How do meteorologists predict wind

Create weather maps

 

Here you can learn about

A weather map contains a wealth of individual information that describes the weather in an area at a given point in time. For this purpose, the measured values ​​for air temperature, air pressure, cloud cover, precipitation, wind direction and wind speed and the course of fronts are entered on the map. In order to be able to read a weather map correctly, these symbols must be recognized and correctly interpreted. Then the values ​​compiled in the map are analyzed and interpreted. The recognizable fronts and occlusions are then entered in the map series in the form of symbols. With the drawing of the isobars, the lines of the same air pressure, in ground weather maps or the isohypses, the lines of the same pressure surface height, in altitude weather maps, the centers and the distribution of the low and high pressure areas become visible. The corresponding satellite and radar images are also used for a more detailed assessment of the weather situation.

This is discussed in more detail in the chapters Weather Maps and Ground Weather Maps.

The weather forecast also includes the creation of forecast maps for the next 1 - 3 days. For this purpose, an expected condition is determined from the past and the current condition of the atmosphere according to physical rules and a comparison of the measured values ​​with model calculations. Of course, the experience of the meteorologist involved also plays an essential role.

The evaluation of the weather maps is therefore an essential prerequisite in addition to the pure weather observation in order to be able to make weather forecasts.

With the mere entry of the ground weather station models on the map, of course, one does not yet have any knowledge of the position of the ground fronts or the pressure distribution. Nowadays, based on the station reports, computers create an isoline printout for the pressure distribution which, as an initial overview, provides valuable information for further analysis. The identification of the position of the fronts is still the task of the meteorologist today, because due to the many factors that ultimately determine the position of a front, even high-performance computers are still largely overwhelmed by it.

The following procedure is available for this:

 

Work steps  

example

map

1. Analysis of the map

Ground weather map

1st step: collect basic information
Type of map (ground weather map or altitude weather map), date and time, region, source or author of the map

Ground weather map of Europe,
valid for March 1st, 2008 at 12 noon UTC,
Data: MeteoSwiss

Step 2: Collect individual weather data
Evaluation of the weather situation; Air pressure, temperature, cloud cover, precipitation and wind conditions at different locations (station reports)

e.g. Berlin:
983.7 hPa, 8 ° C, wind from WSW, relatively strong wind with 25 kt (close distance between the isobars), overcast, rainy (immediately after the cold front)

3rd step: description of the weather situation;
Location of the high and low pressure areas and the resulting main wind directions, course of the fronts, general weather situation, supply of weather-effective main air masses

East Central Europe under the influence of the cold front of a low centered over southern Sweden, western and southern Europe influenced by the Azores high, which extends to the Black Sea, supply of maritime polar air to Germany

2. Weather forecast for the room to be examined

 

Forecast taking into account the characteristics of the pressure areas, fronts, main air masses, changes in pressure conditions

Precipitation subsides after the cold front has passed through, which also warms up. The intermediate high brings a brief loosening and the wind turns to W. The subsequent passage of the warm or cold front brings new showers and the air temperature drops.

Note

The origin and the path of the main air masses is usually read from the course of the isohypses on the altitude weather map. With a ground weather map, this can be deduced from the wind direction. If you draw the direction of flow of the wind on the map, whereby it should be noted that the wind blows approximately parallel to the isobars, namely around a high pressure area clockwise and around a low counterclockwise, the picture on the right results in our example.

 

So if you have the necessary basic meteorological knowledge of high and low pressure areas, main air masses, etc. and uses it accordingly, you can quickly get an overview of the expected weather with the help of weather maps. This first overview should be supplemented and refined regularly with your own weather observations (e.g. clouds, wind) and the latest reports from the weather services. Under no circumstances should you, especially in aviation, rely entirely and exclusively on your own forecasts. What is needed is professional weather advice and the necessary meteorological flight preparation. Warning notices received should be strictly observed!

 

Meteogram

A meteogram summarizes the forecast details of various meteorological model parameters in their temporal development at a location at a corresponding altitude over a certain period of time and represents this graphically with curves, diagrams and profiles what height the forecast was calculated. In areas with mountains and valleys, the average altitude of the surrounding area for the forecast area is displayed.

The update time is usually indicated in the meteogram in the top left under the location information. If no details are given, the meteogram will be created at 00:00 and 12:00 UTC based on the global standard forecast initialization.

The meteograms issued by the DWD are calculated 4 times a day and (00, 06, 12 and 18 UTC).

 

Weather forecast

The basic idea of ​​a weather forecast is to derive a weather condition in the future from an already past and the current condition of the atmosphere, using the relevant physical rules. The starting point of the weather forecast is therefore the precise analysis of the current weather condition using the weather maps. In the ground weather map, the pressure field is represented by the course of the isobars, so that the position of the high and low pressure areas can be seen. Correspondingly, the temperature field can also be determined by identifying and delimiting the air masses and analyzed by entering the associated fronts. This gives an overview of the distribution of the warm and cold air masses in the observation room. The analysis of the altitude weather maps, in which the measurement data of the radiosonde ascents are entered, is carried out through the topographical representation of certain pressure areas. For this purpose, for example, contour lines of the 500 hPa area are drawn on the map. In this way, the weather effectiveness of a possible low altitude or high trough can be recognized and estimated.

In a next step, the possible changes for the forecast period are to be derived from the analyzed weather map and forecast. So a "forecast map" has to be created. A comparison with previous weather maps is helpful for this. Once the probable relocation of the high and low pressure areas and the associated front systems has been identified, the actual weather forecast for a specific location or for a specific area can be made in a further step. While the prediction of the pressure distribution used to be semi-empirical according to so-called "synoptic rules", since the 1950s the changes in the meteorological field parameters (pressure, temperature, etc.) have been increasingly calculated with the help of mathematical equations and taken into account as so-called computer models The mathematical constructs that describe these physical rules are so-called non-linear equations, in which even small changes in the initial state can lead to relatively large changes in the result of the calculation The use of modern supercomputers has made it possible to solve these complex calculations within a useful period of time and thus made this type of prediction possible.
A basic distinction is made between manual or synoptic weather forecasting and numerical weather forecasting, although a combination of both methods is still used today. The reason for this is that, in view of the chaotic weather conditions, current numerical forecast models also provide inadequate results. In order to better take into account the local statements from weather stations, statistical methods, i.e. empirical values ​​of past weather events, are now used after the numerical calculations.

With the help of this procedure, a weather forecast for the coming week is about as reliable today as it was thirty years ago for the next day. The 24-hour forecast achieves an accuracy of more than 90%. The accuracy for the next 3 days is a little more than 75%. The reliability of the forecast, however, fluctuates very strongly depending on the weather situation. With a stable winter high pressure situation, it is sometimes possible to forecast a week in advance with 90% certainty. In contrast, the forecast quality is often well below 70% for an unstable storm situation in summer for the next 24 hours. A distinction must also be made between temperature and precipitation in the forecast quality. Temperatures can be forecast much more precisely than precipitation.

In this context, a word about the probabilities given by the DWD for precipitation and severe weather forecasts outside of the narrower flight weather report. The DWD differentiates between information regarding the spatial and temporal distribution of weather events. The following definitions apply:

  • For spatial Details:
    • sporadic or individual: less than 10% (of the area)
    • local: 10 - 20%
    • by strokes: 10 - 30%
    • regionally: 20 - 50%
    • common: more than 50%.
  • For temporal Details:
    • hardly: less than 10% (of the forecast period)
    • occasionally: less than 30%
    • temporarily: 30 - 60%
    • longer lasting: longer than 60%
    • predominantly (no precipitation): over 80%
    • mostly (no precipitation): over 90%.

The forecasts of other weather services, from which the media often obtain their weather forecasts, differ in part. The definitions used for this can be found on the relevant websites.

On the basis of these professionally created forecasts, relatively good forecasts can then be made at the local level, e.g. for the airfield or for extended traffic areas, with comparatively few tools, which, however, also requires sufficient knowledge, which is hopefully available thanks to this website (?).

A fundamental problem in weather forecasting is the amount of measurement data and the density of the measurement points. The closer the network of measuring points, the more accurate the forecast is potentially. Unfortunately, thunderstorms, which are particularly dangerous in aviation, often fall through the cracks. Thunderstorms, especially in their formation, are very small-scale, which can only be captured poorly by the weather models. As a rough illustrative example, you can compare this with a fishing net: the smaller the mesh of the net, the smaller the fish you can catch. However, if the mesh size between two knots is 50 cm, for example, it will be difficult to catch a goldfish. The situation is very similar with the weather models. The DWD's high-resolution weather model currently has a mesh width from node to node of 2.8 km. Thunderstorms, however, are sometimes much smaller and, especially during their formation, have a diameter of only a few hundred meters. Their recording and timely and locally accurate forecast is therefore still almost impossible.

So what remains is always good advice in aviation:

open eyes!