Pattern matching for a laugh...
First. current synoptics and ECMWF forecast for just over a week later:
http://www.wetterzentrale.de/pics/Recm241.gif
http://www.wetterzentrale.de/pics/Recm1921.gif
Next, the start and peak of some historical "heatwaves", focusing on first heatwaves of the summer.
June 1975, after the famous snow:
http://www.wetterzentrale.de/pics/archive/ra/1975/Rrea00119750606.gif
http://www.wetterzentrale.de/pics/archive/ra/1975/Rrea00119750611.gif
Very different origin, with pressure rising to the East and a heat pump from depressions to our South West.
Late June 1976, the big one:
http://www.wetterzentrale.de/pics/archive/ra/1976/Rrea00119760623.gif
http://www.wetterzentrale.de/pics/archive/ra/1976/Rrea00119760703.gif
Again, very different. Pressure rises to the South, depressions pump hot air over W Europe, and as the heatwave matures the pressure gets very slack. I have a feeling this is very similar to August 2003 - we'll see later.
July 1983:
http://www.wetterzentrale.de/pics/archive/ra/1983/Rrea00119830705.gif
http://www.wetterzentrale.de/pics/archive/ra/1983/Rrea00119830714.gif
A bit more like ours, a classic case of Azores high extending over the UK and then becoming detached, but like 1976 it peaks with pressure getting slack and a very messy set of charts. Basically the hot air just gets stuck for weeks and not moved on.
June 1995:
http://www.wetterzentrale.de/pics/archive/ra/1995/Rrea00119950622.gif
http://www.wetterzentrale.de/pics/archive/ra/1995/Rrea00119950628.gif
http://www.wetterzentrale.de/pics/archive/ra/1995/Rrea00119950629.gif
Starts very like ours, and high pressure sits over us for a long time just to the NW. It ends with HP migrating to Greenland. Maybe that's our fate this time.
August 2003:
http://www.wetterzentrale.de/pics/archive/ra/2003/Rrea00120030802.gif
http://www.wetterzentrale.de/pics/archive/ra/2003/Rrea00120030810.gif
Starts with pressure rising to the South, and ends with almost no pressure gradient and Europe stewing.
Finally, June 2006 (the real start of the July 2006 heat):
http://www.wetterzentrale.de/pics/archive/ra/2006/Rrea00120060602.gif
http://www.wetterzentrale.de/pics/archive/ra/2006/Rrea00120060612.gif
Starts like ours with a big high moving over, peaks with a heat pump.
Make up your own minds, but to me the forecasts suggest something most akin to June 1995.
Brockley, South East London 30m asl