Federal Meteorological Handbook No. 1 - Marrella

Table 6-1. Reportable Visibility Values
Source of Visibility Report
Automated Manual
a
M1/4 2 9 0 5/8 1 5/8 4 12
1/4 2 1/2 10 1/16
1 3/4 5 13
1/2 3 1/8 7/8 1 7/8 6 14
3/4 4
3/16 1 2 7 15
1 5 1/4 1 1/8 2 1/4 8 20
a 1 1/4 6 5/16 1 1/4 2 1/2 9 25
1 1/2 7 3/8 1 3/8 2 3/4 10 30
a 1 3/4 8 1/2 b
1 1/2 3 11 35
a. These values may not be reported by some automated stations.
b. Further values in increments of 5 statute miles may be reported, i.e., 40,
45, 50, etc.
6.6 Summary of Visibility Observing and Reporting Standards
Table 6-2 summarizes the applicability of visibility standards.
Table 6-2. Summary of Visibility Observing and Reporting Standards and
Procedures
Visibility
Surface
Variable
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3/4
Type of Station
Automated Manual
Represents 10-minutes of sensor Visual evaluation of
outputs. visibility around the horizon.
Reported when the prevailing visibility varies by 1/2 mile or more and the
visibility is less than 3 miles.
Tower Augmented.
Reported at stations with an
ATCT.
Sector Not reported. Reported at all stations.