|Q||Quadrant of globe|
|LLL||Latitude to nearest tenth of a degree|
|lll||Longitude to nearest tenth of a degree|
|GG||Time of observation to nearest hour|
|DD||Wind direction - 32 possibilities|
|F||Wind force on Beaufort scale|
|PP||Pressure in millibars|
|TT||Temperature in degrees Centigrade|
|ClCmChN||Amount and type of cloud|
|Td||Temperature difference between sea and air|
|DKk||Direction and type of swell|
|a||Characteristic of pressure change in past 3 hours|
The synoptic was Cyphered by a trigram substitution from one of a series of tables which were changed every 6 days or so, though each series of tables was used twice, the second appearance being about a month after the first. The actual table used depended on time of day and date, and it was usual for each synoptic to be broadcast several times, encyphered on different tables each time. The trigram substitution was broken in Mr. Archer's party in the Met Section, and the resulting synoptic decodes (normally referred to as Archery) provided a good crib into WWs.
The 1st edition of the Wetterkurzschluessel was captured early in the war, the 2nd edition with Weimar, Eisenach, and Naumburg from U 559 in October 1942; and the 3rd edition in June 1944. It was this providential pinch off U 559 in the Mediterranean which enabled us to start breaking Shark once more; without it breaking would have been delayed many months although the book and indicator tables had already been reconstructed to a considerable extent.
3. RECONSTRUCTION AND EXPLOITATION:
August 1941 - December 1941:
Operational Breaking of Dolphin (which at that time included Shark) started in earnest in August 1941 - at a time when not only had the previous two months' keys been captured and decoded, but also all Short Signal code books and indicator tables were in our hands; (except those associated with Rossaries which were being reconstructed).
At this time two or three long E-bars (reporting sightings) could be expected from U Boats every 24 hours; many of them started GUSTAV GELB (Feindlicher Geleitzug in Sucht) or FRITZ IDA