695  
FXUS10 KWNH 291646  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1245 PM EDT SUN MAR 29 2020  
 
VALID MAR 29/1200 UTC THRU APR 2/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION WITH PRELIMINARY PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
CLOSED LOW OVER GREAT LAKES AND NEW ENGLAND WITH SURFACE  
CYCLOGENESIS NEAR THE COAST  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
THERE IS VERY GOOD SYNOPTIC SCALE AGREEMENT ON THE EVOLUTION OF  
THE PARENT UPPER LOW OVER THE UPPER GREAT LAKES THAT PROGRESSES  
EASTWARD TO NEW ENGLAND BY MONDAY NIGHT. THIS WILL SUPPORT THE  
DEVELOPMENT OF A COASTAL LOW NEAR SOUTHEAST NEW ENGLAND THAT IS  
FORECAST TO TRACK SLOWLY EASTWARD ROUGHLY NEAR 40 DEGREES NORTH.  
IN REGARD TO THE DEVELOPING SURFACE LOW, THERE ARE MINOR PLACEMENT  
DIFFERENCES THAT DEVELOP, WITH THE 00Z UKMET SLIGHTLY CLOSER TO  
THE COAST AND THE CMC A TAD FARTHER TO THE SOUTH, BUT STILL CLOSE  
ENOUGH TO MERIT A DETERMINISTIC MULTI-MODEL BLEND.  
 
SOUTHWEST SHORTWAVE SPURRING SOUTHERN PLAINS CYCLOGENESIS  
MON-TUES, SLIDING THROUGH SOUTH EARLY IN THE WEEK  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z NAM/GFS AND 00Z ECMWF  
CONFIDENCE: AVERAGE  
 
SHORTWAVE CURRENTLY ALONG THE CA COAST WILL PROGRESS EASTWARD  
ACROSS THE SOUTHERN TIER STATES THROUGH EARLY WEEK. THE 00Z CMC  
IS ALREADY OUT OF PHASE, A BIT SOUTH, AND MORE COMPACT THAN OTHER  
GUIDANCE AND IS QUICKLY DISMISSED FROM PREFERENCE. THE REMAINING  
DIFFERENCE INITIALLY THROUGH TUESDAY ACROSS THE SOUTHERN PLAINS  
AND INTO THE SOUTHERN MS VALLEY IS IN DEPTH AND TIMING, WITH THE  
UKMET AND GFS A TAD WEAKER THAN THE ECMWF/NAM; WHICH LEADS TO  
SLIGHTLY DIFFERENT PLACEMENT OF THE DEEPER MOISTURE/UNSTABLE  
ENVIRONMENT AHEAD OF IT. THE WEAKER/FASTER SOLUTIONS SUGGEST A  
SLOWER TRANSPORT NORTH AND STRONGER CONVECTIVE RESPONSE FARTHER  
SOUTH NEAR THE GULF. THIS SEEMS LOGICAL AT THIS TIME OF YEAR, BUT  
CONTINUITY AND OVERALL FORCING/MASS FIELDS SUGGEST NORTHWARD  
SHIFT. THE 00Z UKMET IS MUCH FLATTER THAN THE ENSEMBLE/CONTINUITY  
AND IS MORE DRAMATICALLY SO ON DAY 3 ACROSS THE SOUTHEAST. WHILE  
THIS IS PLAUSIBLE, IT IS MORE DRAMATIC THAN THE GFS/GEFS WHICH  
WILL REPRESENT THE UNCERTAINTY WITH ITS INCORPORATION OVER THE  
UKMET IN A PREFERRED BLEND. STILL, THE UNCERTAINTY HERE IS GOING  
TO BE MESOSCALE CONVECTIVE PLACEMENT AND ITS UPSCALE INFLUENCE.  
SO THE PREFERENCE WILL BE NEAR A 12Z GFS/NAM AND 00Z ECMWF BLEND  
AT AVERAGE CONFIDENCE.  
 
CLOSED LOW AND UPPER LEVEL TROUGH APPROACHING PACIFIC NORTHWEST  
THROUGH MONDAY...THEN THE NORTHERN ROCKIES/HIGH PLAINS BY LATE WED.  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z GFS/00Z UKMET WITH SOME 00Z ECMWF/CMC AT LOWER  
WEIGHT  
CONFIDENCE: AVERAGE  
 
BROAD TROF DEVELOPING OVER THE GULF OF AK WILL CONTINUE TO PRESS  
SOUTHEASTWARD WITH UPSTREAM SHORTWAVE ENERGY SWINGING THROUGH TO  
PRESS HEIGHT-FALLS/TRIPLE POINT AND COLD FRONT THROUGH VANCOUVER  
ISLAND AND THE PAC NW BY EARLY MONDAY. THIS UNDERCUTTING  
SHORTWAVE WILL SWING ACROSS THE NORTHERN ROCKIES AND THE SOUTHERN  
CANADIAN ROCKIES BY EARLY TUESDAY, SUPPORTING A WESTERN HIGH  
PLAINS SURFACE CYCLONE. HERE THE 12Z NAM IS VERY STRONG/QUICK AS  
IT ROTATES EASTWARD. THIS WILL OVERALL SHIFT THE CORE OF THE  
UPPER LOW FARTHER EAST THAN HAS BEEN/CURRENTLY IS SUGGESTED BY THE  
ENSEMBLE SUITE AND TRENDS. THE 12Z GFS AND 00Z UKMET ARE AS FAST  
AS THE NAM BUT MUCH WEAKER OVERALL, SO THESE WOULD BE GENERALLY BE  
FAVORED OVER THE NAM. THE SLOWER SOLUTIONS OF THE ECMWF/CMC, BY  
LATE TUESDAY/WED, BOTH SUGGEST A GREATER INFLUENCE/TUG ON THE  
SHORTWAVE LIFTING ACROSS THE CANADIAN ROCKIES FROM THE ARCTIC  
STREAM, DRAWING BOTH NORTH AND WEST, AND STRENGTHENING THEM. THE  
ECMWF IS MORE SO, INCLUDING AGAINST ITS ENSEMBLE SUITE MEMBERS.  
THIS DOES NOT SEEM TO PLAY MUCH OF A ROLE IN THE REMAINING  
UPSTREAM ENERGY/JET STREAK THAT PRESSES THROUGH THE PACIFIC NW  
LATE TUESDAY INTO WED; SO FROM A CONUS PERSPECTIVE, THE ECMWF IS  
VIABLE IN PREFERRED BLENDS. THE CMC IS A TAD WEAKER BUT MAY BE  
VIABLE AS WELL IF DESIRED. SO ALL IN ALL, A NON-NAM SOLUTION IS  
PREFERRED ACROSS THE NORTHWEST/NORTHERN ROCKIES AND THE NORTHERN  
PLAINS, THOUGH WITH GREATER WEIGHTING TO THE GFS/UKMET.  
CONFIDENCE IN THE OVERALL PATTERN IS HIGH, BUT WITH SOLID  
DIFFERENCES IN TIMING/STRENGTH OF THE KEY INTERNAL SHORTWAVES AND  
THEIR INFLUENCE ON SURFACE CYCLONE DEPTH/ORIENTATION, CONFIDENCE  
REMAINS AVERAGE IN THIS BLEND.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
GALLINA/HAMRICK  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page