What do meteorologists do?
The human-machine partnership is very important in producing accurate weather forecasts.
What do meteorologists do?
Meteorologists look at the forecast produced by the computer model and ensure it is going to plan by comparing it to the observations coming in. If it is slightly different to the computer forecast, this can have knock on effects on other parts of the forecast, and to the forecast a few days ahead. This is why it is always best to ‘stay up to date’ and check the forecast every day. The meteorologist will use their scientific knowledge of how the atmosphere works in conjunction with experience from previous weather events to tweak the forecast for customers.
Let’s look at an example:
If there was more cloud than expected in one area during the day time, it would stop the sun from warming the temperatures as much as expected in this location.
The lower temperature that day would then mean that temperatures that night could fall even lower than was expected originally.
On some nights, this could mean the difference between fog forming or not (this requires temperatures to drop to a specific value, click here for more detail).
If the temperature was now low enough for fog to form, it may be thick enough to cause delays at airports, or tricky driving conditions in places.
It may also mean that when the sun rises the next morning, the energy from the sun goes into dispersing the fog rather than increasing the temperature that day. So the temperatures the following day may now be a few degrees lower than was originally forecast.
With lower temperatures now expected that following day, it may mean the difference between clouds forming, and whether those clouds would grow big enough to produce showers (find out more here).
The chaotic nature of the atmosphere
These are just a few examples of how the forecast could change. However, all parts of the atmosphere are interlinked, and there are an endless number of ways the forecast would now be different, just due to that small difference in the amount of cloud initially.
The meteorologists have the expertise to identify when the forecast is different, and calculate whether it will have impacts on the weather further ahead, and change the forecast accordingly.
Further information about the role of meteorologists can be found below.
Model versus model comparisons
The meteorologist is able to compare the results from the Met Office models with those from other forecasting centres around the world, as they all produce weather forecasts for the entire globe, but differ slightly in the way the weather is calculated. For example, these include the ECMWF (European Centre for Medium-Range Weather Forecasts), NCEP (National Centers for Environmental Prediction) and DWD (Deutscher Wetterdienst).
Model versus model comparisons are helpful further ahead in the forecast when you cannot compare to observations as the forecast is too far in the future and carrying forward any errors from the start of the model would be unreliable. It also gives the meteorologist an idea of what other possibilities could occur and the reasons why things may differ from the most likely forecast.
This is also where ensembles become very important to meteorologist; ensembles are models that use the same starting conditions, but instead of running through their equations and giving one forecast, they do this multiple times to give a range of possible outcomes, these different outcomes are referred to as members.
If all models, or all ensemble members, are producing approximately the same solution then the confidence in the forecast would be high. Confidence is also decided by the consistency between model runs. If the model run at midnight is consistent with the model run at midday, then confidence may be high, but if it suddenly changes or 'flip-flops' between runs, then confidence falls rapidly. In these situations the solutions of other models may be crucial. Sometimes, alternative forecasts may be issued with probabilities assigned.
Empirical techniques are just very simple equations which can be calculated quickly by the meteorologist. They plug in current values such as temperature, humidity etc and can see if this is different to what the model has computed. Before computer models and even during the early days of modelling, empirical techniques were crucial to producing weather forecasts. These scientifically developed techniques are still used by meteorologists to this day. These techniques can be used for many weather parameters, including calculating maximum and minimum temperatures, the likelihood of fog or showers, whether there will be rain or snow, using observations.
This not only gives the meteorologist a guide to how accurate the models are, but also gives them an opportunity to add value to the forecast produced by the models – a good example of this is in marginal situations, for example if precipitation will fall as rain or snow or sleet or if fog will form.