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Distance travelled ~ 876'413'600 km

The depression is expected to bring gales and heavy rain from the west for Thursday.

Snow is likely for a time on Thursday morning across parts of central and northern Scotland, particularly affecting higher ground, but with some slushy deposits locally to lower levels, and all parts of the UK will have heavy rain for a time during the day.

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But the main feature of this depression is the gale to storm force winds it will bring. Gusts of 60 to 70 mph likely to become quite widespread across northern and central Britain, but 70 to 80 mph are expected across much of Scotland with 90mph gusts are possible in exposed places, particularly central and southern Scotland. Elsewhere across England and Wales the wind will gusts of 50-60 mph. ()

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As the storm passes through and moves away to the east of the UK on Friday north-westerly winds will bring in cold air which will see a drop in temperatures. This is expected to bring snow to northern and western parts of the UK, giving accumulations to low levels in the north. Accumulations will tend to be confined to higher ground across north Wales and much of northwest England. Untreated surfaces will also become icy at times. Other parts of the country will see a cold night on Friday with widespread frost.

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The forecast for the rest of the month is for the unsettled weather to continue, with spells of wet and windy weather interspersed with brighter, colder periods when we can expect to see frost and snow showers - the heaviest of any snowfalls are expected across higher ground from North Wales northwards, but we could occasionally see some snow cover at lower levels as well.

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Distance travelled ~ 853'365'600 km

UK and World weather report:

The UK's recent quiet weather took a dramatic turn last week as fog gave way to gales and heavy rain. The foggy start to the week, with visibility down to below 50m in places in the south and east on Monday and Tuesday.

Despite a colder night on Tuesday, with a minimum of - 2.3 °C and widespread ground frost across England and Wales, temperatures remained a little above normal throughout the week, with a high of 15.9 °C at Fyvie Castle in Aberdeenshire on Saturday.

On Thursday, a rapidly deepening area of low pressure moved past the north west of the UK, bringing severe gales over the far north west as well as persistent and increasingly heavy rain that continued into Friday and over the weekend.

Cassley in Sutherland recorded 66.6mm of rain in 12 hours, gales affected northern Scotland, peaking with a gust of 90mph at Fair Isle on Sunday morning. The storms left about 400 homes without power in Orkney, caused landslides, and A cargo ship sunk after reportedly being rolled over by a wave and breaking in two in the Irish Sea.

Elsewhere in the world, heavy rain is continuing to cause problems. In the Philippines, six people were killed in flash floods after continuous rains in the area caused local rivers to overflow. In Australia, floods have left thousands cut off in the town of Wee Waa in New South Wales. The town will only be accessible by boat and helicopter for at least a week.

Meanwhile, Mexico is suffering its worst drought in 70 years. Due to the lack of rainfall the government has forced been to supply water to nearly 2.5 million people across eight states.

The week ahead

UK:

• A very unsettled week for the whole country, with several deep depressions moving in off the Atlantic.

• Periods of heavy rain, especially in the west of Scotland, could cause some flooding problems. Also windy at times, with a continued risk of gales. There is risk of snow over the higher ground of northern Britain at times.

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Across the North America:

• A deep depression is moving eastward across Canada, bringing strong winds and snow to many areas.

By Tuesday, it is expected to lie over the Hudson Bay, with particularly windy conditions on its southern flank possibly affecting coastal Ontario, Manitoba and Quebec.

• Another depression, moving northwards towards the Great Lakes from the Gulf of Mexico over the next few days, will also bring heavy rain to places in between as it passes.

Across Africa:

• Cooler than average conditions extending from Saudi Arabia across Sudan, Chad and perhaps even reaching northern Nigeria. Conversely, warmer than average across much of Madagascar.

Across Asia:

• A spell of wet weather is expected for Saudi Arabia, Kuwait, Bahrain, Qatar and the northern Gulf on Monday and Tuesday. Rainfall totals of 40-60 mm are likely, with flash flooding a possibility. This is the first significant rainfall since the spring in this area. It is also unseasonably cold, both in this region and more widely across the Middle East.

• Some rather windy conditions likely for Oman, especially coastal regions and particularly later in the week, in association with a deep depression. This is also likely to impact on coastal parts of Karnataka, Kerala and Goa in India for the next day or two.

Across Australasia:

• Some large temperature variations across southern Australia this week, with south western parts going from cool to warm and south eastern areas swinging from warm to cool.

• Heavy rainfall is set to continue in Australia and Asia due to a La Nina pattern in the Pacific Ocean.

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d ~ 349'900'800 km : day 136

In Antarctica, it's getting colder. The sun last shone on the south pole in March, and the tilt of our planet means that each day complete darkness swallows up a bit more of the continent. Since there's no incoming energy from the sun, the land and the ocean can only cool down. And it's at this time of year in the south that an innocuous little fact, one that most of us take entirely for granted, quietly makes the huge Southern Ocean a much more hospitable place for almost all marine life.

Ice floats. Icebergs, ice cubes, ice on a freezing river... they all float. And this is weird, because when most substances freeze they get more dense and so the bits that are frozen solid will sink to the bottom of the unfrozen liquid. Water has the quirk that when it freezes, the molecules form a rigid crystal structure with gaps between the atoms that weren't there before. The consequence is that ice is less dense than the water it froze from, and so it floats.

If frozen water sank, just imagine what would happen. Ponds, lakes and the oceans would freeze from the bottom up. There would be nowhere warm and protected under the ice for living things to hide, and the water would just keep freezing upwards until there was no liquid left. All water-based life would have much more of a struggle to survive.

As it is, ice actually acts as an insulating lid, keeping the water below it warm. Heat is lost from the liquid water surface about a hundred times faster than from the ice surface, so less heat is lost overall from an ice-covered ocean. At this time of year, sea ice is growing rapidly in the Antarctic, and it's as if the ocean is responding to the cold by growing itself a blanket. Every year in the Antarctic, of sea ice is formed, and each summer almost all of it melts.

This ice is also a bit like a floating pantry. Lots of algae and krill live on the bottom of it, and these are an important source of food for fish and other Antarctic life.

Sea ice is amazing stuff. It's different to icebergs - those are huge lumps of ice that have fallen off glaciers into the ocean. Sea ice is the ocean freezing at its surface, thickening into large mobile slabs as the winter season goes on. My favourite thing about this ice is that even though the ocean is salty, sea ice isn't. As the water freezes, the salt molecules are squeezed out, first into little brine pockets and later (especially if the ice lasts more than one year) into the ocean. You could hack off a bit of multi-year sea ice, stick it in your drink and never notice its salty origins.

So when you look at ice cubes jostling around in your glass this summer, think about the ice on the other side of the world, jostling around Antarctica in the dark. It's keeping a huge amount of extra heat in the Southern Ocean until the sun comes back, and all just because it floats.

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d ~ 246'988'800 km: day 96

As we say goodbye to winter and enjoy the start of spring there's one thing here in the Northern Hemisphere that most of us don't notice, but never the less we should be thankful for. Our winter ends sooner than it does in the southern hemisphere - 4 days shorter in fact. Which is good news for us because we get four less days of colder weather but bad news for people down-under who get four days more.

It's all down to our orbit around the sun. We can't really see it, but it's not a perfect circle, it's an ellipse with the sun slightly offset in the middle. This was first explained by Johannes Kepler in 1609 in his first law of planetary motion.

The part of the orbit when the earth is closest to the sun is called Perihelion and currently it occurs during the Northern Hemisphere winter. At Perihelion the earth is 5 million kilometres closer to the sun than in July when it's at it's furthest.

So why does that have an effect on the length of the winter. Well that's down to Keplers second law. This states that a line joining a planet and the Sun, sweeps out equal areas during equal intervals of time. Ok that's the scientific description of the law but what does that mean when it comes to our journey around the Sun? Put simply the law explains that when the planet is closer to the sun it moves faster round its orbit, and when it is further away it moves slower.

So during Perihelion and the northern hemisphere winter the planet is moving faster making the season shorter. The southern hemisphere winter is four days longer because it occurs at aphelion when the planet is further away from the sun and therefore moving slower.

But there's a flip side to this because that means that the Northern Hemisphere summer is four days longer than the southern hemisphere summer. Which helps explain why July is our planet's warmest month, At that point the Northern continents that are pointing towards the sun get a few days more to bake in the sun and raise the average temperature of the entire globe.

Most of the other planets in our solar system have orbits that are more elliptical than Earth's. The dwarf planet Pluto's orbit is the most eccentric of all and is so lopsided that at its Perihelion it is actually closer to the sun than Neptune.

Mars's orbit is not as elliptical as Pluto but a lot more than Earth's. At Perihelion Mars is 43.5 million kilometres closer to the sun than at Aphelion and receives 40 percent more sunlight, with an abundant rise in temperatures of around15-20 degrees. The larger degree of eccentricity in the orbit also affects the lengths of the seasons because the planet moves slower at Aphelion, as it is further away from the sun. As a result the Northern Hemisphere summer is not four days longer than the northern winter, but 25 days longer. This has a big impact on the Red Planet's seasons. Northern summers are long and cool while the winters are short and mild. Conversely for the southern hemisphere, summer is short and relatively hot while winter is long and cold.

So we should be quite glad that our orbit is only slightly elliptical - we barely notice our shorter winter, but if we were on Mars we certainly would.

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d ~ 108'057'600 km in Earth's orbit

We are 42 days into our journey around the Sun and already so much has taken place. Every step of the way the 23 Degrees team will be charting the progress of the Earth's orbit around the Sun. We orbit inside the atmosphere of the Sun so the impact of space weather on our planet is also of particular interest to us. As part of the process we will be providing regular roundups on the conversations on the blogosphere, YouTube and Twitter. What have you been talking about this week?

For us the top story this week has been the three dimensional images captured by NASA's Solar TErrestrial RElations Observatory (STEREO) satellites giving us a full 360 view of the Sun. This new 3 dimensional view will be of huge significance to scientists' better understanding of solar physics and therefore improve space weather forecasting.

What has made an impact on you this week?

For some winter is slowly winding down - and the arrival of spring is a hot topic, or has spring already sprung? Ö÷²¥´óÐã Nature UK has been keeping their eyes peeled and Twitter is full of 'spring has arrived' tweets. What signs of spring have you spotted?

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