290  
FXUS10 KWNH 300656  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
155 AM EST THU JAN 30 2020  
 
VALID JAN 30/0000 UTC THRU FEB 02/1200 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
...PRIMARY MID-LEVEL TROUGH OVER THE FOUR CORNERS NOW, CROSSING  
SOUTH TEXAS THURSDAY AND THE SOUTHEAST FRIDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF 29/12Z ECMWF/UKMET WITH SOME 29/12Z CMC AND  
30/00Z GFS  
CONFIDENCE: AVERAGE  
 
A LEADING SHORTWAVE TROUGH OFF A RIDGE OVER THE INTERIOR PACIFIC  
NORTHWEST EARLY THIS EVENING WILL SWING ACROSS NORTHERN MEXICO  
THROUGH THURSDAY THEN SOUTH TEXAS ON THURSDAY NIGHT. A SECONDARY  
TROUGH DIGS IN BEHIND THURSDAY NIGHT, WEAKENING THE MID-LEVEL  
ENERGY AS IT CROSSES THE SOUTHEAST FRIDAY. THE 30/00Z NAM HAD  
DECENT RUN TO RUN CONSISTENCY, BUT THAT LEFT THE NAM ON THE SLOWER  
SIDE OF THE ENVELOPE OF SOLUTIONS.  
 
...EVOLUTION OF TROUGH OVER EASTERN HALF OF THE U.S. FRIDAY INTO  
SATURDAY  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
~~~~~~  
PREFERENCE: BLEND OF 30/00Z ECMWF/GFS/NAM  
CONFIDENCE: BELOW AVERAGE  
 
COMPLEX INTERACTION OF SEVERAL STREAMS LEADS TO A BELOW AVERAGE  
CONFIDENCE FORECAST FROM THURSDAY NIGHT/FRIDAY MORNING THROUGH  
SATURDAY. AT JET-STREAM LEVEL, THE FLOW PATTERN SEEMS STRAIGHT  
FORWARD ENOUGH WITH THE NOSE OF A 110 TO 130 KT UPPER LEVEL JET  
TOPPING THE WESTERN U.S. RIDGE AND NOSING INTO THE UPPER MIDWEST  
AND WESTERN GREAT LAKES REGION...WITH THE AXIS OF 130 TO 150 KT  
UPPER LEVEL JET ORIENTED FROM SOUTHWEST TO NORTHEAST FROM THE GULF  
OF MEXICO INTO THE MID ATLANTIC REGION AND APPROACHING SOUTHERN  
NEW ENGLAND.  
 
PART OF THE JET ENERGY DROPS SOUTHWARD ACROSS THE MIDDLE OF THE  
COUNTRY, WITH THE 30/00Z NCEP GUIDANCE FORMING A TROUGH WHICH  
DROPS SOUTH INTO THE CENTRAL/SOUTHERN PLAINS IN THE WAKE OF THE  
SYSTEM MENTIONED ABOVE...WHILE THE NON-NCEP GUIDANCE WAS MORE  
INCLINED TO HAVE A MORE UNIFIED FLOW WITH LITTLE MID-LEVEL  
DEVELOPMENT WITHIN THE FLOW. FOCUS IS GREATEST HERE CONSIDERING  
ITS IMPACTS ON THE DEVELOPMENT OF A SURFACE LOW ALONG THE  
SOUTHEAST COAST THAT WOULD CLIP PARTS OF THE MID-ATLANTIC AND  
NORTHEAST U.S ON DAYS 2/3. WITH THE 30/00Z ECMWF MOVING TOWARDS  
THE IDEA OF A SPLIT BETWEEN NORTHERN AND SOUTHERN STREAM...SUSPECT  
THERE WAS A SLOW CONVERGENCE ON A COMMON SOLUTION. HOWEVER, THERE  
WAS STILL DISAGREEMENT ON HOW DEEP/STRONG THE SOUTHERN STREAM WILL  
BE...WITH THE NCEP GUIDANCE SOME 60 METERS TO 80 METERS DEEPER  
THAN THE ECMWF. FOR NOW, THINK STARTING WITH THE NCEP GUIDANCE  
AND TEMPERING THE DEPTH OF THE SYSTEM WITH THE ECMWF SHOULD BE A  
REASONABLE FIRST GUESS. THE UKMET STARTED TO SHOW A SPLIT FLOW  
BUT NOT NEARLY TO THE EXTENT WHILE THE CANADIAN HELD ITS GROUND ON  
A MORE UNIFIED FLOW.  
 
FARTHER TO THE NORTH, THERE REMAINS SOME DISAGREEMENT IN TERMS OF  
HOW QUICKLY THE NORTHERN STREAM WAVE WILL PROPAGATE EASTWARD  
TOWARDS THE NORTHEAST U.S...BUT A BLEND OF THE ECMWF/GFS SHOULD  
PROVIDE A DECENT FIRST GUESS THAT MINIMIZES THE DIFFERENCES.  
 
...LONGWAVE TROUGH APPROACHING THE WEST COAST OF CANADA FRIDAY  
NIGHT/SATURDAY AND DOWNSTREAM ATMOSPHERIC RIVER INTO THE PACIFIC  
NORTHWEST LATE THURSDAY INTO SATURDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 30/00Z ECMWF/UKMET/ECENS/NAM  
CONFIDENCE: AVERAGE  
 
THE PASSAGE OF A SHORTWAVE AND ACCOMPANYING COLD FRONT INTO  
BRITISH COLUMBIA ON THURSDAY WILL BRING INITIALLY ZONAL FLOW INTO  
WESTERN CANADA THAT AMPLIFIES AS RIDGING INCREASES AHEAD OF AN  
UPSTREAM SHORTWAVE FRIDAY. GIVEN REASONABLY GOOD RUN-TO-RUN  
CONSISTENCY IN THE 30/00Z NCEP GUIDANCE, DETERMINISTIC CONSENSUS  
AND ENSEMBLES CONTINUE TO FAVOR A 30/00Z ECMWF/UKMET/NAM FOR THE  
TROUGH POSITION AND THE DOWNSTREAM ATMOSPHERIC RIVER MOVING INTO  
THE PACIFIC NORTHWEST.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
BANN  
 

 
 
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