What's the deal with the WRF

[Alex Lamers]

Did it get implemented today? And if so...two questions. (1) Will it say NAM there forever or are they gonna change it to WRF_ARW or whatever it is? (2) Is the WRF below it just for higher resolution or what?

Thanks, just curious because I saw WRF ARW in an AFD and I remembered the scheduled implementation was a week ago.

 

[Jeff Snyder]

The WRF/ETA switch was delayed from last week because of Tropical Storm Alberto.
<div class='quotetop'>QUOTE("Central Operations")</div>

NCEP/NWS HAS DECLARED A CRITICAL WEATHER DAY PERIOD FOR
TROPICAL STORM ALBERTO AFFECTING FLORIDA AND THE
SOUTHEASTERN US. THE CWD PERIOD CONTINUES UNTIL 15/0000Z.

DUE TO THE CWD BEING IN EFFECT..THE SCHEDULED WRF-NAM
IMPLEMENTATION SCHEDULED FOR JUNE 13TH WILL BE POSTPONED
UNTIL JUNE 20TH DUE TO THE CWD DECLARATION. SEE WWW.NCO.
NCEP.NOAA.GOV/PMB/CHANGES(ALL LOWER CASE) FOR ADDTL DETAILS.[/b]

--> http://www.srh.noaa.gov/printable.php?pil=...=20060613132006

The 12z run later today will officially change to the WRF package from the ETA package. Again, it'll still be called the NAM, and it'll be run at 12km. I think the NCEP run of the WRF (the NAM) will use the NMM core, and I'm unsure if NCEP will still run the WRF-ARW.

Rob Dale posted a link to a COMET module/presentation made for use in training NWS forecasters about the changes this represents... If you're interested in this (and I think we all should be given how we use model output for chasing), I suggest going through it. For example, it's important to realize that there is a known bias for the WRF-NMM ("NAM") to over-intensify / over-amplify longwave-troughs, which has serious implications for forecasts, particularly beyond 48 hours. What Is the WRF? Multimedia Presentation

Also see NAM - Eta to NMM conversion for some details regarding the changes expected in the change from Eta to WRFNMM.

 

[rdale]

NAM is now running the WRF_NMM (nested meso model.)

WRF_ARW is the Advanced Research WRF - the local model that NWS offices run. This has NOTHING to do with the NAM WRF_NMM.

I've been playing with it and still tweaking the config files to make something new, I don't know how to get it going well at a 2km resolution because it really struggles with convection but I'm sure it's just a matter of playing with the physics models.

 

[Alex Lamers]

NAM is now running the WRF_NMM (nested meso model.)

WRF_ARW is the Advanced Research WRF - the local model that NWS offices run. This has NOTHING to do with the NAM WRF_NMM.

I've been playing with it and still tweaking the config files to make something new, I don't know how to get it going well at a 2km resolution because it really struggles with convection but I'm sure it's just a matter of playing with the physics models.
[/b]

I think I saw one run at 2 km once that was relatively successful with convection. MQT office ran one once, I can't remember if it was 2, 4, or 8 km resolution but that one did fairly well too. Good luck! It'd be awesome if you could get it running with good accuracy at that resolution.

 

[Jeff Snyder]

I know this isn't the run that Alex is speaking of, but it's a good reminder... The 4.5km WRF-NMM explicit convection run seem to be pretty good, particularly with forecasting storm mode. Only precip and reflecitivity products are available, and it's important to remember that it's still a model, subject to all the usual caveats that apply to other 24-36hr forecast model solutions. Regardless, in my experience, it tends to give very good insight into the storm mode expected.

 

[Jim Bishop]

To clear up some major confusion I am having, this is a change in the WRF model, not the ETA/NAM avaialbe from UCAR/NCAR?

 

[rdale]

NAM = the name for the model that runs first at NCEP, concentrating on the US.

Previously the Eta was the actual model that ran. Tuesday - the WRF became the model that runs first. So it is still the NAM - but it is running the WRF NMM instead of the Eta.

The Eta now only runs in the background to generate Eta MOS - you cannot view the Eta output anywhere anymore. So any reference to Eta needs to be dropped completely.

 

[Dan Dawson]

NAM is now running the WRF_NMM (nested meso model.)

WRF_ARW is the Advanced Research WRF - the local model that NWS offices run. This has NOTHING to do with the NAM WRF_NMM.

I've been playing with it and still tweaking the config files to make something new, I don't know how to get it going well at a 2km resolution because it really struggles with convection but I'm sure it's just a matter of playing with the physics models.
[/b]

I'm pretty sure the letters NMM stand for nonhydrostatic mesoscale model. Also, in what way is the 2 km run you are attempting struggling with the convection?

 

[rdale]

You're right on the abbrev - I can't imagine where I came up with that one from!

Some days it works very well - others it will have stationary high-qpf's for several hours before returning to reality. I tweaked the parameters more towards those suggested for DX < 3km and much happier now.

 

[Dan Dawson]

You're right on the abbrev - I can't imagine where I came up with that one from!

Some days it works very well - others it will have stationary high-qpf's for several hours before returning to reality. I tweaked the parameters more towards those suggested for DX < 3km and much happier now.
[/b]

Sounds like the "grid point storm" issue. I don't have much experience running WRF, but I sometimes see this in ARPS. I'm not exactly sure what causes it, but it probably has to do with the development and amplification of stationary small-scale waves that aren't resolved well by the model (i.e. on the order of 2 times the grid spacing, which is the smallest wave that can be resolved in any gridded model). Once, when performing a 3 km simulation on a bow echo, I initialized the model with some radial velocity data that were a little too noisy. I ended up getting two stationary (for the entire 12 hour forecast) convective downdraft sources over Oklahoma that kept pouring out cold air, completely wrecking my simulation. It was as if a wormhole opened up in space over these two spots! I'm sure it was because the radial velocity data was not properly analyzed. When I took out that data from the initial analysis, everything was fine. Then again, this could be a completely different phenomenon from what you are describing.