4Traditional Short-Range MOS Guidance KGTF GFS MOS GUIDANCE 10/21/ UTCDT /OCT /OCT /OCT /HRX/NTMPDPTCLD OV OV OV SC CL CL SC SC SC SC SC CL SC SC SC CL CL CL CL CL CLWDRWSPPPQQT / 1 0/ 0 0/ 2 0/ 0 0/ 0 0/ 0 0/ 0 0/ 0 0/ 0 1/ 0T / / / / / 0POZPOSTYP R R R R R R R R R R R R R R R R R R R R RSNWCIGVISOBV N N N N N N N N N N N N N N N N N N N N N
7Objectives of Gridded MOS Project Produce MOS guidance on high-resolution grid (2.5 to 5 km spacing)Generate guidance with sufficient detail for forecast initialization at WFOsGenerate guidance with a level of accuracy comparable to that of the station-oriented guidance
9MDL Approach to Downscaling High-resolution geoclimatic variablesDiverse observational networksAppropriate MOS equation development (single station, regional, or generalized operator)Analysis on high-resolution grid
20CONUS MOS SitesCONUS grid – with 5-km terrain as background; note station density – standard METAR sites in black; mesowest sites in yellow, co-op sites in red and rfc sites (i.e., data provided by RFC’s) in purple; buoys and C-MAN sites are not shown, though they are in the MOS system
21Western CONUSWhen all was said and done, this is what we had – approximately 300 METAR/marine sites, 1175 mesowest sites, 1325 cooperative observer sites and 80 RFC-supplied sites. This gave us a nominal resolution of about 30 km – if every station reported every observation, and if sites were uniformly distributed. Both assumptions are false, of course.
22Method of successive corrections BCDG AnalysisMethod of successive correctionsLand/water gridpoints treated separatelyElevation (“lapse rate”) adjustment
23Goodness of Fit by Using Terrain VARIABLENO. STA.MAE (°F) (ALL)MAE (°F) (WITHHELD)TMRW’S MAX (terr.)26211.113.00TMRW’S MAX (w.o.)1.384.0827-H TMP (terr.)14060.982.9227-H TMP (w.o.)1.344.29This table shows the results of using the BCDG analysis on a case from July 15, The leftmost column shows the variable, the next column shows the number of stations that influenced the analysis. The third column shows the error of fit for all stations when the terrain correction is used (in yellow) or when the terrain correction is not used (in white). You can see that using the terrain correction improved the analysis fit – by.27 deg F for the max, and by .36 deg F for the spot temperature. The last column represents what happens at randomly withheld sites with and without the terrain correction. This column represents the mean absolute error, when 48 different analyses were done, and 10 randomly selected points were withheld from each analysis. Note the large improvement when the terrain correction is applied.
24MOS Temperature Analysis (w. terrain) Here’s an example of the MOS temperature forecast when the terrain correction is applied. Note the Nevada border and the detail near Death Valley, and along the CO River.
25MOS Temperature Analysis (no terrain) Contrast this with the no terrain elevation correction analysis.
32General information and documentation Gridded MOS ProductsGeneral information and documentationSample graphics (from gempak)NDGD Web Page (graphics ala NDFD)NWS ftp server (grib2)
33Evaluation (objective & subjective) Future of Gridded MOSEvaluation (objective & subjective)Expansion (area & elements)ImprovementUse of remote-sensing observationsDissemination on SBN
34Retrospective sample: December 2004 – September 2005 Objective EvaluationRetrospective sample: December 2004 – September 2005Western CONUS onlyComparison between NDFD, HPC, and MOS gridsMax/min temperature and dew point onlySelected sites – generally RAWS
35Western CONUS Verification Sites When all was said and done, this is what we had – approximately 300 METAR/marine sites, 1175 mesowest sites, 1325 cooperative observer sites and 80 RFC-supplied sites. This gave us a nominal resolution of about 30 km – if every station reported every observation, and if sites were uniformly distributed. Both assumptions are false, of course.
36ScheduleNovember 30, 2005 – wind dir. & speed, relative humidity, PoPs, tstm prob., and snowfall added to NDGD web site (as of 12/13/05, winds and snowfall have been delayed)January 31, 2006 – grib2 products sent on SBN (pending resolution of TOC moratorium)June 30, 2006 – CONUS grid completely populatedSeptember 30, 2006 – sky cover, precip. type, qpf, and wind gusts added to product suiteSeptember 30, 2007 – Alaska grids available
37Issues Quality of observations Inversions Winds Quality Assurance Site representativenessSamplingSkewed samplesInstrumentation biasSmall sample, inconsistent in timeInversionsWindsQuality Assurance