The purpose of this North Atlantic Operations Bulletin (NAT OPS) Bulletin is to inform North Atlantic (NAT) operators of upcoming changes to contingency and weather deviation procedures. These procedures are applicable in the NAT Region 28th of March 2019, coincident with the trial of Advanced Surveillance-Enhanced Procedural Separation (ASEPS) using Automatic Dependent Surveillance- Broadcast (ADS-B) in the Shanwick, Gander and Santa Maria Oceanic Control Areas, and will subsequently replace those currently published in the PANS ATM (ICAO Doc 4444).