Row A
Total concentration: the ice coverage of an area determined by its concentration and expressed in tenth (in this example, 7/10)
Row B
Partial concentration: the break-down of the total ice coverage expressed in tenths and graded by thickness. The thickest starting from the left and in this example, 2/10 is the thickest.
Row C
Stage of development: the type of ice in each of the grades, determined by its age, that is 1/10 is thick lake ice (7), 2/10 is medium lake ice (5) and 3/10 is thin lake ice (4).
Row D
Floe Size: the form of the ice determined by its floe size for each section. In this example, big floes (5) for thick lake ice (7); medium floes (4) for medium lake ice (5); and small floes (3) for thin lake ice (4).
| Column | Description |
|---|---|
| E | Trace of ice thicker/older then Sa |
| F | Thickest |
| G | Second thickest |
| H | Third thickest |
| I | Additional groups |
Lake Ice Symbols
| Open Water | | Ice Free | | Fast Ice |
Stage of Development (SoSaSbScSdSe)
| Description | Thickness | Code |
|---|---|---|
| New Ice | < 5 cm | 1 |
| Thin Lake Ice | 5 - 15 cm | 4 |
| Medium Lake Ice | 15-30 cm | 5 |
| Thick Lake Ice | 30-70 cm | 7 |
| Very Thick Lake Ice | > 70 cm | 1. |
| Undetermined/Unknown | X |
Floe Size (FaFbFc)
| Description | Width | Code |
|---|---|---|
| Pancake ice | 0 | |
| Small ice cake; brash ice | < 2m | 1 |
| Ice cake | 2 - 20m | 2 |
| Small floe | 20 - 100m | 3 |
| Medium floe | 100 - 500m | 4 |
| Big floe | 500 - 2000m | 5 |
| Vast floe | 2 - 10 km | 6 |
| Giant floe | > 10 km | 7 |
| Fast Ice | 8 | |
| Undetermined or unknown | X | |
| Ice in strips |  |
Concentration of Ice
 | < 1/10 | Open Water |
 | 1-3/10 | Very open drift |
 | 4-6/10 | Open drift |
 | 7-8/10 | Close pack |
 | 9/10 | Very close pack |
 | 9+/10 | Very close pack |
 | 10/10 | Compact/Consolidated ice |
WMO Concentration Colour Code - Lake Ice
| Colour* | Description |
|---|---|
 |
Ice Free |
 |
< 1 Tenth Ice |
 |
1-3 Tenths Ice |
 |
4-6 Tenths Ice |
 |
7-8 Tenths Ice |
 |
9-10 Tenths Ice |
 |
Fast Ice of Unspecified Stage of Development |
 |
Undefined Ice |
| Optional | |
| No Information | Areas for which no information is known are identified accordingly. |
* Colour is based on total ice concentration.
WMO Stage of Development Colour Code - Lake Ice
| Colour | Description | Thickness |
|---|---|---|
|
Ice Free | |
|
Ice of Unspecified Stage of Development (open water) | |
 |
New Lake Ice | <5 cm |
 |
Thin Lake Ice | 5-15 cm |
 |
Medium Lake Ice | 15-30 cm |
 |
Thick Lake Ice | 30-70 cm |
 |
Very Thick Lake Ice | > 70 cm |
|
Fast Ice of Unspecified Stage of Development | |
|
Undefined Ice |
Colour is based on stage of development of predominant ice.