161  
FXUS10 KWNH 221850  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
149 PM EST WED JAN 22 2020  
 
VALID JAN 22/1200 UTC THRU JAN 26/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION WITH FINAL PREFERENCES AND FORECAST CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
~~  
   
..CLOSED LOW OFF THE SOUTHEAST COAST
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
CLOSED VERTICALLY STACKED LOW EAST OF FLORIDA WILL MOVE EASTWARD  
AWAY FROM THE COAST THROUGH TONIGHT. SUBTLE VORTICITY LOBES  
ROTATING AROUND THE MAIN CLOSED FEATURE WILL ALLOW SURFACE  
TROUGHINESS TO PERSIST TOWARDS THE FL COAST MUCH OF TODAY, BUT ANY  
SIGNIFICANT SENSIBLE WEATHER IMPACTS WILL REMAIN OFFSHORE. WHILE  
THE NAM WAS MOST AGGRESSIVE WITH LAGGING MID-LEVEL ENERGY, IT  
APPEARS THE LATEST 12Z NAM MASS FIELD IS BETTER CLUSTERED WITH THE  
REST OF THE GUIDANCE RESULTING IN SIMILAR SURFACE TROUGH AXIS  
PLACEMENT. THEREFORE, OPTED FOR A GENERAL MODEL BLEND FOR THIS  
SYSTEM.  
 
...SHORTWAVE MOVING FROM NEW MEXICO TOWARDS THE GULF COAST  
TONIGHT...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
~~~  
PREFERENCE: GEMERAL MODEL BLEND  
CONFIDENCE: AVERAGE  
 
SHORTWAVE AND ACCOMPANYING WEAK SURFACE LOW WILL DIVE SOUTHEAST  
FROM NEW MEXICO THIS MORNING TO THE LOUISIANA GULF COAST TONIGHT,  
BEFORE BECOMING ABSORBED IN THE LARGE MID-LEVEL VORTEX DEVELOPING  
ON THURSDAY. THE OVERALL AMPLITUDE OF BOTH THE MID-LEVEL FEATURES  
AND AT THE SURFACE IS WEAK, AND THERE IS GOOD AGREEMENT IN THE  
EVOLUTION AMONG THE VARIOUS GLOBAL MODELS. THE NAM HAS SLOWED ITS  
OVERALL PROGRESSION OF THIS SHORTWAVE AS COMPARED TO PREVIOUS  
MODEL RUNS. THE ECMWF HAS GOOD SUPPORT FROM ITS ENSEMBLES, AND THE  
GFS HAS ITS OWN ENSEMBLE SUPPORT, WITH SOME MINOR LATITUDINAL  
DIFFERENCES SEPARATING THE TWO CAMPS. THE CMC AND UKMET IS ALSO IN  
THE MIDDLE OF THE EC/GFS/NAM CLUSTERING RESULTING IN A GENERAL  
MODEL BLEND.  
 
   
..TROUGH MOVING ONSHORE THE PACIFIC NORTHWEST FRIDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
~~~  
PREFERENCE: NON-NAM/UKMET  
CONFIDENCE: AVERAGE  
 
A PIECE OF ENERGY SHEDDING FROM A CLOSED LOW NEAR THE GULF OF  
ALASKA WILL EJECT EASTWARD INTO THE PACIFIC NORTHWEST ON FRIDAY,  
ACCOMPANIED BY AN INTENSIFYING, ALTHOUGH STILL MODEST, PACIFIC JET  
STREAK BRINGING HEAVY RAINFALL TO THE NORTHWEST. THE NAM CONTINUES  
TO BE EXCEPTIONALLY FLAT WITH ITS AMPLITUDE OF THIS FEATURE  
COMPARED TO THE GLOBAL CONSENSUS, LIKELY DUE TO A WEAKER  
ANTICYCLONIC JET STREAK AND LAGGING MORE RESIDUAL ENERGY BACK INTO  
THE MAIN TROUGH. THE UKMET SEEMS A BIT TOO AGRESSIVE WITH THE  
MAGNITUDE OF THE SHORTWAVE, EVEN AFTER MOVING ONSHORE. SO WHILE  
THE TIMING LOOKS REASONABLE COMPARED TO THE CLUSTERING, THE  
AMPLITUDE AND STRENGTH OF THE SHORTWAVE WILL RESULT IN TOO HIGH OF  
QPF ACROSS NORTHERN CALIFORNIA. THEREFORE, OPTED FOR A  
NON-NAM/UKMET BLEND FOR THIS SYSTEM.  
 
...BINARY INTERACTION OF CLOSED LOWS THURSDAY-SATURDAY FROM THE  
PLAINS INTO THE OH VALLEY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
~~  
PREFERENCE: 12Z NAM/UKMET/ECMWF, 12Z ECENS  
CONFIDENCE: SLIGHTLY BELOW AVERAGE  
 
MANY DETAILS STILL NEED TO BE IRONED OUT WITH TWO MID-LEVEL  
IMPULSES MOVING THROUGH THE PLAINS TODAY INTO THURSDAY, AND HOW  
THEY WILL INTERACT THROUGH THE REST OF THE WEEK. MULTIPLE FEATURES  
INTERACTING CREATE LOWER THAN USUAL CONFIDENCE, BUT THE LEADING  
SHORTWAVE MOVING THROUGH THE NORTHERN ROCKIES SHOULD EVENTUALLY  
BECOME DOMINANT AND INTENSE, ESPECIALLY LATE ON RIDAY NIGHT FROM  
THE MISSOURI VALLEY AND INTO THE OHIO VALLEY. THIS SHOULD LEAD TO  
STRONG CYCLOGENESIS ALONG A TRIPLE POINT ACROSS THE MID-ATLANTIC  
BY SATURDAY, WITH THIS TRIPLE POINT EXTENDING FROM A PRIMARY  
SURFACE LOW BENEATH THE TRAILING UPPER TROUGH OVER THE UPPER  
MIDWEST. MOISTURE DRAWN NORTHWARD AHEAD OF THIS SYSTEM COULD BE  
SIGNIFICANT. WHEN LOOKING AT THE GUIDANCE, IT APPEARS AS IF THE  
GFS STRUGGLES TO HANDLE A SHORTWAVE DIVING SOUTH THROUGH THE  
DAKOTAS LATE THURSDAY THROUGH FRIDAY. THIS WILL ULTIMATELY IMPACT  
THE EVOLUTION OF THIS SYTEM AND HOW FAR NORTH THE MOISTURE GETS  
PULLED NORTHWARD AND EVENTUALLY THE PROGRESSION OF THE SURFACE LOW  
INTO THE MID-ATLANTIC REGION. IN ADDITION, THE GFS HAS LACKED RUN  
TO RUN CONSISTENCY WHICH CERTIANLY HAS CONTRIBUTED TO LESS  
CONFIDENCE IN THE MODEL. THEREFORE, THE NAM/ECMWF/ECENS/UKMET ARE  
IN GOOD AGREEMENT THROUGH 60 HOURS, WITH THE CMC TOO QUICK WITH  
THE MID-LEVEL SHORTWAVE/TROUGH AXIS.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
PAGANO  
 

 
 
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