Windy Tutorial: What is the difference between the reference time and the update time
pavelneuman last edited by pavelneuman
Each model has a different update and reference times and it could be confusing what connection does it have to actual update. Before we get to how often are the weather models updated and where to find the update/reference time on Windy, let's see what's the difference between the reference time and the update time.
1. Reference time
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.
- 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, that means the first reference time will be 00:00:00Z (Zulu time) and second one 12:00:00Z.
2. Update time
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. For example the ECMWF model update times are 07:15:00Z and 19:15:00Z.
When and how often are the weather data updated?
The table below describes when and how often are the weather models updated. All times are in UTC.
Where to find the reference and the update time
While on desktop, to get the reference and the update time, just click the clock icon in bottom right corner of the screen. In app, you have to dig deeper into the menu. See the screenshots below.
@pavelneuman Sorry for replying to such an old article, but I'm quite confused. My limited understanding is that each model begins its update process at the listed reference times, but the time when the model update is actually publicly available for viewing within the Windy app is much later (by 8-9 hours after the reference according to this article). But this is confusing since it states this and then gives lists 07:15 Z as the update time for the ECMWF model's 00:00 Z reference time, which is less than the 8-9 hours stated in this very same article). To confuse matters further, the "update interval" listed on the app for the ECMWF model states "6-7 hours," which is less than the "update time" stated in this article.
Also, the reference time currently listed at 2:18 PM EDT for the ECMWF model says 06:00:00Z (which is 2:00 AM EDT), but it says that it was last updated at around 10:44 AM EDT (14:44 Z) with the next update time at 3:44 PM EDT (19:44 Z). Why would it be showing a forecast with a 06:00:00Z reference time when it was last updated at 14:44 Z? I suppose that falls within the 8-9 hour update time range listed in the FAQ article though. If that's the case, then why is the next update time listed as being 7 hours and 44 minutes after the 12:00 Z reference time (which is when the next model update runs for ECMWF)? That falls neither within the 6-7 hour "update interval" listed on the app or within the 8-9 hour range listed in this article.
Additionally, the HRRR model is said to update hourly, but the updates seem to only occur every two hours at about about 33 minutes past the hour. The reference time currently listed for the HRRR model at 2:18 PM EDT is 16:00:00Z, which is 2:00 PM EDT. However, the app states that the last update occurred at 1:33 PM EDT with the next update occurring at 3:33 PM EDT. How can the reference time be later than the update time? I'm super confused by all of this.
I understand many different factors affect the processing and download times of each update, but is there an approximate average of how long it takes between the reference time and when the Windy app shows the latest update for each model? Can anyone help shed some light on this for me? Thanks!
The dissemination of the Hi Resolution model data from ECMWF is about 7 hours after the reference time (run time) for the 10 days :
Then an additional post-processing time is needed by Windy to transform the raw data into the nice Windy weather maps and upload them. It is about one hour, depending on the servers location used throughout the world.
@idefix37 okay, so why does the Windy app show the 12:00Z run time for the ECMWF model as being updated at 19:15Z today? I'm not complaining or claiming there is anything wrong. I'm just trying to better understand the data I'm looking at. Thanks for your help!
Today in CEST time zone (UTC + 2) I had the 12 UTC update at 19:43 UTC
So 48 minutes after ECMWF dissemination.
I don’t know what the 07:15 update after ref. time means, when the real update is 07:48 after ref.time.