Killer Weather

Violent Weather: Floods

Flash floods, rapid rises in water levels with high flow velocities – can occur in a matter of seconds. Make sure you monitor weather service announcements during big storms in case of a flash flood warning. If you live in a region that is prone to flash floods, make sure you have a map to the quickest region of high ground. With these figures readily available, weather services can provide predictions and early warnings to give inhabitants of the region time to move to higher ground. Flash flood guidance is the amount of rainfall for a given duration necessary to produce flash flooding.

The forecast center for your region calculates flash flood guidance for all the bodies of water in the area. Areas with a high risk of flash floods (such as the land surrounding large dams) often have warning systems in place to help alert the population in advance of a flood. Dry riverbeds can channel water long distances and create dangerous flood waves, due to the ground being too dry to quickly absorb the water and the lack of plant life to slow the water’s course. Even deserts are not immune to flash flooding. A similar situation occurred in Rapid City, South Dakota, in 1972 when 237 people were killed.

In mountainous regions the rainfall can run down a steep mountain and pick up so much speed that it becomes a dangerous wave moving too fast for people to escape. The roofs, sidewalks, and roads of a city create dangerous amounts of runoff water during big storms, and this runoff can easily become a flash flood if an adequate storm sewer system is not in place. Urbanization is also an important cause of flash floods. Factors such as rainfall intensity and duration, as well as regional topography, can all contribute to a flash flood situation.

Violent Weather: Tornadoes

If a new mesocyclone develops, the cycle may begin again, generating a new tornado, and in some cases there may be 2 or more funnels touching the earth at any one time. As the first mesocyclone and associated tornado dissipate, the storm’s inflow is concentrated into a new area closer to the center of the storm. As the tornado enters the dissipating stage, its associated mesocyclone often weakens as well, as the rear flank downdraft cuts off the air flow powering it.

As the mesocyclone nears the ground, a visible funnel appears from the base of the storm clouds. This downdraft accelerates as it approaches the ground, and drags the rotating mesocyclone towards the ground with it. As rainfall in the storm increases, it drags with it an area of quickly descending air known as the rear flank downdraft. The life cycle of a tornado begins when a strong thunderstorm develops a rotating mesocyclone high up in the atmosphere.

Tornadoes have been observed on every continent on earth except Antarctica, the majority the world’s tornadoes occur in the United States and in particular Tornado Alley. Some tornadoes can have winds of more than 280mph, can be more than a mile across, and stay on the ground for tens of miles. Most tornadoes have winds of 100mph or less, are approximately 90 meters wide, and travel a few miles before fizzling out.

Tornadoes typically have a visible funnel, with the narrow end touching the surface of the earth. Tornadoes are defined as an aggressively rotating column of air which is in contact with both a cloud base and the earth.

Violent Weather: Hurricanes

Those caught up in a hurricane know only too well when the eye is above them, and although it can buy a bit of valuable time to move, help, or rescue victims, many often describe this moment as a deafening silence. There is an eerie silence within this eye and often clear blue skies and light winds can be usual. A characteristic of a hurricane is the eye and the eye of the storm can be anything from 4 to 25 miles in diameter. The condensation releases latent heat and this heat then powers the hurricane.

Moisture then condenses, clouds are formed, and the rains begin. As this warm air rises around the storms center, it cools. Therefore, the perfect conditions for a hurricane to form are basically warm water and humid air. Hurricanes occur over oceans where the water is 27°C (80°F) or above, and the air has to also be extremely humid and thick. Katrina, by the way, sustained winds of up to 140 mph.

In order to reach hurricane status it has to have sustainable winds exceeding 74 miles per hour. But a hurricane is not just any tropical storm. Well, without going into to much meteorological detail, a hurricane is basically a tropical storm so therefore can only be found in the tropics, namely the Southern Atlantic Ocean, Caribbean Sea, Gulf of Mexico, and in the eastern Pacific Ocean. So just what are hurricanes and why do they occur in certain parts of the world and not others? It’s not the purpose of this short piece to look for someone or something to blame, as lessons have probably already been learnt from the powers that be, but I just hope that the United States governments and responsible departments do everything in their power to ensure such a catastrophe, as was caused by Katrina, never happens again.

Hurricanes can be highly destructive to say the least. Depending which part of the world you come, from you may here about natures ravaging winds being called tropical cyclones or typhoons, but where I come from in the USA, we know them as hurricanes.