030  
FXUS10 KWNH 130424  
PMDHMD  
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1223 AM EDT SAT JUN 13 2020  
 
VALID JUN 13/0000 UTC THRU JUN 16/1200 UTC  
 
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..EXITING TROUGH ACROSS MID-ATLANTIC TO NORTHEAST
 
   
..CLOSED LOW DEVELOPING IN SOUTHERN APPALACHIANS MON/TUES
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-GFS BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
LINGERING SHORTWAVE ENERGY OVER THE LOWER GREAT LAKES WILL  
CONSOLIDATE IN THE MID-LEVELS LATER TODAY INTO EARLY SUNDAY AND  
START TO SLIDE NORTHEAST INTO SE CANADA BY MONDAY, WITH LITTLE  
FANFARE OR MODEL DIFFERENCES.  
 
THE TRAILING EDGE OF THE LONGER WAVE PATTERN UPSTREAM ACROSS THE  
UPPER GREAT LAKES WITH A SMALL 90KT NW-SE ORIENTED JET WILL  
AMPLIFY INTO A SMALL BUT COMPACT WAVE THROUGH THE MIDWEST LATER  
TODAY AND DROP INTO THE CENTRAL OHIO VALLEY. GUIDANCE HAS  
FINALLY COME INTO STRONG AGREEMENT WITH THE PLACEMENT/MAGNITUDE OF  
THE WAVE THROUGH 48HRS AS IT PIVOTS/STALLS IN S OH/E KY/W WV,  
ENOUGH TO HAVE ABOVE AVERAGE CONFIDENCE IN A GENERAL MODEL BLEND  
THROUGH THIS PERIOD. AFTERWARDS, THE MODELS SPREAD AS THE WAVE  
EXITS THE TIGHT LOOP EXPANDING INTO A BROADER CLOSED LOW ACROSS  
THE SOUTHERN APPALACHIANS INTO THE COASTAL PLAIN OF GA/SC. THE  
00Z GFS IS SLOWEST TO WOBBLE OUT AND DRAWS STRONGER ENERGY FROM  
THE NORTHERN STREAM TO DELAY THIS FURTHER, LEADING TO AN OVERALL  
NORTHWARD ORIENTATION TO THE REST OF THE GLOBAL/ENSEMBLE SUITE.  
THE 18Z GEFS SHOWS SOME CLOSENESS INITIALLY BUT BY 84HRS IS  
FURTHER SOUTH AND CLOSER TO THE ECMWF/NAM. THE 12Z UKMET/CMC ARE  
A BIT EAST OF THE ECMWF/NAM BUT THE EVOLUTION/PLACEMENT AND SHAPE  
ALL SUGGEST A NON-GFS BLEND IS PREFERABLE AT SLIGHTLY ABOVE  
AVERAGE CONFIDENCE.  
 
IT SHOULD BE NOTED THAT THE 00Z NAM IS A BIT STRONG WITH  
RETROGRADING A LOW LEVEL WAVE THROUGH THE CAROLINAS AND TIGHTENING  
THE OVERALL LOW LEVEL FLOW FOR A STRONG QPF SIGNAL...THIS IS  
LIKELY OVER-INFLATED BUT GIVEN THE MODEL RESOLUTION AND CAPABILITY  
FOR RESOLVING SOME MESOSCALE MOISTURE/INSTABILITY BETTER THAN THE  
GLOBAL GUIDANCE...IT SHOULD BE INCORPORATED BUT WITH SOME CAUTION  
GIVEN THE BIAS TO OVER-STRENGTHEN SYSTEMS ESPECIALLY IN THE LATE  
DAY 2 TO DAY 3 PERIOD.  
 
...LONGWAVE TROUGH OFF THE WEST COAST AND SHORTWAVE LIFTING  
ONSHORE CALIFORNIA BY THE WEEKEND, INTERACTING THROUGH NORTHERN  
ROCKIES/SW-CENTRAL CANADA SUNDAY-TUES...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-GFS BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
A TIGHT SHORTWAVE IS LIFTING NORTH THROUGH CA AT THIS TIME, ALONG  
THE EASTERN SIDE OF A CLOSED LOW NEAR VANCOUVER ISLAND. THE 00Z  
GFS CONTINUES TO BE SLIGHTLY FASTER LIFTING INTO SW CANADA  
RELATIVE TO THE OTHER GUIDANCE AND IN DOING SO FINDS A MORE  
FAVORABLE ENVIRONMENT/POSITION RELATIVE TO THE UPSTREAM CLOSED LOW  
TO RAPIDLY DEEPEN AND BECOME THE DOMINANT CIRCULATION IN THE  
BINARY INTERACTION RELATIVE TO THE REST OF THE GLOBAL GUIDANCE  
SUITE. T THIS DOESN'T SEEM TO NEGATIVELY AFFECT THE  
TIMING/STRENGTH OF THE REMAINDER OF THE CLOSED LOW AS IT SWING  
AROUND THE BASE OF THE LARGER SCALE CLOSED LOW, AS WELL AS, THE  
EASTWARD PROGRESSION OF THE FRONTAL ZONE INTO THE NORTHERN PLAINS  
WHERE SPREAD IS SMALL. STILL THE GFS IS NOT GENERALLY FAVORED  
OUTSIDE OF THE CONUS, WHERE A MORE ELONGATED WEST TO E SHEARED  
TROF IS PREFERRED FROM THE UKMET/ECMWF/NAM THAN THE MORE COMPACT  
CMC, BUT ONLY IN WEIGHTING WITHIN A NON-GFS BLEND. CONFIDENCE IS  
SLIGHTLY ABOVE AVERAGE.  
 
...NEXT CLOSED LOW/EMBEDDED SHORTWAVES ENTERING PACIFIC NW  
MON-TUES...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND; WEIGHT HEAVIER TO 12Z ECMWF/CMC  
CONFIDENCE: AVERAGE  
 
UPSTREAM, A CLOSED LOW IS DEVELOPING IN THE WESTERN GULF OF AK  
LATER TODAY INTO SUNDAY, THOUGH REMAINS FAIRLY PROGRESSIVE IN  
NATURE. THERE IS A FORECAST SLOW DOWN AS THE DEEPER CYCLONE  
OCCLUDES/WOBBLES WEST OF HAIDA GWAII/CHARLOTTE ISLAND. THIS WILL  
ALSO ALLOW FOR RETURN SUBTROPICAL SHORTWAVE ENERGY TO PRESS  
EASTWARD AND BRING SOLID DPVA INTO THE PACIFIC NW BY MIDDAY  
HELPING TO BROADEN THE LARGER SCALE PATTERN INTO A DUAL LOBE  
GLOBAL SCALE GYRE FROM THE EASTERN GULF OF AK THROUGH MUCH OF  
WESTERN CANADA (SEE SYSTEM IN ABOVE SECTION). THE TYPICALLY  
FASTER SOLUTIONS OF THE GFS/UKMET AND NAM CONTINUE TO TREND FASTER  
BUT NOW SUGGEST THE MAIN BODY OF THE WAVE WILL DROP THROUGH THE  
MOUTH OF THE COLUMBIA RIVER AT 84HRS. THIS IS OPPOSED BY THE  
ECMWF/CMC WHICH CONTINUE TO LAG AND FAVOR MORE OF AN AMPLIFICATION  
OF THE SUBTROPICAL SHORTWAVE RELATIVELY SPEAKING TO THE  
GFS/UKMET/NAM. THE EFFECTS ON QPF ARE ACTUALLY MINIMAL, THOUGH  
THE MASS FIELDS ARE SHOWING INCREASED SPREAD LEADING TO INCREASED  
CONFIDENCE THERE, BUT LESSER SO ON THE MASS FIELD SIDE. THE  
FASTER TREND HAS BEEN NOTED THROUGH MULTIPLE CYCLES OF THE  
ENSEMBLES, YET THIS FASTER SOLUTION IS ALSO ALIGNED WITH THE  
GENERAL NEGATIVE BIAS OF THESE MODELS RELATIVE TO THE ECMWF/CMC.  
SO AT THIS TIME WILL KEEP WITH MORE CONTINUITY OVER THE TREND, AND  
PREFER A HIGHER WEIGHTING TO THE ECMWF/CMC; HOWEVER, LEAVING THE  
DOOR OPEN TOWARDS A POTENTIAL SHIFT WITH THE NEW 00Z ECMWF/CMC  
SOLUTIONS. AS SUCH A GENERAL MODEL BLEND IS PREFERRED BUT  
WEIGHTED MORE HEAVILY TOWARD CONTINUITY/ECMWF/CMC.  
 
GALLINA  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 

 
 
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