Page 344 - PPL-engelsk 2025
P. 344
Meteorology
Computers calculate the development and movement direction of the pressure
centers.
Using the isobars, we can indicate wind directions, and here we might assume
that the high-level wind in Ireland will be about 210 degrees at 10 to 15 knots.
From this, we can estimate the ground wind to come from 30 degrees less, and
half the speed, so 180/8 knots is a good estimate.
Over Denmark, there is almost no wind. In central Jutland, we will have light
winds from an easterly direction.
We can also see that it’s blowing strongly northwest of England. The positions
of fronts and front systems are marked on the chart.
Weather typically moves from west to east at our latitudes, so this allows us to
predict weather development.
Note that we have a low pressure of 1012 and a high pressure of 1003, so it
cannot be said that because the pressure is above a certain level, it is a high
pressure.
It is just that if the pressure at the center is higher than the pressure a little
farther away, it can be called a high pressure.
The analysis chart is a weather forecast for the next 24 hours.
Based on these calculations, forecast charts can be made for up to 120 hours
ahead at 12-hour intervals.
3.11.3.2 SIG-WX
If we need to look at the weather for the next few hours, we use a Significant
Weather Chart (SIG WX).
On the next page, you can see a SIG weather chart from November 19, 2024.
At the top left, you can read that the chart applies from the surface up to FL
450, and it is a forecast chart that shows the expected weather at 12:00 UTC.
Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 344
