by Jonathan M. Stern
Global Weather Settings
To create a user-defined global weather situation, take the following steps:
- Select World/Weather.
- Select Global for the Weather Area.
- Select Clouds.
- Select Create, Edit, or Delete. If you select Create, you have the opportunity to program an additional layer of clouds. If you select Edit, you can edit the presently selected cloud layer (change the tops, bases, coverage, or deviation). If you select Delete, the currently selected layer of clouds are removed after you confirm this selection.
- When creating or editing a cloud layer, you may define the bases and tops of the clouds with an MSL altitude, the coverage (the fraction of the sky covered by cloud from 1/8 to overcast), and the deviation of the layer, which is the maximum random variation of the tops and bottoms of the cloud layer. With version 5.1, you may also select the degree of turbulence to be found in the cloud layer and whether or not airframe icing will occur within the cloud layer. Alternatively, with version 5.1, a cloud type may be selected, which will automatically program certain other cloud factors to correspond to conditions associated with the selected cloud type (e.g., altitude, turbulence level, and icing).
TABLE 13.2 Cloud Types Family Type Description Typical Altitudes High Cirrus Appear as thin feather-like ice crystal clouds in patches or narrow bands. Larger ice crystals often trail downward in well-defined wisps called "mares' tails." Wispy cirrus clouds usually do not contain significant icing conditions or turbulence. Dense, banded cirrus are often turbulent. Bases range from 16,500 to 45,000 feet in the middle latitudes. High Cirrostratus A thin whitish cloud layer appearing like a sheet or veil. Cloud elements are diffuse, at times partially striated or fibrous. Due to their ice crystal composition, the clouds are associated with halos—large luminous circles around the sun or the moon. They contain little or no turbulence or icing conditions. They may, however, restrict visibility, making the strict use of instruments necessary. Bases range from 16,500 to 45,000 feet in the middle latitudes. High Cirrocumulus Thin clouds; the individual elements appear as small white flakes or cotton patches. Cirrocumulus may contain some turbulence and icing conditions. Bases range from 16,500 to 45,000 feet in the middle latitudes. Middle Altostratus Appear as a bluish veil or layer of clouds. They are often associated with altocumulus, and can gradually merge into cirrostratus. The sun may be visible dimly through altostratus. These clouds produce little or no turbulence but moderate icing conditions. Bases range from 6,500 to 23,000 feet in the middle latitudes. Middle Altocumulus Composed of white or gray layers or patches of solid clouds. They may have a waved or roll-like appearance. Altocumulus tend to contain some turbulence and a small amount of icing conditions. Bases range from 6,500 to 23,000 feet in the middle latitudes. Middle Nimbostratus A gray or dark massive cloud layer, diffused by more or less continuous rain, snow, or ice pellets. Although classified in the middle cloud family, nimbostratus may merge into very low stratus or stratocumulus clouds. These clouds contain very little turbulence but may pose a serious icing problem if temperatures are near or below freezing. The prefix "nimbo" means rain cloud. Bases range from 6,500 to 23,000 feet in the middle latitudes. Low Stratocumulus These clouds are stratified cumulus clouds with bases that differ from the flat bases of stratus clouds in that their bases are globular masses or rolls. Some turbulence and possible icing at subfreezing temperatures should be expected in these clouds. Visibility is usually better than when low stratus clouds are present. Bases range from near the surface to 6,500 feet in the middle latitudes. Low Stratus Appear as gray, uniform, sheet-like clouds. They have relatively low bases. When associated with fog or precipitation, the combination can be troublesome for visual flying. These clouds contain little or no turbulence, but may contain hazardous icing conditions in temperatures near or below freezing. Bases range from near the surface to 6,500 feet in the middle latitudes. Low Cumulus Fair weather clouds that form in convective currents and are characterized by relatively flat bases and dome-shaped tops. Fair weather cumulus do not show extensive vertical development and do not produce precipitation. More often, cumulus indicate a shallow layer of instability. These clouds produce some turbulence but no significant icing. Bases range from near the surface to 6,500 feet. Extensive vertical Development Cumulonimbus Cumulonimbus clouds are the ultimate manifestation of instability. They are vertically developed clouds of large dimension with large boiling tops, often crowned with thick veils of dense cirrus (the anvil). Nearly the entire spectrum of flying hazards are contained in these clouds. Avoid them at all times! Bases may be as low as 1,000 feet. At the middle latitudes, tops can be as high as 65,000 feet.
Significantly, clouds are programmed in MSL altitudes in Flight Simulator even though they are generally reported in AGL altitudes in actuality. It is necessary, then, that you add the ground elevation to the desired height above the ground in programming clouds.
- Thunderstorms are also created from the Clouds menu. After choosing Create or Edit, Thunderstorms may be selected from the Type block. Thunderstorms cannot be used on Flight Simulator running with an EGA display. With version 5.1, thunderstorms are selected by the name of their corresponding cloud type (cumulonimbus).
- Select OK.
- Select Winds.
- Select Create, Edit, or Delete.
- When creating or editing a wind layer, select Winds Aloft or Surface Winds. Winds aloft are programmed in Flight Simulator (and forecast by meteorologists) with reference to true north, whereas surface winds are programmed (and reported by air traffic controllers) with reference to magnetic north. Go figure!
- If surface winds are being programmed, select whether steady or gusty winds are desired, a depth of the surface winds, a speed and direction, and turbulence level, if desired.
- If winds aloft are being programmed, select steady or gusty, base and tops of wind layer, speed and direction, and a turbulence level (if desired).
- Select OK.
- Select Temperature.
- Select Create, Edit, or Delete.
- Enter an MSL altitude at which you wish to control the temperature.
- Enter a temperature in degrees Fahrenheit.
- Select OK.
- If you want to program a variation between daytime and nighttime temperature, select the Day/Night box and enter the number of degrees in Fahrenheit by which you want the temperature to vary between day and night.
- Select Baro.
- Enter the desired barometric pressure (altimeter setting).
- If you want the altimeter setting to vary along the flight, select Drift.
- Select OK.
- With version 5.1, visibility can be controlled with selections from "unlimited" down to 1/16 mile. In order to control visibility, there must be a programmed cloud layer other than cumulonimbus, and visibility will be affected only below the clouds. To control visibility, press Visibility and select the desired visibility level. Then select OK.