Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 176; Flight Crew Total 21850; Flight Crew Type 2766
Deviation - Track / Heading All Types; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Issued New Clearance; Flight Crew Took Evasive Action
Procedure; Weather
Approaching JAINS on L451 had to deviate around a line of thunderstorms.  Received a clearance to deviate left of course.  It turned out that we needed an additional 30nm.  We were unable to contact ATC on HF; so we used weather deviation procedures; (lights on; blind broadcasts of pan pan and our position).  Approximately 1 min later while typing a request on CPDLC established comm with ATC and was cleared direct ILIDO int.
Air Carrier Captain reported difficulty communicating with ATC over the western Atlantic.  Emergency authority was exercised to avoid weather prior to receiving clearance.