N?o s?o só folhas e galhos: estudo revela que troncos de árvores abrigam trilh?o de microrganismos e funcionam como ecossistemas vivos
Why_has_the_Atlantic_hurricane_season_gone_remarkably_quiet_-_BBC_Weather.txt
Why has the Atlantic hurricane season gone 'remarkably' quiet?resultado mega sena 28/03/2018Image source, NOAA / NESDISImage caption, Satellite view of the Atlantic on the peak of the hurricane season...and there are no tropical storms or hurriances to be seenBySimon King Lead Weather PresenterPublished10 September 202518 CommentsIt's the peak of the Atlantic hurricane season but - very unusually - there are currently no tropical storms or hurricanes.The last named tropical storm - Fernand - weakened in the mid-Atlantic on 28 August.And there are no storms predicted by the National Hurricane Centre over the next week, despite forecasts for a busier than average season, which runs from 1 June to 30 November.However, forecasters suggest the current lull in activity will be short-lived with a flurry of storms to come later in the season.Image source, NOAA / NHCImage caption, The peak in the Atlantic hurricane season comes on 10 September according to climatological records from NOAAStatistically 10 September marks the peak in the Atlantic hurricane season and in an 'average' season we would have expected to have had eight named storms, three of which would have become hurricanes and one a major hurricane.So far in 2025, there have been six named storms, one of which became major hurricane Erin in mid-August.With no activity expected in the next seven days, this will have been only the second year since 1950 where there will be no named storm from the end of August to mid-September.This quieter period may come as a surprise considering the pre-season forecasts all suggested an 'above average' season.Dr Philip Klotzbach, senior meteorologist at Colorado State University (CSU), said: "This pronounced quiet period is quite remarkable at this time of year given that it coincides with the climatological peak of the Atlantic hurricane season."'Above average' Atlantic hurricane season forecast for 2025Published22 MayBusy hurricane season expected as forecasters fear Trump cutsPublished22 MayMultiple factors for lullIn a special report from CSU addressing the quiet spell, there are three main factors explaining why the season has become so quiet.The first is that the tropical Atlantic has become 'dry and stable'. This means there isn't enough moisture and atmospheric instability for big thunderstorms to develop and sustain themselves to grow into tropical cyclones. Another factor is that there has been an increase in the wind shear - changes in wind speed and direction with height - over the western Atlantic.This wind shear is important in tropical storm development. If it is too high it can rip apart developing storms.And lastly, there hasn't been a supply of increased thunderstorm activity in west Africa, which would normally travel west into the Atlantic where they can be the starting mechanism for developing tropical cyclones.We've had lulls in hurricane activity before. Indeed, there are similarities to only last year.In June and July 2024, Hurricane Beryl devastated parts of the Caribbean and broke records as the earliest storm ever to reach Category 5 - an intensity usually seen during peak season.It then became unusually quiet with no activity between 21 August and 9 September, the most prolonged lull in hurricane numbers for around 50 years.Activity dramatically increased in late September with multiple major hurricanes until the end of the season in November.Category 5 hurricane Milton at the start of October tied as the most intense hurricane to form in the Gulf of Mexico causing $34 billion in damage and led to 45 deaths.2024 Atlantic hurricane season breaks records despite unexpected lullImage source, GettyImage caption, Major Hurricane Milton made landfall in Florida in October 2024 bringing widespread damageActivity expected to ramp upDr Klotzbach said that "we still anticipate the season picking up given that conditions appear to become more favourable later in September".Instability over the tropical Atlantic is expected to increase - a trigger needed for air to rise high into the atmosphere - thereby allowing big storms to grow.The wind shear that has been restricting storms recently is also expected to weaken.Atlantic sea surface temperatures remain above average for the time of year, and in excess of 27C - a key temperature for the formation of tropical storms and hurricanes in the main development areas.So the ingredients to produce and help sustain tropical storms and hurricanes will slowly come back together.And forecasters are still expecting the 2025 season to be 'above average' with 16 named storms, eight of which will be hurricanes with three of those major, according to CSU.After this quiet spell we still need to be prepared for activity to ramp up quite quickly between now and the end of November.More on this storyIs climate change making hurricanes and typhoons worse?Published16 December 2024What has changed 20 years on from Hurricane Katrina?Published29 AugustComments can not be loadedTo load Comments you need to enable JavaScript in your browserView comments | 18
