005  
FXUS10 KWNH 120639  
PMDHMD  
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
238 AM EDT FRI JUN 12 2020  
 
VALID JUN 12/0000 UTC THRU JUN 15/1200 UTC  
 
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..TROUGH AMPLIFYING ACROSS THE EAST
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
07Z UPDATE: THE ECMWF/CMC BOTH TRENDED A BIT STRONGER INITIALLY  
WITH THE WAVE EMERGING FROM THE GREAT LAKES, WHILE THE NAM/GFS  
CONTINUE TO BE THE STRONGER/SYMMETRIC, THE UKMET/CMC BOTH ARE LESS  
CONCENTRATED BUT STILL GENERALLY LOCATED IN THE SAME AREA. THIS  
LEADS TO BETTER QPF CLUSTERING BUT STILL GIVEN THE MESOSCALE  
NATURE IT REMAINS HARD TO LOCK DOWN ESPECIALLY BY DAY 3...BUT IT  
IS ENOUGH TO INCREASE CONFIDENCE TO SLIGHTLY ABOVE AVERAGE  
 
---PRIOR DISCUSSION---  
A THE START OF THE FORECAST PERIOD, A FAIRLY DRY AVERAGE LONG-WAVE  
TROF SITS ACROSS ONTARIO/QUEBEC WITH THE MOISTURE STREAM/FRONTAL  
ZONE DISPLACED ALONG THE COASTAL CAROLINAS. AS THE TROF MATURES  
AND THE CORE MOVES OFF TOWARD THE LABRADOR SEA, THE POSITIVE TILT  
BASE WILL SWING THROUGH THE NORTHEAST UNDER LITTLE FANFARE/MODEL  
DIFFERENCE. UPSTREAM JET ENERGY/SHORTWAVE WILL DIG THROUGH THE  
GREAT LAKES ON SAT INTO THE UPPER OHIO VALLEY/CENTRAL  
APPALACHIANS, EVENTUALLY BUILDING TO THE GREATER MODEL  
UNCERTAINTY; ALIGNED WITH TYPICAL MODEL BIASES. THE 00Z GFS/NAM  
AND LESSER SO, 12Z UKMET ARE FASTER TOWARD EVOLUTION AND A MORE  
COMPACT/SYMMETRIC CLOSED LOW BY LATE SUNDAY, WHILE THE SLOWER TO  
EVOLVE ECMWF/CMC ARE FLATTER AND PROGRESS SOUTHEAST OF THE HIGHER  
TERRAIN TOWARD THE LINGERING FRONTAL ZONE/MOISTURE AXIS THROUGH  
THE PIEDMONT REGION OF THE CAROLINAS/VIRGINIA. THE LATTER, BEING  
WEAKER BUT CLOSER TO THE MOISTURE, PRODUCE CONVECTION A BUT EAST  
RELATIVE TO THE STRONGER BUT MORE DISTANT DRAWING OF THE GFS/NAM.  
A COMPROMISE BETWEEN THE CAMPS IS PREFERRED AS BOTH SEEM  
ESTABLISHED IN THEIR INHERENT BIASES. CONFIDENCE IS AVERAGE GIVEN  
NO ONE SOLUTION PROVIDES THE IDEAL PLACEMENT OF THE  
FORCING/INSTABILITY AND MOISTURE ELEMENTS AND A BLEND OF ALL THE  
MODELS WILL SMEAR THE SENSIBLE WEATHER ELEMENTS.  
 
...LONGWAVE TROUGH OFF THE WEST COAST AND SHORTWAVE LIFTING  
ONSHORE CALIFORNIA BY THE WEEKEND...   
..CLOSED LOW DEVELOPING ACROSS THE NORTHERN ROCKIES SUNDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z NAM/ECWMF/UKMET BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
07Z UPDATE: THE ECWMF/UKMET CONTINUE TO PROGRESS SIMILARLY TO  
PRIOR RUNS AND MATCH THE NAM GENERALLY. THE 00Z CMC TRENDED  
SLOWER WITH THE LEAD WAVE, AND THEREFORE DEPICTS A TIGHTER BINARY  
INTERACTION WITH THE INNER CORE OF THE CLOSED LOW AS IT CUTS  
ACROSS THE NORTHERN ROCKIES INTO SW CANADA. THIS LEADS THE  
AMPLIFICATION TO BE GREATER AND DISPLACE THE BINARY NORTH AND WEST  
RELATIVE TO THE REST OF THE SUITE (AS THE GFS INNER CORE TRENDS  
BETTER TOO. AS SUCH A 00Z NAM/ECMWF AND UKMET BLEND WILL BE  
PREFERRED THOUGH SOME INCORPORATION OF THE CMC WITH THE LEAD WAVE  
IS TOLERABLE, MUCH LIKE SOME INCLUSION OF THE GFS IS OK WITH THE  
INNER CORE WAVE BY DAY 3 IN THE NORTHERN ROCKIES. CONFIDENCE  
REMAINS SLIGHTLY ABOVE AVERAGE.  
 
---PRIOR DISCUSSION---  
GOES-W WV SUITE DEPICTS A CLOSED LOW TO THE NW OF VANCOUVER ISLAND  
PRESSING EAST WITH A SHORTWAVE FEATURE LENGTHENING THE LONG-WAVE  
TROF SOUTHWARD AS IT APPROACHES THE SW/OR/N CA COAST. THE  
SHORTWAVE WILL MOVE FULL-BODILY INTO N CA TOMORROW, WITH THE  
CLOSED LOW DRIFTING EAST. THE MODELS ARE IN GOOD AGREEMENT IN THE  
EVOLUTION AND TIMING OF THE CLOSED LOW, BUT THE 00Z GFS CONTINUES  
TO SNAP THE BASE SHORTWAVE NORTHWARD THROUGH THE US ROCKIES INTO  
THE S CANADIAN ROCKIES MUCH TO FAST. THIS LEADS THE DEVELOPING  
SURFACE WAVE TO BE TUCKED TIGHT TO THE TERRAIN AND WELL WEST OF  
THE BEST OVERALL ENSEMBLE CLUSTER, INCLUDING THE BULK OF THE GEFS  
MEMBERS. THE FASTER EVOLUTION ALSO ALLOWS FOR THE WAVE TO BE  
FAVORABLY LOCATED IN THE UPPER LEVEL JET PATTERN, TO FURTHER  
DEEPEN/STRENGTH RELATIVE TO THE OTHER GUIDANCE.  
 
EVENTUALLY, THE INNER CORE OF THE UPPER-LOW WILL SWING THROUGH THE  
PACIFIC NORTHWEST UNDER THE PRECEDING SHORTWAVE, EVEN THOUGH THE  
GFS IS NOT SOLID WITH THE PRECEDING WAVE, THE CORE IS STILL OK AS  
IT SWINGS NEGATIVE TILT THROUGH THE NORTHERN HIGH PLAINS EARLY  
MONDAY, PROVIDING CONFIDENCE IN THE OVERALL PROGRESSION. AS SUCH  
A NON-GFS BLEND IS PREFERRED AT SLIGHTLY ABOVE AVERAGE CONFIDENCE.  
 
...APPROACHING CLOSED LOW TO THE PACIFIC NORTHWEST BY EARLY  
MONDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
~~~  
PREFERENCE: 00Z NAM/ECMWF/CMC BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
07Z UPDATE: THE 00Z ECMWF TRENDED A BIT WEST/FASTER TOWARD  
AMPLIFICATION OF THE WAVE, BUT STILL RELATIVELY CLOSE TO THE 00Z  
NAM. THE CMC REDUCED THE MOISTURE PLUME/FLUX INTO THE WEST COAST;  
AND WHILE STILL A BIT EAST OF THE NAM IN THE MASS FIELDS, APPEARS  
A BIT MORE TOLERABLE OVERALL IN THE SUITE TO SUPPORT A 00Z  
NAM/CMC/ECMWF BLEND AT SLIGHTLY ABOVE AVERAGE GIVEN THE UKMET IS  
TRENDING EASTWARD TOO.  
 
---PRIOR DISCUSSION---  
ON THE HEELS OF THE BINARY INTERACTION ACROSS THE PACIFIC  
NORTHWEST/NORTHERN ROCKIES IN THE LATE WEEKEND, ANOTHER SHORTWAVE  
WILL PROGRESS ALONG THE ALEUTIAN CHAIN INTO THE GULF OF AK BY  
SUNDAY. THE 00Z GFS AND 12Z UKMET ARE IN TYPICAL FASTER POSITIONS  
WITHIN THE GUIDANCE SUITE, WHICH EVENTUALLY LEADS TO EARLIER AND  
THEREFORE FURTHER WEST POSITIONING OF THE WAVE AS IT BECOMES A  
CLOSED LOW LATE SUNDAY INTO MONDAY. THE NAM/ECWMF AND CMC ALL  
PRESS EASTWARD AND SLOWER TO OCCLUDE, LEADING TO THE MODEL SPREAD.  
OVERALL, IT IS NOT LARGE (WITH EXCEPTION TO THE PLACEMENT OF THE  
SURFACE LOW), BUT THE ONSHORE FLOW/MOISTURE FLUX IS FAIRLY  
AGREEABLE WITH THE EXCEPTION OF THE CMC WHICH IS  
UNCHARACTERISTICALLY WET ACROSS THE WEST COAST BY THE END OF THE  
SHORT-TERM FORECAST PERIOD (84HRS). THINK THE TIMING ISSUES FAVOR  
THE THE SLOWER EVOLUTION, SO WILL FAVOR A 12Z ECMWF/00Z NAM BLEND  
THOUGH SOME INCORPORATION OF THE GFS/UKMET SEEMS PLAUSIBLE TO  
ACCOUNT FOR SOME OF THE REMAINING UNCERTAINTY, BUT GENERALLY  
AVOIDED THE CMC IN QPF. CONFIDENCE IS AVERAGE IN THIS BLEND  
 
GALLINA  
 
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