knocker

The cold front clearing the south east midday Tuesday as the ridge starts building in from the SW

The gfs/ecm medium term anomalies are a tad tricky this evening. No significant changes upstream and still the tpv aligned north Canada > north Russia with a strong westerly jet exiting south of the former lobe. But during the period the ecm has a split flow developing as the subtropical high builds in mid Atlantic around a cut off upper low, and this opens the door for some unsettled weather to move east across the UK. Obviously in the unreliable time frame so just to be noted

A rather strange Nottingham midday ascent including a 164kt jet

Dr Simon Lee tweeted December 2021 absolutely obliterated the ERA5 record for number of days assigned to the "Arctic Low" (also known as "Pacific Ridge") North American weather regime: 29 days. The previous record holder was 24 days in 1984. 29 days is the average for all of DJFM! This is computed by minimum Euclidean distance assignment of the 4 clusters of the k-means solution of the leading 12 EOFs of daily 00Z linearly-detrended ERA5 1.5° DJFM Z500 anomalies in 20-80°N 180-30°W over Jan 1979-Dec 2021 I have to admit I couldn’t have put it better myself.

And the rain has arrived here satellite image from NOAA-18 overhead at 2022/01/09 10:33 UTC

The salient points of the ext mean anomalies this morning. Ridge NE Pacific linking to Siberia, adjacent to tpv northern Canada > north Russia although there is some disagreement on the alignment of this which impacts on the amplification of the subtropical high in mid Atlantic This in turn impacts the veering of the upper flow to the Euro trough and thus the weather and temps of the UK. The latter likely below average but to what degree?

Frequent heavy rain showers this morning

A fairly widespreasd frost this morning but still plenty of squally showers around in western regions, particularly the NW, where a little feature will produce a concentration of showers with snow in the mix, that will track south east through the morning/early afternoon.Elsewhere plenty of sunshine but cloud and patchy rain will arrive in the SW, courtesy of a warm front, and then track north east through the evening and overnight Monday is essentially about the warm front/patchy rain tracking NE and then on Tuesday the cold front clearing to the south east whilst the ridge starts to build from the soutrh west And over Weds/Thurs high pressure becomes established over the southern half of the country amnd thus N/S regional variations And out of interest a sounding for 12 Thursday

The medium term anomalies this evening illustrate that very fine margins can make big differences to the detail at this range. Essentially it is about the orientation of the tpv, and in particular the lobe over northern Russia, in conjunction with the strong upper flow that suppresses the amplification of the subtropical high. Towards the end of the period both the gfs/ecm are struggling to retain this, thus trending towards a N/S split

Front now through here

Moderate rain now on the cold front

The double front feature towards the south west? satellite image from NOAA-18 overhead at 2022/01/08 10:45 UTC

A quick glance at the ext mean anomalies this morning and the salient points. Aleutian trough/NW Pacific ridge extending into siberia adjacent to the tpv aligned north Russia > north Canada; a strong westerly upper flow exiting the eastern seaboard veering NW around the subtropical high pushing north to the Euro trough extending down to the Med. Likely fairly dry with a NW/SE bias and temps a tad below average

Windy with moderate rain here at the moment

A wet and windy day today as a frontal system tracks east across the country, clearing most areas by mid afternoon. Initia;ly some snow in the NW this morning and then later squally wintry showers in northern and western areas in the strong NW wind A sunnier day for most on Sunday, albeit still wintry showers in the north before another frontal system arrives from the west with more rain on Monday And then the well sign posted tpv/cold plunge down the NE North America, boosting the jet, splitting the upper trough and creating a cut off upper low, whilst promoting the subtropical ridge NE over the UK. All leading to more settled and milder weather through the rest of the week

It’s fair to say that high pressure remains influential over the medium term once the ridge has been established. But the detail still remains elusive with, for example, the gfs indicating some quite complex energy distribution in the Atlantic which the ecm is not quite so keen on. Generally speaking a relatively warm anticyclonic airmass over the UK/western Europe which is not necessarily reflected in the surface temps

Main rain belt through here about an hour ago, now back into the blustery showers routine

Moderate rain here at the moment satellite image from METOP-B overhead at 2022/01/07 10:47 UTC

Not really John as I haven't been using it for very long.

http://hebweather.net/wrf/wrf.php?run=00z&region=BritishIsles&chart=Overview&time=1

The frontal system tracking east across the country tomorrow with some snow on the leading edge and then perhaps some snow showers on the higher ground in the north behind the cold front

The main clusters indicate a fairly mobile Atlantic flow with the next batch giving a tad more influence to the Atlantic subtropical HP. A reasonable summation of the ext period at the moment

Very windy with frequent rain showers

The position of the tpv lobe/trough northern Russia during the latter half of the ten period continues to be paramount regarding the European detail as illustrated by the gfs/ecm this morning

Frequent squally heavy showers around at the moment, mainly in western regions, of snow down to quite low levels in the north west. Likely to get less frequent as the day progresses but a littler frontal feature will track south east over south Wales/sw and southern England around lunchtime bringing rain and snow over the moors