Compare and contrast
For a change today here are a few statistics from my weather in the Chilterns:
March 2013 22 air frosts.
Winter 2013/14 (December, January and February) 4 air frosts with all of these occurring in January. Incredibly during December and February the temperature didn’t drop below 0C (32F) even once.
March 2013 maximum temperature 16.2C on the 5th. Minimum temperature -4.3C on the 31st. So far in March 2014 the maximum recorded was 16.1C, but I’m hopeful tomorrow will beat this.
Winter 2012/13 total rain recorded: 190mm.
Winter 2013/14 total rain recorded: 431.6mm
Some massive differences between the winters and although we’re only 8 days in March 2014 is shaping up to be very different to March 2013 which was very cold. One caveat to add is there are some signs of colder weather developing during the last third of month, so don’t rule out the chance of a wintry blast despite the current warm sunny weather.
Sat, 08 Mar 2014 16:57:35
How warm this weekend?
It won’t be dry and fine everywhere this weekend but there is the potential for some exceptional weather. Saturday looks cloudier at times with rain at times in the north west but further south brighter spells are likely, and where the sun shines becoming very mild again. What sort of maximum temperatures are likely? The GFS temperature charts give a good indication of what to expect but in my experience they often underestimate the local maximum values. As an example, this morning’s run suggests a maximum of 13C (55F) this afternoon in the Chilterns but my Davis VP2 weather station is currently recording close to 15C (59F).
The GFS temperatures charts for Saturday and Sunday are showing maximum values of about 16C (61F) but I think these could be too low by 2C to 3C. Here’s the GFS temperature chart for Sunday afternoon.
In other words I’d not be surprised to see 18C or even 19C recorded somewhere in England weekend. Could we get to 21C (70F)? Very unlikely but I’d not completely discount it. It’s all a massive contrast with March 2013 which brought an extended period of cold weather with snow falling in much of the UK. Next week high pressure looks set to bring more fine weather and after temperatures take a dip early in the week it could become quite warm again later.
We’ve certainty seen some very odd and varied weather in the last couple of years in the UK. Fingers crossed for a sunny and very warm summer!
Fri, 07 Mar 2014 13:21:30
High pressure and spring arriving?
There’s uncertainty about the details of the weather during the coming days, but the general picture is for high pressure to have more influence on things at any time since early December. This should mean a much better chance of drier spells especially further south east. Temperatures are going to be dependent on factors such as where the high pressure becomes centred and cloud cover, but at the moment it’s looking quite promising with temperatures climbing quite nicely at times during the coming days. I’m never quite sure when the word mild is swapped for warm, but temperatures of about 16C (61F) look possible late this week.
The GFS chart for Saturday morning shows things quite well with an area of high pressure centred over eastern England bringing at this point mostly dry weather across all of the UK. As I said it’s not plain sailing and at times cloudy conditions with possibly heavy rain are still likely further north west. At times that wetter weather will try and extend more widely over the country, but the rain probably becoming lighter and patchier as it sinks south.
Next week needs watching very closely, but a lot of the computer model runs are suggesting high pressure will remain in charge of things. There are signs of more of a continental air flow developing and if this happens temperatures will take a dip. In summary there’s a decent chance of a high pressure dominated spell of weather bringing drier weather but with rain more likely further north. Temperatures could climb nicely for a while, but nighttime frosts are still possible and next week could see a cooler continental air flow picking up.
Tue, 04 Mar 2014 08:43:26
A couple of days ago I mentioned the possibility of a snow risk this Saturday. It now looks as though this will be confined to higher ground in northern regions. Some rain showers are possible in southern regions, but most of the precipitation will be in the north west of the UK and in the afternoon it looks like becoming heavy. The Hirlam model chart below is for Saturday evening.
The GFS model precipitation type chart for the same time shows the precipitation in roughly the same place, with blue indicating rain and pink snow. It looks as though over the Scottish mountains the snow could become heavy for a time.
Probably no real surprise to see the snow risk becoming confined to high ground in the north as it has been the repeating pattern in the last few months. One thing of note is the chance of some early spring warmth this time next week. High pressure building from the south could see temperatures reach close to 15C (59F) late next week, which is about 10C higher than maximum values in many areas today.
Fri, 28 Feb 2014 20:47:08
Snow risk this Friday and Saturday?
The last day of a very mild and wet meteorological winter could bring the risk of the first falling snow of the season to parts of lowland Britain. The culprit is an area of low pressure which is expected to push east across England and Wales bringing quite a lot of rain. The exact track isn’t certain, but on its northern flank some of the rain may turn to snow in colder air as evaporative cooling begins to take effect. Things do look marginal, and I’m certainly not expecting much of a snow event for low ground where rain or sleet is currently looking more likely. Higher ground obviously has more chance of seeing snow.
The chart below is from this afternoon’s GFS model run and shows the precipitation forecast for mid-day Friday. Details will change, but it looks likely to be north of London, with the northern extent depending on the track the low pressure takes.
Rain, sleet or snow? The GFS precipitation type charts (you can check them out on the Chart viewer) are currently suggesting mostly rain away from higher ground in Wales, but with a marginal set-up the implication is things are quite finely balanced. The derived dewpoint forecast chart below for the same time doesn’t look promising with values widely several degrees above freezing. These should really be showing 0C or lower for snow rather than rain or sleet. I’ll keep an eye on subsequent GFS runs to see if they do become more favourable for snow.
What about Saturday? The first day of spring is looking quite cold with the risk of showers or longer spells of rain. Again the details will change as the time approaches but this afternoon’s GFS run was quite bullish about the risk of snow falling over quite a large area. The precipitation type chart for Saturday afternoon below shows this, with blue indicating rain and pink snow, but I wouldn’t take this too literally because previous runs were less keen on the idea. Forecasts temperatures at the same time are widely between 4C and 6C, so even if there is snow mixed in to the precipitation it would be a wet affair over low ground.
In summary the next few days are interesting bringing the risk of rain, sleet and snow. The sleet and snow mostly over higher ground, but this could be the best chance of the season for some lowland areas in more southern location to at least see falling snow.
Wed, 26 Feb 2014 20:14:24
Spring probably starting mixed
In my last post I talked about the potential for a colder couple of days at the beginning of match. True to recent form this now doesn’t look very likely, and temperatures are more likely to stay close to the average this weekend. Possibly a little colder in the north for a time. In other words it looks like more of the same general pattern to begin the meteorological spring.
The plot below is from this afternoon’s GFS run, and shows forecast Mean Surface Level Pressure (MSLP) and 500hPa heights this Saturday. Low pressure remains close to the UK with a weak ridge of higher pressure possibly building from the south west and starting to come into play. This would give daytime temperatures would of close to 10C (50F) on Saturday, so as I said, not cold.
What happens longer term? The GFS run shows high pressure building from the south for a time next week, possibly bringing mild and drier conditions to southern regions. This afternoon’s operational ECM model run also shows high pressure at times influencing the weather in the south, but remaining mostly unsettled further north.
The most likely outcome? My take is more rain for all parts in the next couple of weeks, but on the whole a gradual improvement, particularly in the south. At this time of year if the sun does make an appearance it does begin to feel quite warm unless the air mass is unusually cold (like last March), so at least it should feel quite spring like in the drier spells.
Mon, 24 Feb 2014 19:51:52
The irony of ironies?
Next week is looking mostly unsettled but some of the computer model runs are suggesting high pressure will have more influence for a time later on. This could pause the conveyor belt of low pressure systems from the Atlantic and open the gate to a short lived plunge of colder air from the north. Ironically this may coincide with the arrival of the meteorological spring! I should quickly add that we’re not looking at a major freeze, but the chance of a couple of colder days.
The irony of ironies is if this could allow wintry showers to develop, and even bring a few flakes of snow down to lower levels where winter remained snow-less. Again I’ll quickly add that I’m not talking about widespread disruptive or accumulating snow. I’m really just flagging up the possibility of an unusual anomaly for some areas; the possibility of the first snow flake of the year arriving in spring!
This afternoon’s GFS run shows the colder flow moving down from the north later next week before high pressure moves over the UK and cuts it off. This chart is for 3am, Saturday 1st March, showing the 850hPA temperatures and Mean Surface Level Pressure, and shows the cold air moving down from the north.
In summary it does look as though we could see March begin in a slightly different vein, with a chance of colder and drier conditions for a time. Longer terms things remain uncertain, but perhaps high pressure will have more influence at least in southern regions.
Sat, 22 Feb 2014 18:05:43
A change on the horizon?
Well if there is I can’t really see it at the moment. The next week and beyond are looking unsettled across the UK. The differences between computer model runs are mostly focused on the details, so there’s quite a high degree of confidence in the bigger picture.
One of the interesting things this winter has been the almost complete absence of GFS outlier runs showing very cold medium range outcomes. Usually we see cold outlier runs from time to time in the winter months, and although there has been odd one since December they have been in very short supply. This suggests cold air hasn’t really been close to the UK for most of the season, and I think that’s backed up by much of western Europe also having a relatively mild winter with a westerly flow dominating.
Despite much of the UK having a snowless, it’s been a very different picture over the Scottish mountains. The succession of low pressure systems which have caused flooding over much of lowland Britain have brought frequent and heavy snowfall to the Scottish mountain, and the potential for a very late end to the ski season this spring or even early summer! The difference a few hundred metres in altitude makes to the weather can be vast in the UK, and this winter illustrates it perfectly.
Back to the outlook, and as I said it remains unsettled. All areas are likely to see more wet and windy weather with the rain becoming heavy at times. The GFS chart below is for Monday 24th February and shows things well, with low pressure areas in the Atlantic, and a west our south westerly flow across the UK. The general pattern this winter hasn’t really been unusual, but the persistence of it has. We’ve not really had any significant spells of high pressure dominated weather since mid-December.
In summary it’s more of the same. Hopefully as we head through March the jet stream will migrate further north, allowing drier spells to develop. At the moment there isn’t much evidence of this from the computer model runs but it is the sort of thing which tends to happen in spring.
Thu, 20 Feb 2014 13:40:44
More rain and possibly windy
In a word the outlook remains unsettled with little sign of things drying out. Today there’s heavy rain in parts of the south west, and during the rest of the week all regions can expect further wet weather. On the plus side it’s generally not looking as severe as last week with less stormy conditions for most of the time, however, it’s not all plain sailing. This morning’s GFS 6z run shows very strong winds returning to the west on Thursday, and although it could be overestimating things developments are worth watching closely.
The GFS 6z chart below shows the windy conditions on Thursday with gusts of close to 70mph just off near to coastal parts of Wales. Remember these charts update 4 (next update begins at 15:30) times every day, so the key will be to see if this pattern showing strong winds is repeated in coming runs.
Finally, the web site refresh is progressing well and I’m still expecting it to be completed during middle March. It’s designed to work all the web browsers the existing site supports except for Internet Explorer 7. Page addresses and names won’t be changing, so your existing bookmarks will continue to work as now without you needing to make any updates.
Mon, 17 Feb 2014 14:08:32