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Aviation Weather


Notes:

The aviation weather forecasts are my personal favorite. They are updated frequently during the day. More importantly they predict weather phenomena that directly impact Astronomy. The code for these forecasts is rather terse, but can be understood with some simple instruction.

On the actual site the columns each have labels. I have removed the labels here for the purpose of the slide.

The forecasts that the web site refers to are partially decoded. They present the forecast in 1 hour intervals. The first column is the forecast time in local time. So for the first row the forecast applies to 5 PM.

The second column describes the winds. In the case of the first row this is a wind from 250 degrees(WSW) magnetic at 8 knots.

The third column is visibility. This tends to have limited use. In this case it is at least 6 Statute Miles.

The forth column is any weather. The first row has no weather.

The last column is the cloud configuration (up to 4 layers). Each layer is described by a code that is reproduced at the bottom of the slide. In this case there are two layers

1) The first covers 1/8 to 2/8 of the sky and is at 14,000 feet
2) The second covers 3/8 to 4/8 at 20,000 ft

The next two forecasts are from a different station (actually LAX) and show fog coming in. The 11PM forecast shows some mist (BR) and the sky is 5/8 to 7/8 covered at 2000 ft. By 5AM the sky is overcast.

The forecast is updated at least twice per day. The afternoon update is usually at 4 PM.

The web page reproduces all of the these definitions and documents the main weather codes.