Date: 201907
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Weather elements / visibility: Thunderstorm; Turbulence
Aircraft: EMB ERJ 145 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Confusion; Communication Breakdown
Anomaly: ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Returned To Clearance
Contributing factors: Procedure; Weather; Airspace Structure
Primary problem: Procedure

Narrative: I was Pilot Monitoring on flight from ZZZ-ZZZ1. We were deviating around thunderstorms building at FL 330. On the hand off to the next Center sector; the Pilot Flying asked the Pilot Monitoring to request a climb to FL250 and deviate an additional 10 degrees left to avoid a buildup. On the check-in; I; (Pilot Monitoring); provided the flight number and altitude along with the Captains request to deviate and climb. I misspoke and said '10 right' instead of '10 left'. The Captain corrected me on the hot mic as ATC approved 10 degrees right deviation. I cannot recall the exact verbiage of the initial ATC approval as the radio was saturated with approval from ATC; the Pilot Flying (Captain) correcting me on the hot mic and other aircraft calling Center. I then transmitted our correct intentions to ATC and said 'apologies; [Aircraft X] request 10 left' the controller said 'Ok; but I have to work on the 10 left'. The Captain then initiated a climb to FL350 in our current heading. Leaving 33;100 ft.; ATC came back and said '[Aircraft X]; confirm you're still at FL330' followed by '[Aircraft X]; the climb to 350 was not approved' followed in rapid succession by '[Aircraft X] climb and maintain FL 340.' We stopped our climb at 340. ATC came back and said '10 degrees left was approved (it wasn't) but not the climb; I didn't approve that.' To the best of our knowledge; no loss of separation occurred; no TCAS advisory was provided and no pilot deviation Brasher Statement was issued. I believe [because of] the high workload for the controller in the sector; almost all aircraft around us were deviating for weather as well; with very similar requests and altitudes including other [Company] flights; was a contributing factor. I also believe the change in direction of our initial requested deviation confused the controller and Captain about what was and wasn't approved. We effectively had three separate clearance requests at hand; 10 right; 10 left and climb to 350. The ambiguity around which of the 3 was approved was a cause. The immediate urgency to climb above the storm was also a contributing factor. I would believe that an expectation bias was a factor in the Pilot Flying's actions to interpret the clearance as quickly as he did; and climb. There was not enough time for me to remove myself from the ATC requests and discuss the clearance with the Pilot Flying/Captain; because he drives the whole MCP in [Company]'s CRM. I recognize this as a learning event. Emphasizing the importance of clarifying any ambiguity in the crews understanding of clearances issued by ATC. The immediate urgency to climb above the thunderstorm and the traffic associated with the frequency created a tough environment. I would also like to add that there is one glowing factor that I cannot ignore in this and I hope the committee discusses: At my previous 91 and 135 jobs flying jets; the Pilot Flying and Pilot Monitoring are always physically in agreement with altitude changes because the Pilot Monitoring sets the altitude selector (set it and shoot it/announce it) followed by the Pilot Flying manipulating the mode control panel to 'get there' (V/S; FLC etc). The 'set it and shoot it' method is a legacy way of accomplishing altitude changes. This 'Pilot Flying drives the whole MCP solo' idea is a [Company] thing and creates a normalization of deviance with altitude changes; as the Pilot Flying gets accustomed to accomplishing altitude changes alone with simple verbal cues (or less) from the Pilot Monitoring. In high work load environments the first thing to go seems to be the verbal 'me too' agreements from the Pilot Monitoring in altitude changes. The obvious example here is when the Pilot Monitoring is communicating on the radio and the Pilot Flying has an urgency to climb. I'd be happy to discuss this subject further; as it would have prevented this event from occurring.




Synopsis: EMB145 First Officer reported mis-communications with ATC and CRM failure resulting in altitude deviation.