Station Models

Q: Where is each element plotted round a station?

Left: temperature TT, visibility VV and weather ww, dew point TdTd. Right: pressure PPP, 24-hour change P24P24, past weather W1W2, rain RRR. Above: high and medium cloud CH, CM. Below: low cloud CL and Nh/h. The circle is shaded for total cloud N; the wind shaft points to where the wind comes from. Coastal stations add wave data; ships add ppa, course and speed, and sea temperature.

Q: Can you decode a whole station model?

Wind 330° at 15 kt, temperature 34 °C, visibility 500 to under 1000 m in fog, dew point 27 °C, cirrus and thick AS/NS above, 8/8 in all, 3/8 fracto-stratus based at 100-199 m, QFF 999.8 hPa, a 24-hour change of 1.5 hPa, past weather fog, and a trace of rain since 0300 UTC.

Meteorology · Chapter 24 · DGCA CPL and ATPL

How a whole weather observation is squeezed round one small circle on a chart, and how to read it back.

Remember

Left: TT, VV ww, TdTd. Right: PPP, P24P24 (ship: pp a), W1W2, RRR. Above: CH, CM. Below: CL, Nh/h. Circle shading = N.
PPP is QFF in tenths, last three figures: 962 → 996.2, 186 → 1018.6. RRR: rain since 0300 UTC.
VV: 90-93 fog (< 1 km), 94-95 mist, 96-99 good. h: 0 < 50 m, 2 100-199 m, 9 nothing below 2500 m.
ww tens: 0-1 nothing falling, 2 in the last hour, 3 DS/SS, 4 fog, 5 drizzle, 6 rain, 7 snow, 8 showers, 9 TS. W1W2 3-9 the same order.
Barbs: half 5, full 10, pennant 50 kt; the shaft points to where the wind comes from.

Where is each element plotted round a station?

Where everything goes

Build the station model one side at a time, then see what coastal stations and ships add. Tap Next.

The circle and the wind The circle marks the station. How much of it is shaded shows the total cloud N, in octas (eighths of the sky). The wind shaft points to where the wind blows from. Barbs on its end give the speed: a half barb is 5 kt, a full barb 10 kt and a pennant 50 kt. Add them up.
Left side On the left, top to bottom: TT, the air temperature in °C; VV, the visibility code, with ww, the symbol for the weather now; and TdTd, the dew point in °C.
Right side On the right: PPP, the sea-level pressure (QFF) as its last three figures in tenths; P24P24, the change over 24 hours; W1W2, the past weather; and RRR, the rain since 0300 UTC.
Above and below The clouds go in the same order as in the sky. CH (high cloud type) is at the top and CM (medium cloud type) just above the circle. CL (low cloud type) is just below the circle. Under it, Nh is the amount of low cloud (or medium cloud if there is no low), and h is the code for the height of its base.
Coastal stations and ships A coastal station adds the sea: the wave (swell) height HwHw and period PwPw. A ship plots ppa (the 3-hour change in tenths, with a tendency symbol) instead of P24P24. It adds its course and speed Vs (averaged over 3 hours), the sea temperature minus the air temperature TsTs, and W1 tR, how long the rain lasted.

Memory hook: Left: temperature-weather-dew point. Right: pressure-change-past-rain. Clouds above and below.

Takeaway: Left: temperature TT, visibility VV and weather ww, dew point TdTd. Right: pressure PPP, 24-hour change P24P24, past weather W1W2, rain RRR. Above: high and medium cloud CH, CM. Below: low cloud CL and Nh/h. The circle is shaded for total cloud N; the wind shaft points to where the wind comes from. Coastal stations add wave data; ships add ppa, course and speed, and sea temperature.

Can you decode a whole station model?

An example, decoded

One real-looking plot, decoded one group at a time. Tap Next.

The plot Here is everything one observer reported, packed round one circle. It looks busy, but each part always sits in the same place. Read it in groups, as the colours show: wind, temperature, visibility and weather, cloud, then pressure and past weather. Once you know the places, you can read any plot the same way.
Wind The shaft points north-north-west, so the wind blows from there. It carries one full barb (10 kt) and one half barb (5 kt): 330° at 15 kt.
Temperature and dew point Upper left, 34: the air temperature is 34 °C. Lower left, 27: the dew point is 27 °C. The dew point is the temperature the air would have to cool to before its moisture condenses. The closer the two numbers, the more humid the air.
Visibility and weather 93 is the visibility code for 500 m to under 1000 m. The three lines next to it are the symbol for fog, the weather right now.
Cloud Above the circle: cirrus filaments (CH 1) and thick altostratus or nimbostratus (CM 2). The circle is filled: 8/8, the whole sky covered. Below it: fracto-stratus of bad weather (CL 7), 3/8, with base code h = 2, which means 100 to 199 m.
Pressure, past weather and rain 998 is the last three figures of the QFF in tenths: 999.8 hPa. 15 means the pressure changed by 1.5 hPa in 24 hours. Past weather: fog. The dots for RRR: a trace of rain since 0300 UTC. PPP: add 9 in front if it starts 5-9 (998 → 999.8), 10 if it starts 0-4 (186 → 1018.6).

Memory hook: PPP 998 → 999.8. 93 → 500-1000 m. h 2 → 100-199 m.

Takeaway: Wind 330° at 15 kt, temperature 34 °C, visibility 500 to under 1000 m in fog, dew point 27 °C, cirrus and thick AS/NS above, 8/8 in all, 3/8 fracto-stratus based at 100-199 m, QFF 999.8 hPa, a 24-hour change of 1.5 hPa, past weather fog, and a trace of rain since 0300 UTC.