The MAFOR code was created to transmit weather forecasts in a simply form that is easy to hear and transcribe from a radio broadcast. The code begins with a date/time group, followed by the name of the area the forecast applies to, and one or more five-digit groups beginning with "1" for weather forecast, which may be followed by an optional group beginning with "2" for visiblity and wave height. Each MAFOR broadcast is followed by a brief description of centers of high and low pressure areas, and their forecast location, direction and speed.
Date Group: DDHHMM/
DD is the day of the month
HHMM is the time of the beginning of the forecast period in Coordinated Universal Time (UTC).
"/" the last digit of this group is not used.
Weather Group: 1HDVW
1 - weather group identifier
H - period of time covered by the forecast
0 - Existing conditions at beginning of period
1 - 3 hours
2 - 6 hours
3 - 9 hours
4 - 12 hours
5 - 18 hours
6 - 24 hours
7 - 48 hours
8 - 72 hours
9 - Occasionally
D - wind direction
0 - Calm
1 - Northeast
2 - East
3 - Southeast
4 - South
5 - Southwest
6 - West
7 - Northwest
8 - North
9 - Variable
V - wind velocity
0 - Beaufort Number 0-3 (0 - 10 knots)
1 - Beaufort Number 4 (11 - 16 knots)
2 - Beaufort Number 5 (17 - 21 knots)
3 - Beaufort Number 6 (22 - 27 knots)
4 - Beaufort Number 7 (28 - 33 knots)
5 - Beaufort Number 8 (34 - 40 knots)
6 - Beaufort Number 9 (41 - 47 knots)
7 - Beaufort Number 10 (48 - 55 knots)
8 - Beaufort Number 11 (56 - 63 knots)
9 - Beaufort Number 12 (64 - 71 knots)
W - forecast weather
0 - Moderate or good visibility (greater than 3 n.mi.)
1 - Risk of ice accumulation (temperature 0?C to -5?C
2 - Strong risk of accumulation of ice (air temperature below -5?C
3 - Mist (visibility 1/2 to 3 n.mi.)
4 - Fog (visibility less than 1/2 n.mi.)
5 - Drizzle
6 - Rain
7 - Snow or rain and snow
8 - Squally weather with or without showers
9 - Thunder storms
Optional Group: 2VS
2 - supplementary group identifier, same period as preceding group.
V - visibility
0 - Less than 50 meters
1 - 50 - 200 meters
2 - 200 - 500 meters
3 - 500 meters to 1/2 nautical mile
4 - 1/2 to 1 nautical mile
5 - 1 to 2 nautical miles
6 - 2 to 5 nautical miles
7 - 5 to 12 nautical miles
S - sea state (wave height in meters)
0 - Calm
1 - Calm (rippled) 0 - 0.1m
2 - Smooth (wavelets) 0.1 - 0.5m
3 - Slight 0.5 - 1.25m
4 - Moderate 1.25 - 2.5m
5 - Rough 2.5 - 4m
6 - Very Rough 4 - 6m
7 - High 6 - 9m
8 - Very High 9 - 14m
9 - Phenomenal over 14m
MAFOR 0403/ Ontario 12548 14755 245H 12720
0403 Marine forecast valid starting the 4th day of the month at 03 UTC time
Ontario Lake Ontario
1 Weather forecast indicator
2 First 6 hours
5 Southwest wind
4 at 28 - 33 knots
8 Squally weather with or without showers.
1 Weather forecast indicator
4 Next 12 hours of forecast period
7 Northwest wind
5 at 34 - 40 knots
5 with drizzle.
2 (for same period)
4 visibility 1/2 - 1 nautical mile
5 rough seas, wave heights 2.5 - 4 metres
1 Weather forecast indicator
2 Final 6 hours of the forecast period
7 Northwest wind
2 at 17 - 21 knots
0 visibility greater than 3 nautical miles.
Weather
Beaufort Scale
Saffir-Simpson Hurricane Scale
