As explained by @idefix37, there is no way for Windy to draw fronts. There are websites where fronts are drawn tha you can use.
Having said that, there are alternatives to visualise fronts that you can use with Windy. One way is to use the humidity map at 700 hPa. A front is materialised at this altitude with a humidity above 90%. Another way, combined with the humidity map is the temperature map at 850hPa. Ideally we should use the potential temperature (thêta’w) but still it can give you an idea of the temperatures differences between air massa so in fact discontinuity which is the sign of a front.
Again, those 2 maps don’t replace fronts map but it works quite well
Best posts made by Yves70
RE: How to interpret the Rain forecast
If you look your data for Saturday the 13th of August, you see 0.4mm at 5.00AM. This is the total of rain accumulation between 2.00AM and 5.00AM. Then you see 0.9mm at 8.00AM. This is the total of rain between 5.00AM and 8.00AM.
If you go for Windy Premium, by splitting from 3h forecast to 1h forecast, you will see how the rain fall is spread by 1h in place of seeing the accumulation over 3h : for instance, you could have 0.2mm at 4.00AM and 0.2mm at 5.00AM as a potential example
Mediterranean sea - Temperature
The temperature of the Mediterranean sea is quite high this year. In some ares, temperature at the surface is around 28°C. This is of course due to the hot spring and summer.
This situation is not without consequences :
a medicane was formed close to the Libyan coasts and hit last Friday Greece creating a lot of damages because of the wind and rain
yesterday, in the South of France, because (but not only !) of the intrusion of very warm and humid air from the sea, combined of course with other factors (instability, anomaly in altitude, wind shear), it created a multi cellular thunderstorm which was stationary : each new convective cell (this is why it is a multicellular system) is created in the exact opposite way of the move of the system in altitude because of the wind shear. This creates therefore a stationary thunderstorm which is terrible in terms of rain accumulation because you can get huge quantities of water at the same place during 24h or even more.
This thunderstorm created floating and a lot of damages in France (more than 600mm of rain in 24h)
Unfortunately, other episodes like the ones mentioned above could happen in the coming weeks,...
RE: Rain forecast
First of all, please start to check the posts published on this forum and discussing rainfall forecast.
Example : https://community.windy.com/topic/13586/about-rain-calculate/2?_=1602329137551
There are many others, use the advanced search tool to fine them and to read them. You will find a lot of advices.
Principles are always the same :
- compare the different models to verify the consistency within the forecast from the different models. It is a kind of statistic approach to give you a level of confidence
- don’t look only the meteogram which is focus on one location. You should check with the Windy rain map, the rain forecast in an area of let’s say 20km around the location. Often, models foresees no rain at the location but for instance 5mm at only 10km from the location. Thereofore risk is high to get rain at the location.
Combining 1) and 2) should tell you the probability of getting rain or not
RE: Windy.com updates ECMWF model each 6h, with 1h detailed resolution
The model from ECMWF is called IFS. This model has 4 run per day: 0z, 6z, 12z and 18z. So far, Windy gave us access to only 2 run, 0z and 12z (the main run). Now, the Premium users have access to the other 2 run, 6z and 18z
RE: Rain Value Meaning In Meteogram?
Yes, the way the ensemble model calculates the probability is as you explain : for instance for the rain, each dot of the 21 dots can give a different level of rain (1mm, 4mm, 10mm,...). Based on that set of different levels of rain, the model can calculate several probabilistic values such as the average, variance,... This will allow you to quantify the risk of rain
Now, if the model has to adopt the same approach for many other parameters, such as pressure, temperature,... And for each parameter do the 21 calculations (do not forget that each calculation is the equivalent of a single deterministic calculation), computional limitation will be the issue if the model keeps the same grid. To overcome this problem, grid is bigger, calculation of the 21 dots for the different parameters becomes ok but accuracy will decrease.
Computational calculation is key. In average, weather forecast improves by one day every 10 years thanks to the computer (super calculator) progress
RE: A medicane ...
One of the typical feature of a medicane is the hot core which is much warmer than outside. It is very interesting and instructive to follow it at different levels. At the beginning, you could notice the difference at low levels, 850 hPa for instance but day after day, you can see the differences, in the core and outside, also at much higher levels. This is because in the development process of an hurricane, the system releases latent heat, among others because of the condensation of warm and humid air at higher and higher level. Here you can see it clearly on the follwing map at 600hPa : +2°C in the core, -2 or -3°C outside. Huge difference !
Very instructive to follow the development of this medicane
RE: Inaccurate Current Weather
I would like to add 2 comments :
- as @idefix37 and I already highlighted couple of times, Windy doesn’t make any weather forecast model, Windy doesn’t do any calculations with the models, Windy only publishes the data coming from several models and present those data in a very nice and useful interface. Therefore, Windy has no responsibility regarding the accuracy of the data. Only the institutes making the models have this responsibility. Having said that, it is also the responsibility of the user to study the different models and determine which one is the most appropriated for the location and for what he or she is expectating as accuracy. It is also key not to mix the concept of a FORECAST and CURRENT weather. Do not look at models to check the CURRENT weather but check then weather stations or satellite images.
- In general, severe and local phenomena are still difficult to be modelized by the current models. It is the case for instance for thunderstorms. The reason behind this issue has a name : convection. Convection unfortunately do break one fundamental assumption used by all models : hydrostatism. At synoptic level, atmosphere is stable and this is what hydrostatism is telling. Convection, locally, creates an air circulation starting from the bottom, from the ground or from the see, to the altitude. Therefore, atmosphere is not stable anymore and we are locally in a non hydrostatism assumption which is not yet well modelized by the models even if they did a lot of improvement, especially Arome. While it is easy to predict that a region will have all ingredients to get potentially a thunderstorm, it is very complicated for all models to be accurate enough to tell you the exact localisation of the thunderstorm, the exact timing and the exact intensity (wind speed, rainfall, hail,...). More severe phenomena, as hurricanes, have the same issue for more or less the same type of reason.
RE: Temperature of Forecasting Model
All details and documentation about GFS model are here : https://www.emc.ncep.noaa.gov/emc/pages/numerical_forecast_systems/gfs.php
RE: paid subscription and the free version, because i can't experience that there is any difference?
As a Premium user you can get 1h forecast (you have to activate It in the meteogram) and soon 4 updates a day with ECMWF Model in place of 2 (already available on the desktop)
RE: Rain cloud anomaly south of France, can someone explain?
Your question is more related to climatology than weather forecast
The large scale atmospheric circulation in our latitudes is characterized by fluctuating jet streams between different
quasi-stationary states, called weather regimes. The best known one is the famous zonal regime : this regime brings extratropical cyclones (depressions) over Europe and is especially responsible of storms during the winter.
During the last months, we observed a blocking regim with anticyclonic conditions in the North, forcing the cyclones coming from the West to go down and pass by the South of Europe generating a lot of regular rain like in the South of France. On the contrary, we observed a very dry situation in the North of France and Belgium with almost no rain during several months in a row, which was unusual.
On top, there were also several situations called cut-off or « goutte froide » on Spain, Portugal and Atlantic sea generating a stong warm and humid wind coming form the South. This warm and humid air advection, covered by cold air in altitude, created convection and therefore huge thunderstorms in the South of France.
The position of the jet-stream and his strength is playing a role in this situation
RE: Adding new weather models for premium users?
I agree with you, IFS from ECMWF is probably the best model to predict all changes in the atmosphere at synoptic level. I will never prepare a forecast without checking it.
Having said that, there is still a weakness : convection, convective cells and thunderstorms in general. This is where a model like Arome is important to have with Windy because Arome has a certain superiority to predict such a event.
To complete what @idefix37 said, with the infrared, the colder the tp the higher the cloud is so potentially it could be a cumulonimbus type of cloud associated with thunderstorms but cirrus is also high and cold cloud and not associated at all with thunderstorms. As always in meteo, before taking a conclusion you should check other paramters, for instance check the visible channel as well to see if the cloud is thick or not. If not, what you are seeing with the infrared is probably a cirrus
RE: favorite or hide models
Confusion comes from the fact that each model is made by a company or an institute and each model has a specific name. Problem is that people use often the name of the institute in place of the name of the model :
Meteoblue makes a model called NEMS
ECMWF makes a model called IFS
The National Centers for Environmental Prediction (NCEP) produces a weather forecast model called GFS
German Weather Service and the Max Planck Institute for Meteorology work together to propose a model called ICON
RE: Local Adjustment to temperature forecasts
In every country, there are what we call cold spots so spots which are always lower in temperature than what model forecasts even regional model so model with a small grid aroun 2km. I know this issue very well because I am part of group with professional weather forecasters (BCMB) following those cold spots in Belgium. Our network of professional weather stations identified a lot of those spots and even compared to model like Arome, those spots can be 6-8°C below the minima forecasted by Arome and other models. This is linked to the orography of the place/spot leading to radiatives nights where temperatures go down much faster than models can predict. A deep understanding of the region is key to improve the forecasts so professional weather forecasters are still needed !!!