Problems have arisen in the operational T170L42 MRF Analysis/Forecast System, which was implemented on 15 June 1998, and updated 21 July. The symptoms were a general decline in forecast quality as measured objectively by the standard statistics and noted subjectively by forecasters. It was also noticed that the analysis was not drawing well for the data. Since limited computer resources have precluded testing any improvements at full resolution, we have therefore prepared a reduced-resolution version of the system, tested it in parallel with the operational version and scheduled it for emergency implementation
This new parallel version of the NCEP MRF has been running routinely since 00Z 1 September. It contains a reduction in resolution from T170/L42 to T126/L28 and additional iterations of the analysis to enable it to draw closer to observations. Although it is customary to allow much longer periods of pre-implementation testing of significant model changes, it was considered prudent to accelerate the implementation in this case due to the consistently superior performance of the parallel run and the increasingly obvious shortcomings of the T170.
The new T126 MRF was implemented 5 Oct, 1998, with the 12Z run of the AVN.
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