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WRF 4km - Difference in forecast between 00Z &12Z runs 1 year 2 months ago #945

  • ameerrh
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Hi,
In recent days I have noticed that the (WRF Israel 4km) model forecasts for the two runs 00Z & 12Z differ from each other especially for the precipitation and simulated radar reflectivity (dBZ).
Is this due to the use of different cumulus, micro-physics and radiation schemes in the two runs 00Z & 12Z?

Please let us know what new changes have recently been made to the WRF 4km model and the reasons for the difference between the two runs, as I am no longer able to know which run is more accurate and which forecasts to take.

Thank you.

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WRF 4km - Difference in forecast between 00Z &12Z runs 1 year 2 months ago #946

Hi Ameer,
The 00Z and 12Z runs are on different machines but they are using the same version of WRF and the same setup for physics schemes. You might try to check the difference in precipitation between the 00Z and 12Z GFS forecasts as this might be the source of the difference that you noticed.
Regards,
David

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WRF 4km - Difference in forecast between 00Z &12Z runs 1 year 2 months ago #947

  • ameerrh
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Hi David,
I have checked the 00Z and 12Z GFS forecasts and there is no difference between the two runs.
As I mentioned, the difference between the 00Z and 12Z WRF forecasts is large and clear and it has happened many times.

The difference is clear in the precipitation forecast for yesterday 00Z30SEP and 12Z30SEP, and also for today 00Z01OCT and 12Z01OCT.
Precipitation in the 12Z run appears to have been overestimated for both days. This issue also occurred last month as I observed it starting with the 12Z12SEP2023 run when the precipitation forecast was significantly overestimated.

Thank you.

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WRF 4km - Difference in forecast between 00Z &12Z runs 1 year 2 months ago #948

Hi Ameer,
I checked again and found that the two runs were using different cumulus schemes. They are now both set to the less sensitive scheme that should not grossly overestimate precipitation.
Best,
David

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WRF 4km - Difference in forecast between 00Z &12Z runs 1 year 2 months ago #949

  • ameerrh
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Hi David,
Are both runs (00Z and 12Z) now using the same cumulus scheme?

Besides, I also noticed in the last two days and today (for both runs 00Z and 12Z) that the WRF model predicted the simulated radar reflectivity (dBZ) with high values (40-55 dBZ) in many areas but without predicting any precipitation in these areas.
Is there any issue regarding simulated radar reflectivity forecast (i.e., issues in schemes or settings used)?
I believe that these high values (40-55 dBZ) mean that there is rain, thunderstorms and possibly hail.

Thank you very much.

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WRF 4km - Difference in forecast between 00Z &12Z runs 1 year 2 months ago #950

Yes, both runs are using exactly the same physics schemes including the cumulus scheme.
I hope to see improvement in precipitation forecasts.

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