Weather depiction charts are a valuable tool used by meteorologists, pilots, and weather enthusiasts to visualize current weather conditions. These charts provide a snapshot of a wide range of meteorological information, allowing users to quickly assess the state of the atmosphere.
What is a Weather Depiction Chart?
The Weather Depiction chart is computer-generated from METARs and is a graphical representation of weather conditions at a specific point in time. The weather depiction chart gives a broad overview of the observed flying category conditions at the valid time of the chart.
This chart is generated at every three-hour intervals starting from 01z every day.
Data Elements
1. METAR Station Type (Automated / Manual)
The chart data will be created based on observations reported by both manual and automated observation locations. The automated stations are denoted by a bracket ( ] ).
2. Sky Cover
The approximate amount of sky cover can be determined by the circle at the centre of the station plot. The amount that the circle is filled reflects the amount of sky covered by clouds.
The sky cover plotting is used the same as the Surface Analysis Chart except for the coding of Sky Obscured. Refer, https://www.letslearnaviation.com/post/surface-analysis-chart.
The symbol X will be used to denote the totally obscured sky condition and symbol M will be shown in case of Missing or Partial obscurations.
3. Ceiling
The ceiling on a weather depiction chart is a parameter that indicates the height above the ground or water at which the lowest broken or overcast cloud layer is present. In other words, it represents the altitude at which the sky is obscured by clouds.
In the weather depiction chart, the Ceiling is entered under the station circle in hundreds of feet. In this example, the ceiling is observed as 300 feet and coded as 3 in the chart.
4. Visibility
The visiblity will be shown in the weather depiction chart left side of the station symbol when it's 5 statue miles or less.
Vertical Visiblity is not included in the weather depiction chart.
5. Weather
The weather conditions (Rain, Snow etc..) reported will be shown in the weather depiction on the left side of the station symbol. Each weather phenomenon will be shown in the chart with the respective symbols as mentioned in the Weather Depiction Symbols Chart.
During multiple weather situations, the chart will be included with the most significant weather phenomena.
6. Flying Conditions / Categories
Weather depiction charts play a crucial role in helping pilots understand and assess flying conditions and categories, which are often referred to as IFR (Instrument Flight Rules), MVFR (Marginal Visual Flight Rules), and VFR (Visual Flight Rules).
IFR (Instrument Flight Rules)
IFR Definition: Ceiling is less than 1,000 feet and/or visiblity less than 3 miles.
Station with IFR conditions marked as hatched/shaded by a smooth line.
MVFR (Marginal VFR)
MVFR Definition: Ceiling 1,000 feet to 3,000 feet inclusive and/or visiblity 3 to 5 statue miles.
Station with MVFR conditions marked as non-hatched/shaded outlined by a smooth line.
VFR (Visual Flight Rules)
VFR Definition: Ceiling is greater than 3,000 feet or none and visiblity is greater than 5 statue miles.
Stations with VFR conditions are not outlined in the chart.
7. Others
The weather depiction chart also shows the Fronts and Troughs from the surface analysis chart to understand significant weather situations or changes.
Conclusion
The weather depiction chart gives graphical representation of observed weather conditions including significant weather phenomena. This will help in flight planning process and as well as for pilot to understand the flying conditions in short span of time.