:00:00. > :00:00.Hi guys, Ayshah here, with your last weekend update from the Newsround
:00:00. > :00:09.team. On the way: It's been called BMXing
:00:10. > :00:12.on snow - we'll tell you how Great Britain got on in the awesome
:00:13. > :00:16.Snowboard Cross. And from snowboards to surfboards - we'll bring you the
:00:17. > :00:27.curly tale of the pig who rides the waves. This is Newsround.
:00:28. > :00:29.So, first - all this week we've been telling you about some truly
:00:30. > :00:32.extraordinary weather conditions that have been causing terrible
:00:33. > :00:36.problems, not just here, but in America, too. So what's causing all
:00:37. > :00:48.this weird weather? As I've been finding out, it's all to do with a
:00:49. > :00:54.global wind, high above us: the jet stream.
:00:55. > :00:58.The UK has been lashed by waves and thrashed by winds and rain. Over in
:00:59. > :01:02.the US, they are in the grip of a bitterly cold winter that shows no
:01:03. > :01:06.signs of easing off. Some scientists don't think this prolonged bad
:01:07. > :01:09.weather is just a coincidence. They believe the recent warming of the
:01:10. > :01:12.Arctic has moved the weather system that drives conditions here in
:01:13. > :01:24.Northern Europe, and over in North America. But this current here in
:01:25. > :01:28.red - it's called the jet stream. This year, it dipped lower than
:01:29. > :01:31.normal, making the weather stay the same for longer. It's caused months
:01:32. > :01:34.of heavy rain and storms for us, and extreme cold for America. Scientist
:01:35. > :01:38.Jennifer Francis has been studying the jet stream. She thinks we could
:01:39. > :01:41.be seeing more of the same in the future.
:01:42. > :01:44.I think we can expect more of the same. I think we should expect it to
:01:45. > :01:47.occur more frequently. It being these wavy patterns in the jet
:01:48. > :01:50.stream that tend to result in weather conditions being very
:01:51. > :01:54.persistent in one place. It's too early to judge whether the
:01:55. > :01:57.jet stream's change in shape will be permanent, but the research suggests
:01:58. > :02:03.that we may have to get used to winter weather that stays the same
:02:04. > :02:06.for weeks or even months. Back here in Britain, the Prime
:02:07. > :02:09.Minister has warned that flooding misery is likely to continue for
:02:10. > :02:12.millions of people, despite a break in the bad weather. David Cameron
:02:13. > :02:18.said that many places in southern England, where the ground is already
:02:19. > :02:21.soaked, may see further flooding. One of the biggest threats is not
:02:22. > :02:31.from rivers bursting their banks, but from water underground, coming
:02:32. > :02:35.to the surface. Check this out. One of the reasons we are seeing so
:02:36. > :02:38.much flooding at the moment, in some parts of the country, is ground
:02:39. > :02:41.water flooding. This happens when water rises from rocks under the
:02:42. > :02:45.ground and comes out at the ground surface. When rain falls, some of it
:02:46. > :02:49.soaks into the soil, and the rocks beneath the soil can also carry and
:02:50. > :02:52.store water. When enough rain falls in these areas, water keeps moving
:02:53. > :02:56.down beyond the soil layer into the rocks beneath. Ground water tends to
:02:57. > :03:00.flow from the higher ground to the lower ground. When we have a lot of
:03:01. > :03:03.rain, ground levels rise and the water starts to come out of the
:03:04. > :03:06.ground surface in places that are usually dry. We call this ground
:03:07. > :03:09.water flooding. It takes longer to go away than flooding rivers. Over
:03:10. > :03:13.flooding tends to last days or weeks, where is ground water
:03:14. > :03:22.flooding can last weeks or even months.
:03:23. > :03:25.Next, we're off to Russia and the Sochi Winter Games. Today, we've
:03:26. > :03:31.been enjoying a thrill-packed sport that's been likened to BMXing on
:03:32. > :03:34.snow - it's the snowboard cross. Six riders carve down the course,
:03:35. > :03:37.braving huge jumps and sharp corners, and with everyone so close
:03:38. > :03:40.together you can have some nasty crashes. Team GB's Zoe Gillings
:03:41. > :03:44.qualified for the semi-finals this morning - you're watching the end of
:03:45. > :03:47.her semi here. Zoe came within just a few centimetres of making the
:03:48. > :03:51.final, but unfortunately she just missed out. She was gutted to be so
:03:52. > :04:00.close, but says she'll be back for more in four years' time!
:04:01. > :04:03.I thought I'd actually got through at one point, because one of the
:04:04. > :04:08.official guys said I'd got through, but then it turned out I wasn't. It
:04:09. > :04:12.was a real shame to miss out on the final by that small amount, but I
:04:13. > :04:16.rode as hard as I could and as fast as I could, so that's all I can
:04:17. > :04:19.really do. I definitely want to do another Olympics, there's no
:04:20. > :04:23.question. If I can get the funding, and the results keep coming, then I
:04:24. > :04:26.don't see any reason why not. Well, you've been telling us about
:04:27. > :04:43.your Sochi highlights over on the Newsround website.
:04:44. > :04:47.Thanks so much for all those comments, keep them coming in.
:04:48. > :04:51.Im curling, this morning, Britain's men's curling team were beaten 7-6
:04:52. > :04:54.in their second to last round robin match with Norway this morning, so
:04:55. > :04:58.they're not guaranteed a semifinal place yet. The match went down to
:04:59. > :05:01.the final end of the game with the scores level at 6-all, but the
:05:02. > :05:05.Norwegians won with the final stone. Team GB can still make the semis if
:05:06. > :05:11.they beat China tomorrow afternoon. Britain's women play their last two
:05:12. > :05:14.matches tomorrow as well. In today's matches, Arsenal will be
:05:15. > :05:18.hoping to avoid another scoreline like this when they face Liverpool
:05:19. > :05:20.again in the big four o'clock showdown. In the afternoon's other
:05:21. > :05:23.games Everton face Swansea in the early kick off at 1.30PM and
:05:24. > :05:34.Sheffield United play Nottingham Forest at 3PM.
:05:35. > :05:38.Last up, we love to bring you daft animal stories and today is no
:05:39. > :05:42.exception. This water loving piglet called Kama loves to go surfing with
:05:43. > :05:45.his owner in America. Here he is catching the waves at Hawaii's Sandy
:05:46. > :05:49.beach. Kama's love of surfing started when he used to swim with
:05:50. > :05:55.his owner in a pool in the back garden, and look at him now.
:05:56. > :05:58.That's all from me, Newsround's back right here in about half an hour.