During a 3-month period from December 13, 2001 to March 15, 2002, MDL tested the effects of the GFS resolution change on the MOS guidance by using the output of the parallel 0000 UTC GFS run in the MRF MOS max/min temperature and PoP forecast equations. For max/min temperature, the mean absolute errors (MAE) of the test (or parallel) runs were nearly identical to those of the operational MRF MOS guidance at all projections, although a slight decrease in the MAE of the parallel MRF MOS can be seen in the forecast projections of 96 to 192 hours. For PoP, the Brier scores (or mean sqare errors) of the parallel and operational guidance were also approximately identical; yet a very slight decrease in the Brier score was evident in the test runs for projections of 108 to 144 hours. These minor differences in the operational and parallel MRF MOS guidance packages are not significant. Thus, when the resolution of the GFS is change, the foreast should see little or no difference in the MOS forecast quality.
During a 3-week period in March 2002, MDL tested the effects of the GFS change on the MOS guidance by using the new extended 0000 UTC GFS run initialized at 0245 UTC in the MRF MOS max/min temperature and PoP forecast equations. For max/min temperature, the mean absolute errors (MAE) of the test runs were nearly identical to those of the operational MRF MOS guidance at all projections. For Pop, the Brier scores (or mean square errors) of the parallel and operational guidance were also approximately identical. Minor differences in the operational and parallel MRF MOS guidance packages are not significant. When the MRF is discontinued, MDL will continue to produce extended-range guidance during the 0000 UTC forecast cycle. No changes will occur in the AVN or MRF MOS guidance packages. In the short term, the nomenclature of calling the latter package the "MRF MOS" guidance will be retained.