Flight Categories
Category/ |
Ceiling (feet) |
Visibility (km, m) |
|
---|---|---|---|
VFR |
> 3000 ft or None |
and |
> 8 km |
MVFR |
1000-3000 ft |
and/or |
5 to 8 km |
IFR |
500-1000 ft |
and/or |
1.6 to 5 km |
LIFR |
300-500 ft |
and/or |
0.8 to 1.6 km |
VLIFR |
< 300 ft |
and/or |
< 0.8 km |
BECMG and TEMPO
Guidelines for using "BECMG" and "TEMPO" groups:
- Indicate significant changes in the weather elements using the "BECMG" or "TEMPO" groups showing the time duration expected. The beginning and end times are included in whole hours UTC (encoded Z).
- TEMPO indicator and its time group are used for expected fluctuations in meteorological conditions that may cross threshold values and last for less than an hour over less than half the forecast period. Longer fluctuations are represented by the "BECMG" group.
- "FM" abbreviation is used when a set of forecast conditions are expected to change significantly. It is followed by a four-figure time group in whole hours and minutes indicating when change is expected to occur.
- "PROB" abbreviation is used to indicate the possibility of alternative values for a forecast element. Include the probability in tens of percent and the time period during which the alternatives are expected after the forecast element followed by the alternative value. PROB can be used with TEMPO to indicate the probability of temporary fluctuations in conditions. Probabilities less than 30 percent should not be indicated using TEMPO, and probabilities greater than 50 percent should be represented instead using BECMG or TEMPO groups, or contained in a separate FM group.
Recommendation: The number of change and probability groups should be kept to a minimum and should not normally exceed five groups.
Conditional Groups
Wind |
|
Visibility |
|
Weather |
|
Ceiling |
|
Vertical Visibility |
|
Note: Other criteria based on local aerodrome operating minima are to be considered in parallel with similar criteria for the issuance of SPECI developed in response to Appendix 3, 2.3.2 l.
Cloud Codes
- 60 = 10km
- 65 = 15 km
- 70 = 20km
- 75= 25km
- 80= 30km