MAFOR marine forecast decode table
Environment Canada issues MARine FORecast (MAFOR) coded forecasts as part of their marine weather products for the Great Lakes and the St.Lawrence and Saguenay Rivers.
| Group 1 | Group 2 | Group 3 | Group 4 | Group 5 |
|---|---|---|---|---|
| YYG1G1 | 0AAAam | 1GDFmWm | (2VSTxTn)1 | (3DkPwHwHw)1 |
Group 1
YYG1G1/
- YY: Day of the month
- G1G1 : Time of commencement of forecast (UTC). Midnight is encoded as 00.
Group 2
0AAAam
The maritime area to which the whole forecast or set of forecasts refers. If the geographical name for the forecast region is used instead of the indicator AAAa , it shall be inserted at the place of this group.
| am Code | Portion of the Maritime Area |
|---|---|
| 0 | Whole of the area AAA |
| 1 | Northeast quadrant of the area AAA |
| 2 | Eastern half of the area AAA |
| 3 | Southeast quadrant of the area |
| 4 | Southern half of the area AAA |
| 5 | Southwest quadrant of the area AAA |
| 6 | Western half of the area AAA |
| 7 | Northwest quadrant of the area AAA |
| 8 | Northern half of the area AAA |
| 9 | Rest of the area AAA |
Group 3
1GDFmWm
- G: Forecast period
- D: Direction from which the wind is blowing
- Fm: Wind speed
- Wm: Forecast weather
| G Code |
Forecast Period Descriptive |
D Code |
Wind Direction |
Fm Code |
Wind Knots |
Wm Code |
Forecast Weather |
|---|---|---|---|---|---|---|---|
| 0 | Beginning of period | 0 | Calm | 0 | 0 - 10 | 0 | Visibility greater than 3 nm |
| 1 | Valid for 3 hrs | 1 | Northeast | 1 | 11 - 16 | 1 | Risk of accumulation of ice on superstructures |
| 2 | Valid for 6 hrs | 2 | East | 2 | 17 - 21 | 2 | Strong risk of accumulation of ice on superstructure |
| 3 | Valid for 9 hrs | 3 | Southeast | 3 | 22 - 27 | 3 | Visibility ≥ 1 nm and ≤ 3 nm |
| 4 | Valid for 12 hrs | 4 | South | 4 | 28 - 33 | 4 | Visibility < 1 nm, including fog |
| 5 | Valid for 18 hrs | 5 | Southwest | 5 | 34 - 40 | 5 | Drizzle |
| 6 | Valid for 24 hrs | 6 | West | 6 | 41 - 47 | 6 | Rain |
| 7 | Valid for 48 hrs | 7 | Northwest | 7 | 48 - 55 | 7 | Snow, or rain and snow |
| 8 | Valid for 72 hrs | 8 | North | 8 | 56 - 63 | 8 | Squally weather with or without showers |
| 9 | Occasionally | 9 | Variable | 9 | 64 + | 9 | Thunderstorms |
Group 4
2VSTxTn M
- V: Visibility
- S: State of the sea
- Tx: Maximum air temperature
- Tn: Minimum air temperature
| V Code |
Visibility | S Code |
State of the Sea Descriptive |
Height (meter) |
Tx,Tn Code |
Temperature (degrees Celsius) |
|---|---|---|---|---|---|---|
| 0 | Less than 50m | 0 | Calm | 0 | 0 | Less than -10 |
| 1 | 50 - 200m | 1 | Calm | 0 - 0.1 | 1 | -10 to -5 |
| 2 | 200 - 500m | 2 | Smooth | 0.1 - 0.5 | 2 | -5 to -1 |
| 3 | 500 - 1000m | 3 | Slight | 0.5 - 1.25 | 3 | About 0 |
| 4 | 1 - 2km | 4 | Moderate | 1.25 - 2.5 | 4 | 1 to 5 |
| 5 | 2 - 4km | 5 | Rough | 2.5 - 4.5 | 5 | 5 to 10 |
| 6 | 4 - 10km | 6 | Very rough | 4 - 6 | 6 | 10 to 20 |
| 7 | 10 - 20km | 7 | High | 6 - 9 | 7 | 20 to 30 |
| 8 | 20 - 50km | 8 | Very high | 9 - 14 | 8 | Greater than 30 |
| 9 | 50km + | 9 | Phenomenal | > 14 | 9 | Not forecast |
Group 5
3DkPwHwHw
- Dk: Direction from which swell is moving
- Pw: Period of waves
- HwHw : Height of forecast waves, in units of 0.5 metres
| Dk Code |
Direction from which the swell is moving | Pw Code |
Period of waves In seconds |
|---|---|---|---|
| 0 | Calm | 0 | 10 |
| 1 | Northeast | 1 | 11 |
| 2 | East | 2 | 12 |
| 3 | Southeast | 3 | 13 |
| 4 | South | 4 | 14 or more |
| 5 | Southwest | 5 | 5 or less |
| 6 | West | 6 | 6 |
| 7 | Northwest | 7 | 7 |
| 8 | North | 8 | 8 |
| 9 | Variable | 9 | 9 |
| / | Calm or not determined |
Note 1: MAFOR groups 4 and 5 are not included in the Canadian MAFOR bulletins issued by the Meteorological Service of Canada and are being provided for reference purposes only. This is consistent with the World Meteorological Organization's coding regulations for the MAFOR bulletins.
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