245  
FXUS10 KWNH 200425  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1124 PM EST SUN NOV 19 2017  
 
VALID NOV 20/0000 UTC THRU NOV 23/1200 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z NAM/GFS EVALUATION WITH PRELIMINARY MODEL PREFERENCES  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
GFS/NAM INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT  
RANGE FORECASTS.  
 
STRENGTHENING UPPER TROUGH OVER THE GULF OF MEXICO  
BAROCLINIC LOW IN THE SOUTHEAST GULF WED/THU  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: CLOSEST TO UKMET; CONFIDENCE AVERAGE  
 
DESPITE GOOD AGREEMENT UPSTREAM ACROSS THE PLAINS AND WEST, THERE  
ARE SUBSTANTIAL ISSUES ALOFT IN THIS REGION WHICH LEAD TO A BIT OF  
SPREAD AT THE SURFACE. THE 12Z ECMWF WAS THE SHARPEST (THOUGH  
WEAKEST WITH THE 500 HPA HEIGHT FIELD) ALOFT, WHICH LED TO THE  
MOST SOUTHWESTERLY SURFACE LOW. THE 12Z CANADIAN WAS MOST  
PROGRESSIVE. THE 00Z GFS HAD THE STRONGEST BUNDLE OF ENERGY ALOFT  
THE FARTHEST NORTH. THE AMPLIFYING FLOW PATTERN SUGGESTS LOWER  
MID-LEVEL HEIGHTS THAN THE ECMWF ADVERTISES, A FARTHER SOUTH  
MID-LEVEL BUNDLE OF ENERGY THAN SEEN IN THE 00Z GFS, AND LESS  
PROGRESSION THAN ADVERTISED BY THE CANADIAN. THE GUIDANCE CLOSEST  
TO THE 12Z/18Z ENSEMBLE MEANS ARE THE 00Z NAM AND 12Z UKMET ALOFT,  
BUT THE 00Z NAM HAS A BONUS SURFACE LOW OFFSHORE NORTHEAST FL NOT  
SEEN IN THE OTHER GUIDANCE WHICH DISTORTS ITS FORECAST RAINFALL.  
A SOLUTION CLOSEST TO THE 12Z UKMET IS PREFERRED WITH AVERAGE  
CONFIDENCE.  
 
NORTHEAST WEDNESDAY INTO THURSDAY  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NAM/ECMWF/GFS COMPROMISE; AVE CONFIDENCE  
 
LIKE THE SOUTHEAST THERE ARE SUBSTANTIAL ISSUES ALOFT. THE 12Z  
CANADIAN/UKMET ARE THE MOST AMPLIFIED/SHARPEST WITH THIS ENERGY.  
SINCE THE NORTHERN STREAM UPPER PATTERN IS BROAD, BELIEVE THEY ARE  
TOO STRONG ALOFT AND TOO FAR WEST WITH THEIR SURFACE LOW  
PROGRESSION. WHILE THE 12Z ECMWF AND 00Z GFS SHOW UNUSUAL  
CONVECTIVE FEEDBACK WITH A SURFACE LOW THEY TAKE INTO ATLANTIC  
CANADA, THEIR SOLUTIONS DO NOT APPEAR TO CONTORT THE RAINFALL  
PATTERNS TOO STRONGLY ACROSS THE NORTHEAST. A COMPROMISE OF THE  
00Z NAM, 00Z GFS, AND 12Z ECMWF IS PREFERRED WITH AVERAGE  
CONFIDENCE.  
 
WARM FRONT LIFTING NORTH NEAR THE NORTHWEST TUESDAY  
DEEP LAYER CYCLONE OFFSHORE SOUTHWEST CANADA/THE NORTHWEST  
LOW MOVING INTO THE NORTHERN PLAINS/MIDWEST WED/THU  
SURFACE LOW MOVING BY THE CENTRAL US/CAN BORDER MON & TUE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
THE GUIDANCE SHOWS GOOD AGREEMENT WITH THESE SYSTEMS. A  
COMPROMISE OF THE 00Z NAM, 00Z GFS, 12Z CANADIAN, 12Z UKMET, AND  
12Z ECMWF IS ADVISED WITH ABOVE AVERAGE CONFIDENCE.  
 
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