Hurricanes, Typhoons and Tropical Cyclones are one of the same and the name indicates where they occur. Hurricanes are found in the Atlantic and north eastern Pacific, Typhoons in the north western Pacific Ocean and Cyclones in the south pacific or Indian Ocean. A hurricane is a low pressure system which has organised thunderstorms but doesn’t have a frontal weather system. There are several sub categories defined as follows. If the sustained surface wind speed is less than 39 mph this is a tropical depression. If the sustained surface speed is greater than 39 mph it is a tropical storm. Once the speed reaches 74mph it is classed as a hurricane. The strength of the hurricane is measured by the Saffir-Simpson Hurricane Wind Scale and has a rating from one to five. The scale to the below shows the wind speeds, category, Storm surge and potential damage.

Hurricanes form the Atlantic Basin, Caribbean Sea Gulf of Mexico and the eastern Pacific Ocean. They may also form in the central North Pacific Ocean. There’s a six year rotating list of names used to identity the storms. The Hurricane season starts from June the 1st and ends of November the 30th although Hurricanes have occurred outside these times. There isn’t a season for Typhoons as these can form in the North Western Pacific at any time. The Tropical Cyclone in the Indian ocean runs from April to December. This is in fact two peaks as there is very little activity between July and August. Hurricanes form over the sea when warm wet air rises forming Thunderstorms and this also creates a low pressure area near the sea surface. As more warm air rises this causes the pressure to decrease at high latitudes. The warm air is under high pressure than the cold air so moves towards the space occupied by the colder low pressure air. Effectively the Low pressure sucks warm air in from the surroundings. Air rotates rotates round the centre of the low pressure at increasing speeds as air is ejected from the top of the storm and the pressure decreases in the eye of the storm. In the centre of the hurricane is the eye. The eye is often clear due to cold descending. Below from the BBC is a cross section of a Hurricane. Inside a Hurricane there will be heavy rain strong winds, Thunderstorms, and Tornado’s. Intense Hurricanes often go through what is called an eye wall replacement. This tends to be in Hurricanes of category 3 and above. The eye wall contracts or if it’s already sufficiently small, some of the outer rain bands may strengthen and organize into a ring of thunderstorms forming an outer eye wall. This slowly moves inward and robs the inner eye wall of its needed moisture and angular momentum. Since the strongest winds are in a cyclone's eye wall, the tropical cyclone usually weakens during this phase, as the inner wall is "choked" by the outer wall. Eventually the outer eye wall replaces the inner one completely, and the storm may re-intensify. A hurricane may fail in the process or try several times before it successfully completes. Eye wall replacement may occur several times during a lifetime of very strong Hurricane. The picture opposite is of hurricane Katrina from nasa. Note the well defined clear eye wall. The following is the typical life time of a Hurricane. Tropical disturbance or wave which is a organised area of Thunderstorms. In the Atlantic they form of the African west coast and have their origin believe or not in the Sahara desert. These waves move west across the Atlantic. The next stage is the Tropical Depression. The weather thunderstorms develop a closed area of low pressure. If the Storm keeps getting stronger it will become a Tropical storm and is given a name. Any further strengthening it will become a Hurricane. The Hurricane will weaken once it reaches unfavourable conditions. When the wind speeds drop below 74 mph t will become a tropical storm. When the wind falls 39 mph it will become a tropical depression. When Hurricanes move over land due to friction will rapidly decline in strength. However if the land mass is small enough and they move back over warm water they may regain strengthen. When Hurricanes move over cold water they will again lose strength as they have lost one of main sources of energy. Again if they move back over warm water they may regain strength. Dry air will also weaken Hurricanes and if it is persistent the Hurricane dissipate. Shear also will destroy hurricanes and any hurricanes entering an area of high level of Shear they will quickly decline in strength. Hurricanes don’t happen in the UK. Although we may experience Hurricane gusts or sustained winds at hurricane force they will not be hurricanes due to having a full system of weather fronts. We often see the end of hurricanes which have been absorbed into another low system as they reach more northern waters. These will bring warm temperatures heavy rain and strong winds.

Hurricanes, Typhoons and Tropical Cyclones are one of the same and the name indicates where they occur. Hurricanes are found in the Atlantic and north eastern Pacific, Typhoons in the north western Pacific Ocean and Cyclones in the south pacific or Indian Ocean. A hurricane is a low pressure system which has organised thunderstorms but doesn’t have a frontal weather system. There are several sub categories defined as follows. If the sustained surface wind speed is less than 39 mph this is a tropical depression. If the sustained surface speed is greater than 39 mph it is a tropical storm. Once the speed reaches 74mph it is classed as a hurricane. The strength of the hurricane is measured by the Saffir-Simpson Hurricane Wind Scale and has a rating from one to five. The scale to the below shows the wind speeds, category, Storm surge and potential damage.

Hurricanes form the Atlantic Basin, Caribbean Sea Gulf of Mexico and the eastern Pacific Ocean. They may also form in the central North Pacific Ocean. There’s a six year rotating list of names used to identity the storms. The Hurricane season starts from June the 1st and ends of November the 30th although Hurricanes have occurred outside these times. There isn’t a season for Typhoons as these can form in the North Western Pacific at any time. The Tropical Cyclone in the Indian ocean runs from April to December. This is in fact two peaks as there is very little activity between July and August. Hurricanes form over the sea when warm wet air rises forming Thunderstorms and this also creates a low pressure area near the sea surface. As more warm air rises this causes the pressure to decrease at high latitudes. The warm air is under high pressure than the cold air so moves towards the space occupied by the colder low pressure air. Effectively the Low pressure sucks warm air in from the surroundings. Air rotates rotates round the centre of the low pressure at increasing speeds as air is ejected from the top of the storm and the pressure decreases in the eye of the storm. In the centre of the hurricane is the eye. The eye is often clear due to cold descending. Below from the BBC is a cross section of a Hurricane. Inside a Hurricane there will be heavy rain strong winds, Thunderstorms, and Tornado’s. Intense Hurricanes often go through what is called an eye wall replacement. This tends to be in Hurricanes of category 3 and above. The eye wall contracts or if it’s already sufficiently small, some of the outer rain bands may strengthen and organize into a ring of thunderstorms forming an outer eye wall. This slowly moves inward and robs the inner eye wall of its needed moisture and angular momentum. Since the strongest winds are in a cyclone's eye wall, the tropical cyclone usually weakens during this phase, as the inner wall is "choked" by the outer wall. Eventually the outer eye wall replaces the inner one completely, and the storm may re-intensify. A hurricane may fail in the process or try several times before it successfully completes. Eye wall replacement may occur several times during a lifetime of very strong Hurricane. The picture opposite is of hurricane Katrina from nasa. Note the well defined clear eye wall. The following is the typical life time of a Hurricane. Tropical disturbance or wave which is a organised area of Thunderstorms. In the Atlantic they form of the African west coast and have their origin believe or not in the Sahara desert. These waves move west across the Atlantic. The next stage is the Tropical Depression. The weather thunderstorms develop a closed area of low pressure. If the Storm keeps getting stronger it will become a Tropical storm and is given a name. Any further strengthening it will become a Hurricane. The Hurricane will weaken once it reaches unfavourable conditions. When the wind speeds drop below 74 mph t will become a tropical storm. When the wind falls 39 mph it will become a tropical depression. When Hurricanes move over land due to friction will rapidly decline in strength. However if the land mass is small enough and they move back over warm water they may regain strengthen. When Hurricanes move over cold water they will again lose strength as they have lost one of main sources of energy. Again if they move back over warm water they may regain strength. Dry air will also weaken Hurricanes and if it is persistent the Hurricane dissipate. Shear also will destroy hurricanes and any hurricanes entering an area of high level of Shear they will quickly decline in strength. Hurricanes don’t happen in the UK. Although we may experience Hurricane gusts or sustained winds at hurricane force they will not be hurricanes due to having a full system of weather fronts. We often see the end of hurricanes which have been absorbed into another low system as they reach more northern waters. These will bring warm temperatures heavy rain and strong winds.