985
FXUS10 KWNH 231632
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1132 AM EST SUN FEB 23 2020
VALID FEB 23/1200 UTC THRU FEB 27/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING FINAL PREFERENCES AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...MID LEVEL SHORTWAVE AND ATTENDANT FRONT CLIPPING THE GREAT
LAKES/NORTHERN ME SUN/MON...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THE DIFFERENCES WITH THIS WAVE STILL REMAIN MAINLY NORTH OF THE
BOARDER RELATED TO PRECISE DEPTH OF THE SHORTWAVE, BUT THE TIMING,
PLACEMENT OF THE CLIPPING FRONTAL ZONE THROUGH THE GREAT LAKES
INTO THE NORTHERN NORTHEAST. THE 12Z NAM/GFS ARE A TAD STRONGER,
BUT THIS DOES NOT SEEM TO AFFECT THE CONUS SUBSTANTIALLY, SO A
GENERAL MODEL BLEND CAN BE SUPPORTED AT ABOVE AVERAGE CONFIDENCE.
...SOUTHWEST CLOSED LOW INTERACTION WITH AMPLIFYING NORTHERN
STREAM WAVE ACROSS PLAINS/GREAT LAKES MON/TUESDAY...ASSOCIATED
SURFACE LOW CROSSING NM TO OHIO VALLEY/GREAT LAKES TUES/WED,
DEVELOPING COASTAL LOW WED NIGHT....
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: THROUGH 26.00Z - 12Z GFS/NAM/06Z GEFS AND 00Z
ECWMF/ECENS BLEND
AFTER 26.00Z - 06Z GEFS/00Z ECENS MEAN BLEND WITH SOME 12Z
NAM/00Z ECMWF
CONFIDENCE: AVERAGE TO SLIGHTLY ABOVE AVERAGE THROUGH 26.00Z
AVERAGE TO SLIGHTLY BELOW AVERAGE AFTER
A COMPLEX EVOLUTION WILL OCCUR FROM THREE MAIN FEATURES ACROSS THE
CENTRAL PLAINS INTO THE GREAT LAKES EARLY IN THE WEEK. CURRENTLY,
A SOUTHERN STREAM SHORTWAVE/CLOSED LOW IS TRACKING ALONG THE CO/NM
BORDER SUPPORTING SURFACE CYCLOGENESIS IN THE HIGH SOUTHERN PLAINS
OF THE OK/TX PANHANDLES, THIS SURFACE CYCLONE WILL TRACK
PROGRESSIVELY THROUGH THE OZARKS TO THE LOWER OHIO VALLEY BY EARLY
TUESDAY WITH VERY LITTLE MODEL DIFFERENCE AS THE MID-LEVEL WAVE
WEAKENS. SIMILARLY, A STRONG/COMPACT STACKED CLOSED LOW AND
SURFACE CYCLONE IN VANCOUVER ISLAND WILL PROGRESS THROUGH THE
NORTHERN ROCKIES WITH INCREASED MODEL AGREEMENT THROUGH ABOUT
25.00Z.
AS THE JET STREAK ROUNDS THE BEND OF THIS NORTHERN STREAM AND
SUPPORTS DIFFLUENT FLOW ALOFT OF THE WEAKENING SOUTHERN STREAM
WAVE, THE TIMING/ORIENTATION DIFFERENCES THAT ARE RELATIVELY SMALL
LEAD TO LARGE MODEL EVOLUTION VARIATION THEREAFTER IN THE BINARY
INTERACTION BETWEEN THE SYSTEMS. THE 12Z NAM/GFS CONTINUE TO BE
MORE AGGRESSIVE AND STRONGER INITIALLY WHICH LEADS TO LEADING EDGE
OF THE NORTHERN STREAM SHORTWAVE TO SNAP THROUGH THE LOWER MO
VALLEY AND DRAW MOISTURE/ENERGY BACK ACROSS THE OHIO VALLEY/GREAT
LAKES AND SUPPORT SURFACE CYCLOGENESIS NEAR CHICAGOLAND/SOUTHERN
LAKE MICHIGAN BY LATE TUESDAY. THE 12Z NAM AND LESSER SO THE 12Z
GFS BOTH TRENDED A BIT SLOWER AND WEAKER TOWARD THE 06Z GEFS/00Z
ECENS MEAN SOLUTIONS THAT HAVE BEEN AND CONTINUE TO BE VERY MIDDLE
GROUND AND FAIRLY CONSISTENT OVER THE LAST 3-4 CYCLES, BUILDING A
PREFERENCE AND CONFIDENCE. THIS WHILE THE 00Z ECMWF IS A TAD SLOW
BUT ALSO MUCH WEAKER WITH THE INNER CORE OF THE DEVELOPING CLOSED
LOW. THE UKMET CONTINUES TO BE WELL SOUTH OF THIS SOLUTION WITH
NEARLY ZERO BINARY INTERACTION, AND STANDS OUT AS A CLEAR OUTLIER
AT THIS TIME. THE 00Z CMC IS BETTER OVERALL, BUT REMAINS SLOW AND
WEST OVERALL...ALSO STICKING OUT, EVEN PRIOR TO 60HRS (26.00Z).
SO THROUGH 26.00Z A NAM/GFS/ECMWF BLEND ANCHORED BY THE 06Z
GEFS/00Z ECENS IS PREFERRED AT AVERAGE TO SLIGHTLY ABOVE AVERAGE
CONFIDENCE.
---DAY 3 GREAT LAKES--
COMPLEXITY/INCREASED UNCERTAINTY WILL ONCE AGAIN BE INJECTED TO
THE DEVELOPING SYSTEM, AS IT MATURES ON WED, BASED ON
TIMING/PLACEMENT OF DRAWING ARCTIC STREAM SHORTWAVE ENERGY THROUGH
THE WESTERN GREAT LAKES ON DAY 3. AS USUAL, THE 12Z GFS FOLLOWED
BY THE NAM, ARE FASTER, BOTH IN TYPICAL SPEED BIAS BUT ALSO
BECAUSE THEY ARE A BIT STRONGER OVERALL RELATIVE TO THE GEFS/ECENS
AND ECMWF SOLUTIONS PULLING THE ENERGY SOUTH. THIS LEADS TO THE
GFS SHIFTING THE DEFORMATION ZONE MUCH FURTHER NORTH AND AWAY FROM
GREATER CONSENSUS AND CONTINUITY BUT ALSO IN LINE WITH TYPICAL
NEGATIVE BIAS. THE NAM SEEMS A BETTER COMPROMISE BUT MAY BE A TAD
TOO FAST LIFTING THE INITIAL COMBINED WAVE THROUGH THE GREAT LAKES
TOO FAST GIVEN IT IS ALSO MUCH STRONGER WITHIN THE MEAN FLOW,
WHICH IS COUNTER INTUITIVE. ONCE AGAIN, THE 06Z GEFS ANCHORS A
MORE CENTRAL/CONSISTENT SOLUTION ADDED BY THE ECENS MEAN. SO WILL
BE FAVORING THE GEFS OVER THE GFS ON DAY 3 IN THE PREFERENCE BUT
CONFIDENCE REDUCED TO AVERAGE TO SLIGHTLY BELOW AVERAGE IN A
GEFS/NAM/ECMWF/ECENS MEAN BLEND.
---DAY 3 MID-ATLANTIC---
THROUGH THE SOUTHEAST/MID-ATLANTIC, THE MOISTURE STREAM/TIMING OF
THE INITIAL COLD FRONT IS QUITE AGREEABLE, BUT THE CMC/UKMET FALL
OUT OF PREFERENCE BY 26.00Z HERE AS WELL. AS THE UPSTREAM ENERGY
OF THE NORTHERN STREAM WAVE SWINGS THROUGH THE BASE OF THE
EXPANDING EASTERN TROF WED, A SURFACE COASTAL LOW WILL DEVELOP
IN/NEAR THE DELMARVA. HERE, THE NAM SHOWS SOME TYPICAL DAY 3
STRONGER SOLUTION, BUT IS NOT TOO BAD. THE GFS IS MUCH TOO FAST
AND NORTH DUE TO INTERACTION DESCRIBED ABOVE ON DAY 3...BUT THE
GEFS IS A GREAT REPLACEMENT...SO BY DAY 3 IN THE MID-ATLANTIC A
SIMILAR 06Z GEFS/00Z ECENS BLEND WITH INCLUSION OF THE 12Z NAM AND
00Z ECWMF IS PREFERRED.
...MID-LEVEL SHORTWAVE TROUGH/SURFACE COLD FRONT CLIPPING THE
PACIFIC NORTHWEST ON TUESDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
IN THE WAKE OF THE DOMINANT/COMPACT CLOSED LOW ENTERING SOUTHERN
BC TODAY, ENHANCED RIDGING WILL BUILD OVER THE PACIFIC COAST.
HOWEVER, THE PACIFIC TRAIN CONTINUES TO SHIFT SHORTWAVE THROUGH
THE SOUTHERN GULF OF AK, WITH A STRONG LEAD WAVE LATE TUESDAY.
WHILE THE WAVE WILL BE FURTHER NORTH, THE TRAILING FRONTAL ZONE
AND MOISTURE TRANSPORT WILL CLIP THE PACIFIC NORTHWEST LATE
TUESDAY INTO WED. WHILE THE SPREAD IS MODERATE FURTHER NORTH, THE
TRAILING EDGE IS QUITE AGREEABLE WITH PERHAPS THE 00Z UKMET A TAD
FURTHER SOUTH, BUT THAT IS FAIRLY MINOR BEFORE THE SURFACE HIGH
PRESSURE BUILDS IN LATE WED INTO THURSDAY. SO A GENERAL MODEL
BLEND CAN BE PREFERRED 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
GALLINA
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