Table 3.4-2
OBSERVATIONAL REPRESENTATIVENESS GUIDANCE |
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| Winds | ||||||
| Direction ± 30° Speed ± 5KTS |
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| Temperature, Dew Point & Altimeter Setting | ||||||
| Allowable Difference | ||||||
| Temperature | Wind £ 6 KT Temp ± 10° F | |||||
| Wind >6 KT Temp ± 2° F | ||||||
| Dew Point | ± 4° F | |||||
| Altimeter Setting | ± 0.02 in Hg | |||||
| Cloud Amounts | ||||||
| Observed (in eighths) | Allowable Report | Allowable Difference |
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| 0 | clear | + 1 reportable value | ||||
| 1/8 - 2/8 | few | ± 1 reportable value | ||||
| 3/8 - 4/8 | scattered | - 1 reportable value | ||||
| 5/8 - 7/8 | broken | + 1 reportable value | ||||
| 8/8 | overcast | - 1 reportable value | ||||
| Visibility | ||||||
| Condition | Allowable Difference | |||||
| up to 2 miles | ± 1/2 mile | |||||
| >2 to 4 miles | ± 1 mile | |||||
| >4 to 7 miles | ± 2 reportable values | |||||
| ³ 8 miles | ASOS reports ³ 7 miles | |||||
AVIATION FLIGHT WEATHER CATEGORIES |
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| Ceiling | Visibility | |||||
| VFR | >3000 | > 5 miles | ||||
| MVFR | ³ 1000 ft but £ 3000 ft | ³ 3 miles but £ 5 miles | ||||
| IFR | <1000 ft | <3 miles | ||||