Battle of the Models: The Old Versus the New U.S. Global Weather Forecasting Model

Early next year, the U.S. will move to new global model.   The new model (FV-3) was developed at the NOAA Geophysical Fluid Dynamical Lab (GFDL) in Princeton and will replace the old Global Forecast System (GFS) model that has been around forever.

The new model is being run in parallel right now and fascinatingly, it is providing very different forecasts than the current system for Hurricane Florence, which is now approaching the SE U.S.. 

 Which will be right?  You will know in a week.   But first, let me show you the amazing differences.  Here is the forecast for 5 AM PDT September 14th of sea level pressure.  Both have Hurricane Florence on the Carolina coast, by the differences in central pressure is HUGE!:   913 hPa for the old GFS, 979 hPa for the new FV-3.

And  the forecast two days later are stunningly difference.  The GFS has a very deep low (913 hPa) hanging around on the coast, but the FV-3 has weakened and moved inland.

The track forecasts (see below--AVNO is the GFS, FV3G is the new model)) are initially similar, but near the coast, FV-3 swings farther south (bottom left) and the intensity forecasts are hugely different, with FV3 having weaker winds.

Considering more general verification, here is a representative upper level (500 hPa, about 18,000 ft) for the five-day forecast (see below).  The field below is anomaly correlation (1 is a perfect forecast) and you are looking at the verification of 500 hPa heights for the five day forecast.  The European Center (ECM) is the best, but new model is tied for second place  with the UKMET office.   This is improved performance.

FV3  (red line) appeared to perform better that the GFS (blue line) for the recent Hurricane Lane near Hawaii, with much lower track errors (see below)

Hurricanes are a big concern and the National Weather Service decided to replace the GFS after problems for Hurricane Sandy in 2012.  Thus, a lot of eyes will be watching the performance for Florence. The implications of the differing forecasts for Florence are huge---the next few days should be interesting.

from Cliff Mass Weather and Climate Blog https://ift.tt/2x3G99O