Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 143 PM EST Tue Mar 03 2020 Valid Mar 03/1200 UTC thru Mar 07/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z model evaluation with final preferences and confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Closed low weakening eastward from the Southern Plains to the East Coast through Friday... ...Surface low tracking from the central Gulf Coast to the East coast and then northward through the western Atlantic... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z GFS/ECMWF/UKMET blend Confidence: Average Model differences show up early with this system over Texas by Wednesday evening with a stronger 700-500 mb low depicted in the 12Z NAM compared to the remaining guidance. The stronger NAM also has a surface low that is farther north in time along the Gulf Coast. The models are in good agreement that the mid-level shortwave weakens into confluent flow but the 00Z ECMWF stood out with a faster timing which translated into a surface low that becomes farther offshore of the East Coast by Thursday evening. The 12Z ECMWF trended slightly slower with the shortwave while the 12Z UKMET trended faster. The 00Z/03 (latest) ensemble scatter low plots showed a notable jump to the east with the surface low valid Friday morning off of the Mid-Atlantic coast compared to the 12Z/02 cycle and previous cycles. For Thursday night, The latest ensemble distribution shows the Canadian members farthest west, with the GEFS toward the middle and the ECMWF members farther offshore. Given the latest deterministic spread and considering ensemble distribution over the past 4 cycles, a placement near the 12Z GFS, 12Z ECMWF and 12Z UKMET is preferred. ...Mid-level trough/closed low nearing the Great Lakes Thursday into Friday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z NAM/ECMWF/UKMET blend Confidence: Average The ensembles have shown better convergence of members regarding the depth and timing of the trough axis as it tracks east. The 00Z UKMET/CMC were noted to be on the slower side of the ensemble members which if anything, have trended slightly quicker over their past 4 12/00Z cycles. The 12Z UKMET trended faster, and is now in good agreement with the consistent ECMWF (12Z and 00Z ECMWF). However, the 12Z CMC remains slower with the trough progression toward the east. Meanwhile, the 12Z GFS was noted to be a bit faster than the remaining model consensus and on the north side with the surface to 850 mb low. The 12Z NAM, 12Z ECMWF and 12Z UKMET showed better agreement with this system and are considered best with thinking the GFS/GEFS are too far north with the low level low. ...Remainder of systems Impacting the lower 48... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average Across the rest of the lower 48, a deepening surface low will track across the Northeast followed by low amplitude shortwave which will track from the central and northern Great Plains to to the northern Mid-Atlantic coast by Wednesday evening. Also, a larger amplitude mid-upper level trough is expected to near the West Coast on Friday. The models are in fair agreement with these systems and so a general model blend is preferred for the remainder of the CONUS. No changes are recommended across the remainder of the CONUS based on the 12Z ECMWF/UKMET/CMC. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto