Real-Time QG Diagnostics

The intended purpose of the real-time analyses and forecasts of the quasi-geostrophic (QG) diagnostic equations web page is to provide an interactive tool that can be used to enhance classroom education and/or weather discussions by providing visualizations of core QG dynamical equations.

The calculations and visualizations are produced using NCAR Command Language version 6.6.2 on computer resources at the NOAA National Severe Storms Laboratory.  All fields are computed using 6-hourly pressure-level data from the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) deterministic forecasts available in GRIB2 format at 1×1 degree latitude-longitude grid spacing. The raw GFS forecasts are smoothed using a 9-point local smoother run 40 times to produce cleaner results for the QG diagnostics. A detailed description of the fields displayed on each set of images is provided in the Users’ Guides and as captions on the animations themselves. While every attempt is made to keep the images up-to-date, it is possible that there will be interruptions to the image generation services as system updates occur.

Each animation provided at the links below includes a 10-day analysis archive and the most recent forecast out to 192 hours. Images older than 10 days are not archived.

1. Sutcliffe Development Theory: (click here for Users’ guide)

2. Petterssen Development Equation: (click here for Users’ guide)

3. Height Tendency Equation: (click here for Users’ guide)

4. Omega Equation: (click here for Users’ guide)

5. QG Energetics: [Lackmann (2011), p. 57–65]

6. Experimental Mesoscale Circulation System Diagnostics:

This section extends QG diagnosis of vertical motion to the mesoscale in the alternative balance framework by replacing the geostrophic wind with the nondivergent wind. The goal is to test the utility of the balanced framework in producing clean diagnostic signatures of mesoscale ascent and frontogenesis in convection-allowing models (CAMs). This work is motivated by Nielsen-Gammon and Gold (2008), Kenyon et al. (2020), and discussions with Dan Keyser. The plots below are derived from the once-daily NSSL FV3-SAR initialized at 0000 UTC and run out to 60 hours. Additional visualizations are available at the NSSL CAMs website.

CONUS-scale overview plots:

Regional-scale vorticity plots: (vg and vnd intercomparison)

  • 250 hPa ζg/vg and ζ/vnd: NW || SW || NP || SP || NE || SE
  • 500 hPa ζg/vg and ζ/vnd: NW || SW || NP || SP || NE || SE
  • 700 hPa ζg/vg and ζ/vnd: NW || SW || NP || SP || NE || SE
  • 850 hPa ζg/vg and ζ/vnd: NW || SW || NP || SP || NE || SE

Regional-scale Q– and F-vector plots:


Regional-scale Petterssen frontogenesis plots:



7. References:

Bluestein, H. B., 1992: Principles of Kinematics and Dynamics. Vol. I. Synoptic-Dynamic Meteorology in Midlatitudes. Oxford University Press, 431 pp.

Carlson, T. N., 1998: Mid-Latitude Weather Systems. Amer. Meteor. Soc., 507 pp.

Davies-Jones, R., 1991: The frontogenetical forcing of secondary circulations. Part I: The duality and generalization of the Q vector. J. Atmos. Sci., 48, 497-509.

Hakim, G. J., L. F. Bosart, and D. Keyser, 1995: The Ohio Valley wave-merger cyclogenesis event of 25-26 January 1978. Part I: Multiscale case study. Mon. Wea. Rev., 123, 2663-2692.

Hoskins, B. J., I. Draghici, and H. C. Davies, 1978: A new look at the omega equation. Quart. J. Roy. Meteor. Soc., 104, 31-38.

Kenyon, J. S., D. Keyser, L. F. Bosart, and M. S. Evans, 2020: The motion of mesoscale snowbands in Northeast U.S. winter storms. Wea. Forecasting, 35, 83-105.

Keyser, D., M. J. Reeder, and R. J. Reed, 1988: A generalization of Petterssen’s frontogenesis function and its relation to the forcing for vertical motion. Mon. Wea. Rev., 116, 762-780.

Keyser, D., B. D. Schmidt, and D. G. Duffy, 1992: Quasigeostrophic vertical motions diagnosed from along- and cross-isentrope components of the Q vector. Mon. Wea. Rev., 120, 731-741.

Lackmann, G., 2011: Midlatitude Synoptic Meteorology: Dynamics, Analysis, and Forecasting. Amer. Meteor. Soc., 345 pp.

Martin, J. E., 1999a: Quasigeostrophic forcing of ascent in the occluded sector of cyclones and the Trowal airstream. Mon. Wea. Rev., 127, 70-88.

Martin, J. E., 1999b: The separate roles of geostrophic vorticity and deformation in the midlatitude occlusion process. Mon. Wea. Rev., 127, 2404-2418.

Martin, J. E., 2006: Mid-Latitude Atmospheric Dynamics: A First Course. John Wiley & Sons Ltd., 324 pp.

Nielsen-Gammon, J. W., and D. A. Gold, 2008: Dynamical diagnosis: A comparison of quasigeostrophy and Ertel potential vorticity. Synoptic-Dynamic Meteorology and Weather Analysis and Forecasting: A Tribute to Fred Sanders, Meteor. Monogr., No. 55, Amer. Meteor. Soc., 183-202.

Petterssen, S., 1956: Motion and Motion Systems. Vol. I. Weather Analysis and Forecasting. McGraw-Hill, 428 pp.

Sutcliffe, R. C., 1947: A contribution to the problem of development. Quart. J. Roy. Meteor. Soc., 73, 370-383.

Sutcliffe, R. C., and A. G. Forsdyke, 1950: The theory and use of upper air thickness patterns in forecasting. Quart. J. Roy. Meteor. Soc., 76, 189-217.

Trenberth, K. E., 1978: On the interpretation of the diagnostic quasi-geostrophic omega equation. Mon. Wea. Rev., 106, 131-137.