119
FXUS10 KWNH 180638
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
137 AM EST SAT JAN 18 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: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
07Z UPDATE: WHILE THE 00Z CMC IS NOT PERFECTLY ALIGNED WITH THE
REMAINING GUIDANCE, IT HAS TRENDED VERY CLOSE TO THE ECMWF
EVOLUTION AND MASS FIELD SOLUTIONS ARE TIGHT ENOUGH THAT A GENERAL
MODEL BLEND IS PREFERRED AT ABOVE AVERAGE CONFIDENCE FOR THE
REMAINDER OF TIME IN THE CONUS/CONUS WATERS.
---PRIOR DISCUSSION---
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: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
07Z UPDATE: THE 00Z ECMWF DID SHIFT A BIT FURTHER EAST WITH THE
TRACK OF THE AMPLIFIED SHORTWAVE CROSSING THE MID-MS AND TN
VALLEYS LATE MON TO TUESDAY, PAIRING WITH THE CMC. THIS WHILE THE
UKMET TRENDED SLOWER TOWARD THE GFS/NAM. AGAIN, THIS HAS LOW
IMPACTS AND SMALL TIMING DIFFERENCES MAINLY IN THERMAL FIELDS THAT
EMPLOYING A GENERAL MODEL BLEND RESULTS IN SLIGHTLY ABOVE AVERAGE
CONFIDENCE.
---PRIOR DISCUSSION---
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-GFS BLEND
CONFIDENCE: AVERAGE
07Z UPDATE: THE UKMET TRENDED A BIT WEAKER/FASTER WITH THE INITIAL
SMALLER/NARROWER TROF ENTERING THE OLYMPICS MONDAY, BUT THIS
SERVED TO SHIFT THE NEXT WAVE A BIT FURTHER NORTH, TOWARD THE
ECMWF/ECENS MEAN AND CMC. THIS WHILE THE 00Z GEFS ALSO TRENDED A
BIT WEAKER, WITH INCREASED SPREAD TOWARD THE NORTH RELATIVE TO THE
00Z GFS. THIS, ALONG WITH SOME FAST TIMING ISSUES TOWARD OR COAST
BY TUESDAY SUGGESTS THE NORTHERN/STRETCHED SOLUTIONS SHOW BETTER
RESULTS, WHICH SEEMS LOGICAL GIVEN THE TIME OF YEAR AND TENDENCY
FOR DISSIPATING CLOSED LOWS/LARGE SCALE GYRE TO SPIN DOWN TOO FAST
IN THE GFS. AS SUCH WILL FAVOR A NON-GFS BLEND OR REPLACE IT WITH
THE 00Z GEFS IN THE BLEND BUT ONLY AT AVERAGE CONFIDENCE.
---PRIOR DISCUSSION---
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: 00Z ECMWF/UKMET/CMC BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
07Z UPDATE: THE ECMWF/CMC AND UKMET ALL TRENDED A BIT LESS DEEP IN
AMPLITUDE IN THE NORTHERN STREAM, THIS DELAYS THE EFFECTIVE
TRAILING SHORTWAVE EMERGING ACROSS THE SUBTROPICAL EPAC (SOUTH OF
30N) AND REDUCING THE SPACING FROM THE INITIAL WARM ADVECTIVE
SHORTWAVE THAT SLOWS ACROSS S CA. THIS ALLOWS THE GFS/NAM TO
SIGNIFICANTLY OUTPACE AND HAVE DIFFERENT AFFECTS ACROSS THE
SOUTHWEST. GIVEN THE REDUCTION IN PREFERENCE IN THE GFS IN THE
NORTHERN STREAM, FEEL SIMILARLY HERE AND PREFER A 00Z
ECMWF/UKMET/CMC BLEND AT SLIGHTLY BELOW AVERAGE CONFIDENCE.
---PRIOR DISCUSSION---
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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