071
FXUS10 KWNH 021847
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
146 PM EST MON MAR 02 2020
VALID MAR 02/1200 UTC THRU MAR 06/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z EVALUATION INCLUDING MODEL PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
AMPLIFYING SHORTWAVE OVER THE NORTHERN PLAINS/UPPER MIDWEST BY
TUESDAY WITH SURFACE LOW DRAWING WEAK SURFACE WAVE CROSSING THE OH
VALLEY AND DEEPENING OVER NORTHERN NEW ENGLAND BY WEDNESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND HEDGING TOWARD UKMET/GFS AFTER
48HRS
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
19Z UPDATE: WHILE THE MASS FIELDS CONTINUE TO BE ALIGNED FAIRLY
WELL THROUGH MUCH OF THE CONUS, THE 12Z UKMET TRENDED TOWARD A
SHARPER/STRONGER NEGATIVE TILT THROUGH THE NORTHEAST WED BEFORE
WRAPPING UP SUBSTANTIALLY ACROSS MARITIME SOUTHEAST CANADA. THIS
MATCHES THE STRONGER/DEEPER SURFACE WAVE OF THE GFS, FURTHER
NORTHWEST OF THE NAM/ECMWF/CMC WHICH SEEMS REASONABLE GIVEN THE
STRENGTH OF THE FAST MOVING FLOW THROUGH THE GREAT LAKES IN THE
PERIOD. AS SUCH WILL STILL SUPPORT A GENERAL MODEL BLEND BUT
HEDGE MORE TOWARD THE UKMET/GFS AFTER 48HRS IN CANADA.
---PRIOR DISCUSSION---
GOES-E WV DEPICTS LEADING SHORTWAVE ENERGY CURRENTLY OVER SE
SASKATCHEWAN MOVING INTO MANITOBA, INCREASING IN SHARPNESS AT THE
LEFT EXIT OF STRONG BUT FAIRLY ZONAL (FROM NNW TO SSE) UPPER JET,
BUT ALSO AT THE LEFT ENTRANCE TO STRONG CONFLUENT 150KT+ OVER THE
OHIO VALLEY. THE NORTHERN STREAM WILL SUPPORT A STRONG SURFACE
WAVE TO RUN ALONG 50N THROUGH MORNING WED. CONCURRENTLY, THE
BROAD UPGLIDE FROM THE SUBTROPICAL EASTERN PACIFIC STREAM PROVIDES
ASCENT IN THE WARM CONVEYOR PROVIDES MOISTURE AND INSTABILITY TO
ENHANCE A WEAKER SURFACE WAVE OUT OF OK/MO TODAY THROUGH THE OHIO
VALLEY TONIGHT. EVENTUALLY, THE COMBINATION OF STREAMS SUPPORTS
THE OHIO VALLEY WAVE TO DEEPEN ACROSS THE LOWER GREAT LAKES AND
BECOME THE DOMINANT LOW OVER THE CANADIAN MARITIMES BY LATER WED,
AS THE UPPER LEVEL SHORTWAVE SHARPENS NEGATIVE TILT. THERE HAS
BEEN SIGNIFICANT MODEL ALIGNMENT OVER THE LAST FEW CYCLES HERE, TO
HAVE INCREASED CONFIDENCE IN A GENERALLY LOWER PREDICTABLE REGIME
(COMBINATION OF STREAMS). THE 12Z GFS HAS TEMPERED BUT REMAINS
THE SHARPEST, FASTEST WITH THE NEGATIVE TILTING AS SO APPEARS TO
SHIFT THE WAVE A TAD FASTER, BUT NOT SIGNIFICANTLY SO.
INFLUENCE OF THE NEXT SHORTWAVE/JET STREAK EXIT IS THE GREATEST
FACTOR TOWARD MODEL SPREAD AFTER WED, THIS SUGGESTS A GENERAL
MODEL BLEND WILL SUFFICE FOR THIS SYSTEM UNTIL THE NEXT WAVE'S
INFLUENCE TAKES GRIP, BUT THIS IS ALSO GENERALLY INTO CANADA AND
ONLY AFFECTS ME/GULF OF MAINE WITH MORE UNCERTAINTY. SO OVERALL,
THE UKMET IS FAVORED A BIT HEAVIER IN A GENERAL MODEL BLEND, AS IT
IS MORE CENTRAL/REASONABLE WITHIN THE OVERALL SUITE WITH THE
APPROACH OF THIS NEXT WAVE. CONFIDENCE IS INCREASED TO SLIGHTLY
ABOVE AVERAGE DUE TO THE OVERALL MASS FIELD ALIGNMENT THROUGH WED,
THOUGH GIVEN SIZABLE BUT STILL NOT STABLE MODEL TRENDS OVER THE
LAST FEW DAYS CYCLES IN A LOWER THAN NORMAL PREDICTABLE PATTERN.
SHORTWAVE APPROACHING BRITISH COLUMBIA ON TUESDAY, SIGNIFICANTLY
AMPLIFYING ACROSS THE NORTHERN PLAINS/UPPER MIDWEST BY EARLY
THURSDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
19Z UPDATE: GENERALLY, THE CMC SHIFTED A TAD NORTH BUT REMAINS
MUCH FURTHER SOUTH OF THE OTHERWISE TIGHTENING CLUSTER. THIS
APPEARS TO BE DRIVEN BUT A MUCH WEAKER AMPLIFICATION OVERALL. THE
UKMET SHIFTED SLIGHTLY TOWARD THE ECMWF/NAM/GFS ENOUGH TO HAVE
SLIGHTLY ABOVE AVERAGE CONFIDENCE IN A NON-CMC BLEND.
---PRIOR DISCUSSION---
PROGRESSIVE NORTHERN STREAM FLOW OUT OF THE GULF OF AK CONTINUES
THROUGH LATE TUESDAY INTO WED, THE TIMING, STRENGTH OF THE SUBTLE
UPSTREAM WAVE CROSSING THE MIDWEST/GREAT LAKES ON WED, LEADS TO
SOME UNCERTAINTY IN INCREASED RIDGING ACROSS THE NORTHERN PLAINS.
HERE THE CMC IS CLEARLY SOUTH/DEEPER MORE AMPLIFIED LEADING TO
STALLED FLOW AND A FURTHER SOUTHWARD DIGGING OF THIS TROF IN THE
NORTHERN PLAINS/MIDWEST; WHILE EVEN THE SLIGHTLY SLOWER ECMWF,
DEEPENS/AMPLIFIES A BIT FURTHER NORTH AND EAST, EVEN FURTHER NORTH
THAN THE SLIGHTLY FASTER GFS/NAM. THE UKMET IS A BIT STRONGER BUT
ALSO FASTER, SHOWING SOME TYPICAL LATE DAY 3 NEGATIVE BIAS, BUT
COULD BE KEPT IN THE PREFERENCE THROUGH THE SHORT-TERM (84HRS) BUT
SHOULD START TO BE WEIGHTED A BIT LOWER. ALL CONSIDERED AT
NON-CMC BLEND IS PREFERRED BUT WILL WEIGHT A TOWARD THE
GFS/NAM/ECMWF AFTER 72 INTO 84HRS. WITH THE GOOD MASS AGREEMENT,
BUT HARDER TO PREDICT FLOW REGIME (AND EVENTUAL BINARY INTERACTION
WITH THE SOUTHERN STREAM WAVE), CONFIDENCE IS CONSIDERED AVERAGE
IN THIS BLEND.
SOUTHERN STREAM CLOSED LOW SYSTEM MOVING FROM NORTHERN MEXICO
THROUGH THE SOUTHERN PLAINS INTO SOUTH WED INTO THURS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND WEIGHTING TOWARD GFS/UKMET
CONFIDENCE: SLIGHTLY BELOW TO BELOW AVERAGE
19Z UPDATE: GREATER AMPLIFICATION IN THE NORTHERN STREAM ALLOWS
FOR THE ECMWF TO BE TUGGED NORTHWARD, MATCHING THE LATITUDE OF THE
SURFACE TRACK THROUGH THE SOUTH INTO THE SOUTHEAST, AN PAR WITH
THE ECENS MEAN/UKMET AND GFS. HOWEVER, THE ECMWF REMAINS A TAD
TOO FAST, MORE IN LINE WITH THE NAM TO BE FULLY FAVORED. THE CMC
REMAINS SUPPRESSED THOUGH TIMES WELL WITH THE ECENS MEAN/GFS AND
UKMET, LIKELY DUE TO THE MUCH WEAKER NORTHERN STREAM...SO LIKE THE
ECMWF, IT WILL CONTINUE TO BE INCORPORATED BUT AT LOWER WEIGHTING.
THE 12Z GEFS HOWEVER, IS EVEN SLOWER THAN THE GFS AND UKMET,
PRESENTING AN EVEN LESS OF A SUBTROPICAL KICKER WAVE TO MOVE IT
ALONG THAN THE OPERATIONAL GFS OR ANY OTHER GUIDANCE MEMBER(S).
SO ALL CONSIDERED A NON-NAM BLEND REMAINS FAVORED BUT A HEDGE
TOWARD FAVORING THE UKMET/GFS IN THE BLEND WEIGHTING. STILL
CONFIDENCE REMAINS SLIGHTLY TO BELOW AVERAGE.
---PRIOR DISCUSSION---
SIZABLE MODEL DIFFERENCE OVER THE LAST WEEK CONTINUE WITH THIS
CLOSED LOW AND HAS GONE FROM NEARLY EQUALLY PHASED WITH THE
NORTHERN STREAM TO BARELY CONNECTED WITH THIS CURRENT SUITE. THE
12Z GFS CONTINUES TO SUGGEST FURTHER SLOWING AND LESS INFLUENCE OF
THE NORTHERN STREAM AND IS IN AN USUAL PLACE WITHIN THE OVERALL
SUITE: SLOWEST AND THEREFORE STRONGEST COMING THROUGH THE
TENNESSEE VALLEY LATE THURSDAY. THIS IS OPPOSED BY THE ECWMF,
WHICH HAD SHOWN THE FIRST INCLINATIONS TO A SLOWER TREND BUT HAS
STOPPED THE TREND AND IS NOW VACILLATING RUN TO RUN, WITH LARGER
JUMPS OVER THE LAST HALF-WEEK, THOUGH SEEMS TO HAVE STABILIZED
AROUND A COMMON SOLUTION OVER THE LAST FEW CYCLES INCLUDING A
FAIRLY TIGHT ENSEMBLE SUITE. CURRENTLY THE CLOSED LOW HAS SETTLED
IN THE CALIFORNIA BIGHT WITH SOME UPSTREAM SUBTROPICAL KICKING
INFLUENCES, SUGGESTING SLIGHTLY FASTER PROGRESSION MAY START
SOONER THAN LATER, TIPPING TOWARD THE ECMWF SOLUTION. THE 12Z NAM
IS SLOW/STRONG AND NORTH OVERALL IN THE SUITE, AND GIVEN THIS IS
IN LINE WITH ITS TYPICAL NEGATIVE BIAS, WILL DISCARD ITS SOLUTION
AT THIS TIME. THE ECMWF/CMC ALSO BEING FURTHER SOUTH, SHIFTING
TOWARD THE INSTABILITY PROVIDES SOME ADDITIONAL CONFIDENCE. BUT
INFLUENCES OUT OF THE NORTHERN STREAM (PARTICULARLY ON DAY 3 IN
THE SOUTHEAST) PROVIDE VERY LOW CONFIDENCE OVERALL. SO WILL FAVOR
THE ECMWF/CMC A BIT MORE IN A NON-NAM BLEND PREFERENCE BUT CANNOT
FULLY DISCOUNT THE GFS/UKMET GIVEN THE INFLUENCES IN THE NORTHERN
STREAM THAT SEEM TO FAVOR THEM OVER THE ECMWF/CMC AT THIS TIME.
CLOSED LOW IN NORTHERN GULF OF AK WITH DEEP LATITUDE TROF ALONG
THE PACIFIC NW BY THURSDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
19Z UPDATE: AN ADJUSTMENT NORTHWEST BY THE ECMWF AND LESSER SO
THE CMC AND THE UKMET SHIFTING SLOWER THEREFORE SOUTHWARD AND
EAST, TIGHTENS THE OVERALL CLUSTER WITH THE GFS, EVEN THOUGH IT IS
MUCH FASTER WITH THE INNER CORE, THE TIMING OF THE FRONTAL ZONE
APPROACHING THE NORTHWEST COAST THURSDAY IS MUCH BETTER OVERALL.
WHILE THE DIFFERENCES WERE NOT LARGE BEFORE, THE SHIFTS ALLOW FOR
A MORE INCLUSIVE BLEND INCREASING SOME CONFIDENCE FURTHER.
HOWEVER, THIS LEADS TO THE NAM AS THE SOLE DETERMINISTIC SOLUTION
AWAY FROM THE OTHERS. AS SUCH WILL FAVOR A NON-NAM BLEND BUT WILL
TEMPER SOME OF THE GFS FASTER/STRONGER INNER CORE SHORTWAVE
NEARING HAIDA GWAII (THOUGH THE AFFECTS ARE NOT APPARENT IN THE
CONUS).
---PRIOR DISCUSSION---
TOWARD THE END OF THE FORECAST PERIOD, FINALLY A LARGER SCALE,
CLOSED LOW DEVELOPS ACROSS THE NORTHERN GULF OF AK LATE WED. A
STRONG UPSTREAM SHORTWAVE WILL SWING AROUND ITS BASE LEADING TO
FURTHER SOUTHWARD BUILDING AND BROADENING OF THE TROF OVER THE
ENTIRE GULF OF AK BY THURS. THE 12Z GFS IS FASTER TO DO SO IN LINE
WITH TYPICAL NEGATIVE BIAS, BUT THE EVENTUAL LOCATION/CENTER OF
THE CLOSED LOW SOLIDIFIES NW OF HAIDA GWAII BY 06.00Z AND IS
SUPPORTED BY THE OTHER GUIDANCE MEMBERS. THIS WILL DIRECT STRONG
SOUTHWESTERLY, MOIST FLOW REGIME INTO BC AND THE PACIFIC NW BY THE
END OF THE FORECAST PERIOD. HOWEVER, THE STRONGER/COMPACT BUT
SLOWER SOLUTIONS OF THE NAM/UKMET FAVOR A DEEPER SURFACE LOW
FURTHER NORTH, DELAYING THE COLD FRONT. THE ENSEMBLES SUPPORT
THE ECMWF/CMC TIMING PLACEMENT OF THE MASS FIELDS AND GIVEN THE
AFOREMENTIONED ISSUES IN THE GFS/NAM/UKMET, WILL SUPPORT AN
ECMWF/CMC BLEND FOR MASS FIELDS AT SLIGHTLY ABOVE AVERAGE
CONFIDENCE.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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