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What is the “NAM”?

David Novak Science and Operations Officer

NOAA/NCEP/ Hydrometeorological Prediction Center

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Motivation

How to make sense of a blizzard of acronyms referring to:

1)Native model differences

2)Display resolution differences

3)NMAP naming conventions

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The NAM

NAM = North American Mesoscale Model

EMC/NCO consider it the name of a computing slot on the supercomputer.

The core model can change, the model physics can change, the resolution can change, and it will still be called the “NAM”

The core model recently changed from the WRF-NMM to the NMMB in October, 2011.

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Native Model Differences“Parent” domain-12 km native resolution-Large North American domain-Uses full convective parameterization-Boundary conditions from GFS

Fixed Nests-High Resolution-6 km Alaska-4 km CONUS-2.5 km OCONUS domains-Boundary conditions from parent NAM domain**Limited or no convective parameterization

12 km

6 km

4 km

1.3 km2.5 km

2.5 km

Fire Weather Nest-Moveable 1.33 km nest-Boundary Condtions from fixed nest

AlaskaAlaska

CONUSCONUS

HawaiiHawaii Peurto Peurto RicoRico

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NMAP Names“Parent” domain nam12

CONUS Nestnam_conest

12 km

6 km

4 km

1.3 km2.5 km

2.5 km

Fire Weather Nestnam_firewx

AlaskaAlaska

CONUSCONUS

HawaiiHawaii Peurto Peurto RicoRico

Puerto Rico Nestnam_prnest

nam12

30 h forecast 6-h accumulated precipitation valid 18 UTC 29 October 2011

nam_conest

30 h forecast 6-h accumulated precipitation valid 18 UTC 29 October 2011

•More detail•Differences in intense precipitation areas

nam_firewx

30 h forecast 6-h accumulated precipitation valid 18 UTC 29 October 2011

•Downscaling of the nest

RFC Stage IV QPE

6-h accumulated precipitation ending 18 UTC 29 October 2011

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nam12

24 h forecast 24-h accumulated precipitation valid 12 UTC 9 Nov 2011

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Nam_conest

24 h forecast 24-h accumulated precipitation valid 12 UTC 9 Nov 2011

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RFC Stage IV QPE

24-h accumulated precipitation ending 12 UTC 9 November 2011

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Native Model Differences Summary

•nam12 and nam_conest can be quite different for precipitation

-Likely mostly due to the limited use of convective parameterization on the 4 km nest and the higher resolution.

•Smaller differences in mass fields (heights, temps, etc)

•FireWx Nest is mostly a downscaling of the 4 km CONUS Nest

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Display Resolution Differences•NCO provides NAM data with variety of domains/resolutions.

Model Display Resolution NMAP name

12 km Parent Domain

80 km nam

12 km Parent Domain

40 km nam40

12 km Parent Domain

20 km nam12_20

12 km Parent Domain

12 km nam12

4 km CONUS Nest 4 km nam_conest

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80 km

16

40 km

17

12 km

18

4 km CONUS Nest

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NSSL QPE

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Can we Simplify this?•NCO / OPC/ HPC in discussions

Model Display Resolution NMAP name

12 km Parent Domain

80 km nam

12 km Parent Domain

~ 40 km nam40

12 km Parent Domain

20 km nam12_20

12 km Parent Domain

12 km nam12

4 km CONUS Nest 4 km nam_conest

18Z

06Z

00Z12Z

00Z,12Z

06Z,18Z

HiResWindow Runs ≠ CONUS Nest•Different model cores (WRF-NMM/ WRF-ARW vs. NMMB)

•Smaller domains

•Arrive later in the cycle

•Forecasts only to 48 h

•Can be preempted by hurricane runs

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Summary

Know what you are looking at

Native model differences

Display resolution differences

NMAP naming conventions

Are your spf’s updated?-Take advantage of new data

Questions, feedback, & ideas welcome!