858  
FXUS10 KWNH 021654  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1253 PM EDT TUE JUN 02 2020  
 
VALID JUN 02/1200 UTC THRU JUN 06/0000 UTC  
 
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z INITIAL MODEL EVALUATION INCLUDING PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
UPPER LEVEL LOW SLOWLY LIFTING INTO OKLAHOMA THAT DRIFTS EAST INTO  
WEDNESDAY  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: MODERATE-HIGH  
 
A BROAD UPPER LOW CURRENTLY CENTERED OVER AT THE SW OKLAHOMA AND  
TEXAS BORDER WILL TURN MORE EASTERLY ACROSS OKLAHOMA INTO ARKANSAS  
INTO WEDNESDAY AS IT BECOMES EMBEDDED IN THE BROAD UPPER LEVEL  
RIDGE. ALL GLOBAL GUIDANCE ARE IN CLOSE ENOUGH AGREEMENT ON THE  
MAIN FEATURES TO MERIT THE USE OF A MULTI-DETERMINISTIC MODEL  
BLEND.  
 
CUT-OFF LOW LINGERING SOUTHWEST OF CALIFORNIA THROUGH THURSDAY  
BEFORE EJECTING EAST  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND, NON-GFS DAY 3.  
CONFIDENCE: MODERATE-HIGH  
 
A CUT OFF UPPER LOW WILL REMAIN NEARLY ANCHORED IN PLACE THROUGH  
THURSDAY WEST OF THE RIDGE AXIS OVER THE SOUTHERN ROCKIES BEFORE  
BEGINNING TO EJECT EAST TOWARD SOUTHERN CALIFORNIA THURSDAY NIGHT.  
THE 12Z GFS REMAINS THE FASTEST WITH THE EASTWARD EJECTION, A  
TYPICAL GFS BIAS OF TOO QUICK EASTERLY MOVEMENT OF THESE LOWS,  
WHILE DEPTH AND POSITION ARE IN EXCELLENT AGREEMENT AMONG THE REST  
OF THE GLOBAL GUIDANCE. THEREFORE, THE PREFERENCE FOR DAY 3 IS  
NON-GFS. HOWEVER, THERE IS LITTLE MOISTURE WITH THIS SYSTEM, SO  
THERE IS NOT MUCH DIFFERENCE IN PRECIP FOR SOUTHERN CA.  
 
ACTIVE FLOW PATTERN ACROSS NORTHERN TIER OF U.S.  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-CMC GENERAL MODEL BLEND THROUGH DAY 2, 00Z  
ECMWF/UKMET DAY 3  
CONFIDENCE: MODERATE  
 
THE WESTERLIES ON THE NORTHERN PERIPHERY OF THE CENTRAL U.S. RIDGE  
WILL REMAIN ACTIVE WITH THREE WELL-DEFINED SHORTWAVE DISTURBANCES  
TRACKING EASTWARD NEAR THE U.S./CANADA BORDER THROUGH MID-WEEK.  
THE FIRST SYSTEM IS THE REMNANTS OF AN OCCLUDED LOW MOVING  
CURRENTLY OVER FAR NORTHEAST ONTARIO THAT WILL SHIFT SOUTHEAST  
ACROSS NY STATE AND SOUTHERN NEW ENGLAND TONIGHT. THE SECOND  
DISTURBANCE IS A SHORTWAVE OVER NORTHERN MANITOBA WHICH WILL TRACK  
SOUTH OF THE HUDSON BAY BY WEDNESDAY AND BE DIRECTED ACROSS  
NORTHERN MAINE BY A DEEP LOW OVER LABRADOR, ALL THE WHILE DRAGGING  
A COLD FRONT STALL OVER THE EAST-CENTRAL CONUS AND PROVIDE A FOCUS  
FOR DAY 2 QPF. THE THIRD SYSTEM REACHES THE BRITISH COLUMBIA COAST  
THIS AFTERNOON AND WILL TRACK JUST NORTH OF THE BORDER AND EVOLVE  
INTO AN UPPER LOW OVER MANITOBA BY WEDNESDAY NIGHT. THIS WILL PUSH  
A COLD FRONT ACROSS THE NORTHERN GREAT PLAINS WEDNESDAY NIGHT AND  
INTO THE MIDWEST THURSDAY.  
 
DESPITE THE QUASI-ZONAL AND PROGRESSIVE FLOW PATTERN IN PLACE  
ACROSS THE REGION, MODELS ARE IN GOOD AGREEMENT THROUGH DAY 2  
EXCEPT FOR THE 00Z CMC WHICH IS MUCH FASTER WITH EASTWARD  
PROGRESSION OF THE THIRD WAVE OVER THE CANADIAN PRAIRIES STARTING  
LATE WEDNESDAY. THERE ARE SOME MORE TIMING AND AMPLITUDE  
DIFFERENCES WITH THE THIRD WAVE THAT BECOME APPARENT ON FRIDAY.  
THE 12Z GFS JUMPS OUT AHEAD OF THE ECMWF/UKMET/NAM, BUT THE 12Z  
NAM IS DEEPER THAN THE UKMET/ECMWF. SO THE 00Z UKMET/ECMWF IS  
PREFERRED FOR DAY 3.  
 
CLOSED LOW DRIFTING SOUTH FROM GULF OF ALASKA OFF BC COAST BY  
FRIDAY.  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND, NON-GFS DAY 3  
CONFIDENCE: MODERATE-HIGH  
 
EXCELLENT AGREEMENT AMONG GLOBAL GUIDANCE FOR LARGE CLOSED LOW  
DRIFTING SOUTH FROM GULF OF ALASKA TO A POSITION WELL OFF THE BC  
COAST BY LATE FRIDAY EXCEPT FOR THE 12Z GFS WHICH IS THE FASTEST  
SOLUTION. GREATER DIFFERENCES ARE EXPECTED BY THE TIME THE  
LOW/TROUGH SWINGS INTO THE PACIFIC NORTHWEST OVER THE WEEKEND.  
 
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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