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Distance travelled ~ 698'568'800 km

iwitness image captured by Abby Thompson

iwitness image captured by Abby Thompson, Philippines

iwitness image captured by Abby Thompson, Philippines

iwitness image captured by Abby Thompson, Philippines

Nesat hit China earlier today and continues west:

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Distance travelled ~ 696'585'600 km

One of the things that amazes me about our planet is how it carries clues to its own past. It's a bit like a giant memory stick, the trick is find the right file. And today Helen Czerski is on the trail of one of these files, but it's not buried underground it's buried deep under water.

Helen is pushing the limits of her endurance, diving 40 metres below the waves, searching for evidence of what our world looked like 20,000 years ago. It might seem odd to be going deep under the water to unearth our climate past but you'd be surprised what you find down there.

Helen's diving the Great Blue Hole 60 miles off the coast of Belize, it's as the name suggest a great big round hole that goes down over 120 metres. It was once a cave but the roof collapsed leaving the deep blue hole. It's more than just a wonderful piece of natural architecture. It's also a window into our past. Because deep down in the hole, are clues to one of the most dramatic events in our planet's history.

It's a very tricky and technical dive as it's so deep, so Helen is accompanied by a very experienced dive team. Fortunately she's an experienced and highly qualified diver herself, so she's the prefect person for the job. Though she did have to learn how to use a special facemask designed for presenters to talk underwater. Even with all the experience on show it's still a daunting dive, but she's following in some famous footsteps. Jacques Costeau explored the Blue Hole back in 1970.

As she descends Helen must carefully monitor her buoyancy, at these depths she doesn't want to go up or down too quickly, that's not good news, plus the sheer walls of the hole will make the dive feel very enclosed.

At around 40 metres she will reach what she's looking for. Here the walls of the hole are cut away and there are some incredible rock formations several metres high. These formations are stalactites, which is kind of an odd thing to find, because if I remember my geology you shouldn't find stalactites in the ocean because they can't form underwater. Stalactites are created when mineral rich water drips from the roof of a cave over hundreds or even thousands of years, leaving behind mineral deposits. Over time these build up to create the beautiful structures. But they can only form on land so what are they doing 40 metres down the blue hole?

Here's what must have happened. At some point back in time, this cave must have been above sea level, which means that when these stalactites formed, the ocean must have been much lower than it is today. These stalactites not only show us that sea levels have changed they also can show us when.

When Cousteau explored the hole they brought up a broken stalactite and when they cut a cross-section they found a series of rings, a bit like tree rings. Each of the rings represents a period of growth when the stalactite was exposed to air. That growth would stop when it became submerged again. Cousteau's stalactite shows three growth stages, so it's a record of changing sea levels over time.

Scientists have precisely dated stalactites from the Blue Hole and by comparing stalactites from around the world with other data like Antarctic ice cores, they've built up a picture of changing sea levels dating back hundreds of thousands of years. What it reveals is that sea levels here in the Caribbean and across the world, have dramatically risen and fallen over time.

Just 20,000 years ago, the sea was an incredible 120 metres lower than it is today. That means almost the entire Blue Hole cave system would have been on dry land. But the world has a finite amount of water in it at any given time. So if that huge mass of water wasn't in the oceans just where was it? Well believe it or not it was on land, but not as water but as ice.

20,000 years ago the earth was gripped by an ice age.

How did this happen, well you'll find out when our series airs...in 2012 mind you :-)

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Distance travelled ~ 693'959'200 km

Here's an interesting video by Paul Gundersen, Met Office Chief Forecaster which tackles this question and explores how long we can expect to see the current warm conditions in the UK.

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Distance travelled ~ 693'316'000 km

Across Europe:

• The high pressure system is also expected to bring very warm conditions over northwest Europe, with highs of 30 Celsius expected in Biarritz, France, on Thursday while 21 Celsius can be expected in Gothenberg, Sweden.

Over the Americas:
• Many parts of Canada and northern USA are expected to have some very warm weather for the time of year, with the warmest conditions gradually extending E'wards by Wednesday.

• Cool, wet and windy conditions are expected to affect Rio de Janeiro, Brazil at the start of the week but conditions should improve again from midweek.

• Winter holds on in the south of South America and the Falklands at times this week - the maximum temperature at Port Stanley is expected to be close to zero Celsius on Thursday with heavy rain and strong winds.

Across Asia:
• There is better news for Pakistan where the weather is forecast to be generally much drier over much of the country following last weeks flooding - however it is expected to be notably cooler than normal through much of the week.

• Tropical Cyclone Nesat is moving steadily westwards across the South China Sea, perhaps intensifying into a Typhoon by Thursday. Nesat will bring torrential rain and severe gale force winds as it passes by.

More info on this image >

For Australasia:
• The cold and unsettled weather that has been affecting New Zealand looks set to be loosing its grip as an anticyclone area over the Tasman Sea extends a ridge of high pressure over the country bringing mostly fine weather.

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Distance travelled ~ 689'564'000 km

The UK experienced a relatively quiet week of weather compared to recent weeks, but tropical cyclones continued to affect some parts of the world.

Scotland and Northern Ireland saw the most unsettled conditions over the UK, with further spells of heavy rain and strong to gale force winds at times. Southwesterly winds peaked at 60mph on Wednesday over exposed coasts with 60mm of rain falling at Cluanie. Across England and Wales the weather settled down with temperatures reaching 21 Celsius in East Anglia on Tuesday and Kent on Wednesday before peaking at 23 Celsius at Gravesend in Kent on Sunday - a pre-cursor for warmer conditions this week.

Early in the week the Alps in Europe experienced very early season snowfalls with 50cm on fresh snow being reported quite widely.

Typhoon Roke brought torrential rain and winds of up to 100mph across central and western Japan as it made landfall on Wednesday. Evacuation advisories were issued to a total of 1.14 million people nationwide and auto giant Toyota said it was temporarily shutting 11 of its 15 Japanese plants, which lay in the path of the approaching storm.

While Hurricane Hilary didn't make landfall on Mexico's southwestern Pacific coast, it was a powerful Category 4 storm on Friday and brought strong winds, heavy rain and surf to the coast. Search teams recovered the bodies of three fishermen caught in the storm.

Heavy rain and flooding hit Orissa, Uttar Pradesh and Bihar in India over the weekend with two million people displaced, and with 80 people reported drowned. Cyclone Nesat threatens Luzon Island in the Philippines.

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Distance travelled ~ 691'332'800 km

On our journey around the Sun for 23 Degrees we are focussing on three main themes that control our climate and weather, Tilt, Orbit and Spin. And at the moment we are filming the show about Spin.

The team are on the road in Ecuador. They have gone to the Ecuador rainforest to learn how solar energy powers a power circulation system in the atmosphere that dictates the climate in bands around the world. Kate is also going to drive along the equator at around 1060 miles an hour. Well not quite - her car's going 60 but the planet at the equator is spinning at 1000mph, so for a few moments she's probably the fastest person on the planet.

The next stop after the heat of South America is the Bay of Fundy in Canada. Fundy has the highest tidal range in the world and Kate and the team are going to witness it first hand.

From there it's down to Bermuda to go snorkelling to learn about our planets spin , nice work if you can get it.

One of the things I find fascinating about our planet is that it carries a record of its own history written in its rocks. Some of this history is obvious - you can't miss the impact of giant craters blasted out by asteroid strikes. But some are less obvious - unless you know where to look. Kate's studying corals as these tiny creatures hold the secret to our distant past - and how fast our planet once spun.

Every day corals lays down growth rings of limestone and these daily growth rings build up to create an annual growth ring [a bit like a tree ring]. If you count the daily rings you get 365 days a year, which is what you'd expect.

Image credit Owen Sherwood

But if you look at 400 million year old corals you get a very different picture. They have rings just like the modern coral but they are a little bit narrower. But what's really surprising is that if you count the daily growth rings you don't find 365 you find 410. That means that when this coral was alive 400 million years ago the world was a very different place.

But however you measure it - in hours or days the Earths' orbit around the Sun always takes the same amount of time. A year is always constant. The only explanation for the ancient corals having 410 daily growth rings is that millions of years ago the days were shorter. So when this coral was in the oceans there were less hours in each day - in fact a day lasted just 21 hours. And for that to happen the Earth must have been spinning faster.

If we calculate back even further in time we find that around 4 billion years ago, when the Earth was still young, a day lasted just 6 hours. Which means the planet was spinning 4 times faster than today.

That's pretty wild - and we know that because of corals. Wonderful.

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Distance travelled ~ 683'292'800 km

We recently launched our September Equinox photo challenge with the question: How can you reflect the equinox in a photo?

A few people on Twitter suggested taking a snapshot of all points of the world at exactly 09:04 UTC and sending us a photo of them merged into one; which we just loved the sound of - but - we hadn't given you enough time. Surely to coordinate such a masterpiece 'alone', you would need to be everywhere at once (superman style stuff). Or have a camera positioned and ready at all points of the world, set to click simultaneously at 09.04 UTC (i'm certain they couldn't have meant a lone project). Well because we're a reasonable bunch over here at 23 Degrees, one location was definitely enough. And here's our top photos, enjoy. Roll on Autumn.

Reflections: A lone tree reflects upon the summer months past

Autumn sunshine through Forest trees

On the move: A flock of birds in the Summer sky

Last sunset of summer: Rail road tracks ablaze

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Distance travelled ~ 680'934'400 km

Radar image showing water vapour near Japan as Post tropical storm Roke moves North East into the Pacific. Great loop image showing the movement of Roke 21/22 september. https://www.ssd.noaa.gov/mtsat/flt/t2/loop-wv.html

Although Typhoon Roke was a smaller storm than Talas (which hit Japan early September), it was stronger in terms of wind strength. When Roke made landfall in the south coast of Japan, in Hamamatsu 14.00 JST 21 September, it reached speeds of 90kts ( 100 mph). Over the period of 48hours prior to Roke making landfall it dropped over in Tokushima. Japan received an average of over 400mm of rain, including Tokyo. Roke is currently moving .

Image captured by A.Wainwright

Image captured by A.Wainwright, Japan. "It was taken from my 4th floor balcony overlooking the tennis courts outside my apartment in Kawasaki City, Greater Tokyo during typhoon Roke, 21st. Sept. 2011"

Image captured by Aaron Robotham

Image captured by Aaron Robotham

The above photos captured by Dr Aaron S.G. Robotham of St. Andrew's University. The top image was taken "outside Shibuya station during our long walk home." The second image was outside Ebisu station in the taxi queue. We queued for a taxi for 1-1/2 hours but eventually gave up and decided to walk back to our hotel. We gave up using the umbrellas since they were just getting blown apart and we couldn't get any wetter."

More on this story: Typhoon Roke in pictures

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Distance travelled ~ 673'323'200 km

UK and world weather report

Last week brought typically varied conditions over the UK and while around the world tropical cyclones continued to dominate the headlines.

In the UK the week got off to a stormy start as post-tropical storm Katia made her presence felt particularly across the northern half of the UK. As forecast by the Met Office, a deep area of low pressure which contained post-tropical storm Katia reached the UK on Monday, bringing severe gales and heavy rain to Scotland, Northern England and Northern Ireland. Scotland and Northern Ireland bore the brunt of the storm, with widespread wind speeds of 60 - 70 mph and gusts of up to 98 mph in the most exposed mountainous areas. There was also heavy rain in parts of Scotland, which resulted in localised flooding in some areas of Central Scotland.

As post tropical storm Katia moved away and winds gradually eased we were left with a rather unsettled and autumnal feel to our weather. It remained breezy with further outbreaks of showery rain and blustery winds in the west, whilst further south and east there were brighter spells. The autumnal feel continued with temperatures falling into single figures overnight Wednesday into Thursday. Temperatures fell as low as 1.7 Celsius at Topcliffe and Exeter airport, and 0.8 Celsius at Redesdale camp.

Across the world flooding continued to dominate the weather - Pakistan's commercial capital, Karachi, has been paralysed by floods as torrential rain continues to lash southern Sindh province. Schools have shut down, many markets were forced to close and commuters had to abandon their vehicles as rain water flooded the streets.

The floods have come at a time when many parts of South Asia expect heavy rainfall as part of the region's summer monsoon, but it has been particularly heavy for the affected areas and it has come late in the season. Observations show there has been a series of low pressure systems passing over Pakistan from northern India over the past two weeks, with little respite in between. This has given no time for water to flow away or seep into the ground, causing a build up of floodwater.

The week ahead
• In the UK, we will see another mixed week with rain across southern parts of the UK through the first part of the week. Once this clears away midweek A northwest-southeast split developing, with the northwest often rather cool and breezy with showers and sunny spells. Further southeast, it should be mainly dry but rather cloudy, with nearer-normal temperatures.

• An intense NE Pacific storm looks set to bring a spell,of very wet and windy weather to NW parts of N America from Tuesday, peaking in intensity on Wednesday.

• Turning very unsettled over much of western Europe and the central Mediterranean.

• Colder than normal in parts of southern Chile and Argentina by mid-week as Antarctic air streams northwards. Risk of frost and snow over the higher ground.

Sonca stays in the Pacific but all eyes on Tropical Storm Roke
Tropical Storm Sonca is expected to turn north and track close to eastern Japan today before turning away east as it becomes absorbed into the mid-latitudes. The track should stay far enough E not to have significant impact over Japan.

Tropical Storm is potentially more dangerous. The track over the next few days brings it into the area between southern Japan and Taiwan. There is a strong signal for the track to then turn north and NE across the length of Japan later in the
week.

Image courtesy of Japan Meteorological Agency

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Astronaut photograph ISS015-E-10469, courtesy NASA/JSC

Distance travelled ~ 665'122'400 km

Autumn Equinox photo challenge:
On the journey around the Sun we are approaching another key moment in our celestial dance with our star. Next Friday September 23rd is the Autumn Equinox. Equinox means equal night, and that day Earth is in balance. There are approximately 12 hours of day and 12 hours of night. In a sense the planet is in neutral, but from that moment onward the northern hemisphere marches towards Autumn while the southern hemisphere approaches Spring. In the north days will be getting shorter and the Sun won't rise as high in the sky and it will gradually get colder.

To mark this moment we plan on featuring the best photos on our blog next week friday that reflect the Equinox. What we're looking for are shots that show the Sun and it's relationship to our planet and the journey into Autumn, or Spring if you live down-under. Let your imagination run wild. The more creative the better! Get those shutters snapping and see what you can capture.

To ensure they are considered for this special feature email them to 23degrees@bbc.co.uk, or add them to our or hashtag your photos with #bbc23degrees on twitter.

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Distance travelled ~ 659'976'800 km

Hurricane hunting was not supposed to be like this. The Sun was shining, there were butterflies everywhere, and there wasn't enough wind to blow out a candle on a birthday cake. On the plus side, we had to give ourselves top marks for trying and I didn't have to get drenched again.

Twenty four hours earlier, things had looked very different. We had been tracking several Atlantic storms, and finally Tropical Storm Nate was forecast to make landfall in the Gulf of Mexico as a hurricane. I've never paid that much attention to tropical storms in the past, but it turns out that storm-monitoring is surprisingly addictive. Tropical disturbances in the Atlantic often start out near the coast of Africa, and then they crawl across the ocean to the west, growing or petering out as they go. The storms move at about 15 mph, so they'd lose a race to any half-decent cyclist. That gives the nascent addict many happy days of monitoring storm strength and direction. There are also exciting milestones such as the day the storm is given its name, and most important of all, the day the maximum sustained winds first reach 74 mph and the storm is declared to have graduated to hurricane status. Most storms don't make it that far. If they drift too far north, they get broken up or run out of fuel, and they can be decapitated by high-level winds, never giving them a chance to grow.

Satellite image captured 09-sep-2011

Tropical Storm Nate was interesting because it had skipped the slog across the Atlantic ocean, and had instead formed entirely inside the Gulf of Mexico, stuck in the gap between the Yucatan and the rest of Mexico. It was pootling westwards at only 3 or 4 miles an hour, feeding off the nice warm bath it was trapped in, and forecast to hit the Mexican coastline near Veracruz as a category 2 hurricane. We thought that we finally had a winner, and off we went.

The five of us arrived in Veracruz in the dark, only 18 hours before the centre of the storm was due to hit the coastline. It was horribly hot and sticky, and the evening gloom made everything feel very ominous. The wind was picking up and we were excited and a bit nervous about what would happen in the morning.

What happened was that we learned that Tropical Storm Nate had apparently become "disorganized" overnight. I've got friends like that, but I wasn't expecting it from a giant atmospheric whirlpool. Josh Wurman (our hurricane expert) inspected the satellite images on his computer screen and made "meh" noises whenever the director asked him where exactly the storm had gone.

This visible image from the GOES-13 satellite on Sept. 12 at 10:45 a.m. EDT shows Nate's remnant clouds southwestern Mexico and moving into the eastern Pacific Ocean. Credit: NASA/NOAA GOES Project

The tight spiral that we had seen the previous day had widened, split and was indeed looking pretty disorganized. It rained hard for a couple of hours that morning, so we did film some nasty weather, but soon the sun and the butterflies came out again. We stared at the flat calm ocean and wondered whether to blame the butterflies for flapping their wings.

In our absence, of course, the remnants of Hurricane Katia were passing over Scotland. The winds in Scotland this weekend reached twice the speeds we saw in Mexico. We are not bitter about this. Honest. We had all thought that filming a hurricane would be much easier than filming a tornado, just because hurricanes last for weeks and their tracks can now be predicted very accurately. But we learnt the hard way that the complications of our atmosphere are still not perfectly understood, and that even a large storm can vanish almost overnight if the conditions are right. But still, it's all part of experiencing the weather, and I'm actually quite glad that the town where we were was able to have a normal Monday morning, rather than dealing with the damage and flooding that a hurricane would have left behind.

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Distance travelled ~ 657'564'800 km

Image taken by Bob Johnson, Saskatoon Saskatchewan, Canada, September 9 2011 with a Canon 40D camera and Tokina fisheye lens. "All the Solar activity happening lately causing all the Auroras, even with a nearly Full Harvest Moon they came through."

To submit your images and video into 23 Degrees for a possible feature or for Friday's 'weekly roundup blog' - email them to 23degrees@bbc.co.uk or add them to the .

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Distance travelled ~ 657'404'000 km

Remnants of Katia hit UK but warnings now cancelled:

• In the UK, the gales and heavy rain resulting from the deep area of low pressure which contained post-tropical storm Katia will slowly ease across northern parts and a couple of fine, quiet days can be expected later in the week.

Image courtesy EUMETSAT. Latest satellite imagery. Central Europe. MET9 RGB-3-3-1 2011-09-13 10.00 UTC

• Northwestern Europe will also be very unsettled as the low pressure area moves across Scandinavia. Some areas can expect to have unusually strong winds with southern Scandinavia, Denmark and far north of Germany most at risk of severe gale/storm force winds.

Tropical storm watch for Bermuda whilst Nate dissipates:
• Tropical Storm is expected to move towards the Bahamas during the first half of the week before turning northeast and heading out over the open waters of the Atlantic.

Image courtesy of National Hurricane Center/NOAA. The Bermuda weather service has issued a Tropical storm watch for Bermuda. Maria is moving toward the North-NorthWest near 5 mph.

• Meanwhile Tropical Storm Nate has dissipated over Mexico but will continue to give heavy rains for a time.

Possible tropical formations:

• There is the risk of further tropical cyclone formation later in the week to the northeast of Taiwan and southwest of Japan.

• Potential for tropical storm formation in Arabian Sea with heavy rainfall risk adjacent land areas of Pakistan.

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Distance travelled ~ 655'367'200 km

Last week brought typically varied conditions over the UK and while around the world tropical cyclones continued to dominate the headlines.

It was unsettled across many parts of the UK last week. In a theme that would be repeated later in the week strong winds caused some disruption on Tuesday as an Atlantic depression crossed northern Scotland. Winds reached 80 miles per hour at the Needles on the Isle of Wight as ferries were cancelled and trees uprooted in Dorset, while over 80 mm of rain fell in Snowdonia.

From midweek temperatures started to rise in eastern areas as warm air was drawn north from the continent. Highs of 24.8 Celsius were recorded at Wainfleet in Lincolnshire on Friday and 25.0 Celsuis at Leconfield, North Humberside and Weyborne in north Norfolk on Saturday.

The wind started to pick up once again on Sunday with gales developing across Scotland and cloud and rain spread from the Atlantic. This was the pre-cursor to today's particularly stormy weather as a deep area of low pressure which contained post-tropical storm Katia brought gales and heavy rain to parts of the UK. The strongest winds were recorded in exposed areas of Northern Ireland, Southern Scotland, North Wales and parts of Northern England with gusts of 76 miles per hour at Malin Head and 73 miles per hour in Glasgow.

Across the world tropical cyclones dominated the weather last week - Typhoon Talas struck the west of Japan early in the week, Tropical Depression Kulpa gave heavy rain and flooding over southern South Korea. Tropical Storm Lee drenched New York leading to complete loss of a days play at the US Open Tennis, Tropical Storm Maria passed by the islands of the northeast Carribean, Tropical Storm Nate affected the southwest of the Gulf of Mexico leading to the closure of Mexico's two main crude oil export ports.

Typhoon Talas nears the southern islands of Japan in this NASA MODIS image from September 2, 2011

Typhoon Talas was the most destructive typhoon to hit Japan since 2004. The typhoon swept through the west of the country on Sunday, dumping heavy rain and bringing winds of up to 68 miles per hour. Entire villages have been flooded, with bridges and houses destroyed.

Tropical Storm Lee caused catastrophic flooding on the US coast, flooding streets, homes and businesses, reportedly leaving eight people dead and causing more than 130,000 people to be moved for their own safety. The storm struck Maryland to New England and dropped up to a foot of rain outside Harrisburg, Pennsylvania, which declared a state of emergency. Eight feet of water covered the river towns of Tunkhannock and Shickshinney. Elsewhere, the strong winds spread wildfires that destroyed homes and killed two people in Texas.

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Distance travelled ~ 649'203'200 km

(After almost getting killed flying into hurricane Hugo as a flight meteorologist for Hurricane Hunters, Dr. Jeff Masters left to pursue a Ph.D in air pollution meteorology from the University of Michigan. While working on his Ph.D he cofounded the very popular weather internet service 'The Weather Underground'. Here he shares his thoughts on the current tropical storm developments, just as the 23 Degrees team touches down in Mexico to film Nate.)

Tropical Storm is pounding the Lesser Antilles Islands with heavy rains and strong gusty winds. Maria's 45 mph winds are expected to steadily increase for the next five days as the storm takes advantage of warm ocean temperatures near 29.5°C and light winds aloft that put little shear on the storm's core. By Monday, Maria is expected to be a Category 1 hurricane, and may intensify to a Category 3 hurricane with 115 mph winds by Wednesday. Maria is headed northwest at 15 mph, and will pass through the Virgin Islands and skirt the eastern side of Puerto Rico on Saturday. The storm is expected to dump 100 to 200 mm of rain on the islands, with isolated amounts as high as 250 mm. Maria will turn to the north early next week and miss the U.S., but may be a threat to Canada late in the week.

A Hurricane Watch has been posted along the Mexican coast from Tampico to
Veracruz for the arrival of . Nate is nearly stationary in the Bay of Campeche, but is expected to move steadily westwards on Saturday and Sunday, and make landfall on Sunday as a strong tropical storm with 70 mph winds between Tampico and Veracruz. The primary danger from Nate will be heavy rains; 100 - 150 mm of rain is expected in coastal Mexico, with isolated amounts as high as 300 mm. Unfortunately, Nate will be too far south to being
rains to Texas, which is enduring its worst drought in recorded history.

Figure 1. True-color MODIS image of Tropical Storm Nate taken at 12:45 pm EDT Friday, September 9, 2011. At the time, Nate was a tropical storm with 50 mph winds. Image credit:

Hurricane is a few hundred kilometers south of Newfoundland, Canada, and is accelerating east-northeastward towards the open Atlantic. The hurricane is expected to pass over much colder waters of 18°C on Saturday afternoon. A hurricane cannot survive in waters less than about 25°C, and the cold waters will force Katia to transition into a powerful extratropical storm. Extratropical Storm Katia will continue east-northeastward towards Europe, and on Monday, the storm will pass very close to northern British Isles. The offshore waters of Northern Ireland and Western Scotland can expect storm-force winds of 50 - 65 mph as Katia roars past to the north. Hurricanes that transition to powerful extratropical storms hit the British Isles several times per decade, on average. In September 2006, two major hurricanes named Gordon and Helene transitioned to strong extratropical storms that hit the British Isles. Only once since accurate records began in 1851 has an actual hurricane with full tropical characteristics hit Europe. This happened on September 16, 1961, when Category 1 hit northwestern Ireland. Wind gusts reached 106 mph at Ballykelly and 104 mph at Tiree and Snaefill, and coastal radio stations reported the airwaves were jammed with calls for help from small ships and fishing craft. Eleven people were killed and 50 injured in the storm.

Figure 2. Image of Hurricane Katia taken from the International Space Station at 15:00 GMT September 9, 2011, by astronaut . At the time, Katia was a Category 1 hurricane with 85 mph winds. Long Island, New York is visible
at the lower left.

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Distance travelled ~ 647'488'000 km

Hurricane Katia, currently in the western Atlantic is set to steam due east towards the UK and is expected to . With it will come the risk of severe gales and heavy rain to parts of the UK. The strength and depth of this September storm is quite unusual, but similar storms that originated as hurricanes have affected the UK in the last 20 years several times.

Hurricane Bill - 2009

You only have to look back as far as 2009 to find a storm that crossed the Atlantic. Hurricane Bill formed on August 15th and reached the UK as a post tropical storm on August 25th, bringing severe gales and heavy rain two days after being downgraded from a hurricane to a tropical storm.

Hurricane Alberto, Gordon and Helene - 2006

In 2006, three post tropical storms reached the UK. Alberto, Gordon and Helene all brought wet and windy weather to the UK. Alberto combined with a cold front to the west of the UK whilst Gordon brought record warm temperatures as tropical air pushed north across the UK, but also strong winds that brought down power lines in Northern Ireland.

Hurricane Isaac and Leslie - 2000

These two hurricanes both affected the British Isles in the year 2000.

Hurricane Karl - 1998

Hurricane Karl made its way to southern Britain in 1998.

Hurricane Lili - 1996

Perhaps the most similar storm to Katia was in 1996 when the remains of hurricane Lili pushed across the UK just one day after being downgraded from a hurricane. The post tropical storm ran across Britain on 28th and 29th October. The storm brought gusts in excess of 90 mph, bringing widespread impacts across the UK and causing significant disruption.

Hurricane Katia - 2011

Katia is currently a category one hurricane off the east coast of the US and will run across the Atlantic through the weekend bringing the risk of severe gales and storm force winds in places later on Sunday and through Monday.

Although it is expected to be windy everywhere, it is uncertain as to exactly which parts of the country will see the very strongest winds and therefore you should stay up to date with .

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Distance travelled ~ 647'166'400 km

(Peter Gibbs is a Ö÷²¥´óÐã weather forecaster and a regular blogger for 23 Degrees. With all the current Atlantic hurricane activity, here Peter tackles some of the questions flying around as hurricane Katia makes it's way to the UK.)

"Do we get hurricanes in the UK?"

No, it's not possible.

"But what about the 1987 storm, wasn't that a hurricane?"

Well, it did have hurricane force winds, which was why it knocked down 15 million trees, but it wasn't a hurricane.

"How does that work, then?"

I've lost count of the number of times that I've had that conversation during my career, but it's a reasonable question and one that's worth exploring during this very active Atlantic hurricane season.

Katia moving toward the northeast over the open atlantic

Weakening is indicated since the hurricane is already reaching cooler waters and Katia is forecast to become post-tropical in about 36 hours.

Hurricanes are creatures of the tropics, they need the warmth and humidity of tropical seas to develop and survive. The core of the storm consists entirely of warm air and it's the release of latent heat as this air rises and condenses into clouds which gives the hurricane its power. It's a bit like a pan of water coming to the boil as you apply heat from below.

Once formed, a hurricane moves through the surrounding atmosphere like a cork floating down a stream, becoming almost a separate entity. The strongest winds form in the lowest layers of the storm, close to the storm's centre just outside the eye.

Move into temperate latitudes and weather works differently. Extratropical storms (more commonly known as mid-latitude depressions) form over much colder waters and get their energy instead from the contrast between masses of warm and cold air. The bigger the contrast, the stronger the storm. Cold air makes up the core, digging under the warmer air mass and lifting it until it forms clouds and rain along a front.

The storm becomes an integral part of the atmospheric circulation, like an eddy in a river. Strongest winds are found high up, in the form of the jetstream, at around 30,000ft while the strongest surface winds tend to occur at some distance from the storm's centre and are spread out over an elongated area. All very different to a hurricane.

Where it gets messy is when a hurricane heads out of the tropics and into higher, temperate latitudes. It goes through an identity crisis as the supply of warmth from below is cut off and cold air is drawn into the circulation, eventually emerging as an extratropical storm after a fuzzy intermediate stage.

Fortunately, the long sea track ensures that any ex-hurricanes reaching the UK have gone through full transition before they arrive. The different amounts of available energy mean that even the most powerful of extratropical storms would barely make it onto the bottom of the hurricane scale.

So that's how it works

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Distance travelled ~ 646'826'400 km

(Alex Deakin is a Ö÷²¥´óÐã weather forecaster and a keen sports fan. His previous post for 23 Degrees discussed the weather at the British Open. Here Alex explores how the weather will affect the start of the Rugby world cup in New Zealand, which kicked off earlier today)

Although it snowed heavily only last month in New Zealand further dumps of the white stuff are not expected as Spring kicks in for the start of the Rugby World Cup

Image courtesy of wikicommons

Being surrounded by water New Zealand, like the UK, has a mild climate for its latitude. The Islands have some of the best skiing in the southern hemisphere so they get some snow but that's thanks to the huge mountains. Snow at low levels is rare. When it snowed in August in Christchurch it was described as a once in 30 year event, so it's about as rare as a New Zealand rugby world cup win!

Another cold snap hit NZ at the start of Spring (Meteorologically speaking that's the start of September) when temperatures again dropped to freezing but now temperatures have climbed and this weekend looks fairly typical with some sunshine on Saturday and a more showery picture on Sunday. Temperatures look pretty average for the start of the tournament too, peaking in the mid to high teens.

As the tournament gets underway rain and wind will be the major weather players. Like the UK New Zealand regularly gets flown over by areas of low pressure or depressions in Spring and Autumn, these bring spells of rain and strong winds.

A strong wind will have an impact of the kicking game (penalties, conversions etc). The stadia play a big part here too with some designed to shelter the playing surface (some of the grounds being used have a roof) but other, older ones likely to create their own swirling winds and interesting micro-climates.

Rugby players are well known to be a tough bunch and a bit of rain won't hurt, however a wet pitch and a slippery ball will have an impact. A wet game is usually a low scoring game, and with so many of the group games expected to be rather one sided this could be a bit of a leveller. i.e. a shock result is more likely if its raining.

So the weather will have an impact on the rugby world cup, but if it's a typical Spring in New Zealand we shouldn't expect any snow. For updates on the weather for the games try , here you can catch my old colleague Dan Corbett (yes that's where he's gone) giving video forecasts.

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Distance travelled ~ 639'876'800 km

Visible satellite images indicate that the shower activity associated with a low pressure area centred about 680 miles west-southwest of the southernmost Cape verde islands, is gradually becoming better organised and a tropical depression could form later today or wednesday.

NOAA

Chances are that this system will move toward the west or west-northwest at about 15mph and has a high chance..........70 percent.........of becoming a tropical cyclone during the next 48 hours according to the National Hurricane Center.

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Distance travelled ~ 637'304'000 km

Across the UK

Much of last week saw large amounts of cloud and fairly quite conditions through across the UK. However, temperatures increased with the arrival of September and there was some very warm weather across parts of the country towards the end of the week with temperatures peaking at 27 Celsius in eastern England during Friday and Saturday.

At the same time, wet weather moved in across some northern and western regions, with the rain turning heavy and persistent on western hills, especially over the Lake District and Snowdonia where over 50mm fell in places.

Around the world

In Nigeria there were reports that flash floods during the last week across the south west of the country killed at least 102 people and left 15-hundred displaced. According to the Nigerian Red Cross the major flood hit hardest in Oyo state's capital of Ibadan where heavy rains made a local damn overflow, sending water through the settlements surrounding the city and many homes were washed away.

Surging flood waters in northern and eastern have affected 5.2 million people. Many have been forced from their homes as swollen rivers wash away roads and make rescue work difficult, government and aid officials said on Friday. Monsoon rains swept the heavily-populated states of Uttar Pradesh, Bihar and Assam. 70,000 people were homeless and around 300,500 hectares of mainly rice paddy had been destroyed. In the most severely affected state of Uttar Pradesh in north central India, 125 people have died and around 2 million have been affected, according to a government official.

At least 19 people were killed and more than 50 are missing after powerful Typhoon Talas crossed western Japan. The storm brought heavy rain and winds of up to 68 miles an hour after making landfall on Shikoku Island on Saturday with flooding and landslides.

The week ahead...

Image © Met office

• Typhoon Talas is moving generally in a northerly direction and then dissipating in east Russia near Vladivostok. The typhoon is likely to give very heavy rain and possible flash flooding in this part of Russia and then risk heavy rain over wider area to the north and east.

• Warm or very warm weather in south east Australia at first but turning cool and unsettled by Tuesday.

• Heavy monsoon rains in parts of Pakistan and western India until tomorrow.

Latest satellite image © India Meteorological department

• Potential for tropical storm development in the Arabian Sea over the next few days threatens land areas in southern Pakistan, though main risk likely to be exceptional rainfall and flooding.

• Hurricane Katia remains over the open North Atlantic Ocean and has the potential to become a Category 3 storm during this week, although currently expected to remain clear of land for the next five days.

• Unsettled and locally wet and very windy conditions in parts of north east Canada and north east USA until Wednesday.

• Cold, windy and wet with hill snow in south west Chile at times this week.

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Distance travelled ~ 626'155'200 km

Last week we all watched Hurricane Irene march up the east coast of the US, a gigantic atmospheric whirlpool that caused a huge amount of damage. Out in the mid-Atlantic, tropical storm Katia has just graduated to being Hurricane Katia on her way west, and there are likely to be more as the season goes on. These storms start as isolated disorganized thunderstorms, but as they grow, they also start to rotate.

(This GOES-13 satellite image is of Hurricane Irene just 28 minutes before the storm made landfall in New York City. The image shows Irene's huge cloud cover blanketing New England, New York and over Toronto, Canada. Shadows in Irene's clouds indicate the bands of thunderstorms that surrounded the storm. Credit NASA/NOAA GOES project.

Spinning tops and sycamore seeds, wind turbines and the wheels on the bus... lots of things in our world go round and round. But all of those examples are solid objects with an obvious central axis to rotate around. A hurricane is a pattern of flowing air and there's no visible container to hold that air together. The air on one side of it is not attached to the air on the other side of it. Even an average hurricane can be 1400 km across, covering 13 degrees of latitude. What could possibly be happening to make that much of our atmosphere spin in such a coordinated way?

The short answer is that a hurricane spins because our planet spins, and the link is a funny thing called the Coriolis force. It's funny because it's not actually a force at all, but a consequence of the fact that we're going round and round in circles while we're looking at the weather. Ours is an odd point of view, but since we're stuck with it, science came up with the idea of this extra force to compensate. It's a neat psychological trick - instead of accepting that we're the ones doing odd things, we claim that we're normal and the weather is behaving oddly by adding in the Coriolis force. So what is this mysterious force?

Imagine that you're on a roundabout. You want to play catch with a friend, but they don't like roundabouts so they're standing on the ground a few metres away. The roundabout is going round anticlockwise and you are standing on the edge facing outwards. Next time you pass your friend you throw the ball to them, and as soon as it's in the air, it travels in a straight line. You keep rotating around, so it looks to you as though the ball is mysteriously curving to the right. It isn't, it's just that you're rotating to the left. This magic force that seems to have taken over the ball from your point of view is called the Coriolis force. Try it, next time you're at a children's playground. You'll find that whatever direction you throw the ball in, if you're on a roundabout going anticlockwise, the ball always looks as though it's curving mysteriously to the right. And since in the northern hemisphere, Earth is rotating anticlockwise beneath us, anything that moves always ends up slightly to the right of where you think it should be.

Let's get back to that hurricane. Its centre is a huge area of low pressure, so all the air is trying to rush from the outside where the pressure is high towards the middle. But as it moves inwards, all that air is curving to the right because of the Coriolis force. The last part of the puzzle is something you can see in action on our roads all the time. Next time you're at a roundabout, stop and look.

These forces are relatively small, and to see their effects you need a very large weather system. So the spin of a hurricane is just a reminder that we travel 17 thousand miles every single day in the UK, as we spin around the Earth's axis. I feel dizzy just thinking about it...

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