Flight Crew Air Transport Pilot (ATP)
Communication Breakdown
ATC Issue All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented
Human Factors; Procedure; Weather
We were on our filed route LAS direct to BCE; then J100 approaching an area of thunderstorms prior to BCE with tops to FL450. We requested a left deviation for weather and were cleared to deviate 'left of course; direct to EKR when able.' We deviated approximately 12 NM left of course to get past the first line of cells. In the vicinity of BCE was another line of cells north of our original course and straight in front of us. We initiated a right turn to avoid those cells; remaining left of our original course line of LAS-BCE-J100. We were still left of our original course and turning toward EKR as we cleared the second line of cells; when SLC Center asked us why we had turned right. We informed them we had been cleared left of course and remained left of our original course the entire time. The Controller indicated that a right turn was not allowed. My understanding was my clearance was to remain left of my original course and that ATC would provide separation for us as long as we did not deviate right of our original course. I was asked to contact SLC Center on arrival; which I did. They informed me the situation would require further review.
An Air carrier had clearance to deviate left of course for weather and direct EKR when able. After clearing the first cell a right turn was made to avoid a second cell; still remaining left of the original course line. ATC informed the crew that they should have received clearance for the right turn.