Weather models
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Started by metmike - March 11, 2019, 4:24 p.m.

WxFollower brought up weather models the last couple of days and this is a very interesting topic.

 This sort of got things going earlier:

What are weather models, exactly, and how do they work?

The foundation for models are mathematical equations based on physics that characterize how the air moves and heat and moisture are exchanged in the atmosphere. Weather observations (pressure, wind, temperature and moisture) obtained from ground sensors and weather satellites are fed into these equations. The observations are brought into the models in a process known as data assimilation.


In a model, the atmosphere is divided into a three-dimensional grid and each grid point is given the assimilated data. These are called initial conditions.  Then at each grid point, the mathematical equations are applied and stepped forward in time. The outputs over many time steps specify future weather at all grid points.




By metmike - March 11, 2019, 4:28 p.m.
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Euro Vs. GFS: The Weather Model Wars Take A New Turn In March


The top-line finding is that yes, the FV3 core generally performs a bit better than the GFS model..... it is nice to see some modest improvement from the FV3, but it still is not the best in the world. For the entire globe, the FV3 model would still rank behind the best-in-class European model (0.910) and the United Kingdom Met Office (0.887).



Berger pointed out that the upgrade brings the U.S. from fourth to third place. Improvements were observed in how GFS intensifies tropical cyclones and represents track within the first five days, according to Berger. I highly recommend Berger's article because he provides details on the metrics used in the comparison. He also highlights weaknesses in the "new GFS" such as a dry bias for high-impact precipitation events and a tendency to be too cold with nocturnal temperatures.

By WxFollower - March 11, 2019, 5:02 p.m.
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"NOAA delays launch of ‘next generation’ weather forecast model...."

"The launch of the new model, which had been slated for March 20, was postponed because of 'two issues' found during testing. Its forecasts for snow depth were 'unrealistically high' and the model exhibited a 'a cold bias in the lower atmosphere,' a memo from the Weather Service said. These issues were independently identified by private-sector forecasters and university researchers, and reported by the Capital Weather Gang in early February."

"While the model undergoes further testing and evaluation, the memo said its implementation is 'paused' with no new target date."