FAX - fronts drifting SE-wards across Britain today but running into high pressure 1030mb Brittany tomorrow. This anticyclone moves slowly eat up the Channel, to Holland by Tue 22nd; then a repeat performance on Wed with front moving SE-wards and HP moving in from the west to suppress it.
GFS Op 00z - the second anticyclone above settles over the N Sea with ridge to Scandi and brings up warmth from the S/SE by Thu 24th. The Scandi part of the anticyclone takes over, and for several days Britain weather is in the balance between a continental HP and an Icelandic trough; mild weather from the south, wetter in west and drier in the east but liable to flop either way. As forecast today, the trough is dominant Mon 28th & Sat 3rd, and HP is dominant Thu 1st. Eventually LP moves up from the south to SE England 1010mb Mon 5th to break the pattern.
ECM - similar to GFS though the continental HP is less intense
AIFS - London, maxima 20-22C to Mon 28th, then 27C for a couple of days before down to 18C with rain. Edinburgh, maxima rather variable 15-19C all the way to Sat 3rd, rain Wed 23rd, a little for the following weekend, a lot more Thu 1st and after.
GEFS - in the S, mean and ens temps agree on above norm to Sun 27th, as much as 5C above for that weekend, and dry. Then a big ens spread develops, temps between 8C above and below (as might be expected form the GFS synoptics) and rain appears in several runs. In the N, similar, but add a cool day with rain in the middle of the warm spell, Wed 23rd.
It looks like there will be a heat wave around the end of next week, but quite likely short-lived, and models disagree as to whether the peak will be before or after the weekend, Still very dry in the south.
I can calculate the movements of stars, but not the madness of men - Isaac Newton
Chichester 12m asl