An Air Carrier Crew reported that on approach to SFO Runway 28R at dusk in windy conditions; they were concentrating on finding traffic on final and forgot to call tower prior to landing for clearance.

Narrative

We flew to San Francisco (SFO). The conditions in SFO that evening were winds out of the west at about 20-25 KTS and a broken layer at about 8000 FT. SFO was only using Runways 28L and 28R for arrivals and departures. On final approach into San Francisco we were given a high right downwind and to expect the visual to 28R. As we descended out of the broken layer NORCAL Approach asked us to find an Airbus and a turboprop at our 1-2 o'clock. We were to follow those aircraft. Because of the sunset conditions it was hard to visually locate aircraft. We found the Airbus and were then given a base turn. On base we had the airport in sight and finally located the turboprop. NORCAL Approach gave us a late vector onto the localizer. This caused us to overshoot final and the localizer for 28R with no conflict to other traffic. We corrected and established ourselves on the localizer for 28R and were then given the visual approach. The late vector caused us to lose sight of the turboprop 2 miles ahead on the visual for 28L. With the setting sun and evening conditions we continued to look for the turboprop but could not see them. Also; the strong winds made us focus more on maintaining a nice stabilized approach into 28R. NORCAL was heavily involved in communication with other aircraft and NEVER handed us off to SFO Tower. Upon flying over the numbers of 28R we realized we were still on NORCAL frequency. The Captain felt for the safety of the flight in regards to the phase we were in to land the aircraft on the unobstructed runway. We rolled out and held short of 28L on taxiway Echo. We contacted Tower and were advised to continue holding short for landing traffic. Once the traffic landed we were instructed to cross 28R and contact Ground Control. We did just that and taxied to the gate with Ground and Ramp Control. We were never instructed to contact the SFO Tower. Knowing of our mistake; the Captain felt it necessary to take it upon ourselves to call the Tower. The Captain discussed with the Tower the distractions and the series of events that took place that caused us to not obtain a landing clearance. The Tower was very understanding; assured us no conflict ensued; and advised us to have a good evening.