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Major NAM Upgrades/Changes This Summer


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http://www.nws.noaa....nam_changes.htm

I thought this deserved its own thread.

Going through the list of changes--this sounds like a significant overhaul. Personally I am pretty excited as the current NAM is pretty awful. Hopefully some folks in the know (dtk or anyone else in the modeling department) can shed some more additional information.

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Honestly though--the only bias the NAM has is being wrong. I am pretty excited in seeing what this overhaul does. Looks promising.

This hasn't been my experience. The NAM, just like any other model, is always wrong to some degree, but there are times when one model can certainly outperform others or have a better soln.

I've seen the NAM have a better idea with CAD events as far as dissipation timing and convective initiation along the TMB, when other models kept conditions wedged and stable. I think the NAM's non-hydrostatic packages aide it across complex terrain and baroclinic zones. A couple days ago, the NAM outperformed the GFS significantly with the DPVA field supporting MCV development across the NC mtns and fhills. The NAM also slowed the upper forcing and stalled a meso vort across the mtns for the next day's breaking of the cap in that area.

I could go on...but I've see the NAM have the right idea just as often as other models and vice versa. New updates to models are always good, but they can also have unseen adverse consequences.

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Adam can never complain about people posting NAM model runs for TCs again?

NDAS Changes:

a) Initial first guess at T-12hr will reflect relocation of tropical cyclones

B) Will use 1/12 degree high resolution real-time sea surface temperature (RTG_SST_HR) analysis instead of the 1/2th degree real-time SST analysis.

c) Will update 2 m temperature and moisture and 10 m wind with portion of first layer correction

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This hasn't been my experience. The NAM, just like any other model, is always wrong to some degree, but there are times when one model can certainly outperform others or have a better soln.

I've seen the NAM have a better idea with CAD events as far as dissipation timing and convective initiation along the TMB, when other models kept conditions wedged and stable. I think the NAM's non-hydrostatic packages aide it across complex terrain and baroclinic zones. A couple days ago, the NAM outperformed the GFS significantly with the DPVA field supporting MCV development across the NC mtns and fhills. The NAM also slowed the upper forcing and stalled a meso vort across the mtns for the next day's breaking of the cap in that area.

I could go on...but I've see the NAM have the right idea just as often as other models and vice versa. New updates to models are always good, but they can also have unseen adverse consequences.

Yeah I know--I was being a bit hard on it. Overall it is pretty bad and very unreliable, but it can be quite useful in cases where rapid positive feedback cyclogenesis is possible, and it is useful in the mountains, especially for downslope windstorm forecasting. Unfortunately it has a number of crippling aspects including the "phase shift" problem which has yet to be solved.

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Yeah I know--I was being a bit hard on it. Overall it is pretty bad and very unreliable, but it can be quite useful in cases where rapid positive feedback cyclogenesis is possible, and it is useful in the mountains, especially for downslope windstorm forecasting. Unfortunately it has a number of crippling aspects including the "phase shift" problem which has yet to be solved.

Yeah it usually outperforms the GFS for many types of mtn weather...especially fire wx. Probably why it's used so much here and given much weight at times.

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Yeah I know--I was being a bit hard on it. Overall it is pretty bad and very unreliable, but it can be quite useful in cases where rapid positive feedback cyclogenesis is possible, and it is useful in the mountains, especially for downslope windstorm forecasting. Unfortunately it has a number of crippling aspects including the "phase shift" problem which has yet to be solved.

Can you elaborate on the bolded?

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Can you elaborate on the bolded?

Basically a "phase shift" in the height field where all the upper fields are shifted westward/too slow. Typically it starts to rear its ugly head by 24-48 hours, and it typically gets worse with time in the run. Sometimes it is just so bad the model is unusable by 24 hours in. For whatever reason it is sometimes hardly noticable--other times it can be just awful. I always do a comparison of the NAM with respect to the global guidance to see if this problem occurs. This becomes a major problem in feedback situations where the errors just amplify rapidly with time.

Here is a classic example--I made a simple animated GIF with the NAM/GFS at 18 hrs and 24 hrs into the forecast to illustrate this. Note how every single feature in the domain is phase shifted.

b9de5e8fc38e9858a5991008b2a9e2ff.gif

3f9d25ecb73d16c30bb75e2ff5a7050e.gif

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Global Forecasting System/Gridpoint Statistical Interpolation System

The GFS/GSI implementation is expected May 10. Several bugs in the GFS model will be addressed, including a low-level temperature warm bias. The NCEP OD decisional briefing is May 3rd. The TIN detailing the upgrades included in the implementation can be found at:

http://www.nws.noaa.gov/os/notification/tin11-07gfs_upgrade.htm

I get my info from the following site below

http://www.hpc.ncep.noaa.gov/html/model2.shtml#synergy

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Global Forecasting System/Gridpoint Statistical Interpolation System

The GFS/GSI implementation is expected May 10. Several bugs in the GFS model will be addressed, including a low-level temperature warm bias. The NCEP OD decisional briefing is May 3rd. The TIN detailing the upgrades included in the implementation can be found at:

This went in last Monday (09 May), a day early actually. It was a fairly minor modification to the package that has been running since last July. There probably won't be another big change (like the one last summer) for a while; at least in terms of the model itself. We are working toward a pretty significant change to the data assimilation algorithm (model initialization); hopefully to be implemented sometime in spring 2012.

I don't have much to add to the NAM upgrade, unless anyone has specific questions/comments that need to be addressed.

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I am looking for the actual model output.

Once the "official" parallel run is going courtesy of NCO (at least 30 days prior to implementation), graphics similar to the operational NCEP graphics can be found in the NAM section of:

http://www.nco.ncep.noaa.gov/pmb/nwpara/analysis/

There are various internal runs going on from the mesoscale branch development team, links available here:

http://www.emc.ncep.noaa.gov/NAM/exdata.php

And even more specifically yet, you can get a comparison of the NEMS-based NAM output and compare it to the operational NAM here (00z/12z):

http://www.emc.ncep.noaa.gov/mmb/mmbpll/nampll_nmmb/

or (6z/18z):

http://www.emc.ncep.noaa.gov/mmb/mmbpll/nampll_nmmb_offtime/

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