298  
FXUS10 KWNH 111841  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
141 PM EST SAT JAN 11 2020  
 
VALID JAN 11/1200 UTC THRU JAN 15/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION WITH FINAL PREFERENCES AND FORECAST CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..OVERALL PATTERN ACROSS THE CONUS
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z GFS/12Z ECMWF BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
   
..19Z UPDATE
 
 
THE 12Z UKMET SPED UP RELATIVE TO ITS PREVIOUS 00Z CYCLE WITH THE  
EXITING EAST COAST SYSTEM ON SUNDAY AND THE WEAK SYSTEM  
APPROACHING THE GREAT LAKES EARLY MONDAY. OUTSIDE OF THIS CHANGE  
IN THE UKMET, ONLY MINOR CHANGES WERE NOTED WITH THE 12Z  
ECMWF/UKMET/CMC RELATIVE TO THEIR PREVIOUS 00Z CYCLES. THERE WAS  
SOME CONVERGENCE WITH THE AMPLITUDE OF THE WESTERN TROUGH FOR  
TUESDAY, BUT TIMING DIFFERENCES INCREASED SLIGHTLY. A 12Z  
GFS/ECMWF BLEND STILL LOOKS REPRESENTATIVE OF THE MIDDLE OF THE  
MODEL SPREAD FOR THE CONUS.  
   
..PREVIOUS DISCUSSION FOLLOWS
 
 
A POWERFUL MID-LEVEL TROUGH OVER THE SOUTHERN PLAINS THIS MORNING  
IS FORECAST TO TRACK NORTHEASTWARD ATOP AN ANOMALOUS RIDGE  
CENTERED JUST OFF OF THE EAST COAST. THE ACCOMPANYING SURFACE  
CYCLONE WILL QUICKLY TRACK FROM THE OHIO VALLEY ACROSS NEW ENGLAND  
WITH GOOD MODEL AGREEMENT. HOWEVER, THE 00Z UKMET WAS SLIGHTLY  
SLOWER TO EXIT THE CYCLONE EASTWARD RELATIVE TO THE REMAINING  
AVAILABLE DETERMINISTIC/ENSEMBLE GUIDANCE.  
 
AFTER THE DEPARTURE OF THE SYSTEM CROSSING THE NORTHEAST EARLY  
SUNDAY, THE UPPER LEVEL PATTERN WILL FEATURE A BROAD TROUGH  
CENTERED OVER THE WESTERN 2/3 OF THE NATION WITH THE  
AFOREMENTIONED RIDGE OVER THE WESTERN ATLANTIC. A SERIES OF  
SHORTWAVES WILL TRACK ACROSS THE WESTERN U.S. INTO THE GREAT  
PLAINS FOLLOWED BY WEAKENING TOWARD THE GREAT LAKES. THE WESTERN  
PORTION OF THE FRONT EXITING THE EAST COAST ON SUNDAY WILL BE LEFT  
DRAPED FROM ENSEMBLE AGREEMENT IS FAIR TO GOOD FOR THE SHORT  
RANGE PERIOD (ENDING TUESDAY EVENING) WITH THE OVERALL PREFERENCE  
TO BE NEAR THE MIDDLE OR 00Z ECMWF MEAN GIVEN CONSISTENCY FROM RUN  
TO RUN AND ITS POSITIONING TOWARD THE MIDDLE OF THE LATEST  
DETERMINISTIC/ENSEMBLE SPREAD.  
 
THE 00Z UKMET WAS NOTED TO BE SLIGHTLY SLOWER THAN IDEAL WITH THE  
FIRST OF THE SHORTWAVES EXPECTED TO REACH THE GREAT LAKES REGION  
LATE SUNDAY NIGHT/EARLY MONDAY MORNING. REGARDING THE SECOND  
SHORTWAVE, MODEL CONSENSUS SHOWS THE 12Z GFS TO BE A LITTLE SLOW  
AS A SURFACE LOW NEARS THE GREAT LAKES ON TUESDAY, WITH THE 12Z  
NAM AND 00Z ECMWF IN BETTER ALIGNMENT WITH THE MODEL CONSENSUS.  
HOWEVER, THE 12Z NAM DEVELOPS TIMING ISSUES WITH A SYSTEM UPSTREAM  
WHICH IMPACTS THE FLOW DOWNSTREAM OVER THE EASTERN HALF OF THE  
NATION. A TRANSITION TOWARD A 12Z GFS/00Z ECMWF BLEND IS  
RECOMMENDED FROM MONDAY NIGHT INTO TUESDAY.  
 
THE LAST SHORTWAVE TO MENTION FOR THE SHORT RANGE WILL REACH THE  
WEST COAST TUESDAY MORNING. OUTSIDE OF THE MUCH FLATTER 12Z NAM,  
AMPLITUDE DIFFERENCES SHOW THE 12Z GFS/00Z UKMET FLATTER COMPARED  
TO THE DEEPER 00Z ECMWF/CMC. A BLEND TOWARD THE MIDDLE (12Z  
GFS/00Z ECMWF) IS RECOMMENDED HERE AND WILL WORK FOR MOST OF THE  
REMAINDER OF THE CONUS THROUGH TUESDAY EVENING.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
OTTO  
 

 
 
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