EMB ERJ 145 ER/LR
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Conflict NMAC
Flight Crew Overrode Automation; Flight Crew Took Evasive Action
Human Factors; Procedure
At 13;000 feet ATC informed flight of VFR traffic at 12 O'clock 500 below. The traffic was not speaking to ATC. Moments later the TCAS issued a TA. Shortly after the TCAS issued an RA to MONITOR VERTICAL SPEED but no vertical maneuver. Then the TCAS issued an RA to climb. Crew disengaged the Autopilot and responded to the RA. Crew notified ATC. When clear of conflict flight returned to normal cruise altitude. Closest approach noted was -400 on the TCAS directly below when flight reached an altitude of 13;400.
EMB-145 Captain reported an NMAC during cruise requiring the crew to disengage the autopilot and execute a climb maneuver to clear the conflict.  The conflicting VFR aircraft was not in communication with ATC.