731
FXUS10 KWNH 180437
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1136 PM EST FRI JAN 17 2020
VALID JAN 18/0000 UTC THRU JAN 21/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..PROGRESSIVE CENTRAL TO EASTERN U.S. STORM SYSTEM
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
GOES-WV SUITE DEPICTS PIVOT HUB/CLOSED LOW OVER W MN AT THIS TIME
WITH SHARPENING PACIFIC STREAM SHORTWAVE PROGRESSING THROUGH THE
LOWER MO VALLEY INTO THE CENTRAL MS/LOWER OHIO VALLEY CURRENTLY
WITH A STREAM OF DEEPER CONFLUENT/STRONG LOW LEVEL JET STREAKING
ACROSS S MO INTO S IL/IND. THIS PACIFIC SHORTWAVE WILL CONTINUE
TO PRESS EASTWARD QUICKLY AND THROUGH THE NORTHEAST BY EARLY
SUNDAY, ELONGATING THE BINARY INTERACTION WITH THE CURRENT HUB IN
MN ACROSS THE GREAT LAKES...WITH SOLID MODEL AGREEMENT. AS THE
HUB WAVE TRACKS EASTWARD UNDER STRONGER WESTERLY FLOW ALOFT THE
CMC IS THE ONLY LAGGING/COMPACT WAVE WHICH LEADS TO SUFFICIENT
MASS FIELD DIFFERENCES AS WELL AS SURFACE LOW DEVELOPMENT
DIFFERENCE. THE 00Z NAM CONTINUES TO BE STRONGER THAN THAN THE
OTHER GUIDANCE, AND AS THE TWO WAVES TIGHTEN THE BINARY
INTERACTION ACROSS SOUTHEAST CANADA THE NAM IS STRONGEST/MOST
COMPACT, BUT THIS HAS LITTLE IMPACT FOR THE REMAINING CONUS AS THE
TRAILING MID-LEVEL TROF AND FRONTAL ZONE ARE OFFSHORE. SO A
NON-CMC IS PREFERRED AT ABOVE AVERAGE CONFIDENCE.
...AMPLIFYING SHORTWAVE DROPPING SOUTH ACROSS THE MIDWEST INTO
SOUTH SUNDAY-TUESDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-GFS BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
A CUT-OFF WARM RIDGE OVER THE YUKON/N NW TERRITORIES WILL BE
BREAKING DOWN WIT A VERY STRONG CROSS-POLAR 250MB JET DROPS SOUTH
ON SUNDAY. THIS PHASES WITH SHARPER RIDGING ACROSS
ALBERTA/SASKATCHEWAN TO PRESS MID-LEVEL SHORTWAVE ENERGY DUE SOUTH
ACROSS THE UPPER MIDWEST INTO THE LOWER MS VALLEY COMBINING WITH
LINGERING TRAILING TROF ENERGY ACROSS THE GREAT LAKES BY LATE
MONDAY. THIS IS A DRY TROF BUT DOES AFFECT THE MID-LEVEL FLOW AND
JET ORIENTATION FOR UPSTREAM RIDGE/PATTERN EVOLUTION, AS WELL AS
DRAWING COLDER THAN NORMAL AIR SOUTH ACROSS THE OHIO/TENNESSEE
VALLEY. HERE THE 00Z GFS HAS TRENDED TOWARD CONSENSUS BUT STILL
REMAINS INCONSISTENTLY SLOWER THAN THE ECMWF WHICH MATCHES BETTER
WITH THE NAM/UKMET AND CMC. GIVEN THE IMPACTS AND INCREASINGLY
SOLID MODEL AGREEMENT A GENERAL MODEL BLEND IS PREFERRED.
..PACIFIC NORTHWEST TO NORTHERN CALIFORNIA
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-UKMET BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
A PROLONGED ATMOSPHERIC RIVER WILL BE DIRECTED ACROSS VANCOUVER
ISLAND TODAY THROUGH MONDAY WITH THE APPROACH OF THE NEXT
SHORTWAVE. THIS WAVE IS A BIT SMALLER AND ELONGATED
NORTHWEST-SOUTHEAST RELATIVE TO A STRONGER/BROADER COMPACT WAVE
UPSTREAM ACROSS THE SOUTHERN GULF OF AK. THIS LEAD WAVE WILL
CONTINUE TO SHARPEN AND CLIP THE PACIFIC NORTHWEST, MAINLY
AFFECTING THE OLYMPIC PENINSULA AND EXTREME NORTHERN WA CASCADES
THROUGH MONDAY AFTERNOON. THIS IS A HARD SYSTEM TO LOCK DOWN BOTH
IN TIMING AND SHARPNESS HOWEVER, THERE IS STRONG AGREEMENT WITH
THE EXCEPTION OF THE UKMET WHICH IS A BIT STRONGER AND FURTHER
SOUTHEAST IN THE TROF. THE NEXT WAVE HAS SOLID AGREEMENT BUT THE
PRECISE INTENSITY WILL DETERMINE THE ANGLE OF ROTATION AROUND THE
RAPIDLY WEAKENING/DEVOLVING GYRE IN THE GULF OF AK INTO S AK
ITSELF. THE FASTER TO WEAKEN ARE THE GFS/NAM WHICH THEREFORE
ALLOW FOR LESS NORTHWARD SHEARING OF THE VORTICITY ENERGY INTO THE
DYING CLOSED LOW...COMPARED TO THE ECMWF/CMC, MAKING THEM A BIT
FURTHER NORTH WITH THE TRACK OF THE SURFACE LOW. THE AFFECTS WITH
TIMING OF QPF SEEM TO BE MORE TRADITIONAL WITH THE GFS LEADING
FASTER WHILE THE ECMWF/CMC LAG AND THE UKMET/NAM ARE BETWEEN.
GIVEN THE UKMET IS LESS FAVORED WITH THE LEADING WAVE AND IT SHOWS
SIMILAR UNCERTAINTY HERE THROUGH THE VERTICAL DEPTH OF THE
CYCLONIC SYSTEM, WILL CONTINUE A NON-UKMET BLEND HERE WITH ONLY
SLIGHTLY BELOW AVERAGE CONFIDENCE, GIVEN SPREAD AND DIFFICULTY TO
LOCK DOWN ON THE LARGER SCALE PATTERN DEVOLUTION.
...SUBTROPICAL SHORTWAVE ENTERING CENTRAL/SOUTHERN CALIFORNIA
MONDAY-TUESDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND (HEDGE TO ECMWF)
CONFIDENCE: SLIGHTLY BELOW AVERAGE
AS LARGER SCALE GYRE OVER THE GULF OF AK DIRECTS THE PAIR OF
SHORTWAVES TOWARD THE PACIFIC NORTHWEST SUNDAY INTO MONDAY, IT
TAPS THE SUBTROPICAL FLOW NORTHEAST TOWARD CENTRAL/S CA. THE
UPSTREAM RIDGE OVER THE ROCKIES WILL BLOCK PROGRESSION ALLOW FOR
THE FIRST SHORTWAVE (MORE ASSOCIATED WITH WARM ADVECTIVE
PROCESSES) TO STALL/DELAY ACROSS S CA BEFORE THE A SECONDARY
SHORTWAVE TO REACH TUESDAY EVENING. THE NAM IS MUCH TOO STRONG
AND FAST PARTICULARLY WITH THE SECONDARY SHORTWAVE...WHILE THE
ECMWF/CMC ARE TAPPING GREATER MOISTURE. THIS IS ALWAYS A
DIFFICULT REGION FOR THE GLOBAL MODELS TO ASSIMILATE DATA TO HAVE
HIGHER CONFIDENCE, BUT THE ECMWF TENDS TO BE A BIT BETTER GIVEN
RELIANCE ON SATELLITE OBSERVATIONS; YET THE GFS IS TIMED WELL WITH
IT THE THE GEFS/ECENS MEANS SUPPORT IT AS WELL. AS SUCH WILL
FAVOR A NON-NAM BLEND OVERALL BUT MAYBE HEDGE A BIT MORE ECMWF
WITH THE MOISTURE ADVECTION. CONFIDENCE IS SLIGHTLY BELOW AVERAGE.
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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