Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 245 AM EDT Thu May 02 2019 Valid May 02/0000 UTC thru May 05/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Southern stream trough/wave activity over the South... ...Energy lifting northeast across the OH/TN Valleys... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS/ECMWF and 12Z ECENS mean blend Confidence: Average A series of southern stream shortwave impulses will continue to lift northeast from the southern Plains up across the OH/TN Valleys and into the Mid-Atlantic region going into the weekend. This will allow multiple waves of low pressure to lift up along a frontal zone draped across the region. The 00Z UKMET trended weaker this cycle with the convectively induced wave lifting up from the Arklatex region early Thursday and into the OH Valley on Friday, and is close to the multi-model consensus which supports a modest wave. A separate low pressure center will also be noted a bit farther north up across the lower Great Lakes region and interior of the Northeast which the models show good agreement with. Finally, yet another shortwave impulse and associated low center will track from the lower MS Valley to the Mid-Atlantic region Friday through Saturday. The 00Z GFS tracks this wave overall a little north of the model consensus, with the 00Z CMC a bit farther south. The GFS though did trend a bit farther south, and is actually fairly close to the 00Z ECMWF/12Z ECENS mean solutions. The 00Z UKMET is a tad south of this consensus, and the 00Z NAM appears to be too progressive by the end of the period with this last surface wave. Based on the latest degree of model clustering, and ensemble support, a blend of the 00Z GFS/ECMWF and 12Z ECENS mean will be preferred. ...Low to mid-level trough impacting the FL Peninsula... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average The models take a low to mid-level trough near the Bahamas off to the northwest over the next day or so and gradually recurve this system around the western periphery of a weakening subtropical ridge off the Southeast coast. The guidance overall hints at there being a weak surface low that forms as the energy reaches the FL Peninsula later Thursday afternoon, before then recurving on Friday back off the Southeast coast. The 00Z NAM and 00Z UKMET suggest some intensification of the low center east of the Carolinas on Saturday as the system accelerates off to the northeast. A general model blend will be preferred at this time with this system. ...Southern stream closed low approaching CA... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z GFS/UKMET/ECMWF Confidence: Above average The guidance allows for a southern stream closed low to approach central/southern CA by late Saturday and into Sunday. The 00Z GFS is still overall the most progressive solution, but the 00Z non-NCEP guidance has all trended a bit faster and is now very close to the GFS solution. The 00Z NAM is now overall the slowest solution. The NAM and CMC also both appear to be a tad too weak when compared to the GEFS and ECENS member output. Based on this, will prefer a blend of the GFS/UKMET and ECMWF. ...Height falls traversing the northern Plains/Midwest... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend...through 36 hrs 00Z ECMWF/12Z ECENS mean blend...after 36 hrs Confidence: Slightly above average A series of northern stream troughs will cross the northern Plains and upper Midwest through the period. There is good agreement with the initial energy lifting northeast across the upper Midwest on Thursday. A second impulse crosses the northern Plains and upper Midwest on Friday, with the 00Z CMC being still somewhat of a stronger outlier with this system. Then the guidance supports a closed low feature crossing southern Canada on Saturday and Sunday which will allow drive a cold front southeast down across the Midwest. The 00Z NAM ends up on the slower side of the model spectrum, with the 00Z GFS suggesting a more progressive solution with its initial closed low, but then suggests a notably slower pocket of trailing energy. The 00Z non-NCEP models all more progressive than the NAM. The 00Z ECMWF and the 12Z ECENS mean overall best approximate the model consensus with this last feature. Will prefer a general model blend through 36 hours, and then lean toward a ECMWF/ECENS mean blend thereafter. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Orrison