Bangladesh Meteorological Department (BMD) on Saturday asked the maritime ports of Chattogram, Cox’s Bazar, Mongla and Payra to hoist local cautionary signal No 3.   A deep convection is taking place over North Bay and adjoining areas, said a Met Office bulletin.   The bulletin said under the influence of the deep convection, squally weather may affect the maritime ports, North Bay and adjoining coastal areas of Bangladesh.   It advised all fishing boats and trawlers over North Bay to remain close to the coast and proceed with caution until further notice.   They were also advised not to venture into the deep sea.