Hurricanes and tornadoes are both stormy atmospheric systems that have the potential of causing destruction. They are caused due to instability in atmospheric conditions. According to the region and severity of stormy conditions, these storms may be referred to as typhoons or tropical cyclones.
edit Definitions of Hurricanes and Tornados
A hurricane is a type of tropical cyclone with sustained winds that exceed 74 mph and accompanied by rain, thunder and lightning.
A tornado is defined in the dictionary as "a rotating column of air ranging in width from a few yards to more than a mile and whirling at destructively high speeds, usually accompanied by a funnel-shaped downward extension of a cumulonimbus cloud". The wind speeds of tornados range from 40 mph to 110 mph, span about 75 m across and can travel a few miles. In extreme cases, tornados have also reached a speed of 300 mph.
edit Geographical location
Hurricanes are found near the tropical zone, over warm waters in the Atlantic and Pacific ocean. Tornados have been spotted in all continents except Antarctica though a large number have been seen in the United States.
edit Characteristics and types
Hurricanes develop over ocean water warmer than 26.5 °Celsius and heat and moisture from the ocean forms the basis of this type of storm. Thus, hurricanes weaken rapidly over land and over cold waters, which cannot provide enough heat or moisture to sustain this storm. The low pressure centres of hurricanes are known as the "eye" and are warmer than their surrounding areas. The eye is surrounded by strong winds and rain and this area is called the "eye wall". Hurricanes have no fronts. The hurricane season peaks from the middle of August to late October in the Atlantic Ocean.
There are many shapes and sizes of tornadoes. Tornadoes look like big funnels low in height with a cylindrical profile are referred to as stovepipe tornados, whereas those that are like large wedges stuck to the ground are called wedges. Tornadoes can also be a small swirl of dust close to the ground and not easily identifiable. Similarly tornadoes can assume twisted and rope-like shape that narrow and extends from the clouds down in a long and narrow tube like fashion; these are referred to as "rope tornado". Tornadoes with more than one vortex can swirl around one common centre and appear as a single funnel. The types of tornadoes include multiple vortex, waterspout, gustnado, dare devil, fire whirls and steam devils.
The color of the tornadoes varies according to the region they occur in and depends on the color of the soil and debris collected. For instance, tornadoes with little debris appear gray or white, tornadoes in the Great Plain have a reddish hue because if the color of the soil, and tornadoes that occur in the mountainous snow-covered region turn white.
edit Vertical Shear
Tornadoes require substantial vertical shear of the horizontal winds (i.e. change of wind speed and/or direction with height); tropical cyclones (including hurricanes) require very low values (less than 10 m/s [20 kt, 23 mph]) of tropospheric vertical shear in order to form and grow.
edit Temperature Gradient
Tornadoes are produced in regions of large temperature gradient, while tropical cyclones are generated in regions of near zero horizontal temperature gradient. Therefore tornadoes typically occur over land (where the sun's heat can produce the required temperature gradient) while tropical cyclones are an oceanic phenomenon. Hurricanes lose momentum after land fall because the required moisture is not available on land.
Hurricanes and Tornadoes turn clockwise in the Southern hemisphere and counterclockwise in the northern hemisphere.
edit Life span
The lifespan of a tropical cyclone (hurricane) is in days while a tornado lasts only a few minutes.
The diameter of a tornado is hundreds of meters. It is powered by one convective storm. On the other hand hurricanes span hundreds of kilometers and comprise several convective storms.
edit Intensity and Damage
Hurricanes are classified into five categories according to the Saffir-Simpson scale. The wind speed and intensity of damage increases as from Category 1 to category 5. Category 1 hurricanes cause minimal damage with wind speeds of 74-95 miles per hour (mph), category 2 cause moderate damage with wind speeds varying from 96-110 mph, category 3 cause extensive damage, with wind speeds of 111-130 mph, category 4 causes extreme damage with wind speeds of 131-155 mph, and category 5 has catastrophic damage with wind speeds of over 155 mph.
The intensity of tornadoes can also vary in intensity those with a longer track being stronger. The scale used for rating the strength of tornadoes is called the Fujita (F), Enhanced Fujita (EF), and TORRO (T) Scale. The range varies from F0, EF0 or T0 for minimal damage (damages trees but not buildings) up to F5, EF5 or T11 for vast degree of damage (buildings and skyscrapers end up getting damaged).In the United States, maximum tornadoes (80%) fall into the EF0 and EF1 (T0 to T3) category and less than 1% are violent (EF4, T8 or more).
In the Atlantic ocean, hurricanes occur about five or six times a year. The Caribbean is a focal area for many hurricanes. A series of low pressure systems develop off the West coast of Africa and make their way across the Atlantic Ocean. While most of these systems do not become tropical storms, some do. The Caribbean hurricane season is from June through November, with the majority of hurricanes occurring during August and September. On average around 9 tropical storms form each year, with 5 reaching hurricane strength. According to the National Hurricane Center 385 hurricanes occurred in the Caribbean between 1494 and 1900.
The United States records about 1,200 tornadoes per year, whereas the Netherlands records the highest number of tornadoes per area compared to other countries. Other countries that have frequent occurrence of tornadoes include South Africa, Paraguay, parts of Argentina, and parts of Europe, Australia and New Zealand. Tornadoes occur commonly in spring and the fall season and are less common in winters.
Hurricanes and tornadoes are detected by Pulse-Doppler radar, photogrametry, and ground swirl patterns.
edit Recent News
edit Hurricane News
- National Oceanic and Atmospheric Administration - The difference between a tropical cyclone and tornado
- Hurricane Tracker - Wall Street Journal
- All hurricane names since 1950