528
FXUS10 KWNH 261617
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1216 PM EDT SUN APR 26 2020
VALID APR 26/1200 UTC THRU APR 30/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
DEVELOPING NORTHEAST COASTAL LOW TODAY THROUGH MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-GFS BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THE MILLER-B COASTAL CYCLOGENESIS IS ALREADY WELL ON ITS WAY ALONG
THE EAST COAST/LOWER CHESAPEAKE AS THE OHIO VALLEY SURFACE WAVE
WEAKENS UNDER INCREASINGLY SHEARED MID TO UPPER LEVEL PATTERN (AS
EVIDENCED BY GOES-E WV SUITE). THE GFS CONTINUES TO BULGE
SLIGHTLY WARMER 850MB TEMPS ACROSS THE CATSKILLS/POCONOS AND NJ IN
EXITING MAKING IT LESS FAVORABLE WITHIN INCREASINGLY STRONGER
SW-NE GRADIENT IN THE REMAINDER OF THE GUIDANCE SUITE. OTHERWISE,
A MORE TRADITIONAL ALIGNMENT OF GUIDANCE MEMBERS WILL OCCUR WITH
THE WAVE LIFTING NORTH. THE GFS IS FASTEST AND GENERALLY WEAKER
THAN THE SLOWER BUT STRONGER UKMET, AND EVEN DEEPER 12Z NAM. THE
00Z CMC/ECMWF LAG A LITTLE SLOWER; BUT ALLOWS FOR A MORE
TRADITIONAL BLENDING SCENARIO. THE TRAILING SOUTHERN STREAM
SHORTWAVE ENERGY WILL ENHANCE SOUTH OF THE 40N70W BENCHMARK LATE
MONDAY INTO EARLY TUESDAY, UNDER THE INFLUENCE OF THE UPSTREAM
(SEE SECTION BELOW) 'KICKER' WAVE. THE GFS REMAINS FAST/LIKELY
TOO FAST, BUT THE UKMET/NAM DEPICT A SLOWER, MORE REASONABLE
SIMILARITY. THE 00Z CMC/ECMWF ARE TOO SLOW, ALLOWING FOR THE
SURFACE OCCLUSION TO LINGER LIKELY TOO LONG. THIS ALLOWS FOR THE
ECMWF TO SHIFT WELL NORTH OF THE OTHER CONSENSUS SOLUTIONS. WHILE
NEITHER CAMP LOOKS IDEAL, A COMPROMISE OF THE NAM/UKMET AND THE
ECMWF/CMC SEEMS PRUDENT AFTER 28.12Z (48HRS); AS SUCH A NON-GFS
BLEND IS SUPPORTED AT SLIGHTLY ABOVE CONFIDENCE.
TROUGH AXIS CROSSING CANADIAN PRAIRIES, CLIPPING UPPER
MIDWEST/GREAT LAKES THROUGH MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
GOES-WV SUITE DENOTES MATURING CYCLONE ACROSS CENTRAL
ALBERTA/SASKATCHEWAN, THIS WILL DROP A FRONTAL ZONE THAT CROSSES
THE NORTHERN PLAINS LATER TODAY INTO MONDAY. WHILE THE BULK OF
THE SHORTWAVE ENERGY WILL LIFT NORTH OVER THE DOWNSTREAM BLOCKING
RIDGE IN ONTARIO, THE BASE OF THE SHORTWAVE WILL SLIDE UNDERNEATH
ACROSS THE GREAT LAKES EVENTUALLY ACTING AS A KICKER TO THE LARGER
COASTAL CYCLONE (SEE SECTION ABOVE). UNTIL THE WAVE IS
UNDER-CUTTING THE RIDGE ON MONDAY, THERE IS SOLID MODEL AGREEMENT.
THE GFS STARTS TO ACCELERATE EAST-SOUTHEAST THEREAFTER BUT THAT
IS DRIVEN MORE BY THE DOWNSTREAM FASTER EXIT. ADDITIONALLY, THE
FRONTAL ZONE WILL DRAPE ACROSS THE NORTHERN PLAINS AND ACT AS A
SEEDING OF THE APPROACHING SHORTWAVE (SEE SECTION BELOW) MONDAY.
HERE THE GUIDANCE IS TIGHTLY AGREED UPON TO AT LEAST START THE
NEXT SYSTEM ON SIMILAR FOOTING. SO A GENERAL MODEL BLEND CAN BE
AFFORDED AT ABOVE AVERAGE CONFIDENCE
PACIFIC NORTHWEST SHORTWAVE ON MONDAY DIGGING ACROSS NORTHERN
PLAINS TUES AND INTO A CLOSED LOW OVER MIDWEST BY
WED...ACCOMPANYING FRONT THRU SOUTHERN PLAINS (TUES) AND MID-MS TO
TN VALLEYS (WED)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL BLEND THROUGH 28.12Z
12Z GFS AND 00Z UKMET/ECMWF BLEND THEREAFTER
CONFIDENCE: AVERAGE
STRONG GULF OF AK GYRE, WILL EJECT THE BASE OF SHORTWAVE AND
STRONG ANTI-CYCLONIC UPPER LEVEL JET FEATURES ACROSS BRITISH
COLUMBIA THE END OF MONDAY INTO TUESDAY. PRECEDING THE MAIN
WAVE, THE LEFT EXIT OF THE JET PROGRESSES THROUGH THE NORTHERN
ROCKIES. THIS FEATURE LINKS UP WITH THE FRONTAL ZONE FROM THE
PRIOR SHORTWAVE (SEE SECTION ABOVE) AND PROGRESSES THROUGH S MT
INTO THE NORTHERN PLAINS AT THE SAME TIME. SOLID MOISTURE FROM
THE PACIFIC STREAM WILL REMAIN AND INTERSECT WITH RETURN MOISTURE
ACROSS THE PLAINS. THIS WILL SPARK SOME CONVECTION AND SPUR
SURFACE CYCLOGENESIS. GUIDANCE HAS BEEN FLIP-FLOPPING ON WHICH
SOLUTION WILL BE OVER-AGGRESSIVE WITH THE CONVECTION. YESTERDAY'S
RUNS WERE THE ECMWF FOLLOWED BY THE UKMET. THE LAST FEW CYCLES
HAS BEEN THE GFS. THIS IS STILL THE CASE WITH THE 12Z RUN, BUT
HAS TEMPERED A BIT BUT STILL SHOWING STRONGER MOISTURE FLUX
CONVERGENCE ON THE ELEVATED BOUNDARY VERSUS MORE SURFACE ROOTED
CELLS, WHICH TENDS TO BE A WEAKNESS OF THE GFS.
AS THE MAIN WAVE EXITS THE TERRAIN EARLY TUESDAY, IT WILL DIG AND
LEAD TO A BINARY INTERACTION WITH THE INITIAL SHORTWAVE...THE
STRONGER THE INITIAL WAVE THE FURTHER NORTH AND BROADER THE TROF
WILL BE. WHILE, MOISTURE IS THERE, IT IS MEAGER AND LATENT HEAT
RELEASE TO BUILD THIS NORTHWARD SOLUTION IS LOOKING LESS LIKELY.
THE 12Z GFS/NAM AND 00Z UKMET ARE STRONGER WITH THIS THAN THE
ECMWF SO ARE A TAD NORTH INITIALLY. HOWEVER, THE 00Z CMC IS MUCH
SLOWER OVERALL AND QUICKLY MOVES OUT OF PREFERENCE BY 29.00Z. AS
THE UPSTREAM WAVE DIGS BY WED, THE STRONG 12Z NAM, TIGHTENS EVEN
FURTHER SHOWING SOME TYPICAL DAY 3 OVER-AMPLIFICATION BIAS...THAT
SLOWS ITS OVERALL PROGRESSION. OTHERWISE, THE WEAKER/SOUTH ECMWF
IS NOT TOO FAR FROM THE STRONGER/NORTH UKMET/GFS AND THE
GEFS/ECENS SOLUTIONS TO SUPPORT A BLEND OF THE THREE BY THE END OF
DAY 3. THERE ARE NUMEROUS INTERNAL INTERACTIONS AND IMPORTANCE OF
CONVECTIVE UPSCALE ENHANCEMENT VIA LATENT HEAT RELEASE TO HAVE
TREMENDOUS CONFIDENCE IN A LOWER THAN NORMAL PREDICTABILITY
FORECAST. HOWEVER THE AGREEMENT IS SOLID TO SUPPORT AVERAGE
CONFIDENCE AT THIS POINT IN A 12Z GFS AND 00Z UKMET/ECMWF BLEND.
GLANCING EFFECTS(FRONT) OF LEAD SHORTWAVE LATE TUES/WED IN
PACNW...FULL BODIED SHORTWAVE REACHING PACNW BY 00Z THURS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH 29.00Z
NON-NAM THEREAFTER
CONFIDENCE: SLIGHTLY ABOVE AVERAGE THROUGH 29.12Z
SLIGHTLY BELOW AVERAGE THEREAFTER
THE NEXT PACIFIC SHORTWAVE HAS TRENDED A BIT NORTH, SLOWER AND
THEREFORE A BIT FLATTER. GIVEN THE OLDER GULF OF AK BINARY GYRE
WILL BE ERODING LATE MONDAY INT TUESDAY, THE UPSTREAM WAVE'S
ARRIVAL LATE TUESDAY WILL RESET THE LARGER SCALE TROUGH BUT SHIFT
IT EASTWARD. THIS WILL ALLOW FOR SOLID SOUTHWESTERLY MOISTURE
TRANSPORT MAINLY INTO SOUTHWEST BRITISH COLUMBIA BUT IS EXPECTED
TO CLIP THE OLYMPIC PENINSULA BY LATE TUESDAY/EARLY WED. ANOTHER
TRAILING PACIFIC WAVE WILL QUICKLY APPROACH ON WED AND WITH THE
LINGERING FRONTAL ZONE DIRECTED TOWARD THE WA COAST...STRONGER
MOISTURE FLUX WILL ENTER W WA BY 00Z ON THURS. THERE IS SOLID
AGREEMENT IN TIMING/DEPTH AND POSITION OF THE INITIAL WAVE/FRONTAL
ZONE THROUGH WED, WITH PERHAPS THE 12Z NAM A TAD TOO STRONG
(TYPICAL BY D3). THIS LIKELY LEADS THE NAM TO BE A TAD TOO
FAST/SOUTH WITH THE SECONDARY PUSH. HOWEVER, THE 12Z GFS AND 00Z
UKMET ARE QUICK ON THE HEELS, WITH THE ECMWF/CMC BOTH LAGGING IN
TYPICAL FORMATION. BEING A BIT FASTER, THE UKMET/GFS ARE A BIT
DEEPER AND MORE MATURE IN THE CYCLOGENESIS PROCESS, ALSO TYPICAL.
THE ENSEMBLE SUITE SHOWS MODERATE TO HIGH SPREAD ACROSS THE TIMING
OF THIS WAVE, TO NOT REALLY HELP DETERMINE WHICH SIDE TO GO
TOWARD...AS SUCH WILL SPLIT IN A NON-NAM COMPROMISE. CONFIDENCE
IS SLIGHTLY ABOVE AVERAGE THROUGH THE FIRST WAVE 29.12Z BUT
BECOMING SLIGHTLY BELOW AVERAGE GIVEN THE SPREAD FOR THE LAST FEW
TIME-STEPS OF THE SHORT-TERM FORECAST.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
GALLINA
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page