Visibilities and Obstructions to Vision

CHAPTER TWO

METEOROLOGY FLIGHT PLANNING

Ceiling Heights

The height of the sky cover is plotted in the 6 o'clock position of the station model. Heights

are given in hundreds of feet AGL. Recall the definition of a ceiling, because it also applies to

the Weather Depiction Chart. If the sky cover is broken, overcast, or if the sky cover is an

obscuration, the height will represent the height of the ceiling. If the sky cover is scattered, the

height represents the height of the lowest scattered layer of clouds. When a broken or greater sky

cover is plotted without a height entry, the clouds are thin. If an obscuration is plotted without a

height entry, it indicates a partial obscuration.

Visibilities and Obstructions to Vision

Visibilities of 6 statute miles or less will be entered at the 9 o'clock position of the station model

and will be indicated in miles and fractions of miles. Visibility of greater than 6 statute miles will

be omitted. Precipitation and obstructions to vision will follow the visibility, using the same

weather symbols as presented in Figure 2-3. When several types are occurring simultaneously,

only the most significant one or two types will be entered. One symbol unique to the Weather

Depiction Charts is used when clouds are topping the ridges of mountains, as shown in Figure 2-16.

Figure 2-17 Clouds Topping Ridges Symbol

Legend

In addition to the frontal symbols on the Weather Depiction Chart, three areas associated with

ceilings and visibilities are also depicted by a set of lines and shadings. The legend on the lower

right-hand corner of the chart describes each of these three areas, which is summarized in Figure

2-17. A solid line enclosing a shaded area indicates IFR conditions: ceilings below 1000 feet

and/or visibilities below three miles. A line enclosing an unshaded area indicates marginal VFR

(MVFR) conditions: ceilings between 1000 and 3000 feet and/or visibility between three and five

miles. The portion of the chart that is not enclosed by linesshaded or unshadedindicates VFR

conditions: ceilings of greater than 3000 feet and visibilities over five miles.

2-18 DATA DISPLAYED ON WEATHER IMAGERY PRODUCTS