Large Transport; Low Wing; 2 Turbojet Eng
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Other / Unknown
Aircraft Equipment Problem Less Severe; Inflight Event / Encounter Weather / Turbulence
General None Reported / Taken
Weather
The flight proceeded normally; the entire route was with light to moderate turbulence; our flight level was 360; and this level like all had reported light turbulence. Approximately 100 NM before PSX the turbulence increased to moderate. Turbulence levels were requested below; and we asked to descend to FL300.  Center reported that at this level there was occasional light turbulence. We noticed very light icing in the windshield wipers; and turned engine anti-ice on. Minutes later the icing increased and we asked to descend to a lower level. However the frequency was saturated and seconds later we felt vibration accompanied by Engine 1 Vibration of 4.0. The conditions were reported and we requested descent immediately flight to FL260. Severe icing level was encountered during this time and the Engine 2 Vibration reached 4.0. We performed the non-normal checklist as both motors presented icing and vibration which reached levels of 5.0 for no more than 5 seconds. This was during the descent to FL260; then both engines returned to normal vibration values. After our report we heard that several aircraft in the same sector reported severe icing conditions at the same altitudes; and some airplanes reported the same conditions in the Gulf of Mexico area.I want to say that during the preparation for our flight we did not receive information about the icing along of our route by Dispatch. They did not have reports of icing in the area; though our Jeppesen application also had information about icing conditions. The rest of the flight was carried out without a hitch.
Air carrier Captain reported severe icing in cruise in the vicinity of IAH.