The Collaborative International Dictionary of English v.0.48:

Barometric \Bar`o*met"ric\ (b[a^]r`[-o]*m[e^]t"r[i^]k),
Barometrical \Bar`o*met"ric*al\ (b[a^]r`[-o]*m[e^]t"r[i^]*kal),
   a.
   Pertaining to the barometer; made or indicated by a
   barometer; as, barometric changes; barometrical observations.
   [1913 Webster]

WordNet (r) 3.0 (2006):

barometrical
    adj 1: relating to atmospheric pressure or indicated by a
           barometer; "barometric pressure" [syn: barometric,
           barometrical]