Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 243 AM EDT Thu Oct 24 2019 Valid Oct 24/0000 UTC thru Oct 27/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with latest Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Initial trough over the Upper Midwest/Great Lakes... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average An initial upper trough over the upper Midwest will cross the Great Lakes region on Thursday and dampen out by Friday as the energy shears northeast into southeast Canada. The models are in very good agreement on the details of this system, and so a general model blend will be preferred. ...Secondary trough over the Upper Midwest/Great Lakes on Fri... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average A secondary shortwave trough clipping the northern Plains by later Thursday will cross the the upper Midwest Thursday night and cross through the Great Lakes on Friday, before then advancing east over the Northeast by Saturday. The latest guidance is collectively in sufficiently good enough agreement that a general model blend can be preferred. ...Amplifying trough over the southern High Plains... ...Closed low evolution toward the lower MS Valley... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z NAM/ECMWF/GEFS mean Confidence: Slightly below average The models show very good agreement in taking an amplifying shortwave currently over CO farther south down across the southern High Plains through Thursday and then gradually east across the broader southern Plains on Friday. Significant model disagreements though take shape this weekend though as the system closes off and advances east toward the lower MS Valley and then northeast toward the OH/TN Valley region. After about 48 hours, the 00Z GFS becomes a progressive outlier with the height falls and is notably more progressive than even the 00Z GEFS mean. Meanwhile, the 00Z UKMET gradually becomes a slower and more amplified outlier with the system. The UKMET also shows much more interaction with the area of disturbed weather over the Gulf of Mexico. The 00Z NAM is rather close to the 00Z ECMWF, and both of these models are strongly supported by the 00Z GEFS mean. The 00Z CMC is a bit slower than this consensus, and based on the model clustering and ensemble agreement, a blend of the NAM/ECMWF and GEFS mean will be preferred, but again with somewhat limited confidence on the mass field front. ...Low pressure development over the Gulf of Mexico... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z GEFS/12Z ECENS mean Confidence: Below average The latest satellite imagery confirms an area of disturbed weather over the Bay of Campeche which the models unanimously depict lifting north across the western and then north-central Gulf of Mexico over the next few days. There is substantial support among the deterministic global and hires model suites for a low pressure center to develop either Thursday night or early Friday over the Bay of Campeche before the system likely merges with a strong front entering the western Gulf of Mexico. The 00Z UKMET, which is an outlier solution with the height falls over the lower MS Valley by Saturday, suggests the low center gets picked up by the amplifying trough and deepens as an extratropical cyclone across portions of the central Gulf Coast states this weekend. The consensus of the remaining deterministic guidance suggests a low center gets left along the front across the central Gulf of Mexico by Sunday as the upper trough over the lower MS Valleys lifts well northeast across the OH/TN Valleys, although there is substantial latitudinal spread with where the low is centered among the various models. The 00Z GFS is farthest south by Sunday, with a low northwest of the Yucatan Peninsula whereas the 00Z CMC is much farther off to the northeast and inland by Sunday over the Southeast. The 00Z NAM and ECMWF are both slower than the CMC, but well north of the GFS. The GEFS and ECENS suites overall support at least a weak low center in the vicinity of the central Gulf of Mexico by Sunday, but there are a number of GEFS members that actually support a separate low center developing over the northwest Gulf of Mexico by late Friday along the aforementioned front that then impacts south-central LA by Saturday. So, in essence, there is GEFS support for three low centers, with one over the Bay of Campeche, one over the northwest Gulf of Mexico and one farther north over the lower MS Valley by early Saturday. Given the highly uncertain evolution of this low center and degree of model spread, a blend of the 00Z GEFS and 12Z ECENS means will be preferred. ...Upper trough digging across the Intermountain West by Sat... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z ECMWF/12Z ECENS mean Confidence: Average A strong deep layer ridge is forecast to evolve over the Gulf of AK this weekend which will allow shortwave energy to dig south across southwest Canada and then into Intermountain West and northern Plains by Sunday. There is support for some stream separation over the Intermountain West by Sunday which is more strongly supported by the 00Z non-NCEP models. The 00Z NAM and 00Z GFS both appear to be generally a tad too progressive. There is a bit better ensemble support overall for a slightly slower evolution of the energy, although the 00Z UKMET appears to be too slow. A preference toward 00Z ECMWF and 12Z ECENS mean will be preferred which overall better fits the model consensus. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Orrison