@Sybiljamie

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

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 :

1. 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

2. 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,...

@ginop
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 :

1. 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
2. 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

@Joerg78
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

@hgk209
First of all, we should get the confirmation about the exact meaning of the shades of grey. Is it humidity level or cloud cover ? High level of humidity doesn’t necessary mean clouds

@Korina
@ivo
Could you let us know ? Thanks

@nwindy
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

@CR
No, in general with Windy, you cannot combine different maps, except pressure, geopotential, temperature and isotherm that can be display on any other maps.

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

@disaster999
I would like to add 2 comments :

1. 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.
2. 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.

@petra-pik
@Korina

I have seen a change in the satellite views : it seems that infra view has been replaced by blue channel view. I guess it is still infra but with another treatment.

Could you please comment on this change ?

Thanks !

@korina
Windy should use the correct value everywhere : 6.5km for ICON-EU and 1.3km for AROME

@gkikas-lgpz
Thanks for the reference to the old post. I did a search but didn’t find it

By checking the isotherm 0°C map, I discovered something that I didn’t notice so far.

It seems that IFS takes into account the altitude of the location which is not the case of ICON-EU. Look the two following screenshots for the same location which is roughly at 500m, at the same moment :

ISO 0°C with ECMWF (IFS)

ISO 0°C with ICON-EU

As you can easily see, the delta between the 2 values is 500m so the exact altitude of the location. If you choose other locations, you will see the same behaviour. There is always a delta fitting more or less with the altitude of the location, and not because the models are giving two different values,...

This means that the data of the 2 maps are not coming from the same calculation. IFS is given the altitude of the isotherm 0°C using the location as a reference so here 200m above Hockai (200+500=700m) while ICON-EU seems to give the altitude of the isotherm with the sea level as a reference.

@matikru
It should be the temperature at 2m forecasted by the model used for the sounding

@keyon-hendricks
No, it is not possible as explained here : https://community.windy.com/topic/16000/please-indicate-fronts/2?_=1617344617388

@becky4756
As explained by @idefix37, this is not possible.
As an alternative, you can use Humidity map at 700hPa with a specific color above 90%. This level of humidity will indicate a potential front. You can combine it with the temperature map at 850hPa to see the air mass with different temperatures indicating fronts as well

@idefix37
No, it is not yet over. Will be finsihed tomorrow (48h outage)

@idefix37
Strange, I cannot reproduce it on my iPad. I can switch from Fog to Low Cloud without problems

@stevecrye
I know that it looks simple to allow people to set up in their preferences the weather model they would like to see when they open Windy. Unfortunately, if I remember well, there is a technical issue which so far prevents Windy developers to propose what it looks like a basic feature

@mrwestra
Visibility data come from ECMWF, the weather institute making the famous weather model IFS