869   
FXUS10 KWNH 111838  
PMDHMD  
  
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
237 PM EDT THU JUN 11 2020  
  
VALID JUN 11/1200 UTC THRU JUN 15/0000 UTC  
  
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
  
12Z FINAL MODEL EVALUATION INCLUDING PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..TROUGH AMPLIFYING ACROSS THE EAST  
  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-NAM BLEND  
CONFIDENCE: AVERAGE  
  
19Z UPDATE:  
THE NON-NCEP GUIDANCE, AS WELL AS THE 12Z GEFS MEAN ALL TRENDED  
TOWARDS A LESS AMPLIFIED LONGWAVE TROUGH ACROSS THE EAST BY  
SUNDAY. THIS APPEARS TO BE IN RESPONSE TO MORE SPLITTING OF  
SHORTWAVE ENERGY LEADING TO LESS INTERACTION AND AN OVERALL WEAKER  
EVOLUTION. THERE HAS BEEN LITTLE RUN-TO-RUN CONTINUITY NOW OF THE  
PLACEMENT AND AMPLITUDE OF THE IMPORTANT SHORTWAVE/CLOSED LOW D3,  
SO AM HESITANT TO SUGGEST A MAJOR CHANGE IN THE PREFERENCES UNTIL  
MORE CONSISTENCY CAN ARISE. HOWEVER, THERE IS POTENTIAL FOR AN  
OVERALL LESS AMPLIFIED SOLUTION, WHICH, SINCE THE ENTIRETY OF THE  
NON-NCEP CAMP MOVED IN THAT DIRECTION, STILL SUPPORTS THE PREVIOUS  
BLEND.  
  
PREVIOUS DISCUSSION:  
THREE DISTINCT SHORTWAVES WILL DIG INTO THE EAST FROM CANADA, EACH  
ONE REINFORCING THE TROUGH WHICH IS LIKELY TO BECOME ANOMALOUSLY  
DEEP BY MONDAY. THROUGH THE FIRST 60 HOURS, THE SPREAD IN  
INTENSITY AND POSITION OF THESE SHORTWAVES IS MINIMAL, SO A  
GENERAL BLEND SEEMS REASONABLE. HOWEVER, LATE D2 INTO D3, SATURDAY  
INTO SUNDAY, THE MOST ROBUST SHORTWAVE BEGINS TO SLIDE SOUTHEAST  
AND WILL EVENTUALLY CLOSE OFF ATOP THE OHIO VALLEY. THE NAM IS A  
CLEAR OUTLIER DURING THIS EVOLUTION AS IT SHARPENS THE TROUGH WELL  
WEST OF THE GLOBAL CONSENSUS LEADING TO A CLOSED LOW TOO FAR WEST,  
AND ENHANCING QPF INTO THE APPALACHIANS. WHILE THERE IS SOME  
EAST-WEST SPREAD IN THE POSITION OF THE TROUGH AXIS AND CLOSED LOW  
BY D3, NOTABLY THE ENSEMBLE MEANS BEING A BIT EAST OF THE  
DETERMINISTIC SOLUTIONS, THE SPREAD FOR D3 SEEMS WITHIN TOLERANCE  
AND THE REMAINING GUIDANCE CAN BE INCLUDED IN THE PREFERENCE.  
  
...LONGWAVE TROUGH OFF THE WEST COAST AND SHORTWAVE LIFTING  
ONSHORE CALIFORNIA BY THE WEEKEND...   
..CLOSED LOW DEVELOPING ACROSS THE NORTHERN ROCKIES SUNDAY  
  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-NAM THROUGH 48 HOURS, ECMWF/ECENS/GEFS/UKMET  
THEREAFTER  
CONFIDENCE: SLIGHTLY BELOW AVERAGE  
  
CLOSED LOW POSITIONED OFF BRITISH COLUMBIA WILL SPIN NEARLY IN  
PLACE THROUGH FRIDAY, WHILE A SHORTWAVE ROUNDING THE BASE OF THE  
LONGWAVE TROUGH EXTENDING SOUTH FROM THE BC CLOSED LOW WILL LIFT  
ONSHORE CA LATE FRIDAY. THE NAM IS BY FAR A SLOW OUTLIER WITH THE  
EASTWARD EJECTION OF THIS SHORTWAVE, LAGGING THE CONSENSUS AND ALL  
OTHER AVAILABLE GUIDANCE TOO MUCH TO BE INCLUDED IN THE BLEND.  
THEREAFTER, THE EVOLUTION BECOMES MESSY. THE SHORTWAVE LIFTING  
FROM CA INTO THE GREAT BASIN WILL ENCOUNTER PROGRESSIVELY GREATER  
SHEAR AS THE BC LOW BEGINS TO DIG SOUTHEASTWARD TOWARDS WA STATE.  
THE NAM, WHICH WAS ALREADY SLOW, IS MUCH TOO STRONG WITH THIS  
FEATURE SO CONTINUES TO BE REMOVED FROM THE BLEND. BY LATE D2 INTO  
D3, THE GFS PRODUCES A PRONOUNCED JET STREAK ROTATING AROUND THE  
BC LOW. WHILE A JET STREAK DEVELOPMENT SEEMS LIKELY, THE STRENGTH  
OF THIS FEATURE IS MUCH STRONGER ON THE GFS THAN ANY OTHER  
GUIDANCE, WHICH ALLOWS FOR BETTER UPPER VENTILATION AND A STRONGER  
SURFACE LOW, MID-LEVEL IMPULSE, AND HEAVIER QPF. THE GFS THEN  
CLOSES OFF A LOW WELL NORTH OF THE CONUS BORDER, VASTLY DIFFERENT  
FROM THE NON-NCEP CAMP, AND MUCH FURTHER NORTH THAN ITS OWN  
ENSEMBLE MEAN. WHILE THERE ARE SOME DISCREPANCIES INTO THE  
AMPLITUDE OF THE TROUGH IN THE NW INTO D3, THE REMNANTS OF THE  
OPENING BC LOW, THE NON-NCEP GUIDANCE IS WELL CLUSTERED OVERALL TO  
THE ECENS/GEFS MEANS. THE CMC MAY BE A BIT STRONG WITH THE  
REMAINING ENERGY, SO AFTER D2 THE PREFERENCE CHANGES TO THE 06Z  
GEFS WITH THE 00Z ECENS/ECMWF/UKMET.  
  
WEISS  
  
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
  
  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.


The Nexlab HPC Page

Main Text Page