In meteorology, there is a special representation of ensemble forecasts call “spaghetti plots”. This is an ensemble forecast in which a meteorological variable, usually the height of the geopotential, is plott as an isoline (isohypse). All members of the ensemble are plott on the same map. Each line or “spaghetti” represents a single simulation (i.e. a member of the ensemble forecast) with slightly different initial conditions. The result is a plate of spaghetti, where the lines show. The different ways in which the variable could evolve over time.
What is a spaghetti plot for?
The uncertainty of a priction increases the further into the future we look. Analyzing a spaghetti plot helps us to gain an overview and assess. The uncertainty of the priction. If the lines follow a similar, clearly defin pattern, the priction is usually reliable. However, if we look at a plate. Of spaghetti with chaotic lines running in all directions, the forecast is less certain. In this case, the spaghetti plot tells us that the reliability of the priction is low.
The slide show below shows how the spaghetti plot is a useful visualization tool for possible mium-term weather scenarios, compar to the individual ensemble members of the model.
Spaghetti and the Trajectory of the Cold Air Drop
A practical example of the use of these plots is the analysis of the trajectory of a cold air drop (upper low) that has separat from the main circulation and can bring unstable conditions. Such an upper low has split off from the circulation today and is now locat over the Iberian Peninsula.
IFS-HRES 500 hPa geopotential lines and brazil mobile database temperature at 500 hPa. This weather development is only one of several possible solutions. (MeteoSwiss)
Will this low pressure system move towards Switzerland and affect our weather? To do this, let’s take a closer look at the spaghetti plots: The isohypses (lines with constant geopotential) in the graphic show us the possible development from Sunday to Wnesday.
The spaghetti plot shows the development
of the cold air drop from Sunday 27 October to Wnesday 30 October (MeteoSwiss)
For the next four days, the various members are relatively unanimous about the formation and development of the cold air drop. From Monday to Wnesday, individual spaghetti can be clearly seen, but their distribution is not chaotic. They show very clearly how the low pressure system will gradually shift its center towards the Strait of Gibraltar.
As far as the weather in Switzerland is concern, the discovering wordpress divi theme southern side of the Alps will continue to be influenc by the southern current until Sunday. As the low pressure drops and the low pressure moves southwest, moist and mild air will be numbers continue to be drawn towards the Alps and the southern blockage will be extend. From Monday, the low pressure will gradually move away and the Alpine region will increasingly come under the influence of a high pressure area, which will ensure stable weather. But be careful, with the autumn period, fog or high fog in the lowlands is also on the agenda. With ever shorter days and decreasing sunshine, sun-seekers will have to head to the mountains to enjoy the sun.