03/12Z: The Eta package has been upgraded to use fortran 90 and
to be Y2K compliant. Changes have also been made to several codes to
use the same 2-D grid indexing that the model has been using for some time.
This also means that 'native' Eta grid output has changed, the new grid
number is 192 and the GDS has also changed to include more information
(type 203). Modifications have been made to the 3DVAR to fix an error
that was resulting in the exclusing of almost all surface data, and
to improve the analysis fit to data.
From this set of corrections to the 3DVAR, forecasters should expect to see
improved Eta surface and low-level analyses which better reflect the
observations. In terms of impact on forecasts, these will be generally
minor. What we saw from tests were less in magnitude than the impact we saw
from the AVN going from T170 back to T126.