B737-800
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 241; Flight Crew Total 7231; Flight Crew Type 3181
Situational Awareness
Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Issued Advisory / Alert; Flight Crew Took Evasive Action; General Declared Emergency
ATC Equipment / Nav Facility / Buildings; Weather; Human Factors
While proceeding southbound on AR24; approaching OHLAA intersection; there was a line of weather running southwest to northeast across the airway; for which we requested and received a clearance to deviate towards the East; and to proceed direct to URSUS intersection afterwards. The controller reported to us; and other aircraft on the frequency; that around that area of weather there was reported moderate turbulence from FL320 all the way up to FL360 or FL380; I cannot recall but we were about to hit that area. Being downwind of the weather; with the wind at around 63 knots out of the southwest and the reported turbulence; we decided to take a wide deviation to try to be as clear as possible of any eddies and/or downwind turbulence we may encounter; on top of the already reported moderate turbulence. Throughout the deviation we experienced 3 pockets; of about 10 seconds each; of moderate turbulence; while experiencing continuous light turbulence; most of it was due to erratic wind speed and direction changes inside the reported area. While deviating; the controller became worried that we were leaving radar coverage; and asked us how far or how long before we could turn on course to URSUS. I was still deviating; although we didn't have that much to go; and I told him that we had about another twenty miles before we could turn on course. He said that he was not painting any weather and I needed to turn to a heading of 220; I believe; to which I replied that we were unable to do so; that the most I could turn in about a minute would be a heading of 200 or 210; I cannot recall. He said he understood that I was using my PIC's emergency authority to not comply with an ATC instruction; to which I replied that that was affirmative. A minute later we were clear of the weather and we turned towards URSUS; letting the controller know we were done deviating. It is worth mentioning that while we were deviating; we could see on our Navigation Display's TCAS information; that there were a number of airplanes inside the area of weather we were painting; and where the controller said he wasn't painting anything. Those same airplanes were reporting moderate turbulence; so strong; we could actually hear the voice of the pilot talking; jumping around and changing tone due to the jolts they were experiencing. There was no way I was going to turn the aircraft any sooner towards URSUS. One; we were painting weather; and Two; those guys to our right were getting an awful ride; while ours was manageable. I'll also like to add that the controller was very professional and courteous throughout the event; not just to us; but to all aircraft deviating.
B737 Captain reports using his Captain's emergency authority to avoid turbulence associated with a thunderstorm; beyond what the Controller would authorize due to Radar coverage.