527  
FXUS10 KWNH 010634  
PMDHMD  
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
233 AM EDT WED NOV 01 2017  
 
VALID NOV 01/0000 UTC THRU NOV 04/1200 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z MODEL EVALUATION WITH PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
SHORTWAVE ENTERING NORTHERN TIER LATE WED AND THROUGH GREAT LAKES  
THURS/FRI AND SOUTHEAST CANADA FRI/SAT WITH ASSOCIATED SURFACE  
LOW... SECONDARY SURFACE WAVE ALONG LEE OF ROCKIES INTO SOUTHERN  
PLAINS  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND (WEIGHT TOWARD ECMWF/NAM/UKMET)  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
GOES-WV MOSAIC DEPICTS VERY LINEAR BUT STRONG JET ACROSS NW CANADA  
WITH LIKEWISE FAIRLY FLAT SHORTWAVE STARTING TO EMERGE IN THE LEE  
OF THE CANADIAN ROCKIES ALREADY SPURRING A 996MB SFC LOW. UNDER  
INCREASING DIFFLUENT FLOW...THE FLOW SPLITS WITH THE SHORTWAVE  
ANGLING ACROSS THE NORTHERN TIER WITH ONE SURFACE WAVE WHILE THE  
NORTHWESTERLY FLOW OVER THE ROCKIES CONTINUES TO SUPPORT ANOTHER  
LEE CYCLONE THAT WILL EVENTUALLY SETTLE AT THE TRAILING END OF THE  
FRONT ACROSS THE RED RIVER. THE NORTHERN AMPLIFICATION HAS BEEN  
GETTING BETTER AGREED UPON THOUGH THE 12Z UKMET CONTINUES TO FAVOR  
AN EASTERN STRONGER INFLECTION AT THE SURFACE THROUGH THE GREAT  
LAKES...OPPOSED BY THE 12Z CMC AND 00Z NAM WHICH HOLD BACK THE  
ENERGY IN FAVOR OF A DEEPER MAIN WAVE. THE 00Z GFS SHIFTED TOWARD  
A FASTER LEAD SHORTWAVE WITHIN THE PACKET EVEN OUTPACING THE UKMET  
A BIT. THIS LEAVES THE 12Z ECMWF AS THE MIDDLE SPLITTING THE  
DIFFERENCES WITH THE GFS/UKMET AND NAM/CMC THOUGH SHOWING  
SIMILARITIES TO BOTH. THE DIFFERENCE BETWEEN THE CMC/NAM BECOMES  
LARGEST THROUGH THE NORTHERN GREAT LAKES...WHEN THE NAM/ECMWF PAIR  
BETTER. OVERALL A NON-CMC BLEND SEEMS APPROPRIATE THROUGH WILL  
HEAVILY WEIGHT TOWARD THE EVOLUTION/TIMING OF THE ECMWF WITHIN THE  
BLEND. CONFIDENCE REMAINS AVERAGE GIVEN THE REMAINING VARIABILITY  
WITHIN FAIRLY FLAT FLOW WHERE SMALL WAVE AMPLIFICATIONS/TIMING  
DIFFERENCES CAN LEAD TO MODEST MASS DIFFERENCES.  
 
07Z UPDATE: THE 00Z CMC REMAINS A BIT DEEPER AND SLOWER BUT HAS  
MATCHED TIMING ESPECIALLY THROUGH THE MID TO UPPER ATMOSPHERE.  
THE 00Z ECMWF TRENDED A BIT FASTER AND WHILE NOT MATCHING THE GFS  
IT LOOKS LIKE A GOOD BLEND OF THE NAM/UKMET. OVERALL THE 3-7H  
LAYER LOOKS QUITE GOOD IN MASS FIELDS...BUT THE SURFACE PATTERN IN  
PARTICULAR CONTINUES TO BE A BIT MORE MESSY THOUGH THE TIMING OF  
THE FRONT LOOKS GOOD THERE IS A MODEST SPREAD IN THE  
PLACEMENT/STRENGTH OF THE OCCLUDED LOW AND TRIPLE POINT/NEW CENTER  
TO HAVE SOME REDUCTION IN CONFIDENCE BUT A GENERAL MODEL BLEND  
SHOULD HELP CENTER THE SFC FEATURES TOWARD THE ENSEMBLE MEANS.  
CONFIDENCE REMAINS SLIGHTLY ABOVE AVERAGE IN THIS BLEND.  
 
AMPLIFYING UPPER LOW NEAR VANCOUVER ISLAND BY THURSDAY AND SURFACE  
LOW JUST OFF THE PACIFIC NORTHWEST  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z GFS/UKMET BLEND (WITH *12Z* ECMWF/ECENS MEAN)  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
A POTENT DISTURBANCE IN AMPLIFIED NORTHERLY FLOW OVER BRITISH  
COLUMBIA EVOLVES INTO A CLOSED MID-LEVEL LOW BY FRIDAY NEAR THE  
PACIFIC NORTHWEST COAST. SUBTLE DOWNSTREAM RIDGING IN GENERALLY  
SWLY FLOW...ALLOWS THE SHORTWAVE TO EXPLOIT THE WEAKNESS OVER THE  
PACIFIC AND WITH THE HELP OF UPSTREAM STRONG ANTICYCLONIC CURVED  
JET STREAK BEGINS TO STRETCH THE TROF SOUTHWESTWARD. SMALL TIMING  
DIFFERENCES REMAIN INITIALLY BEFORE THE STRETCHING OCCURS.  
UNCHARACTERISTICALLY THE 12Z ECMWF REMAINS SLIGHTLY FORWARD (MORE  
NEUTRAL ORIENTATION) EVEN COMPARED TO THE 12Z ECENS MEAN... WHILE  
THE 12Z CMC IS IN A TYPICAL VERY SLOW WESTWARD POSITION COMPARED  
TO THE ENSEMBLE MEANS. THE 00Z NAM HAS SHIFTED A BIT FASTER THAN  
THE PRIOR RUNS BUT STILL LAGS THE AVERAGE POSITION OF THE  
ELONGATED TROF OR SHOWING GREATER POSITIVE TILT ORIENTATION  
COMPARED TO THE 12Z UKMET/ECMWF OR THE 00Z GFS. EFFECTS TO THE  
SENSIBLE WEATHER DO NOT SEEM VERY LARGE BUT FROM A MASS STANDPOINT  
WILL FAVOR A 00Z GFS AND 12Z ECMWF/UKMET BLEND (WEIGHTING THE  
ECMWF A BIT LESS HEDGING TOWARD THE SLOWER ECENS MEAN).  
 
07Z UPDATE: SMALL SOUTHWARD ADJUSTMENTS WERE NOTED BY THE  
ECMWF/UKMET 00Z RUNS...WITH THE SOUTHERN PORTION OF THE ECMWF TROF  
CONTINUING TO PRESS A BIT TOO FAST INTO N CA. THIS KEEPS THE  
UKMET IN LINE WITH THE INITIAL PREFERENCE BUT THE ECMWF MAY BE  
GETTING A BIT TOO FORWARD EVEN FROM ITS OWN MEAN ESPECIALLY IN  
SOUTH TO PERHAPS SCALE BACK THE PREFERENCE A BIT. THE 00Z CMC  
LIKEWISE MADE A SOUTHWARD AND SLIGHTLY EASTWARD SHIFT TIGHTENING  
WITH THE 00Z NAM SOLUTION BUT STILL LAGGING THE INITIAL PREFERENCE  
AND ENSEMBLE MEANS. AS SUCH WILL FAVOR A 00Z GFS/UKMET BLEND AND  
BLEND IN A BIT OF THE 12Z ECENS MEAN OR 12Z ECMWF AS A PROXY  
INSTEAD OF THE 00Z RUN. CONFIDENCE REMAINS SLIGHTLY ABOVE  
AVERAGE.  
 
SOUTHERN STREAM SHORTWAVE CROSSING SOUTHWEST US INTO SOUTHERN  
PLAINS BY FRI SPURRING SURFACE LOW OUT OF RED RIVER VALLEY TOWARD  
MO ON SAT  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z GFS/12Z ECMWF BLEND  
CONFIDENCE: AVERAGE  
 
HIGHLY ELONGATED SHORTWAVE ACROSS S CA AND GENERAL WEAKNESS  
BETWEEN THE POLAR AND SUBTROPICAL STREAMS WILL CONTINUE TO SUPPORT  
WEAK SHORTWAVES AND MORE RANDOM WEAK VORTEX ROLL UP SOLUTIONS  
THROUGH THE SOUTHERN PLAINS INTO THE SOUTHEAST. THE MAIN CORE OF  
THE SHORTWAVE OVER S CA WILL ENHANCE/RE-CONSOLIDATE OVER THE  
SOUTHWEST INTO SOUTHERN PLAINS...HELPING TO ENHANCE THE DYING  
SURFACE WAVE/STALLED FRONT ACROSS THE RED RIVER VALLEY TO SHIFT  
NORTHEAST INTO THE LOW MO/CENTRAL MS VALLEY SAT...EVEN THOUGH THE  
SHORTWAVE SLIDES INTO THE LOWER MS AND CONTINUED SWLY FLOW  
DOMINATES FROM THE EASTERN PACIFIC THROUGH THE OHIO VALLEY BY SAT.  
WHILE THERE ARE SUBTLE DIFFERENCES IN AMPLIFICATION OF THE  
WAVE...THE 00Z NAM/UKMET A BIT WEAKER...THE CMC MORE  
AMPLIFIED/SLOWER... UKMET A BIT FASTER ACROSS THE GULF COAST BY  
FRIDAY. THE OVERALL PATTERN SUGGEST A 00Z GFS/12Z ECMWF BLEND  
GIVEN MOST CENTRAL SOLUTIONS...MORE RELIABLE VERIFICATION AND GOOD  
REPRESENTATION TO THE ENSEMBLE SOLUTIONS...THOUGH CONFIDENCE  
REMAINS AT BEST AVERAGE IN THIS BLEND.  
 
07Z UPDATE: THE UKMET SHEARS THE SHORTWAVE THROUGH THE CENTRAL  
GULF A BIT TOO MUCH (FAVORING THE SOUTHERN SOLUTION TOO MUCH. THE  
CMC APPEARS TO BE ABOUT CENTRAL TO THE 00Z ECMWF AND GFS TO  
INCLUDE IN THE MASS PREFERENCES. AS SUCH A 00Z GFS/ECMWF/CMC BLEND  
WILL BE PREFERRED AT AVERAGE CONFIDENCE.  
 
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