Metars
EGLL 171350Z 22015KT 9999 FEW021 12/09 Q0995 TEMPO 24018G28KT SHRA BKN015CB
EGLL 171320Z 22016KT 9999 BKN014 BKN020 11/09 Q0996 TEMPO 24020G32KT 6000 SHRA BKN015CB
EGLL 171250Z 20013KT 9999 BKN008 10/08 Q0996 BECMG 24018G28KT SCT012 BKN020
EGLL 171220Z 21014KT 180V240 9999 SCT008 BKN010 09/08 Q0997 TEMPO 21018G28KT 4000 RADZ BKN008
EGLL 171150Z 20014KT 170V240 9999 FEW006 SCT010 09/08 Q0997 TEMPO 20018G28KT 4000 RADZ BKN006
EGLL 171120Z 19017KT 160V230 5000 DZ BKN006 OVC010 09/07 Q0998 TEMPO 19020G30KT 4000
No sign of windshear conditions, but very hard to imagine any other explanation!