I checked back to read JCJ's earlier post (#185) concerning what the captain is supposed to have said about cunims.
Otelli writes that the weather and visibility since takeoff from Rio have been excellent and continue to be so in the vicinity of Natal, the lights of which the crew can see ahead at 00:44:45. Beyond Natal, of course, is the South Atlantic.
Otelli concludes that the captain's comment on cunim must refer to the ITCZ ahead, particularly as, four minutes earlier, the captain and Bonin were discussing the outside air temperature during the crossing of the zone.