383
FXUS10 KWNH 240713
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
212 AM EST FRI JAN 24 2020
VALID JAN 24/0000 UTC THRU JAN 27/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH FINAL PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...SHORTWAVE TROUGH MOVING FROM THE PACIFIC NORTHWEST TO THE
MISSOURI VALLEY BY SUNDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM OR UKMET BLEND, LIMITED 00Z ECMWF ON DAY 3
CONFIDENCE: AVERAGE
07Z UPDATE: THE PREVIOUS BLEND REMAINS SUFFICIENT, BUT NOTE THAT
THE 00Z ECMWF HAS A MUCH MORE SPLIT AND SHEARED APPEARANCE TO THE
SHORTWAVE AS IT DIGS INTO THE MISSOURI VALLEY ON SUNDAY. THIS IS
DIFFERENT FROM THE CONSENSUS OF A CONSOLIDATED AND STRONGER UPPER
FEATURE. WILL MAKE NO CHANGES FOR THE FIRST 60 HOURS, BUT FEEL IT
IS PRUDENT TO REDUCE THE WEIGHT ON THE ECMWF FOR THE LAST DAY OF
THE PERIOD.
SHORTWAVE LIFTING ONSHORE THE PACIFIC NORTHWEST FRIDAY MORNING
WILL MOVE INTO THE NORTHERN PLAINS SATURDAY AND THEN DIG SOUTHEAST
AROUND A BIG CLOSED LOW OVER NEW ENGLAND BY SUNDAY. THE GUIDANCE
IS NEARLY UNANIMOUS IS INTENSIFYING THIS FEATURE AS IT SHIFTS OUT
OF THE PLAINS, BUT DIFFER CONSIDERABLY WITH TIMING AND STRENGTH.
THE NAM IS SHOWING A GENERAL STRONG BIAS ACROSS THE CONUS WITH ITS
00Z/24 RUN, INCLUDING THIS SHORTWAVE CLOSING OFF PRIOR TO THE
GLOBAL CONSENSUS. IT ALSO SHIFTS THIS FEATURE VERY QUICKLY INTO A
SHORT-WAVELENGTH BUT HIGH AMPLITUDE SHORTWAVE RIDGE WHICH DEVELOPS
UPWIND OF THE CLOSE LOW OVER NEW ENGLAND. THIS SEEMS UNLIKELY DUE
TO THE STRENGTH OF THIS LATTER FEATURE. THE UKMET LOOKS REASONABLE
AND IS WITHIN THE CONSENSUS ENVELOPE THROUGH 48 HOURS, BUT THEN
RACES THE SHORTWAVE OFF TO THE SOUTHEAST SUCH THAT BY D3 IS IT
NEARLY 5 DEGREES OF LONGITUDE EAST OF PREFERRED CONSENSUS, SO IS
NOT USABLE AT THE EXTENDED TIMERANGE.
..NEXT SHORTWAVE TROUGH MOVING ONSHORE THE WEST COAST SUN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/ECMWF/12Z ECENS
CONFIDENCE: SLIGHTLY BELOW AVERAGE
07Z UPDATE: THE ECMWF HAS TRENDED STRONGER WITH THE TROUGH OVER
THE FOUR CORNERS ON D3, BECOMING MUCH MORE IN LINE WITH THE GLOBAL
CONSENSUS AND THE PREFERRED BLEND.
A VORTICITY LOBE SHEDDING EASTWARD AROUND A DEEP TROUGH IN THE
GULF OF ALASKA WILL SHIFT ONSHORE SUNDAY AND THEN DIVE TOWARDS THE
FOUR CORNERS SUNDAY NIGHT WHILE AMPLIFYING. THE DEGREE OF THIS
AMPLIFICATION IS THE BIGGEST QUESTION MARK AS FAR AS THE GUIDANCE,
SINCE THE POSITIONING AND SPEED AT WHICH THE SHORTWAVE ADVECTS
EASTWARD IS WELL SUPPORTED BY THE GLOBAL CONSENSUS. THE INTENSITY
OF THIS SHORTWAVE THEN CREATES DIFFERENCES IN THE PLACEMENT OF THE
ATTENDANT SURFACE LOW, ESPECIALLY JUST BEYOND THIS FORECAST
PERIOD. THE GFS AND ECENS MEAN ARE IN GOOD AGREEMENT, WHILE THE
ECMWF HAS SHOWN LESS RUN-TO-RUN CONTINUITY.
...CLOSED MID LEVEL LOW TRACKING FROM THE CENTRAL PLAINS ACROSS
OHIO VALLEY SAT INTO THE NORTHEAST SUN...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM OR CMC BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THE GLOBAL MODELS HAVE COME INTO MUCH BETTER AGREEMENT BOTH WITH
THE EVOLUTION OF THE LARGE CLOSED LOW, AS WELL AS TIMING AND
POSITION OF VORTICITY IMPULSES ROTATING AROUND IT. THE MID-LEVEL
FEATURE SHOULD BE OVER EASTERN MO FRIDAY MORNING, NW OHIO BY
SATURDAY MORNING, AND THEN LIFTING ACROSS UPSTATE NEW YORK SUNDAY
MORNING. WAVES OF VORTICITY ROTATING AROUND THIS FEATURE WILL
PRODUCE SWATHS OF SNOWFALL AND QPF IN THE OHIO VALLEY AND GREAT
LAKES, BUT MORE SIGNIFICANT QPF WILL BE ASSOCIATED WITH THE
LEADING SHORTWAVE ABOVE A TRIPLE POINT IN THE MID-ATLANTIC WHICH
WILL SPAWN SECONDARY SURFACE LOW CYCLOGENESIS SATURDAY. THE
BIGGEST DIFFERENCES IN THE GUIDANCE INVOLVE THESE MORE SUBTLE
FEATURES, AND NOT THE PRIMARY MID-LEVEL CYCLONE.
THE NAM IS GENERALLY A BIT NW OF THE CONSENSUS, AND ALSO SWINGS A
ROBUST VORTICITY IMPULSE ATOP THE CHICAGO AREA, WHILE THE
REMAINING GUIDANCE FOCUSES THIS ENERGY FURTHER NORTH. FURTHER TO
THE EAST, THE CMC SWINGS THE VORT LOBE RESPONSIBLE FOR SECONDARY
SURFACE LOW DEVELOPMENT FURTHER EAST AND FASTER THAN THE REMAINING
GUIDANCE. FROM A MASS FIELDS PERSPECTIVE, THESE ARE THE ONLY TWO
NOTABLE DIFFERENCES. HOWEVER, THE GFS HAS A QPF MAXIMA THAT IS NOT
REPRESENTATIVE OF THE CONSENSUS, WITH HIGH VALUES ACROSS THE
MID-ATLANTIC THAT ARE OUTSIDE THE ENVELOPE AND SEEM TOO ROBUST
BASED ON THE SPEED OF THE FEATURE. THIS SUGGESTS A
UKMET/EC/ECENS/GEFS SOLUTION IS MOST REASONABLE FOR D2 AND BEYOND.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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