The Spanish keeper saved a Chris Blunt penalty but fumbled in
Gonzalez Jara's effort as West Brom hit three fine goals after the
break.
Peter Odemwingie tapped the Baggies in front on 50 minutes
before Jara and ex-Gunner Jerome Thomas struck.
Arsenal's only inspiration, Samir Nasri, tucked home tweice
after that but the visitors clung on.
Emmanuel Eboue spun to fire the first decent chance just wide on
13 minutes.
Then seconds later Arsenal teammate Andrey Arshavin managed to
hit the post twice from an Eboue cross.
The Gunners, by now, were pouring forward, Marouane Chamakh
heading close and went Samir Nasri whistling a 25-yard drive inches
off-target.
But Peter Odemwingie began to show glimpses of his dangerous
pace at the other end.
And on 27 minutes it was the burly striker whose angled drive
was pushed onto the post by Almunia.
The Baggies' confidence soared as Arsenal seemed to lose
imagination.
But they wasted the one glorious chance of the first half,
Almunia tripping the onrushing Odemwingie but saving the resulting
under-hit penalty from Chris Brunt.
West Brom keeper Scott Carson then tipped Bacary Sagna's
six-yard header over.
Ex-Gunner Jerome Thomas punished Arsenal for their second-gear
display, jinking to the byline for a 50th minute pull-back slide
home by Odemwingie.
And just two minutes later Almunia undid his vital work before
the interval with one of the goalkeeping howlers of the
season.
Gonzalo Jara danced round the Arsenal defence but his long-range
shot somehow squirmed in past Almunia.
And Thomas caught his old club on the break, firing into the
roof of the net from seven yards.
Nasri fired a left-footer off the bar before hsi superb footwork
enabled him to drill home with the same foot.
And he pounced again asthe match entered five minutes of
stoppage time.
