Snowy Saturday…

During tomorrow it’s certainly set to become very windy and wet over large parts of the British Isles, but I have my eye set on developments during Friday and into Saturday, which if they pan out as the GFS suggests, might well bring a spell of snow to central and eastern counties before the deepening low exits into the North Sea during Saturday morning. Gradients around the low tighten considerably, even if a lot of that gradient can be discounted because of cyclonic curvature (fig 1).

Surface UK [T+108] 12 UTC on Sat, 25 November 2017

Figure 1 – Courtesy of OGIMET

The only thing I can get out of the Met Office is this T+120 image (PPVO89.tif) for the same time (fig 2). The Met Office model is much faster with this feature, and the low ends up being much more elongated and +5 hPa shallower than in the GFS.

2017-11-21_074050

Figure 2 – Courtesy of the Met Office

Super mild

Figure 1

Somewhere in the UK could see a maximum temperature as high as 20°C this afternoon, in the super mild air behind the warm front that’s pushed northeastward across the country today. The all time maximum according to TORRO for the 24th of October is 21.7°C at Prestatyn in Denbighshire so that looks safe.

Met Office scam

Figure 1

I installed Thunderbird on my computer a few weeks ago, after using Microsoft Outlook as my email client of choice for many year. For some reason Thunderbird flags absolutely everything that I receive from the Met Office as junk, and labels each message ‘This message may be scam’ in red. I can’t help wondering if Mozilla know something I don’t know about the organisation! By the way I’m rather impressed with Thunderbird and wished that I’d made the change much sooner, best as well as being free it’s not cloud based!

Gusts to hurricane force 12 on south coast of Ireland

Figure 1

I notice that there are a couple of reports of gusts to 64 knots along the south coast of Ireland at 09 UTC. That’s hurricane force 12 on the Beaufort scale for mean wind speeds (fig 1). I notice that at the Weather buoy K1 last hour there was a wave height of 11.1 metres (>36 feet) reported, the pressure has now bounced back there amazingly from when Ophelia passed close by to the west or to the east (fig 2).

Figure 2

Winds starting to pick up in southwest

Figure 1

I get the feeling from the latest 08 UTC observations (fig 1) that Ophelia might be staying just that little bit further west than was expected yesterday. Storm force gusts across the southwest of Ireland and the Scilly Isles.

Spot the front

It’s very easy today to find the cold-warm front strung out across northern England and central Ireland on just temperature alone (fig 1).

Figure 1

The temperature at Hawarden in Flintshire and Rostherne in Cheshire are already around 19°C, which wasn’t particularly difficult, as they didn’t fall below 17°C overnight (fig 2). But it’s another very mild day across all southern areas again today.

Figure 2

There is a possibility that if somewhere gets a maximum higher than 23.0°C early this afternoon, we’ll see a new record warmest 14th of October (fig 3). The extremes for the 14th to the 17th all look a little weak and vulnerable, and it maybe that we see more records broken tomorrow before Ophelia’s cold front finally sweeps through on Monday. I am grateful for the TORRO web page on daily extremes for the UK, why can’t the Met Office maintain a list of daily extremes for the UK like this? Oh silly me, I know why, they won’t make any money out of it.

Figure 3 – Courtesy of TORRO

TORRO don’t mention when their listing of extreme high and low daily temperatures started, but I notice that there are records from the 1880’s in the list, so it’s safe to assume that they began in the same year that the monthly weather reports started publication in January 1884, or maybe even a few years earlier.

The impact and likelihood of a storm Aileen or Sebastian?

Looking at the latest yellow warnings issued this morning for strong winds and heavy rain later on Tuesday and Wednesday, the Chief forecaster at the Met Office thinks that the likelihood of rainfall, is higher than that of strong winds (fig 1). This is a curious decision on his part, because if anything I would have thought that it was the other way round, and that the likelihood of strong winds were just if not more likely, than that of heavy rain alone. But the Chief does think, that any impacts from the strong winds are higher than the impact from heavy rain (fig 1).

Figure 1 – Courtesy of The Met Office

I think this is a game that they play using the impact/likelihood grid that determines if a storm is to be named. As far as I can see, if they issue two alerts or more, and they’re both amber, then the storm will be named, but I’m unclear if just one of them being amber would trigger the naming process.

Figure 2 – Courtesy of the Met Office

The rain from the warm and cold fronts fairly zips across the country, but the occlusion sticks around a while across southern Scotland and hence the limited area for the heavy rain warning. According to the latest T+48 forecast chart that I can access from Met Office, it looks like they see the tightest gradients being from the Midlands and Northern England, I can’t see why they’ve taken the yellow warnings area as far north as Edinburgh, but without their model data it’s impossible to say. Obviously they’ve included gusts to 75 mph that may occur down the lee side of the Pennines.

Figure 3

The Met Office have forgotten to label the central pressure of ‘Sebastian’ (the name already given it by BIM) on their T+48 chart (fig 3), which I reckon is somewhere around 980 hPa. The UKMO solution is very similar to that of the GFS (fig 4), the only real difference is that the tightest gradients lie south of northern England, and across most of the Midlands and southern England. It will be interesting to see if this area gets adjusted southwards in the next 24 hours.

Figure 4

European heatwave in perspective

I couldn’t think of a much better way of getting some kind of perspective on the heatwave over southeast Europe, so I decided to display temperature anomalies from thee 2.5° six hourly gridded air temperature data, which I download from the NCEP reanalysis site. So this chart (fig 1), shows temperature anomalies for 12 UTC on August 2nd, which is a bit unfair on the rest of the northern hemisphere, but does go to show the size and magnitude of the positive anomaly centred over Ukraine, and extending southwestward across the Balkans and Italy, towards the western Mediterranean.

Figure 1

Good week, bad week

Figure 1

We seem to be caught up in a cycle of good week bad week at the moment, and next week looks pretty grim, at least from Tuesday onwards looking at the latest run of the GFS model (fig 1). It’s not well supported by the T+84 forecast chart from the UKMO though (fig 2). The GFS does hint at a return to Summer by next weekend (T+180) to keep the cycle going but don’t hold your breath.

Figure 2 – Courtesy of UKMO

I’m sure that someday the Met Office will move on from the archaic format in which they prefer to display their NWP forecast output (fig 2), but for now we are stuck with the old ‘fax’ chart that’s changed little (apart from the addition of the thickness lines) since I joined the Office in 1970, and the eight forecast charts out to T+120 that they publish.

Goodbye 564 line

It’s Midsummer’s day today, and we can bid a fond farewell to the 564 dm partial thicknesses that we’ve seen across southern areas for the past few weeks, hopefully it will return later in the summer, until then it looks changeable and breezy at times, with some welcome rain over the next week or so, according to the latest run of the GFS model.