713
FXUS10 KWNH 011612
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1212 PM EDT FRI MAY 01 2020
VALID MAY 01/1200 UTC THRU MAY 05/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...DEEP TROUGH/CLOSED LOW IMPACTING THE EAST THROUGH FRIDAY AND
EARLY SATURDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~
PREFERENCE: NON-UKMET BLEND OR GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE TO ABOVE AVERAGE
HIGH AMPLITUDE TROF ALONG THE EAST COAST IS A NORTH-SOUTH STACK OF
TWO SMALLER SCALE FEATURES, THE BROADER/SOUTHERN OF WHICH WILL
CONTINUE TO NARROW AND WEAKEN, WHILE THE NORTHERN WILL ELONGATE
BUT STRENGTHEN ACROSS SW QUEBEC INTO THE NORTHEAST EARLY SATURDAY.
THE MODEL SPREAD IS FAIRLY SMALL AND AGREEABLE WITH THE OVERALL
EVOLUTION INCLUDING THE NEWER SURFACE CYCLONE THAT DEVELOPS ALONG
40N EAST OF 70W EARLY SAT. THE UKMET IS A TAD SLOW WITH THE
SURFACE WAVE ALONG EAST COAST TODAY AND SHIFTS THE DEVELOPMENT OF
THE 2ND SURFACE WAVE FURTHER NORTH. SO FOR A TIGHTER BLEND A
NON-UKMET BLEND IS SUPPORTED BUT A GENERAL MODEL BLEND MAY BE
VIABLE, TO HANDLE SOME OF THE UNCERTAINTY IF DESIRED. CONFIDENCE
IS SLIGHTLY TO ABOVE AVERAGE
...SHORTWAVE/SURFACE LOW TRACKING NEAR THE U.S./CANADIAN BORDER
THROUGH SUNDAY, FRONTAL ZONE THROUGH OHIO VALLEY; NORTHEAST
REINFORCEMENT/SURFACE REDEVELOPMENT SUNDAY TO MONDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC BLEND
FAVORING: 00Z UKMET CANADA/GREAT LAKES/NORTHEAST
12Z NAM/GFS AND ECMWF ACROSS OHIO VALLEY TO MID-ATLANTIC
CONFIDENCE: AVERAGE TO SLIGHTLY BELOW AVERAGE (BY END OF D3)
IN THE WAKE OF LARGER SCALE TROUGH ALONG THE EAST COAST, GENERALLY
FLATTER FLOW EXISTS ACROSS THE WEST INTO THE NORTHERN PLAINS.
SMALLER SCALE SHORTWAVE FEATURES INITIALLY IN THE NORTHERN ROCKIES
AND CANADIAN ROCKIES WILL BE START TO EXPAND AND INTERACT ACROSS
THE SOUTHERN PRAIRIES OF CANADA INTO THE NORTHERN PLAINS AND UPPER
GREAT LAKES BY SAT MORNING. THIS ELONGATION AND MAGNITUDE OF
INTERACTION BETWEEN THE FEATURES ALONG WITH INFLUENCE OF
CONVECTIVE UPSCALE/LATENT HEAT INTO THE SYSTEM LEADS TO LOWER
PREDICTABILITY SCENARIO UNFOLDING ACROSS THE GREAT LAKE INTO THE
NORTHEAST THE THE END OF THE WEEKEND, ESPECIALLY AS A SUBTLE
SHORTWAVE/SPEED MAX EMERGES OUT OF THE CENTRAL ROCKIES AND RACES
ACROSS THE OHIO VALLEY SAT INTO SUNDAY.
INITIALLY, HOWEVER, THE MERGER OF THE WAVES ACROSS SW ONTARIO BY
LATE SAT/SUN IS IN MODERATE AGREEMENT THOUGH WITH TYPICAL TIMING
ISSUES. THE GFS/GEFS ARE FAST AND THE 12Z NAM SHIFTED FASTER TO
JOIN ITS NCEP BRETHREN, WHILE THE ECMWF IS SLOWER. THE CMC IS
ALREADY WELL NORTH AND OFFSET TO REMAIN OUT OF PHASE AND THEREFORE
OUT OF PREFERENCE THROUGHOUT THE REMAINDER OF THE FORECAST PERIOD.
THE UKMET IS BETWEEN THE TWO CAMPS, BUT FAVORS THE NAM/GFS JUST
GENERALLY WEAKER THROUGH EARLY SUNDAY. AS THE NAM/GFS RAPIDLY
DEVELOP THE SURFACE LOW AND STARTS THE OCCLUSION PROCESS EARLIER
AS IT PROGRESSES THROUGH THE GREAT LAKES ON SUNDAY, THE UPSTREAM
(NORTHERN CANADIAN ROCKIES) WAVE SWINGS THROUGH THE BASE AND
PRESSES THE FRONTAL ZONE ACROSS THE OHIO VALLEY. GIVEN THE ECMWF
WAS WEAKER/SLOWER WITH THE INITIAL WAVE THE INITIAL SURFACE WAVE
IS WEAKER AND SOUTH, BUT THE UPSTREAM KICKER IS STRONGER AND
FASTER SUPPORTING A TRIPLE-POINT LOW TO FORM OVER THE NORTHEAST BY
LATE SUNDAY, PRESSING THE FRONTAL ZONE FURTHER EAST WITH TIME,
EVEN MORE AGGRESSIVELY THAN THE BULK OF ECENS MEMBERS. SO THERE
IS LARGE SPREAD BY 60HRS IN THE NORTHEAST WITH THE FOCUS OF
STRONGER SURFACE CYCLONE THEREFOR WIND FIELDS. THE UKMET IS
MIDDLE GROUND, AND FRANKLY IDEAL IN PLACEMENT OF THE CANADIAN
WAVE, BUT BEING WEAKER/ELONGATED INITIALLY...DID NOT PRESS THE
FRONTAL ZONE SOUTH THROUGH THE OHIO VALLEY. BY DAY 3, THERE IS NO
IDEAL SOLUTION/PREFERENCE BUT A COMPROMISE SOMETHING CLOSER TO THE
UKMET NORTH IN CANADA/NORTHEAST BUT SOMETHING CLOSER TO THE
TIMING/ORIENTATION OF THE FRONTAL ZONE ACROSS THE OHIO
VALLEY/MID-ATLANTIC MONDAY BY A NAM/GFS/ECMWF BLEND.
CONFIDENCE IS AVERAGE INITIALLY BECOMING SLIGHTLY BELOW AVERAGE BY
DAY 3.
...DEEP TROUGH OFFSHORE THE WEST COAST TODAY AND SATURDAY WITH
REMNANT SHORTWAVE ENERGY MOVING THROUGH THE NORTHERN ROCKIES
SUNDAY MORNING, NORTHERN HIGH PLAINS SURFACE LOW...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THRU 03.12Z
NON-CMC COMPROMISE AFTERWARD
CONFIDENCE: ABOVE AVERAGE THRU 03.12Z
AVERAGE TO SLIGHTLY BELOW AVERAGE AFTERWARD
DEVELOPING GULF OF ALASKA CYCLONIC GYRE WILL BE SHIFTING SOUTHEAST
WITH AN INITIAL SHORTWAVE THAT IS LIFTING NORTH ALONG 135W TODAY.
QUICK ON ITS HEALS, ANOTHER POTENT SHORTWAVE FURTHER SHIFTS THE
GYRE EASTWARD, WITH THE LEADING SHORTWAVE ENERGY DEEPENING INTO A
STACKED DEEP SURFACE WAVE WITH A FRONTAL ZONE THAT WILL PRESS
THROUGH THE PACIFIC NW BY MIDDAY SATURDAY WITH LITTLE MODEL
DIFFERENCE TO SUPPORT A GENERAL MODEL BLEND THROUGH THE PACIFIC NW.
THE BASE OF THE TROF WILL ACCELERATE EASTWARD INTO THE NORTHERN US
ROCKIES WITHIN THE LEFT EXIT OF A WEAKLY CYCLONICALLY CURVED UPPER
LEVEL JET. WITH VERY STRONG 130-150KT UPSTREAM ENERGY, THERE
COULD BE POTENTIAL FOR VIGOROUS DEVELOPMENT AS IT DETACHES FROM
THE GYRE AND MOVES INTO THE NORTHERN HIGH PLAINS LATE SUNDAY. BY
THIS TIME, TYPICAL TIMING DIFFERENCES START TO MANIFEST, WITH THE
GFS/NAM AND UKMET SHIFTING FASTER THAN THE ECMWF/CMC. IN
COMBINATION OF TIMING OF THE EXITING SHORTWAVE AND RETURN OF
SHORTWAVE RIDGING DOWNSTREAM, AS WELL AS SOME VORTICITY STRETCH IN
THE LEE OF THE MT ROCKIES, THE GFS/NAM BOTH RAPIDLY DEEPEN THE
SHORTWAVE INTO A COMPACT CLOSED LOW THAT LIFTS NORTH INTO
ALBERTA/SASKATCHEWAN BY MONDAY; WITH THE UKMET INITIALLY A BIT
SLOWER IN DEVELOPMENT AND THEREFORE HAVING THE OPPORTUNITY TO
PRESS FURTHER EAST BY 00Z TUESDAY. THE SLOWER CMC IS VERY WEAK
AND MOVES OUTSIDE OF THE ENSEMBLE SUITE AND IS QUICKLY DISMISSED.
THE ECMWF IS SLOWER AND THEREFORE WEAKER REMAINING SOUTH AS IT
CLOSES OFF MONDAY, THIS WILL HELP WITH STRONGER UPSLOPE FLOW AND
CLOSER PROXIMITY TO BETTER INSTABILITY AND MOISTURE ACROSS THE
CENTRAL PLAINS.
ADDITIONALLY AND POTENTIALLY MORE IMPORTANT FOR THE DOWNSTREAM
EVOLUTION (AS WELL AS UPSTREAM SEE SECTION BELOW) IN THE NORTHERN
AND CENTRAL PLAINS, THE NAM/GFS AND LESSER EXTENT SO UKMET SHOW A
STRONG TRAILING SHORTWAVE ENTERING N CA AT 04.00Z. THE
ECMWF/ECENS SOLUTIONS DEPICT THIS FEATURE MUCH WEAKER IF AT ALL,
WHICH ONLY INCREASES THE SPREAD AND UNCERTAINTY 72-84HRS, AS THE
NAM/GFS BOTH SHOW A STRONG SURFACE RESPONSE WITH A NEW SURFACE
WAVE ALONG THE FRONT CROSSING INTO SD BY 84HRS. THIS FALLS INTO
LINE WITH BOTH THE NAM/GFS FAST BIASES AS WELL AS THE ECMWF SLOWER
SOLUTION BIAS; ENSEMBLE SUITE ARE VERY SIMILAR TO THEIR PARENT
OPERATIONAL MODEL, PROVIDING LITTLE HELP ONE SIDE OR THE OTHER.
SO A COMPROMISE OF NON-CMC SOLUTIONS SEEMS PRUDENT AFTER A GENERAL
MODEL BLEND THROUGH 60HRS. CONFIDENCE IS ABOVE AVERAGE THROUGH
60HRS, BUT RAPIDLY SHIFTS TO AVERAGE OR SLIGHTLY BELOW AVERAGE IN
THE COMPROMISE THEREAFTER WITH LIKELY SIZABLE RUN TO RUN VARIATION
EXPECTED WITH UPCOMING MODEL CYCLES.
...NEXT EMBEDDED SHORTWAVE IN GULF OF AK GYRE, CLIPPING NW
MONDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC BLEND
CONFIDENCE: AVERAGE
THE NEXT PACIFIC SHORTWAVE WITHIN THE PARADE ALONG THE SOUTHERN
EDGE OF THE ALASKAN GYRE, WILL PRESS EASTWARD BY SUNDAY. THE
UNCERTAINTY HERE, IS HOW MUCH OF THE INITIAL SHORTWAVE WILL BE
SHED INTO THE ZONE FLOW BEFORE THE WAVE DEEPENS SUNDAY OUT WEST OF
140W. THE GFS/NAM BEING FASTER, SHED MORE BEFORE THE WAVE BUCKLES
THE FLOW (SEE LAST PARAGRAPH OF SECTION ABOVE), RELATIVE TO THE
SLOWER ECMWF. IN RETAINING MORE ENERGY, THIS ALLOWS FOR THE ECMWF
TO BE STRONGER AND THEREFORE DOMINATE THE BINARY INTERACTION WITH
THE LARGER SCALE GYRE...AND SHIFT IT EASTWARD TO THE PACIFIC COAST
LATE MONDAY INTO TUESDAY. WHILE THE GFS/NAM BEING A BIT WEAKER,
RELATIVE TO THE EC LIFTS NORTHWARD TOWARD THE CENTER OF THE GYRE
AND THEREFORE SLOWS RELATIVE TO PRIOR RUNS, WITH BARELY AND QPF
REACHING THE WEST COAST BY THE END OF THE FORECAST PERIOD. THE
00Z UKMET, TYPICAL OF ITS BIAS, WHILE FAST, IS ALSO STRONG IN ITS
EVOLUTION AND SPLITS THE DIFFERENCE, BETWEEN THE ECWMF AND
NAM/GFS. THE CMC REMAINS OUT OF PHASE, WELL EAST OF THE ENSEMBLE
SOLUTIONS AND WITH DOWNSTREAM ISSUES ELSEWHERE THAT ARE IMPORTANT
TO THIS SYSTEM'S EVOLUTION...IT IS DISCARDED. SO A NON-CMC BLEND
IS SUPPORTED AND WITH MILDER SPREAD, CONFIDENCE IS AVERAGE.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
GALLINA
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