Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Situational Awareness
ATC Issue All Types; Conflict Airborne Conflict
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Took Evasive Action
Procedure; Human Factors
The flight was routine up until we entered LA Center. LAX weather deteriorated and the airport had gone into holding. Several aircraft were issued holding instructions on the arrival. Our flight was issued a 'descend via' clearance on the Big Bear arrival. Shortly after the descend via clearance we were issued an amendment to the altitude which was FL260. At this point I began calculating holding fuel to determine how much time we had before a diversion would be necessary as we knew holding instructions were coming our way as well. We were slowed to 250 kts and in a shallow descent to FL260. Within several hundred feet of reaching FL260 LA center issued a clearance to climb back up to FL270 for traffic. There was no sense of urgency in his voice at this point. There should have been.Within seconds of the clearance the nose begins to rise to begin its climb to FL270 (however still in a vertical speed descent) and at that point the aircraft notified us of a DESCEND resolution advisory. I begin complying by increasing the vertical speed since we were so close to the 'green' on the PFD and as I was about to disconnect the autopilot to comply with SOP memory items when we received what I believed to be a very aggressive RA CLIMB literally a second or two into the RA descent. Seeing the aircraft so proximal to ours on the ND (10 mile ring); I disengaged auto pilot immediately and set takeoff thrust and pitch for the 'green'. The event happened so fast. I did see an aircraft in my windscreen for a brief moment somewhere in this process; however I couldn't tell you type or airline. My First Officer and I were very upset realizing how close we may have come to a collision. Also in awe as we never would have thought we would experience a double back to back RA in real life. I'm very thankful we practice events like this in the sim. Weather moved past LAX and they re-opened the arrival corridor; at which we changed gears to focus on our arrival to LAX.Our on board weather radar failed along with predictive wind shear in this process. My familiarity with the Los Angeles area; the current sector communication; the positive situational awareness of the current environmental conditions; along with my first officer's input was the reason I made the decision to continue to LAX as we knew we would be able to avoid the weather that had moved past and was heading in the northeasterly direction of our planned alternate.
Air Carrier Captain reported reacting to two back-to-back RA's on a descend via clearance into LAX.