B737 Next Generation Undifferentiated
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 213
Aircraft Equipment Problem Less Severe
Air Traffic Control Provided Assistance; Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport; Flight Crew Requested ATC Assistance / Clarification
Aircraft
Climbing out of ZZZ; the Captain's altimeter started sticking. At approximately 18;000 feet the Captain's airspeed and altimeter started rolling back. I immediately checked the First Officer's (FO) indications and crosschecked them with the standby altimeter and airspeed indicators. We determined I had the bad indications. I had the FO continue to fly. We were in the processes of deviating around storms so we had to continue to climb and get around a storm. The FO was having difficulty with airspeed and power control. The N1 settings seemed to be erratic and did not match what one would expect for the airspeed. I contacted Dispatch and Ground Operations to let them know we had issues. I ran the loss of airspeed and loss of altimeter checklists. We made the decision to return to the airport. The FO continued to fly and talked with ATC to return. I briefed the Flight Attendants and Passengers and got voice contact with Dispatch. We were 11;000 pounds overweight for landing. I completed preparations and checklist and briefed the FO on bleeds off and overweight landing. I made the decision to have the FO land as I had unreliable instruments. We were in a holding pattern while we made preparations. We decided to [advise ATC of emergency conditions] as we were overweight and ZZZ temperature was 113. We were concerned about a long landing and hot brakes. I chose Runway XY as it was the longest. The landing was very smooth and we did not get on the brakes until about 70 knots. We taxied off the runway and had firemen check the brakes. They determined all was good. We checked with Maintenance and confirmed we were clear to taxi to gate.
[Report narrative contained no additional information.]
B737 flight crew reported that the Captain's airspeed and altitude indications started to display erratically.