form in the Atlantic or Eastern Pacific, the storms are called hurricanes. In the western North Pacific, they are called typhoons and in the South Pacific and Indian Ocean, they are called cyclones.  

Why are roofs blown off during storms?

Brief explanation: When the velocity of the wind is great enough, the air pressure above the surface is lower compared to that underneath. This cause the roof to blow off. High speed winds are accompanied by reduced air pressure So high pressure from inside the house pushes roof to low pressure and gets blown away.