HERE IS MY LATEST ANALYSIS USING DATA SUPPLIED BY THE NWP OUTPUT COVERING 5 OF THE WORLDS MOST POWERFUL WEATHER COMPUTERS ISSUED AT 08:00 ON TUESDAY APRIL 21ST 2015.
THE CURRENT GENERAL SITUATION High pressure will continue to be slow moving over the North of the UK with light winds for all.
http://www.wetterzentrale.de/pics/Rtavn001.gif
MODELS-2 WEEK HEADLINE Becoming unsettled and rather cold with bright spells and showers, heavy and wintry on hills. Local night frosts still likely.
THE GFS JET STREAM ENSEMBLE FORECAST The Northern arm of the jet will weaken over the coming days as it moves slowly South towards the British Isles. The Southern arm will become the more dominant feature located over Spain before moving North to join the Northern arm over the UK later in the period where it remains in situ with it's orientation shifting to more NW to SE axis.
http://www.theweatheroutlook.com/twodata/datukgfshires.aspx?display=jetstream&model=gfs
GFS OPERATIONAL The GFS Operational this morning shows High pressure declining over the coming days with Low pressure edging up from the SW and deepening to the North of Scotland over the weekend and start to next week with rain and showers for all. A changeable pattern is then shown for the remainder of the period though with High pressure never far away from the South or West of Britain some Southern and Western areas may not see too much rain after the innitial period. Winds look like settling NW or even North at times so it will probably feel rather cool at times.
http://www.wetterzentrale.de/pics/Rtavn1441.gif
http://www.wetterzentrale.de/pics/Rtavn3841.gif
THE GFS CONTROL The GFS Control Run though similar for much of the run shows small differences but still has the underlying message that with High pressure close to the South and SW at times the most changeable conditions remain towards northern Britain with longer drier spells in the South. This run too shows rather cool conditions under NW winds at times.
THE GFS CLUSTERS The GFS clusters continue to show a variety of options in condiions by the end of the two week period ranging from a greater bias supporting the operational and control runs of High pressure most likely to the West and SW with West or NW winds and occasional rain the order of the days. The lesser options show Low pressure to the East and well out into the NW Atlantic with a contrasting North flow or milder SW flow so take your pick.
http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=euro&MODELL=gefs&MODELLTYP=2&BASE=-&VAR=cpre&HH=372&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD=
UKMO UKMO shows High pressure declining and being replaced by cyclonic conditions at the weekend with outbreaks of rain or heavy showers for all in cooler conditions overall as Low pressure settles to the North and NE of Britain.
http://www.wetterzentrale.de/pics/Rukm1441.gif
THE FAX CHARTS The Fax Charts mimic the operational run of UKMO today with a decline in conditions from the SW on Friday setting up the weekend with a trough across the UK continung the risk of rain or heavy showers at times in progressively cooler conditions.
http://www.weathercharts.org/ukmomslp.htm#t120.
GEM GEM this morning is one of the coldest and most showery of the outputs this morning with Low pressure developing and becoming anchored to the NE of the UK with a cold and showery North to NW airflow lasting much of next week delivering heavy and wintry showers at times across the UK with some night frost later.
http://www.wetterzentrale.de/pics/Rgem2401.gif
NAVGEM NAVGEM also brings cold NW and Northerly winds down across the UK in association with Low pressure anchoring across NW Europe and the North Sea at the weekend and start to next week with rain and showers in cool conditions and no doubt some wintry showers at times over the hills.
http://www.wetterzentrale.de/pics/Rnvg1681.gif.
ECM ECM too challenges GEM for the coldest mantle this morning as it's run produces Low pressure sluggishly centred on the North Sea and Scandinavia next week feeding cold air down over the UK from the Arctic with plenty of convective and heavy showers all days across the UK with snow on the hills and patchy night frosts where skies clear.
http://www.wetterzentrale.de/pics/Recm2401.gif
ECM 10 DAY MEAN(12z) The ECM 10 Day Mean Chart from last night supports the operational well so I expect little change from this chart to the one produced later this morning with a cold and showery NW or North flow looking likely over the UK in 10 days time.
http://www.wetterzentrale.de/pics/Reem2401.gif
NOTABLE TREND CHANGES FROM PREVIOUS RUNS The trends this morning remain focused towards a much more unsettled spell developing from later this week though there are a few scenarios drifting towards higher pressure possibly developing closer in to the South and West at times.
31 DAY HISTORICAL VERIFICATION STATS FOR GFS, UKM & ECM The current verification statistics for the past 31 days shows ECM leading the way at 3 days with 97.4 pts followed by UKM at 96.9 pts and GFS at 96.1. At 5 days ECM continues to lead the field at 89.1 pts over UKMO at 88.4 pts and GFS at 86.0. At 8 days ECM remains the leader with 62.7 pts over GFS's 57.6 pts. Then at Day 10 ECM retains superiority at 44.4 pts over GFS at 41.1.
http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day3_PMSL_MSL_G2NHX.png
http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day5_PMSL_MSL_G2NHX.png
http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day8_PMSL_MSL_G2NHX.png
http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day10_PMSL_MSL_G2NHX.prig
MY THOUGHTS The last days of fine warm conditions are underway this morning and it looks increasingly like we better make the most of them because from Friday onward it may be some while before temperatures return to the levels currently being experienced across the UK. All models have now underlined the change from Friday as our old friend High pressure declines away and is replaced by deepening Low pressure moving up from the SW towards a point North of Scotland by the end of the weekend. While the weekend itself may still feel pleasant enough in any sunshine between the showers it's as winds swing NW or even North early next week that cold air floods South and sets up what looks like being quite a long period when days will be characterized by bright periods and highly convective conditions with heavy showers delivering a cocktail of rain, hail sleet, snow and thunder coupled with frosts at night as skies stay clear. I would even go as far as to say that anywhere could see a surprise snowfall next week in the heaviest showers and before anyone says that it's too late in the season for that I can say with experience it has happened this late before and could happen again under some of the models synoptics this morning. However, despite the talk of this on the flip side of the coin strong late April sunshine between the showers could feel very pleasant still but frosts at night in this setup look inevitable for some and will prove very unwelcome if some of this morning's charts verify. So a real shock to the system looks likely across the UK this weekend and next week as summer clothes can be put back in the drawer for a time with warm coats and umbrellas becoming much more an accessory when out and about soon.
Next update from 08:00 Wednesday April 22nd 2015
Martin G
Kilmersdon Radstock Bath Somerset