Maritime ports of Chattogram, Cox’s Bazar, Mongla and Payra have been advised to hoist local cautionary signal number three as a deep convection is taking place over the north bay and the adjoining area.   Under its influence, squally weather may affect the maritime ports, North Bay and adjoining coastal areas, said a Met Office bulletin on Thursday.   All fishing boats and trawlers over North Bay have been advised to come close to the coast and proceed with caution until further notice.   They are also advised not to venture into the deep sea.