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HRRR Version 4 Update

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#1
Black Hole

Posted 19 May 2020 - 12:38 AM

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The HRRR will be upgraded to version 4 soon (Rap to version 5). Here are some notes about that change.

1.) HRRRv3 had 36 hour forecasts every 6 hours. That has been updated to 48 hour forecasts every 6 hours.

 

2.) HRRRv3 struggled with convective spin up in the 2-6 hour range, supposedly this issue is less problematic with the new update but not totally resolved. In this case, spin-up problems refer to convection that is initialized correctly but then quickly disappears within 1-2 hours, etc. This is related to the data assimilation system used. Previously the HRRR began with an interpolation from the RAP, but now it will initialize from the HRRR ensemble and statistics from that ensemble. It will likely reduce the spin-up problem. In the future the HRRR ensemble will pick a subset of the ensemble members to advance out 48 hours. This can already be viewed experimentally. 

 

3.) Some issues with a warm bias were also corrected, apparently related to excessive erosion of low level clouds. Verification of cloud stats are MUCH better, especially for low level clouds. This should have a positive impact during inversion events at retaining the low level cold pools. It should also improve low cloud forecasts in marine environments. Possibly related to this, surface wind speed forecasts seem to be better.

4.) A lake model is now being run which will offer improved forecast of wind and other variables near/over lakes. For this audience, that might mean some improvement for features over the Puget Sound region. Ocean wind speeds are also improved. 

 

5.) The variable density snow algorithm was updated. It should almost always increase the forecast snow totals. 

 

6.) 15 minute total precipitation increments are now added. HRRR-smoke is now operational as part of the HRRR. This can affect surface temperature forecasts, which should result in more accurate summer temperatures when fires are burning. 

7.) Version 5 of the HRRR is probably about 2-3  years away, but its dynamical core will be the FV3 whenever it does come out. 


  • Phil, BLI snowman, Jesse and 4 others like this

#2
Tyler Mode

Posted 19 May 2020 - 05:34 AM

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When is this happening do you know?



#3
Jesse

Posted 19 May 2020 - 07:02 AM

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Thanks for the write up. So this will be incorporated into the new GFS?

#4
Phil

Posted 19 May 2020 - 07:34 AM

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Glad to hear this. #3 had rendered the HRRR borderline unusable here during CAD situations.
Winter 2019/20
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#5
Frontal Snowsquall

Posted 19 May 2020 - 08:37 AM

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Fantastic news! 👏

Isaiah 26:20 Come, my people, enter your chambers, and shut your doors behind you; hide yourselves for a little while until the wrath is past.


#6
BLI snowman

Posted 19 May 2020 - 11:44 AM

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#5 should add to stress levels nicely.


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#7
GeorgeWx

Posted 19 May 2020 - 04:10 PM

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#5 should add to stress levels nicely.

Snow totals are always waaayyyy overdone
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#8
Black Hole

Posted 19 May 2020 - 07:58 PM

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#5 should add to stress levels nicely.

Those with weak constitutions should stick to the 10-1 ratio products.


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#9
Black Hole

Posted 19 May 2020 - 07:59 PM

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Glad to hear this. #3 had rendered the HRRR borderline unusable here during CAD situations.

In the PNW I think people will really notice this with a better resolved cold pool in east wind situations.


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#10
Black Hole

Posted 19 May 2020 - 08:01 PM

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When is this happening do you know?

Last I heard was 26th of May, so coming up.