Humberto is the first hurricane in a quiet season so far

11 09 2013

The Atlantic hurricane season is usually reaching its peak during the first half of September, but so far the season has been very quiet.

Humberto has just become the first hurricane of the Atlantic season. In the last 70 years only one season has seen the first hurricane form later.


There are various ways of measuring tropical storm activity including the number of storms, the number of hurricanes and something called the Accumulated Cyclone Energy (ACE) Index. The latter measure takes into account both the strength and duration of storms and so gives a good indication of how active a season it has been. Whilst there have been eight tropical storms in the Atlantic so far, many have been weak and short-lived and thus the ACE Index is only running at 27% of where it would be in an average season at this time in the year.

It is not only the Atlantic which is seeing low levels of tropical storm activity. ACE Index across the whole northern hemisphere is running at 42% of average for this point in the season. There have only been two major typhoons in the west Pacific, which is an unusually low number.

It is worth noting that a quiet start to the Atlantic season does not necessarily mean the season will remain quiet. For example, in 2001 there had only been five tropical storms to this point in the season with just one becoming a hurricane. However, the remainder of the season saw another 10 tropical storms of which eight became hurricanes.

Official forecasts of current Atlantic tropical storms are provided by the National Hurricane Center. Visit our tropical cyclone pages for more information or follow @metofficestorms on Twitter.

Met Office predicts above average Atlantic hurricane season

20 05 2013

The Met Office Atlantic tropical storm forecast for 2013 is for 14 tropical storms between June and November, with a 70% chance that the number will be in the range 10 to 18.

The long-term average over the period 1980–2010 is 12 tropical storms. The last three hurricane seasons have all recorded above average tropical storm activity.

The most likely Accumulated Cyclone Energy (ACE) index — a measure of the strength and duration of storms over the season — is 130, with a 70% chance that the index will be in the range 76 to 184; the 1980–2010 average ACE index is 104.

For the first time this year, the Met Office are also releasing a forecast of the number of hurricanes (storms with winds of at least 74 mph), following the success of experimental forecasts produced throughout the 2012 hurricane season.

Between June and November 2013 the best estimate is for 9 hurricanes, with a 70% chance that the number will be in the range 4 to 14; the 1980–2010 average is 6 hurricanes.

Overall, these indicators point to a preference for above-average activity this year.

The evolution of the El Niño/La Niña cycle over the next few months is likely to play a large part in the North Atlantic hurricane season.

Joanne Camp, climate scientist at the Met Office, said: “El Niño conditions in the Pacific can hinder the development of tropical storms in the Atlantic whereas La Niña conditions can enhance tropical storm activity, so how these conditions develop will be important for the storm season ahead.”

The tropical storm forecast is produced using the Met Office’s new seasonal prediction system GloSea5. The model has higher resolution than its predecessor, with better representation of the complex physical processes that cause tropical storms and hurricanes. The forecast also uses information from the seasonal prediction system of the European Centre for Medium-Range Weather Forecasts (ECMWF).

For regular updates on tropical cyclones worldwide follow @metofficestorms on Twitter.

A challenging forecast for the weekend

20 09 2012

This weekend’s weather forecast is proving more challenging than usual as we see signs of much more unsettled conditions developing for all parts of the UK over the next few days.

Much of the UK is set to have a fine and dry weekend with sunny spells, light winds and temperatures in the mid to high teens Celsius after some cold nights.

There is now increasing confidence that southern parts of the UK (roughly south of a line from south Wales to Ipswich) will see wet and windy weather on Sunday.

This wet and windy weather is not the remnants of tropical storm Nadine – this stays close to the Azores. However, we are expecting a new area of low pressure to develop to the west of Iberia on Saturday which will move northeast, pulling some warm air from Nadine with it. It is this that would bring wet and windy weather to the far south of England and Wales for Sunday and other parts of the UK next week.

The challenge for forecasters is to pinpoint how this low pressure area will move. The weather forecast models available to Met Office forecasters are giving slightly different answers to this problem. As Anthony Astbury, Met Office Deputy Chief Forecaster, explains: “One model brings the low over Brittany giving rain and gales in the south of England, while another brings the low further west, with the risk of wet and windy weather for southwestern England and south Wales.”

There is still uncertainty about how the low pressure area will develop and move on Monday, and therefore which areas of the UK will see the worst of the weather early next week.

However, this heralds a spell of very unsettled weather for the whole of the UK for next week, with all parts seeing unsettled and windy conditions with showers or longer spells of rain.

Keep up to date with the forecast and warnings for the latest information.

Tropical Storm Isaac heads toward New Orleans

28 08 2012

At 1500 UK time on Tuesday 28 August, Tropical Storm Isaac was located about 150 km southeast of the Louisiana coast and heading northwest at about 15 km per hour.  Mean wind speeds of 70 mph at the surface  have been observed by the United States National Hurricane Center aircraft. These mean wind speeds maintain Isaac as a tropical storm, just below hurricane strength which requires mean wind speeds of over 74 mph.

Satellite image showing Tropical Storm Isaac

Satellite image showing Tropical Storm Isaac (Source: NOAA)

Although Isaac is expected to make landfall within the next 12 to 18 hours, there is still time for Isaac to intensify and become a hurricane. The official United States National Hurricane Center (NHC) forecast track predicts an intensification of this system into a category 1 hurricane as it continues its track northwestwards over the very warm Gulf of Mexico with winds increasing to around 80 mph when Isaac makes landfall at around 0600 UK time on Wednesday morning. 

Official National Hurricane Centre Forecast for Isaac on Tuesday 28th August

Official National Hurricane Centre Forecast for Isaac on Tuesday 28th August

The latest forecast from the NHC suggests that Isaac will pass just to the west of New Orleans, though there is still some uncertainty over the exact track and intensity of the storm and the impact of Isaac will be felt quite widely along the Gulf coast region.

Although hurricane Isaac is not expected to be as intense as hurricane Katrina which caused massive damage to New Orleans 7 years ago, there is still a risk of extreme rainfall with up to 500 mm in 48 hours resulting in flash flooding and storm surge along the coast, in addition to the damaging winds.  As Isaac moves inland it will weaken, but is still likely to result in torrential rain, perhaps with tornados or very squally winds.  There is a risk of flooding over the lower Mississippi valley region for the next few days.

You can find out more about Tropical Cyclones on our website or read our case study on Hurricane Katrina on the Met Office Education website. 

Tropical Strom Isaac likely to make landfall as Cat 2 Hurricane

27 08 2012

Tropical Strom Isaac was located about 120km WSW of Key West at 4am (UK time) on Monday 27 August, and continues to move west north west. Mean wind speeds of 65 mph have been observed by the United States National Hurricane Center aircraft. These mean wind speeds maintain Isaac as a tropical storm, just below hurricane strength which requires mean wind speeds of over 74 mph.

Satellite image and forecast track of Tropical Storm Isaac from Met Office StormTracker

Satellite image and forecast track of Tropical Storm Isaac from Met Office StormTracker

The official United States National Hurricane Center (NHC) forecast track predicts an intensification of this system into a hurricane as it passes across the very warm Gulf of Mexico by midnight tonight with a high risk that the Hurricane will be a Category 2 storm, with winds of around 100 mph when it makes landfall along the US Gulf coastline during the early hours on Wednesday morning.

Official National Hurricane Center forecast for Tropical Storm Isaac

Official National Hurricane Center forecast for Tropical Storm Isaac

The NHC notes that there is still a great deal of forecast uncertainty in exactly where Isaac will make landfall, with locations ranging from the Texas/Louisiana border eastward to the Alabama/Florida border. The most likely forecast track has the eye of the storm making landfall close to New Orleans, but the NHC state that it is important not to focus on the exact forecast track due to forecast uncertainties and the fact that significant hazards extend well away from the centre.

Therefore, there is a high risk of very rough, chaotic seas and hurricane force winds across the Gulf of Mexico impacting marine traffic and oil and gas production during the next few days. This will be followed by torrential rain, potentially as much as 500mm in 48 hours, causing flash flooding. There is also the risk of embedded tornados and more general hurricane force winds, with a storm surge and over topping waves along the Gulf coast from Alabama to central Louisiana, with New Orleans at an increased risk of being impacted than previously expected.

The Met Office’s StormTracker allows you to monitor all named storms around  the globe to evaluate risk and enables the comparison of past and present storms. It can be used with the official warnings and guidance from the National Hurricane Center and other Regional Specialised Meteorological Centres (RSMCs) who have responsibility for the issue of tropical cyclone warnings.

Tropical storms update – Damrey, Saola, Ernesto and Haikui

3 08 2012

As reported in yesterday’s blog, the tropical west Pacific has been active recently with typhoons Saola and Damrey both causing disruption in parts of south-east Asia. Saola weakened to a tropical storm before making landfall over the Fujian province of China. Huge amounts of rainfall were recorded in Taiwan and mainland China from the storm. Taichung on Taiwan recorded 316 mm (12.4”) rain in just 12 hours yesterday.

Meanwhile just a few hours earlier Tropical Storm Damrey made landfall near the border of Jiangsu and Handong provinces of China. As a more compact system, it did not produce as much rain as Saola, but still packed winds of over 60 mph as it made landfall.

As expected, the high activity in the west Pacific continues. Tropical Storm Haikui has formed and is expected to develop into a large typhoon as it moves towards south-east Asia. Behind this it is likely that yet another tropical storm will form in the next couple of days.

Tropical Storm Ernesto

Meanwhile in the Atlantic the tropical depression which developed on Wednesday has strengthened into Tropical Storm Ernesto. It is still fairly disorganised, but bringing stormy conditions to the Caribbean islands of St. Lucia and St. Vincent having already passed over Barbados. There is still uncertainty as to how much Ernesto will strengthen, but it is not impossible it could become a hurricane as it continues its track westwards through the warm waters of the Caribbean Sea in the coming days.

For more information visit our tropical cyclone web pages or follow @metofficestorms on Twitter.

Tropical storm season heading towards its peak

2 08 2012

August and September are the months when tropical cyclone activity in the northern hemisphere reaches its peak. As August begins there are currently several active tropical cyclones and possibly more to come.

Typhoon Saola formed in the west Pacific and gave a glancing blow to the northern Philippines. Over 900 mm rain in three days were recorded in Baguio. There were reports of flooding across northern Luzon and a number of fatalities. Saola has now slowly moved on towards Taiwan dumping similar amounts of rain and causing flooding and mudslides. It is expected to move onwards to Fujian province of China in the next day or so.

Meanwhile to the north of Saola the more compact Typhoon Damrey has tracked just to the south of Kyushu in south-west Japan. This area is still recovering from the devastating floods of last month. The typhoon has tracked across the Yellow Sea and is set to make landfall over the Handong province of China just south of the large city of Qingdao.

These two typhoons are part of a large complex area of disturbed weather covering much of the tropical western Pacific. Another storm is forming out at sea and latest forecast suggest it could track close to southern Japan in a few days time. There are even suggestions that yet another storm could develop a few days later in the open waters of the west Pacific.

Meanwhile in the Atlantic after an active start to the season, July was completely stormless. August has started with the formation of a depression which looks set to track through the Leeward Islands and into the Caribbean Sea. However, there is a high degree of uncertainty as to whether this depression will undergo significant strengthening. El Niño conditions are starting to develop as predicted by longer range forecasts for the tropics from the Met Office, which acts to suppress Atlantic tropical storm activity by making atmospheric conditions unfavourable. It is possible that conditions may be hostile towards storm development in this region in the next few days, but it is by no means certain.

The Met Office seasonal forecast for Atlantic tropical storm activity issued in May predicted a near-average season with the most likely number of storms in the June to November period being 10. Since June just two tropical storms have occurred so far in this region.

For more information see our tropical cyclones web pages or follow @metofficestorms on Twitter.

Does the jet stream affect hurricanes?

16 07 2012

Many news and weather articles, including our own blog, have reported recently that the UK’s wet summer is caused by the jet stream being situated further south than usual for this time of year.

However, some have questioned whether there is a link between this and the hurricane activity seen so far in the Atlantic.

So how is the Atlantic hurricane season shaping up and has it been influenced by the weather at higher latitudes?

Atlantic hurricane season so far

The Atlantic hurricane season officially started on 1 June, but in 2012 it began early with two tropical storms, Alberto and Beryl, forming in May.

After a break of almost three weeks there were two more storms, Chris and Debby, in the latter part of June, with Chris becoming the first hurricane of the season.

Since then there has been another lull of almost three weeks in Atlantic tropical storm activity.

Has the Atlantic hurricane season been unusual?

In mid-July it is far too soon to make judgements about how unusual a hurricane season is likely to be based on activity so far. However, it was certainly unusual to see four tropical storms before the end of June as this has never been observed before in over 150 years of records.

The recent quiet spell in Atlantic hurricane activity is by no means unusual. Atlantic hurricane seasons are often characterised by bursts of activity followed by quiet spells.

The peak of activity usually runs from the second half of August through to October. Even in some years which turned out to be very active, early season activity was low.

For example, by this time in 2010 and 2011 there had been just one tropical storm. Each of these seasons ended up yielding a total of 19 storms.

Is the jet stream involved?

The jet stream which affects UK weather is much further north than where the majority of tropical storms develop and hence has no direct impact on their formation.

However, once a tropical storm develops and starts to move to higher latitudes the jet stream can influence where it ends up. For example, in September 2011 as Hurricane Katia moved northwards in the Atlantic it met a powerful part of the jet stream and was swept eastwards as a strong ‘post-tropical’ storm which brought stormy conditions to the northern UK.

Will it be an active hurricane season?

The Met Office seasonal forecast for Atlantic tropical storm activity issued in May predicted a near-average season with the most likely number of storms in the June to November period being 10. Since June two tropical storms have occurred so far (the two May storms fall outside of this prediction period).

One of the major influences on the season’s activity includes the existence of La Niña or El Niño conditions (natural cycles which affect sea temperatures in the equatorial east Pacific).

Having just come out of an extended period of La Niña conditions, forecasts suggests an El Niño could develop before the end of the current hurricane season.

This would suppress hurricane activity in the Atlantic by disrupting the airflow over the regions where they usually develop.

However, it is worth remembering that it is 20 years since the quiet El Niño influenced Atlantic hurricane season of 1992. Despite being a quiet season overall, it still managed to spawn the deadly and powerful Hurricane Andrew which brought devastation to parts of Miami in Florida.

For more information on tropical cyclones worldwide visit our web pages or follow @metofficestorms on Twitter.

Typhoon Roke brings heavy rain and strong winds to Japan

21 09 2011

Typhoon Roke made landfall at about 0600 UTC 21 September near Hamamatsu on the south coast of Japan. Winds were estimated to be close to 100 mph near the typhoon centre and the lowest central pressure recorded was 952mb.

Rainbands extended along way ahead of the typhoon as it approached and 598mm (23.5″) rain were recorded at Tokushima (west of the landfall point) in the 48 hours prior to the centre reaching Japan. Rain and the strongest winds have now cleared from southern and western parts of Japan.

As of 1200 UTC Japan Meteorological Agency still classified Roke as a typhoon centred over eastern parts of Honshu a short distance south-west of Fukushima. Heavy rain is continuing in this region and will do so for a few more hours before clearing. It is likely to be downgraded to a tropical storm soon.

The centre of the storm is currently emerging back out over the ocean east of northern Honshu. It is expected to accelerate north-east and becomes a strong post-tropical storm in the north Pacific Ocean.

Radar imagery of Typhoon Roke

Met Office updates on Twitter: @metofficestorms

Latest update as post-tropical storm Katia reaches the UK

12 09 2011

The deep area of low pressure which contains post-tropical storm Katia  was, at 9 am, centred approximately 200 miles northwest of Sligo, Ireland with a central pressure of 966 hpa. This can be seen on the satellite image below – the swirl of cloud to the west of Scotland/north of Northern Ireland is the low pressure system which was Katia.

Winds are strengthening,  with a recent gusts of up to 82 mph at Capel Curig in the mountains of North Wales. Elsewhere winds are widely gusting to 40 to 50 mph, with further strengthening expected across some northern areas through today.

The swirl of cloud to the west of Scotland/north of Northern Ireland is the low pressure system which was Katia.

Infra-red satellite image of storm affecting the UK at 9 am on Monday 12th September Source: EUMETSAT/Met Office

For the latest update for your area visit our severe weather warnings page. We’ll also be keeping you up to date on Twitter and Facebook. You may also like to follow Met Office storms on Twitter, who are tracking the progress of Katia and other tropical storms, hurricanes, typhoons and cyclones.



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