HERE IS MY LATEST ANALYSIS USING DATA SUPPLIED BY THE NWP OUTPUT COVERING 5 OF THE WORLDS MOST POWERFUL WEATHER COMPUTERS ISSUED AT 09:00 ON WEDNESDAY APR 20TH 2016
THE CURRENT GENERAL SITUATION High pressure across the UK today will persist for a day or so before moving West out into the Atlantic towards the weekend. At the same time Low pressure over Spain will move slowly North pushing some troughs towards Southern England later tonight and tomorrow with a strengthening Easterly flow across the South of the UK today and tonight decreasing again on Thursday.
http://www.wetterzentrale.de/pics/Rtavn001.gif
CURRENT SNOW FORECAST AND FREEZING LEVEL OVER THE UK The freezing level across the UK is much higher than of late with values at around 5000ft in the North and to as high as 8000ft in the South for a time over the next few days. It is set to plunge to as low as 1500ft - 2000ft by the weekend.
http://www.snow-forecast.com/maps/dynamic/uk
http://www.natice.noaa.gov/pub/ims/ims_gif/DATA/cursnow.gif
MODELS-2 WEEK HEADLINE Becoming colder at the weekend with cool nights and sunshine and showers looking likely with a continuing night frost risk thereafter. Perhaps becoming less cold as we enter May.
THE GFS JET STREAM FORECAST The Jet Stream remains split North and South of the UK as High pressure across the UK separates the flow. As the High is pushed West out into the Atlantic the Northern arm of the flow moves South across the UK late this weekend and next week becoming a cyclonic pattern then with the Northern aspect slowly being lost with a more variable flow pattern expected late in the period.
http://www.netweather.tv/index.cgi?action=jetstream
GFS OPERATIONAL The GFS Operational Run today shows the current quiet conditions under High pressure gradually becoming replaced by a chilly Northerly flow by the weekend with some showers. This Northerly will be cold and will last a while before the flow slowly backs Westerly and become less cold later while the weather overall remains rather changeable with some rain or showers at times.
GFS CONTROL RUN The theme of the Control Run follows the Operational to a point before it shows a build of High pressure across the UK in Week 2 with fine and sunny days under chilly nights with some frosts before a warmer Easterly flow develops towards the end of the period.
http://www.wetterzentrale.de/pics/Rtavn1441.gif
http://www.wetterzentrale.de/pics/Rtavn3841.gif
http://www.meteociel.fr/modeles/gefs_cartes.php?code=0&ech=144&mode=0&carte=0
http://www.meteociel.fr/modeles/gefs_cartes.php?code=0&ech=384&mode=0&carte=0
GFS ENSEMBLE DAY 14 DATA The GFS Clusters today are once more very mixed but are less supportive of a cold Northerly now and show a very mixed set of members supporting anything between a slack and benign pressure pattern to Low pressure over Scotland with rain for all.
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 The UKMO model this morning still shows a cold pattern developing as we move through the weekend. The weather itself takes rather longer to take a turn into more unsettled mode though with the weekend apart from a few showers in the North and East largely dry with night frosts. It's not until next week when all areas look at risk of more widespread cold weather with wintry showers in a strong Northerly draught as Low pressure focuses just to the East of the UK.
http://www.wetterzentrale.de/pics/Rukm1441.gif
THE FAX CHARTS The Fax Charts today agree with the theme of the Operational Run with High pressure pulled out into the Atlantic come the weekend and a Northerly flow developing. Rain bearing troughs clear the South but we will have to watch for weak disturbances running South close to Western Britain later in the weekend in the Northerly flow delivering more cloud and some rain or even sleet on the hills.
http://www.weathercharts.org/ukmomslp.htm#t120
GEM GEM this morning shows a cold Northerly flow developing from the weekend and lasting through to the end of the run. With pressure Low to the East and High to the West the Northerly flow will promote daytime showers and in the cold air they could fall as anything including sleet or snow at times across the hills with frosts at night under clearing skies.
http://www.wetterzentrale.de/pics/Rgem2401.gif
NAVGEM NAVGEM too shows Northerly winds becoming the dominant factor in the UK weather from the weekend as the current quiet weather is sucked away out into the Atlantic. In the far South the precursor to this weather will be cloud and rain for a time on Friday before all areas stay chilly with sunshine and cold showers for the rest of the weekend and much of next week with frost at night likely.
http://www.wetterzentrale.de/pics/Rnvg1681.gif
ECM ECM today continues to show the same drift into a cold Northerly flow as the rest of the output. However, it is looking increasingly likely that the South and West may not see too much chance of wintry showers with the focus of these towards the North and East. However, frost at night will be widespread everywhere before winds eventually back towards a Westerly point bringing less cold but changeable conditions to all areas after the turn of the month.
http://www.wetterzentrale.de/pics/Recm2401.gif
ECM 10 DAY MEAN (12z) The 240hr mean Chart from last night shows Low pressure over Scandinavia and High pressure somewhat further South over the Atlantic perhaps allowing more of a backing of wind towards the West and bringing temperatures up a bit from previous days though still with some showers across the North and East.
http://www.wetterzentrale.de/pics/Reem2401.gif
NOTABLE TRENDS & CHANGES FROM PREVIOUS RUNS Changes in the model remains small but there is a slow shift away from the coldest conditions lasting too long this morning as the theme of milder Westerly winds in 10 days increases.
31 DAY HISTORICAL VERIFICATION STATS FOR GFS, UKMO & ECM The verification Statistics of GFS, UKMO and ECM show at 24 hours ECM ahead at 99.6 pts with UKMO at 99.5 pts and GFS at 99.3 pts. At 3 days ECM is leading with 97.3 pts to UKMO's 96.6 pts while GFS lags behind at 95.5 pts. At 5 days ECM leads with 88.8 pts to UKMO at 86.5 pts and GFS at 83.4 pts. Then at 8 Days ECM has the leading spot from GFS with 63.6 pts to 56.0 pts. Finally at Day 10 ECM has the lead from GFS with a score of 44.8 pts to 37.1 pts.
http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/allmodel/daily/cor/cor_day1_PMSL_MSL_G2NHX.png
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.png
MY THOUGHTS There is evidence in the models this morning that the very worst of the cold weather next week may not last too long or be tempered considerably if you live towards the SW of the UK as after a few days the signs of the Northerly losing some of it's impetus is hinted at. The general pattern though remains one of cold Northerly winds enveloping the UK from the weekend. In the North and East in particular this could be come a very showery flow with sleet or snow across the hills. Further West and showers look far less frequent and there will be a lot of dry weather around. We may have to watch for weak disturbances rounding the Atlantic High and slipping South close to the west of the UK bringing some rain or sleet but away from this West looks best from midweek next week. Then as the High slips further South over the Atlantic by some models the winds begin to back more towards NW and eventually West which could cut off the cold source from the UK and bring less cold but still changeable conditions later, a fact well documented by this morning's ECM Operational Run and GFS too. So looking at all of the output in a nutshell it looks like the North and East in particular are going to feel the full blast of a late Spring Northerly with cold winds and April Wintry showers aplenty next week. In the West and South while colder the cold will be somewhat tempered by a lot of dry and bright weather with fewer wintry showers but all areas will likely see some unwelcome late April frosts. Then as we look to the longer term output it does appear that the trend will be towards less cold weather as we enter May under Westerly winds and occasional rainfall especially in the North in an eventually much more standard pressure pattern over and around the UK.
Next Update Thursday April 21st 2016 from 09:00
Martin G
Kilmersdon Radstock Bath Somerset