TOPIC:

Hi,
I noticed today that the WRF Israel 4km & WRF Crusade 12km updated at 3:36 UTC for the Ref: 00Z03MAR2021.
I know that the update time for Ref:00Z is about 5:30 UTC. What is the reason ?
Also, I know that the WRF model uses boundary conditions from GFS model which starts update for Ref:00Z at 3:30 UTC.
Thanks

Hello Seergy,

I have started a new production strategy for several openWRF runs and will eventually convert all runs to the new strategy.
You may have noticed that the reference time of the grib files is 18Z and not 00Z The forecasts are from 00Z - 48 hours for the 4km forecast and 120 hours for the 12km forecast.
The idea is to drop the first 6 hours of the forecast run as this part of the forecast has spin-up artefacts and some harmonic distortions. These artefacts diminish after about 6 hours. The practice of dropping the spin-up time is a common practice by most operators of regional models. It provides a better forecast even though it is based on an earlier reference time.
The entire run is now 30/126 hours with the first 6 hours dropped .
In addition I have enabled grid analysis nudging from the GFS to the WRF run. This nudging, in addition to boundary conditions keeps the 12km domain from deviating too much from the GFS forecast and reduces errors in the WRF especially between 3 and 5 days into the forecast.

David

Thanks
For the 18Z reference time, does this mean that the reference time for GFS boundary conditions is 18Z (GFS update:18Z)?
Why do not use the latest reference time (00Z) and the forecast begin from 06Z?

The run is now 6 hours longer and will publish later than before if 00Z is used. There are also second runs on each server in the AM production runs and these would also be delayed. Using 18Z allows to publish earlier and provide a better forecast. (than before).

Does the 18Z reference time mean that the reference time for GFS boundary conditions is 18Z (GFS update:18Z) ?

Yes, initialization, boundary conditions and nudging are based on the 1800Z GFS. The published WRF begins at 0000Z