151
FXUS10 KWNH 170634
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
133 AM EST FRI JAN 17 2020
VALID JAN 17/0000 UTC THRU JAN 20/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..CENTRAL TO EASTERN US SYSTEM
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH 48HRS
00Z GFS/ECMWF BLEND AFTERWARD
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
07Z UPDATE: THE ECMWF CONTINUES WITH CONTINUITY/TIGHT CLUSTERING
TO THE GFS AND WHILE THE UKMET REMAINS A TAD NORTH IN THE MASS
FIELDS/SURFACE LOW, IT DOES CONTINUE TO PROVIDE OVERALL CONFIDENCE
TOWARD THE GFS/ECMWF BLEND WITH SOME INCLUSION (PARTICULARLY IN
CONVECTIVE AREAS FOR QPF). AS SUCH WILL KEEP WITH INITIAL
PREFERENCE AND CONFIDENCE THROUGHOUT. AS FOR THE ARCTIC
SHORTWAVE, THE ECMWF TRENDED BACK TO MATCH THE NAM/GFS WHILE THE
UKMET SLOWED AND IS WEAKER IT STILL OUTPACES THE BEST AGREEMENT
FOR THAT WAVE (EVEN IF DRY).
---PRIOR DISCUSSION---
SUBTROPICAL SHORTWAVE AND OVERRUNNING PRECIP SHIELD EVIDENT ACROSS
THE SOUTHERN PLAINS, WITH A SHARP NORTHERN STREAM TROF PRESSING
EASTWARD ACROSS CENTRAL CA AT THIS TIME. THE GUIDANCE HAS COME
INTO MUCH STRONGER AGREEMENT IN THE COMBINED SYSTEMS' TRACK AND
INTERACTION ACROSS THE UPPER MIDWEST TO MID-MISSISSIPPI VALLEY
SAT. THERE ARE SOME SMALL DIFFERENCES BUT THE AFFECTS ARE FAIRLY
MINIMAL. HOWEVER, BY SUNDAY (AND AFTERWARD) THE BINARY
INTERACTION HAS LEAD TO AN ELONGATED CLOSED LOW EXTENDING FROM THE
UPPER GREAT LAKES THROUGH THE NORTHEAST; HOWEVER, INTERNAL
SHORTWAVES/JET SPEED MAXES ARE NOT SHOWING MUCH CONGRUITY WITH THE
00Z NAM BECOMING VERY STRONG UPSTREAM AND EVENTUALLY CURLING BACK
INTO A STRONG/COMPACT CLOSED LOW THROUGH THE CANADIAN MARITIME.
THE 12Z CMC IS FRACTURING THE SHORTWAVE INTO TWO SMALLER
COMPONENTS, WHILE THE 00Z GFS, 12Z UKMET AND 12Z ECMWF ARE MORE
MIDDLE GROUND SHOWING LESS VORTEX ROLL-UP. HOWEVER, THE UKMET
AXIS OF ROTATION IS A TAD FURTHER NORTH, OFF-SETTING THE BEST MASS
FIELDS AND ASSOCIATED SURFACE LOW TRACK, EVEN MORE SO THAN THE
WEAKER CMC. SO WOULD BE FAVORING A 00Z GFS/12Z ECMWF BLEND WITH
SOME INCLUSION OF THE UKMET, PARTICULARLY IN QPF/MOISTURE FLUX
CONVERGENCE ACROSS THE SOUTHERN MS VALLEY BACK INTO THE WESTERN
GULF, WHERE THE GFS AND EVEN SO THE ECMWF SEEM TO BE VERY DRY.
ALL IN ALL, THESE MODEL DIFFERENCES ARE QUITE NIT-PICKY, AND A
GENERAL MODEL BLEND COULD BE EMPLOYED AT LEAST THROUGH 48HRS, AS
THE GREATEST MASS DIFFERENCES EVOLVE ACROSS THE NORTHEAST
AFTERWARD; BUT IF A TIGHTER, HIGHER FIDELITY BLEND IS DESIRED,
WOULD FAVOR A 00Z GFS/12Z ECMWF BLEND AT SLIGHTLY ABOVE AVERAGE
CONFIDENCE.
OF NOTE: A VERY SHARP ARCTIC SHORTWAVE DESCENDS AT THE NOSE OF A
WEAKENING/CLOSED WARM RIDGE THAT HAS BEEN OVER N AK INTO THE NW
TERRITORIES REACHING THE GREAT LAKES/NORTHERN PLAINS BY MON. THIS
IS RAPIDLY WEAKENING WITH THE EXCEPTION OF THE UKMET, WHICH HAS A
VERY STRONG SHORTWAVE THAT IS SIMILAR TO THE ECMWF/CMC IN
PLACEMENT BY THE END OF THE SHORT RANGE. IT IS VERY DRY, BUT
WOULD HELP TO ENHANCE FORCING ON ANY ONGOING LAKE EFFECT PLUMES
MONDAY. THE GFS/NAM ARE BOTH SLOWER AND ARE REALLY JUST WEAKER
EXTENSIONS OF THE OLD SHORTWAVE/VORTICITY STRIP NORTH OF THE POLAR
JET AXIS. ALL IN ALL, IT IS MORE OF A REASON TO EXCLUDE THE
UKMET PARTICULARLY LATE IN THE FORECAST PERIOD FOR THIS AREA, BUT
IS NOT A MAJOR PLAYER OVERALL.
..PACIFIC NORTHWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH 20.00Z
NON-CMC BLEND AFTERWARD
CONFIDENCE: ABOVE AVERAGE PRIOR TO 20.00Z
BELOW AVERAGE AFTERWARD
07Z UPDATE: THE MODEL SUITE PARTICULARLY MESSY WITH THE SHORTWAVE
BETWEEN LARGER/AHEAD OF DEEPER COMPACT WAVE, THOUGH THE ECMWF
TRENDED A BIT FURTHER NORTH CLOSER TO THE UKMET/GFS/NAM KEEPING
THE CMC AS A SOUTHERN OUTLIER. SO WILL KEEP WITH INITIAL
PREFERENCE.
---PRIOR DISCUSSION---
THE NEXT COMPACT SHORTWAVE/CLOSED LOW CONTINUES TO SHOW VERY
STRONG AGREEMENT THROUGH THE ENSEMBLE/DETERMINISTIC SUITE
APPROACHING HAIDA GWAII MID-DAY SATURDAY DIRECTING THE TAIL END OF
THE TROF/MOISTURE PLUME INTO THE OLYMPIC PENINSULA BEFORE
DIRECTING A STRONGER ATMOSPHERIC RIVER INTO THE VANCOUVER ISLAND
THROUGH MONDAY. IT IS BY MONDAY THAT THE NEXT SHORTWAVE STARTS TO
ADVANCE PAST 140W. THERE IS A VERY LARGE SPREAD IN THE WAVELENGTH
OF THIS TROUGH AND ITS TIMING MAINLY DEPENDENT ON A VERY STRONG
(OR NOT) UPSTREAM KICKER SHORTWAVE. THE GFS/NAM AND UKMET PRESENT
IT AS VERY STRONG/VERY COMPACT AND THEREFORE SHORTEN THE PRECEDING
WAVELENGTH AND KICK IT FASTER COMPARED TO THE ECMWF/CMC. THE CMC
IS MUCH STRONGER AND EXTENDS SOUTHWARD MORE COMPARED TO THE ECMWF.
THE AFFECTS THROUGH DAY 3 SEEMS TO BE QUITE MINIMAL, ESPECIALLY IN
THE QPF, WITH THE EXCEPTION OF THE TYPICAL DAY 3 TIMING ISSUES OF
THE GFS FAST, ECMWF SLOW. ENSEMBLE TRENDS MAY SUGGEST THE
GFS/UKMET ARE ON TO SOMETHING BUT THE ECMWF IS FAIRLY CONSISTENT
AND TENDS TO HAVE BETTER PERFORMANCE WITH THESE PACIFIC SYSTEMS,
SO THE UNCERTAINTY/CONFIDENCE IS QUITE LOW. BUT WOULD FAVOR MORE
ECMWF/UKMET WITH RESPECT TO QPF, BUT PERHAPS MORE GFS/UKMET IN
TERMS OF MASS FIELDS. SO WILL PREFER A NON-CMC BLEND AFTER 20.00Z,
THOUGH MOSTLY IN TIMING (SLOWING THE UKMET/NAM/GFS AND SPEEDING UP
THE ECMWF). FOR MORE DETAILS FOR THE UPSTREAM SHORTWAVE, PLEASE
REFER TO WPC PMDEPD FOR PREFERENCES.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
GALLINA
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