METEOROLOGY FOR EVERYONE

Prepared by: Dr. Ahmet KILIÇ

SEVERE WEATHER PHENOMENON
   
HAIL

 
THUNDERSTORM

 

 

 

Hazardous weather can take many different forms: heat waves, blizzards, tornadoes, hurricanes, floods, ice storms, and fog, to name just a few. Moreover, weather is a contributor to other disasters like avalanches, mudslides, fires, and crop failures. Since weather is global, it can be hazardous virtually anywhere.

LIGHTNING AND LIGHTNING STROKES
WHEN LIGHTNING STRIKES ?
HOW TO AVOID BEING STRUCK BY LIGHTNING ?
TORNADO
WATER SPOUTS
HURRICANE
 

HAIL

Hail is a large frozen raindrop produced by intense thunderstorms, some thunderstorms provide environment where snow and rain can coexist. Hail forms when strong currents of rising air, known as updrafts, carry water droplets above the freezing level in thunderstorms and the water freezes into ice. Hail often melts before it reaches the ground, but in some cases ice chunks the size of softballs pound the countryside.

 

 

  1. Updraft lifts water droplets above freezing level. Ice chunks grow until hailstone is heavy enough to fall.

  2. A stronger updraft keeps hail aloft longer, allowing bigger hailstones to form.

 
As the snowflakes fall, liquid water freezes onto them forming ice pellets that continue to grow as more and more droplets are accumulated.

 

 

A 15-cm diameter hail
 

 

THUNDERSTORM

A rain or snow shower in which there is lightning. Thunder is always caused by lightning. In general, the upward and downward winds, updrafts and downdrafts, in thunderstorms are more violent than those in ordinary showers.

 

What goes on in thunderstorm ?

  1. Cloud formed in rising air spreads out at storm’s top to form the “anvil”.
  2. Rising warm, humid air feeds the thunderstorm. Rain-cooled air falls. Falling air can reach the ground as a cooling breeze or damaging wind blast.
  3. Electrical charges build up, causing lightning. Shock waves caused by lightning become sound waves we hear as thunder. Some storms produce heavy rain.

   

 

Several thunderstorms moving along a single line can create a dangerous situation. A storm hits a location then additional storms follow. This cycle then repeats. Each storm may dump heavy rain on the region leading to the potential of flooding.
 
 

 

1.Some storm in one place and winds aloft push them out along the same path.

2.One after another, storms move over the same area dumping heavy rain.
 

Thunderstorms always include lightning followed by its noisy companion- thunder. A thunderstorm often lasts for less then an hour but it produces the most dramatic type of weather. The key ingredient that defines a thunderstorm is lightning. Since lightning creates thunder, a storm with lightning is called a thunderstorm. Thunderstorms come in all shapes and sizes with some cells only a few miles in diameter and some clusters of storms.

When a streak of lightning flashes across the sky, a crack of thunder is often heard several seconds later. Thunder happens because lightning heats the air to more than 30, 000 degrees Celsius which is 5 times hotter than the Sun's surface, causing the air to expand. As this air cools, it begins to contract. This quick expansion and contraction of air around the lightning starts air molecules moving back and forth, making sound waves, which we hear as thunder.

 

1.Small hail usually melts before reaching ground, stiff breeze does very little or no damage.

2. Hail’s diameter reaches 2 cm or larger and winds 105 KPH or greater can do extensive damage.
 

Micro Bursts

Thunderstorms contain several hazards to aviation, but few are as dramatic as microbursts. Microbursts are very concentrated bursts of air that blast down from thunderstorms. Microbursts have caused several plane crashes and are sometimes mistaken for tornadoes. New radars and pilot training have reduced the danger in recent years.

 

1. Air cools rapidly, dry air enters thunder-storm and is cooled by rain, forming a chunk of very cool air.

2. Microburst forms, cool air plunges down-ward and has caused planes crash.

 

 

LIGHTNING  AND LIGHTNING STROKES

Lightning occurs when thunderstorms concentrate positive electrical charges in the upper part of cumulonimbus clouds and negative charges in the lower part. When the difference in the charge between the top and bottom of the storm clouds become great enough to overcome air resistance, a sudden and violent electrical discharge occurs in the form of a lightning strike or stroke. Although this lasts for only millionths of a second, the temperature of the stroke rises to 28, 000 degrees Celsius, which causes the flash and the thunderclap.

 

How does it occour ?

 

  1. Electrons, which have negative charge, begin zigzagging downward.

  2. As the stepped leader nears the ground, it draws a streamer of positive charge upward.

  3. As the leader and the streamer come together, powerful electric current begins flowing.

  4. Intense wave of positive charge, a return stroke, travels upward at 100 000 kilometres per second

      
 

WHEN LIGHTNING STRIKES

You can work out how far away the thunderstorm is like this: As soon as you see the lightning, start counting the seconds. Stop when you hear the thunder, and divide the number you have counted by three. The answer you get tells you roughly how far you are, in kilometres, from the thunderstorm. lightning injuries are not the same as electrical shocks. For one thing, the contact voltage of a typical industrial electrical shock is 20 to 63 kilovolts, while a lightning strike delivers about 300 kilovolts. Industrial shocks rarely last longer than half a second (500 milliseconds) because a circuit breaker opens or the person is thrown far from the live conductor. Lightning strikes have an even shorter duration, only lasting up to a few milliseconds. Both industrial shock and lightning victims may be injured from falling down or being thrown, and the leading cause of immediate death for both is cardiac or cardiopulmonary arrest.

 

HOW TO AVOID BEING STRUCK BY LIGHTNING ?

Seek a safe shelter immediately! If you're unable to find shelter in a building or residence that is equipped with a lightning protection system, it is  suggested the following safety guidelines:

Indoors

►Stand clear from windows, doors and electrical appliances.

►Unplug appliances well before a storm nears - never during.

►Avoid contact with piping including sinks, baths and faucets.

►Do not use the telephone except for emergencies.


Outdoors
►Look for a shelter equipped with a lightning protection system like those found at golf courses, public parks and pools.

►If you're caught outside and unprotected:

►Get in a hard topped car.

►Never use a tree as a shelter.

►Avoid areas that are higher than the surrounding landscape.

►Keep away from metal objects including bikes, golf carts, fencing, machinery, etc.

►Avoid standing near tall objects.

►Immediately get out and away from pools, lakes, and other bodies of water.

►Spread out - don't stand in a crowd of people.

►If you feel a tingling sensation or your hair stands on end, lightning may be about to strike! Immediately crouch down and cover your ears. Do not lie down or place your hands on the ground.

 

TORNADO

 

A tornado is a violent, spinning column of air. From a distance, it looks like a cloud in the shape of an ice- cream cone. Tornadoes are most numerous and devastating in central, eastern and north- eastern USA, where an average of five per day are reported every May. They also occur in Australia (where there are around fifteen per year) and in UK, Italy, Japan and Central Asia.

 
   
  1. Tornado acts like a giant vacuum cleaner, sucking in air near the ground.
  2. Storm’s rotation twists tornado’s winds. Dust and debris darken the base of funnel.
  3. Large hail often falls near tornadoes.

 

Tornadoes usually form over land rather than over tropical oceans, when there is warm, moist air near the ground and cold, dry air above it. These conditions occur frequently in late spring and early summer over the Great Plains of the USA. As the sun heats the ground, the warm, moist air rises. As it does so, it cools and from large cumulonimbus clouds. The strength of the updraft produced by the rising air affects how much of the surrounding air is sucked into the bottom of the tornado. >> Dramatic shots like this one, of a tornado in the US Midwest, are taken by "tornado chasers", who enjoy the thrill of getting close to the violent storm.

 

Two things help the tornado to spin violently: Coriolis force and the jet stream. As the jet stream passes over the top of the storm, it adds an extra twist to the tornado.

 

Tornadoes have struck every U.S. state, including Alaska and Hawaii. But most tornadoes form in a belt from Nebraska southward through central Texas known as Tornado Alley and in the Southeast. Wind speeds in tornadoes can vary from 72 to almost 300 mph. Fortunately, only 2 percent of all tornadoes have winds greater than 200 mph.
WATERSPOUTS

Over the sea, waterspouts may form with wind speeds of up to 150 km/h, although 80 km/h is more normal. Waterspouts can cause damage if they cross land, but they never cause as much damage as tornadoes.  Here is an example of a waterspout.
 

 

HURRICANE

A hurricane is a large spinning wind system which develops over warm seas near the Equator. These areas are known as the tropics. Technically hurricanes are called tropical revolving storms, but they also have local names. They are called hurricanes when they occur over the Atlantic Ocean, typhoons in the Far East and cyclones in the Indian Ocean. So by definition, all are characterised by rotating winds, which exceed speeds of 120 km/h on the Beaufort Scale.

 
  1. Air sinking inside eye inhibits clouds and rain.
  2. Maximum wind found in eye wall at surface.
  3. Winds weaken with height and air spirals out-ward clockwise at high altitudes.

 
 

Hurricanes and other cyclones that form in the tropics during summer are very different from the extratropical storms that often form during winter even though both may produce very strong winds and possible flooding. The seven main differences between hurricanes and extratropical storms are:

 

Hurricanes and tropical systems have no fronts.

Hurricane winds weaken with height .

The centers of hurricanes are warmer than their surroundings .

Hurricanes and tropical systems form under weak high-altitude winds.

Air sinks at the center of a hurricane .

Hurricanes' main energy source is the latent heat of condensation.

Hurricanes weaken rapidly over land .