829  
FXUS10 KWNH 190440  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1140 PM EST TUE FEB 18 2020  
 
VALID FEB 19/0000 UTC THRU FEB 22/1200 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z INITIAL MODEL EVALUATION WITH LATEST PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
OVERALL PATTERN ACROSS THE CONUS  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND THROUGH 36 HOURS; THEN  
UKMET/ECMWF/GEFS MEAN  
CONFIDENCE: NEAR AVERAGE FOR MOST AREAS  
 
THE PATTERN AT THE BEGINNING OF THE FORECAST PERIOD WEDNESDAY  
MORNING IS FEATURED WITH A WEST COAST RIDGE, ZONAL FLOW ACROSS THE  
CENTRAL/SOUTHERN PLAINS AND GULF COAST REGION, AND A LONGWAVE  
POSITIVELY TILTED TROUGH DROPPING SOUTHEASTWARD ACROSS THE  
NORTHERN ROCKIES AND THE DAKOTAS. THE TROUGH WILL THEN REACH THE  
EASTERN U.S. BY EARLY FRIDAY AND INDUCE SURFACE CYCLOGENESIS OVER  
THE OFFSHORE WATERS BETWEEN THE CAROLINAS AND BERMUDA. WITH THE  
UPPER LEVEL RIDGE AXIS PROGRESSING TO THE SOUTH-CENTRAL U.S. BY  
THE WEEKEND, A SOUTHERN STREAM CLOSED LOW ALOFT REACHES CALIFORNIA  
AND HERALDS A PATTERN CHANGE FOR THIS REGION.  
 
THROUGH THURSDAY MORNING, A GENERAL MODEL BLEND WILL SERVE AS A  
GOOD STARTING POINT SINCE THERE ARE RELATIVELY MINIMAL  
DETERMINISTIC DIFFERENCES AND LITTLE IN THE WAY OF ENSEMBLE  
SPREAD. BY THURSDAY EVENING, DIFFERENCES BECOME APPARENT WITH THE  
500MB TROUGH CROSSING THE OHIO VALLEY AND MIDWEST STATES, WITH THE  
NAM AND TO A LESSER EXTENT THE GFS BECOMING MORE AMPLIFIED THAN  
THE NON-NCEP GUIDANCE SUGGESTS. THIS HAS IMPLICATIONS FOR  
OFFSHORE SURFACE LOW DEVELOPMENT EAST OF THE CAROLINAS, WITH THE  
NAM BEING A NORTHWESTERN OUTLIER WITH THE TRACK OF THE LOW, THUS  
BRINGING MORE IMPACTFUL WEATHER TO THE INTERIOR SOUTHEAST. THE  
CMC BECOMES A LITTLE MORE PROGRESSIVE WITH THE LOW TRACK, WITH  
GOOD AGREEMENT AMONG THE ECMWF, UKMET, AND THE ENSEMBLE MEANS.  
 
FOR THE LONGWAVE TROUGH AND DEVELOPING CLOSED LOW FOR THE WEST  
COAST REGION, THERE IS NOW BETTER AGREEMENT WITH THE SHORTWAVE  
CROSSING THE PACIFIC NORTHWEST THURSDAY EVENING COMPARED TO  
EARLIER MODEL RUNS OF THE NAM AND GFS. IN REGARDS TO THE CLOSED  
LOW REACHING SOUTHERN CALIFORNIA BY SATURDAY MORNING, THE UKMET IS  
SLIGHTLY MORE PROGRESSIVE BUT STILL CLOSE TO THE ENSEMBLE MEANS,  
AND THE GFS IS SLIGHTLY SLOWER. THE CMC AND ECMWF ARE CLOSEST TO  
THE MODEL CONSENSUS.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
HAMRICK  
 

 
 
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