0:00:03 > 0:00:06Hello. The jet stream will play more and more of an important role
0:00:06 > 0:00:08over the next week or so in our weather.
0:00:08 > 0:00:10It'll turn things more changeable,
0:00:10 > 0:00:13wet spells interspersed with some dry and sunny spells too.
0:00:13 > 0:00:16It'll certainly feel like autumn.
0:00:16 > 0:00:19On Friday we have a fresher feel to things but actually
0:00:19 > 0:00:21most of us are going to have a fine day.
0:00:21 > 0:00:23Another classic scene of autumn is low-pressure
0:00:23 > 0:00:26systems barrelling in from the Atlantic.
0:00:26 > 0:00:28This one will head northwards but its trailing weather fronts will
0:00:28 > 0:00:30dominate our weather through the weekend.
0:00:30 > 0:00:33They're not here yet though so most of us having
0:00:33 > 0:00:36a fine day on Friday after a fresh start.
0:00:36 > 0:00:39Temperatures climbing into the mid-to high teens,
0:00:39 > 0:00:42maybe up to 20 degrees Celsius across the south-east.
0:00:42 > 0:00:44There's that first weather system coming in,
0:00:44 > 0:00:47turning things wet and windy across the North West and actually it will
0:00:47 > 0:00:50stay wet through Friday night across Western Scotland
0:00:50 > 0:00:52and indeed most of Saturday.
0:00:52 > 0:00:54The build-up of rain here could cause some problems.
0:00:54 > 0:00:57We'll also see the weather fronts bringing rain to Northern Ireland
0:00:57 > 0:00:59through the night and for a good part of Saturday
0:00:59 > 0:01:01and the rain edging through Saturday into
0:01:01 > 0:01:03western parts of England and Wales.
0:01:03 > 0:01:05Ahead of it generally dry and bright.
0:01:05 > 0:01:07The winds will be noticeable, getting quite gusty at times.
0:01:07 > 0:01:10Look where they're coming from, the South,
0:01:10 > 0:01:12drawing up warm air so where we see hazy sunshine
0:01:12 > 0:01:15we could get over 20 Celsius across the south-east.
0:01:15 > 0:01:16Even where it's raining,
0:01:16 > 0:01:19temperatures above the average for the time of year.
0:01:19 > 0:01:22Now, the rain will edge Eastwards as the weather front
0:01:22 > 0:01:24trundles across the UK through the night.
0:01:24 > 0:01:27Still likely to have some rain across East Anglia and the
0:01:27 > 0:01:29south-east for Sunday morning but it should tend to scoot away
0:01:29 > 0:01:33and behind that weather front the winds have changed direction,
0:01:33 > 0:01:34now coming in from the Atlantic.
0:01:34 > 0:01:36A much a fresher feel on Sunday.
0:01:36 > 0:01:37Still quite a bit of sunshine,
0:01:37 > 0:01:40temperatures getting into the mid-teens but we'll also
0:01:40 > 0:01:42see showers coming in off the Atlantic too.
0:01:42 > 0:01:44A few showers around on Monday.
0:01:44 > 0:01:47Could be quite chilly start on Monday
0:01:47 > 0:01:50and with lighter winds there could be fog patches around
0:01:50 > 0:01:52as well for Monday morning's commute.
0:01:52 > 0:01:53But in the sunny spells in the afternoon
0:01:53 > 0:01:55we're back up to 14 to 19 Celsius.
0:01:55 > 0:01:59Behind me you will notice a rather ugly looking rain area and that is
0:01:59 > 0:02:02stemming from a rather ugly looking set of weather fronts and isobars.
0:02:02 > 0:02:05A complicated picture into Tuesday.
0:02:05 > 0:02:07It's complicated mostly thanks to Karl,
0:02:07 > 0:02:10we've been talking about this storm system for the past couple of days.
0:02:10 > 0:02:12Could become a hurricane over the weekend,
0:02:12 > 0:02:16drifting Northwards and into the North Atlantic weather systems.
0:02:16 > 0:02:20As it heads towards UK no longer a hurricane but injecting into
0:02:20 > 0:02:22the low-pressure systems energy and moisture
0:02:22 > 0:02:25so we could see quite a bit of wet weather
0:02:25 > 0:02:27and then behind that it remains unsettled.
0:02:27 > 0:02:31Changeable spells of dry and bright weather interspersed with
0:02:31 > 0:02:33cooler, blustery weather.
0:02:33 > 0:02:36Overall temperatures a touch above average through much of
0:02:36 > 0:02:39the second half of the week ahead but then average
0:02:39 > 0:02:43for the end of September, early October only 14-16 degrees.
0:02:43 > 0:02:45Although we may be a little warmer than that,
0:02:45 > 0:02:48it will be tempered by the blustery conditions,
0:02:48 > 0:02:52and we're not talking about the 30 degrees that we had last week.
0:02:52 > 0:02:54Why does it turn changeable in autumn?
0:02:54 > 0:02:56Well, it's all to do with the jet stream,
0:02:56 > 0:02:57that fast moving ribbon of air high up.
0:02:57 > 0:03:01In the summer months obviously the land gets hotter but the poles are
0:03:01 > 0:03:05also reasonably warm and it's the contrast in temperatures
0:03:05 > 0:03:08that drives the jet, so with less of a contrast the jet stream
0:03:08 > 0:03:11is often quite weak in the summer months but in the autumn, well, the
0:03:11 > 0:03:15land retains quite a bit of heat and at the same time the poles
0:03:15 > 0:03:17really start to cool down so you get more of a contrast
0:03:17 > 0:03:20between hot and cold, the jet stream gets more active
0:03:20 > 0:03:24and that creates more changeable weather, changing day on day.
0:03:24 > 0:03:27You throw a tropical storm into the mix like Karl,
0:03:27 > 0:03:28that adds energy and moisture
0:03:28 > 0:03:31and things get very lively.