785  
FXUS10 KWNH 051835  
PMDHMD  
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
235 PM EDT FRI JUN 05 2020  
 
VALID JUN 05/1200 UTC THRU JUN 09/0000 UTC  
 
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION INCLUDING PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
---AMPLIFYING WAVE SHIFTING EAST ACROSS ONTARIO THROUGH TONIGHT  
AND NORTHERN NEW ENGLAND SATURDAY NIGHT...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL BLEND BECOMING NON-CMC BLEND AFTER 48HRS  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
19Z UPDATE: THE CMC IS A BIT SLOWER, BROADER AND FURTHER WEST  
ENOUGH TO SUGGEST ITS REMOVAL AFTER 48HRS...7.12Z. CONFIDENCE  
REMAINS SLIGHTLY ABOVE AVERAGE  
 
---PRIOR DISCUSSION---  
WV SUITE DENOTES A STRONG JET STREAK OVER THE NORTHERN PLAINS INTO  
THE WESTERN GREAT LAKES, WITH AN W-E ELONGATED SHORTWAVE ROTOR TO  
ITS NORTH. THIS WAVE ALONG WITH THE JET SUPPORT BUCKLES AND  
AMPLIFIES THROUGH THE GREAT LAKES, ONTARIO LATER TODAY LEADING TO  
A SOLID POSITIVELY TILTED TROF TO PROGRESS THROUGH THE NORTHEAST  
LATE SAT AND DIGGING THROUGH THE MID-ATLANTIC BY EARLY SUNDAY.  
MODELS CONTINUE TO COME INTO TIGHTER OVERALL AGREEMENT AND WHILE  
THERE REMAINS A SMALL AMOUNT OF SPREAD/DIFFERENCE (GFS/CMC) IN THE  
MASS FIELDS, A GENERAL MODEL BLEND CAN BE PREFERRED AT SLIGHTLY  
ABOVE AVERAGE AGREEMENT.  
 
...INITIAL CUT-OFF LOW OFFSHORE SOUTHERN CALIFORNIA, MOVING  
ONSHORE TONIGHT, INTO GREAT BASIN SATURDAY, THE WYOMING ROCKIES  
SATURDAY NIGHT, AND THE NORTHERN PLAINS SUNDAY.  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
19Z UPDATE: THERE WAS LITTLE SIGNIFICANT CHANGE IN THE 12Z  
ECMWF/GEFS/CMC OR UKMET TO DEVIATE FROM INITIAL PREFERENCE,  
PERHAPS PROVIDING INCREASED CONFIDENCE OVERALL. SO WILL CONTINUE  
WITH A GENERAL MODEL BLEND AT SLIGHTLY ABOVE AVERAGE CONFIDENCE.  
 
---PRIOR DISCUSSION---  
GOES-WEST WV SUITE DENOTES A DRY CLOSED LOW WITH EXCELLENT  
JET/DOWNSTREAM DIFFLUENCE ACROSS THE DESERT SOUTHWEST. CONVECTIVE  
DEVELOPMENT ACROSS THE HIGH TERRAIN LATER TONIGHT INTO TOMORROW  
MORNING LEADS TO SOME MILD DISRUPTION OF THE WAVE AS A WHOLE  
(EXPANDING IT DOWNSTREAM). THE 12Z NAM IS MOST DISRUPTED AND  
STARTS TO ACCELERATE INTO THE NORTHERN HIGH PLAINS MUCH FASTER  
THAN OTHER GUIDANCE; ONCE THERE, THE APPROACHING CLOSED LOW (SEE  
SECTION BELOW) INTERACTS AND FURTHER AMPLIFIES THE WAVE MAKING THE  
NAM SOLUTION A BIT LESS TOLERABLE IN THE OVERALL SUITE,  
PARTICULARLY WITH UPPER LEVEL SUPPORT/FEATURES. THE 12Z GFS IS  
ALSO A BIT FAST AND MORE AMPLIFIED, PARTICULARLY AS THE UPSTREAM  
CLOSED LOW APPROACHES. THE 00Z CMC IS THE OTHER SIDE OF THE  
SPECTRUM, SLOWER, ACCOMPANIED BY THE ECMWF. STILL, THE  
SPREAD/TIMING IS SMALL ENOUGH TO CONTINUE TO FAVOR A MORE  
CENTRALIZED SOLUTION (CLOSE TO THE PLACEMENT/TIMING OF THE  
ENSEMBLE SUITE)...AND SO A GENERAL MODEL BLEND IS PREFERRED AT  
SLIGHTLY ABOVE AVERAGE CONFIDENCE.  
 
...CLOSED LOW OFF BRITISH COLUMBIA DRIFTING SOUTH THROUGH FRIDAY  
NIGHT AND THEN OFF WASHINGTON/OREGON SATURDAY, MOVING EAST AND  
ONSHORE SATURDAY NIGHT-SUNDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
19Z UPDATE: FURTHER SEPARATION OCCURRING IN TIMING WITH THE  
UKMET/ECMWF/CMC TRENDING CLOSER TOWARD CONSENSUS WHILE THE GFS/NAM  
ARE MORE AGREEABLE, WITH THE BULK OF MODAL DIFFERENCES OCCURRING  
WITH THE INTERACTION/AMPLIFICATION OF THE PRECURSORY WAVE ACROSS  
SOUTHERN CANADA BLEEDING INTO MT. STILL, THE AFFECTS IN THE LOWER  
LEVELS/SURFACE A STILL SMALL ENOUGH TO SUPPORT THE GENERAL MODEL  
BLEND BUT CONFIDENCE IS REDUCED TO SLIGHTLY ABOVE AVERAGE.  
 
---PRIOR DISCUSSION---  
WELL DEFINED SYMMETRIC CLOSED LOW IN THE SOUTHERN GULF OF AK IS  
WELL FORECAST THROUGH THE SHORT-TERM AS IT MAKES LANDFALL INTO THE  
PACIFIC NORTHWEST THROUGH THE WEEKEND. THE UNCERTAINTY ARISES AS  
THE CENTRAL CORE ENHANCED BY THE PACIFIC JET ROUNDS THE BROADENING  
BASE INTO THE SNAKE RIVER VALLEY/GREAT BASIN AND BEGINS TO  
INTERACT WITH THE EXITING SHORTWAVE LIFTING THROUGH THE NORTHERN  
PLAINS. STILL, MOST OF THE UNCERTAINTY COMES WITH DIFFERENCES IN  
TIMING WITHIN THE GUIDANCE SUITE AND THEREFORE THE MAGNITUDE OF  
AMPLIFICATION WITH THE PRECURSORY WAVE MOVING INTO SW CANADA. THE  
GFS IS MOST AGGRESSIVE AND SWINGS THE JET THROUGH WY INTO MT  
STRONGER AND FASTER. IT IS SUPPORTED BY THE 12Z NAM BUT BOTH HAVE  
SHOWN THIS TO BE A BIT TOO FAST. THE ECMWF/CMC ARE EQUALLY  
PROBLEMATIC BUT ON THEIR TYPICAL SLOWER TREND SIDE; WHILE THE  
UKMET IS MOST CENTRAL. ALL IN ALL, A BLEND OF THE SOLUTIONS OR A  
HEDGE TOWARD THE CENTRAL UKMET IS PREFERRED BUT CONFIDENCE  
REMAINS ABOVE AVERAGE IN THIS GENERAL MODEL BLEND PREFERENCE.  
 
   
..CRISTOBAL
 
 
~~~~~~~~~~~~~~~~~~  
PREFERENCE: 03Z NHC ADVISORY  
BEST PROXY: 12Z UKMET/ECMWF BLEND  
CONFIDENCE: REFER TO NHC PRODUCTS  
 
19Z UPDATE: THE ECMWF SHIFTED A BIT FASTER AND STRONGER AND WHILE  
INITIALLY A BIT SLOWER THAN THE OFFICIAL FORECAST, IT MATCHES VERY  
WELL NEARING THE LA COAST AND THEREAFTER TO SUGGEST A BEST PROXY  
IS A COMBINATION OF THE 12Z UKMET/ECMWF BLEND.  
 
---PRIOR DISCUSSION---  
THE OFFICIAL TRACK FOR T.D. CRISTOBAL IS A GOOD OF COMPROMISE OF  
NON-GFS 00Z GLOBAL GUIDANCE WITH BEST TIMING LOOKING MOST LIKE THE  
00Z UKMET. THE 12Z GFS CONTINUES TO BE WELL NORTH AND EAST OF  
THE REMAINING GLOBAL GUIDANCE WITH THE BULK OF GEFS SOLUTIONS  
THOUGH EVEN THEY ARE SLOWER THAN THE OPERATIONAL. BY THE END OF  
DAY 2, THE 12Z NAM IS SHIFTING A BIT WEST OF THE REMAINING CLUSTER  
AND THE 00Z CMC IS REMARKABLY WEAK AND DIFFUSE (PARTICULARLY IN  
THE MID TO UPPER LEVELS RELATIVE TO THE REMAINING GUIDANCE AND  
EVEN THE OUTLYING GFS/NAM AS IT LIFTS NORTH.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
GALLINA  
 

 
 
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