The following explanation from LT Eckardt was received in response to an enquiry made by the ratitor to the webmaster of the Fleet Numerical Meteorology and Oceanography Center at http://www.fnmoc.navy.mil/ :

The header stamp is as follows: (taken from the most recent Pac IR image)

F14	which DMSP satellite was used for the image
Merc	type of image projection (mercator)
12.5 km	resolution of image
IR	InfraRed image (vice visual)
0322Z 20Jan	Earliest time of image
0701Z 20Jan	Latest time of image

The time means that the passes that were merged together from F14 to make this conglomeration image were from 0322 to 0701. Because these satellites are polar orbiters, we must paste several passes together to create one useable image over an area so big.

Z time (or Zulu time) refers to the standard world time zones where Z refers to the time in GMT. The West Coast is on +8 (V) time from GMT such that our time V + 8hrs = Z. So the image I refer to above was created from passes valid 1922V 19Jan to 2301V 19Jan ... and so that image is between 14 to 9 hours old.