bookworm, wow do you have a life? I am in awe of your ability to dig up facts like this at short notice!!!
Just a fun little job for Perl .
But you have an unfair advantage: you have cloud tops data.
Only as an aftercast from the Herstmonceux sounding -- so it's cheating a bit as the F215 may be more pessimistic.
Let me share my thoughts. I think the 00Z 01 Jan 2004 situation is potentially nasty. I don't have the synoptic charts available, but I suspect there was a nasty little warm front that hung around most of New Year's Day, drying up in the afternoon. Not a nice night to be airborne in anything without significant icing protection. However, by 12Z the freezing level was at least 3500 ft.
EGKK 010020Z 18009KT 150V210 CAVOK 06/02 Q1015 =
EGKK 010050Z 19010KT 9999 FEW020 SCT026 BKN050 06/02 Q1014 =
EGKK 010120Z 20014KT 150V230 9999 RA FEW012 SCT018 BKN024 05/02 Q1014 =
EGKK 010150Z 21012G23KT 170V230 6000 RA FEW007 BKN016 04/02 Q1014 =
EGKK 010220Z 20015G25KT 8000 RA SCT012 BKN018 04/02 Q1013 =
EGKK 010250Z 20012KT 9999 RA BKN010 03/02 Q1012 =
EGKK 010320Z 19012KT 9999 RA FEW007 SCT009 BKN012 03/02 Q1011 =
EGKK 010350Z 19011KT 150V230 8000 RA FEW008 BKN009 03/02 Q1011 =
EGKK 010420Z 18011KT 140V220 9999 -RA SCT009 BKN012 04/03 Q1009 =
I also think the 00Z 25 Feb 2004 situation was potentially nasty. However, with a bit more context, I don't think this layer is likely to be mistaken for a major icing hazard.
EGKK 242050Z VRB03KT 9999 SCT032 OVC065 04/03 Q1011 =
EGKK 242120Z 27003KT 9999 FEW018 SCT036 OVC070 03/02 Q1011 =
EGKK 242150Z 33005KT 280V360 9999 BKN010 04/02 Q1011 =
EGKK 242220Z 01007KT 9999 SCT009 BKN080 03/01 Q1011 =
EGKK 242250Z 01005KT 9999 FEW007 SCT009 03/02 Q1011 =
EGKK 242320Z 02006KT 9999 FEW007 BKN009 02/01 Q1011 =
EGKK 242350Z 36007KT 9999 BKN010 02/01 Q1011 =
EGKK 250020Z 01008KT 9999 BKN010 02/00 Q1012 =
EGKK 250050Z 04004KT 9999 FEW012 01/M01 Q1011 =
EGKK 250120Z 00000KT CAVOK M00/M01 Q1011 =
EGKK 250150Z VRB02KT CAVOK M01/M02 Q1011 =
EGKK 250220Z VRB02KT 9999 SCT032 M01/M01 Q1011 =
EGKK 250250Z 25002KT 9999 BKN030 M01/M01 Q1011 =
Finally, the 12Z 20 Feb 2004 one is one where you could envisage flying VFR below the cloud (which I'd do in a twin but not a single), but I wouldn't want to spend very long in it.
I'll reassert that I don't think that icing is likely to be an issue as often as other nasty weather. Certainly if you're stuck below the London TMA it makes a difference, with careful planning I don't think the lack of de-icing is as big a deal as is often made of it.