EMB ERJ 170/175 ER/LR
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Situational Awareness
ATC Issue All Types; Conflict NMAC; Deviation - Altitude Excursion From Assigned Altitude
Flight Crew Took Evasive Action
Human Factors; Procedure
On climb out of ZZZ we were told by Kansas City Center to level out at 14000' for traffic. Center then advised us to climb to 15000'. Once level; we received a TCAS TA for an aircraft which was approaching us 500 feet above us. We reacted per FOM and asked ATC where the traffic was. We did not have visual contact. ATC told us VFR traffic was approaching us from 12 o'clock about 2 miles away. We searched vigorously but could not see the traffic. The position of the sun and the high humidity due to convective activity likely hindered our chances of visually seeing the traffic. The TCAS showed the target drop to 400 feet above us and we received a TCAS RA 'monitor vertical speed'. I disengaged the autopilot and soon received an 'adjust vertical speed' command with a -500 fmp command which I also complied with. Simultaneously; the Pilot Monitoring told ATC we were compiling with an RA. According to the TCAS; the traffic passed 400' overhead. We never were able to visually identify it. ATC seemed surprised and responded by saying the separation was fine; but we do not believe that was the case with a 400' overhead pass.
EMB-175 Captain reported an NMAC with a VFR aircraft on climbout.