A New GFS Developmental Model Is Being Tested in Parallel at NCEP. Should provide better forecasts this year.

NCEP has been running a new version of the GFS for a number of weeks in parallel. Some important changes ahead with the new version, which will likely go into production in May.

The current GFS uses an initialization method called 3DVar, which is an older method of initialization and essentially takes a snapshot of the atmosphere when the model is started.

The new version being tested and will likely be put into production this spring will utilize a more modern method of initialization called 4D-Ensemble-Variation.  It is basically a separate model that runs constantly tracking in real-time, changes in the atmosphere so when the GFS run starts it has a much better initialization, in theory.

Verification numbers support 4DEnsVar being a much better solution.  The ECMWF has used 4DEnsVar for quite sometime.  The CMC Global model and the UKMET and even the Navy NAVGEM have  been using a version of the 4DVar for a while now.  This will bring the GFS up to par with the other global models in terms of initialization schemes.  The 4Dvar and 4DEnsVar are quite computationally expensive and up until recently NCEP didn’t have the computing resources to implement 4DEnsVar.  4DEnsVar is somewhat less computationally expensive, while providing most of the benefits of traditional 4Dvar.

More information about the ongoing GFS parallel testing can be found from this technical note from NCEP released today, with many links to various NCEP sites that have output and statistics from the new GFS developmental model.



Mike Dross



Outbreak of Supercells & Tornadoes from North Carolina Northward into Maryland This Afternoon

Conditions favorable for supercells and tornadoes this afternoon will develop across Central and Eastern North Carolina into Western Virginia.  Extremely favorable shear and strong mid-level winds will combine with afternoon heating, to allow destabilization to occur at the time of frontal passage. A broken line of supercells should form by mid to late afternoon across Central North Carolina northward into Western Virginia, These cells will move rapidly northeastward beneath a 100+ knt mid-level jet.   The cells will be capable of producing violent tornadoes as they continue into the evening hours. Straight line winds of 75 mph are also possible in bowing segments or in rear flank down drafts.  There will be a considerable amount of dry air aloft which will limit the coverage of storms, but will aid the formation of the tornadoes, combined with a low lcl.