A difference between reference time and update time

[Paspox]

@vsinceac Thanks a lot for such a thorough reply. Slowly, thanks to people like you, I understand more and more about the details of these weather updates.

FYI, my interest in the "precise" timing of Windy is because I play an e-sailing game (called Virtual Regatta) and it uses real world weather data (GFS model, only wind speed and direction).
So, for example, when the 00z file is released (@3h40 UTC), the game's weather starts to update (takes around 2h) and often, it is interesting to look at Windy but I wanted to know if what Windy shows is still the old (18z) data or already the new one (00z) and when/how it goes from one to the other.

Again, thanks for your reply.

[Paspox]

@vsinceac Me again, with a few more questions, still concerning the GFS model.

In your message, you said "runtime today at 06hUTC, validity for 07hUTC, 515.1 GB, all params/levels"
I believe you meant 515.1 MB, right?
515MB x 209 validities = 110GB for a full run.

Do you know of a website where I can follow live the release of the different validities by the NOAA?
I know about this one (https://www.nco.ncep.noaa.gov/pmb/nwprod/prodstat/index.html#TARGET).
But is there a way to follow the release progress at the file level?

One last question:
Is there a difference in accuracy between the 4 daily updates?
I read in an old article (from 2012) that the 00z and the 12z were better than the other two.
I was surprised to read that and maybe it was the case back then but do you know if that is still the case?

Thanks

[itblocksg]

@matijamet said in A difference between reference time and update time:

@Korina ,

if you look on the "reference time" for NEMS, for example hier, https://www.windy.com/multimodel/44.107/15.326?44.108,14.248,8
you'll see for METEOBLUE (NEMS) :

Updated: 2020-02-27T07:27:42000Z
Reference time: 2020-02-25

Or, I don't understand something?

Thanks!

weird

[idefix37]

@itblocksg
This is not weird and @Korina explained the difference.
NEMS is a model provided by the Meteoblue company.
But this model is different from the model called here METEOBLUE (more exactly Meteoblue AI) in the point forecast:

Additional information:
https://community.windy.com/topic/10316/metoblue-wildly-inaccurate-in-the-sw-usa/8?_=1637514782709

[Korina]

@itblocksg Hello, it would be nice if you could explain why it is weird.

[Zancle10]

Salve, se i tempi di riferimento ufficiali per il modello ECMWF sono 0.00 e 12.00, i due aggiornamenti in più con premium su cosa si basano? Grazie

[Korina]

@zancle10 Hello, this is an old article. You can find the update times at Model updates times.

[ColtonAxel]

I think Reference time is the time when a model starts a new forecast block. The process consists of the following: Initialisation - data are entered into the model, this creates Initial conditions (initialisation time) and then model starts calculating conditions.

[youtubevanced55]

@ColtonAxel thank you so much..

[imran512]

@Korina said in A difference between reference time and update time:

A difference between reference time and update time
Frequently Asked Questions ARTICLE 13 26 12.9k

Reply

Korina
21 Feb 2020, 18:28

Each model has a different update time and it could be confusing what connection does it have with the update time.

Here is the explanation:

Reference time - is the time when a model starts a new forecast block.
It consists of:

Initialisation - data are entered into the model, this creates Initial conditions (initialisation time) and then model starts calculating conditions.
Assimilation - normalisation on data and assembling data for computation.
Computation - calculating the future atmospheric rates of change in time increments.
Data extraction - extracting data into regular forecast intervals.
Data storage - data are stored and written in accessible format.
Data postprocessing - special postprocessing routines

For example model ECMWF has an update interval 12 hours (or 6 hours interval for Premium users), that means the first reference time will be 00:00:00Z (Zulu time) and second one 12:00:00Z.

Update time is time between the reference time and the actual update.
The whole process of data computation takes approximately from 8 to 9 hours.
So for ECMWF model the update times are 07:15:00Z and 19:15:00Z.
See the exact update times here - When and how often are the weather data updated?.

Where to find info about reference and update time:

Thanks for the clarification! The distinction between reference time and update time makes a lot more sense now. It’s interesting to see how much processing goes into generating accurate forecasts.