▁position ed ▁at ▁the ▁cr est . ▁Ar ound ▁the ▁low , ▁flow ▁will ▁become ▁cycl onic , ▁by ▁definition . ▁This ▁rot ational ▁flow ▁will ▁push ▁polar ▁air ▁equ ator - ward ▁west ▁of ▁the ▁low ▁via ▁its ▁trailing ▁cold ▁front , ▁and ▁war mer ▁air ▁will ▁push ▁pole ward ▁low ▁via ▁the ▁warm ▁front . ▁Usually ▁the ▁cold ▁front ▁will ▁move ▁at ▁a ▁quick er ▁pace ▁than ▁the ▁warm ▁front ▁and ▁“ catch ▁up ” ▁with ▁it ▁due ▁to ▁the ▁slow ▁er os ion ▁of ▁higher ▁density ▁a irm ass ▁located ▁out ▁ahead ▁of ▁the ▁cy clone ▁and ▁the ▁higher ▁density ▁a irm ass ▁swe eping ▁in ▁behind ▁the ▁cy clone , ▁usually ▁resulting ▁in ▁a ▁narrow ing ▁warm ▁sector . ▁ ▁At ▁this ▁point ▁an ▁occ l ud ed ▁front ▁forms ▁where ▁the ▁warm ▁air ▁mass ▁is ▁pushed ▁up wards ▁into ▁a ▁tr ough ▁of ▁warm ▁air ▁al o ft , ▁which ▁is ▁also ▁known ▁as ▁a ▁t row al ▁( a ▁tr ough ▁of ▁warm ▁air ▁al o ft ). ▁ ▁All ▁developing ▁low ▁pressure ▁areas ▁share ▁one ▁important ▁aspect , ▁that ▁of ▁up ward ▁vertical ▁motion ▁within ▁the ▁tro pos phere . ▁Such ▁up ward ▁mot ions ▁decrease ▁the ▁mass ▁of ▁local ▁atmos pher ic ▁columns ▁of ▁air , ▁which ▁lower ▁surface ▁pressure . ▁ ▁M atur ity ▁ ▁M atur ity ▁is ▁after ▁the ▁time ▁of ▁occ l usion ▁when ▁the ▁storm ▁has ▁completed ▁strength ening ▁and ▁the ▁cycl onic ▁flow ▁is ▁at ▁its ▁most ▁inten se