Significant Weather and Wind Charts — Page 497, Lesson 479

I want to walk you through the world of significant weather and wind charts. This is where we start to see how meteorology is packaged specifically for aviation, and it's built on a global system. Let's begin with the foundation. The World Area Forecast System, or WAFS, was established by ICAO—the International Civil Aviation Organization—in conjunction with the World Meteorological Organization, the WMO. So right away, you have two major international bodies working together to create a standardised system for aviation weather. Within WAFS, there are exactly 2 world area forecast centres, abbreviated as WAFC. One is in London—though it's actually run by the UK Meteorological Office at Exeter. The other is in Washington—actually run by the National Oceanic and Atmospheric Administration, or NOAA, based in Kansas City. These two centres are the global hubs. Now, what are these centres required to do? They must provide essential real-time meteorological broadcasts for aviation, meeting the requirements of ICAO Annex 3. Specifically, they produce two main types of charts. First, significant weather charts, or SIGWX charts, at two levels: medium level, which covers FL100 to FL250, and high level, which covers FL250 to FL630. Second, they produce spot wind and temperature charts for a specific set of flight levels: FL100, FL180, FL240, FL300, FL340, FL390, FL450, FL530, and FL610. Notice that these are all standard cruising levels for jet aircraft. How does this data get to you? The UK Met Office broadcasts it on the Satellite Distribution System, abbreviated SADIS. NOAA broadcasts it on the International Satellite Communication System, or ISCS. The information is also available online. So you have multiple ways to access it. Let's look at the areas each centre covers. The UK Met Office's area of responsibility extends from the West Atlantic Ocean, through Europe and Africa, all the way to the west coast of the Pacific Ocean. NOAA covers the Pacific Ocean and the Americas. Critically, the two centres work in duplicate. That means each one is capable of meeting the global requirement entirely on its own. So if one centre fails, the other can take over the whole world. That's a key safety and redundancy feature. Now, a very important point about these charts: all the charts are fixed time charts. They are valid only at the time stated on the chart. They are issued at 6-hour intervals, usually 18 to 24 hours in advance. So if you're flying between those validity times, you, as the pilot, will need to interpolate between consecutive charts. That's a practical skill you'll develop. Let me give you a concrete example. Figure 27.1 is an example of a SIGWX chart for Europe and surrounding areas. In the top left corner of that chart, you'll find the details: the WAFC reference, which in this case is PGDE14, and the date and time of issue—280000 (Z). The 'Z' means Zulu time, which is UTC. Below that is the originating agency and issuing authority. So to summarise: you have a global system with two centres, producing standardised charts for medium and high levels, broadcast via satellite, valid at fixed times, and you need to interpolate between them. That's the framework we're working with.