Medium Large Transport
Flight Crew Air Transport Pilot (ATP)
Communication Breakdown; Confusion; Distraction
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Weather / Turbulence
Human Factors; Procedure
On climb out we were cleared to climb unrestricted to FL190 by LAS Departure.  During the climb we needed to deviate around several CB's left over from a line of thunderstorms that passed through the area several hours earlier; and we were cleared to do so via LAS Departure.  Shortly after we were finished deviating we turned back to join the departure when LAS departure handed off to LA Center on 124.62. It appeared that the LA Center controller was working several different frequencies and due to this; communication with LA Center was very difficult. Due to difficulty in communication we were unable to obtain a clearance to continue our climb; and we were also unable to obtain a clearance to perform additional deviations around additional CB's; so we were forced to level at FL190 for several minutes; as well as penetrate two CB's that gave us momentary moderate turbulence with altitude excursions of +/-150 feet. After at least three attempts to contact LA Center; my first officer switched back to LAS Departure to verify that we had been given the correct frequency. After switching back to 124.62 for LA Center it took us at least two or three more attempts to establish contact with the controller before we were cleared to climb to FL340 and then FL360.  Shortly after being cleared to climb; LA Center issued a revised clearance to proceed direct BTY; direct OAL; as filed.  We were on the SHEAD departure at that point and since BTY wasn't part of our original clearance; I asked my first officer to question the clearance with ATC prior to accepting it; since several times recently I've seen LA Center attempt to clear us via BTY when we are on the SHEAD departure only to have them correct the clearance when queried; since BTY is not on our filed/cleared route.  We were unable to establish contact with LA Center for approximately 4 minutes this time and in the meantime we were unsure as to whether we were supposed to overfly BTY; or just proceed direct to OAL since BTY wasn't on our route.  In summary we were basically in a lost comm state twice with LA Center.  Once on initial contact for approximately three minutes while we were stuck in the tops of CB's needing to climb; and the second time for approximately four minutes when we needed to clarify a clearance with the controller.  I fly quite a bit of late night flights and it's becoming more common than it has been in the past to see ATC sectors combined late at night where controllers are placed in a position of being overloaded while working multiple frequencies/sectors.  This is not a safe practice as it places both pilots and controllers in a difficult position.ATC's decision to combine multiple frequencies/sectors late at night which places the controller in a position of often becoming overloaded or task saturated due to combined frequencies/sectors.  While I understand the government's desire to save money on staffing by doing this; it's my opinion that such practices are reducing safety and placing both pilots and especially controllers in a bad position.
Pilot reported of not being able to communicate with ATC on a consistent basis and has questions about the routing that ATC has issued.