Marine Surface Observations - IMMT is digital data set DSI-1183 at the National Climatic Data Center (NCDC). IMMT is International Maritime Meteorological Tape. The IMMT format is the standard for marine meteorological data exchange around the world, and is approved by the World Meteorological Organization (WMO). At NCDC, the data may be stored on digital media other than tapes, but the 131 ... character record format typical of IMMT remains. Data consists of moving and stationary ship observations from the seas and oceans of the world. Data includes: Ship location-course and speed Date and time Wind direction and speed Sea wave height and period Predominant sea swell height-period and direction Secondary sea swell height-period and direction Cloud types, heights, and amounts Visibility Precipitation Air temperature Dew point temperature Wet bulb temperature Sea temperature Sea level pressure Pressure tendency Present weather Past weather primary and secondary Ice accretion thickness and rate Sea ice development, concentration, motion, and bearing.