884
FXUS10 KWNH 251846
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
244 PM EDT SAT APR 25 2020
VALID APR 25/1200 UTC THRU APR 29/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
SHORTWAVE AND ASSOCIATED DEVELOPING LOW PRESSURE MOVING FROM THE
MIDWEST THROUGH THE NORTHEAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC BLEND UNTIL 28.00Z
12Z GFS/UKMET/ECMWF BLEND THEREAFTER
CONFIDENCE: SLIGHTLY ABOVE AVERAGE UNTIL 28.00Z
AVERAGE TO SLIGHTLY BELOW AVERAGE THEREAFTER
19Z UPDATE: THE 12Z CMC SHIFTED NORTH, BEING A BIT STRONGER...BUT
REMAINS ON THE SOUTHERN PERIPHERY OF THE SURFACE LOW CLUSTER; SO
IT BUILDS FURTHER CONFIDENCE TOWARD THE REMAINING CLUSTER.
HOWEVER, AFTER 60HRS, THE SOUTHERN STREAM, LIKE THE 00Z UKMET
BECOMES VERY STRONG/COMPACT WITH THE DIGGING REPLACEMENT
SHORTWAVE. THE 12Z UKMET BACKED OFF THIS EVOLUTION A BIT AND IS
SIMILAR (IF EQUALLY QUICK) AS THE 12Z GFS. THE 12Z GEFS WOULD
SUGGEST THE OPERATIONAL IS A TAD TO AGGRESSIVE; ESPECIALLY AS THE
12Z ECMWF IS SLOWER/WEAKER AND THEREFORE NORTH WITH THE AXIS OF
DEVELOPMENT. EVEN THOUGH THERE REMAINS MODERATE SPREAD DUE TO
MULTIPLE WAVE INTERACTIONS AFTER 60HRS; A 12Z GFS/UKMET/ECMWF
BLEND REMAINS PREFERRED AT AVERAGE TO SLIGHTLY BELOW AVERAGE
CONFIDENCE.
---PRIOR DISCUSSION---
STACKED CYCLONE MOVING ALONG THE OHIO RIVER TODAY AND WEAKENS IN
FAVOR OF A COASTAL LOW THAT MOVES THROUGH THE HUDSON CANYON FROM
THE DE COAST SOUTH OF LONG ISLAND BEFORE PARKING NEAR CAPE COD
TUES. THE TRANSITION IS FAIRLY SOLID IN THE GUIDANCE, WITH THE
EXCEPTION OF THE CMC WHICH IS A TAD WEAKER AND THEREFORE TRACKS
WELL SOUTH OF THE TIGHT CLUSTER. SO A NON-CMC BLEND IS SUPPORTED
UNTIL 60HRS (28.00Z). WHILE THE 12Z GFS CONTINUES TO DEPICT
GREATER LATENT HEAT RELEASE DUE TO CONVECTION ALONG THE
DEFORMATION ZONE ACROSS NE PA/S NY AS IT SHARPENS MONDAY MORNING;
THE TEMPS ARE NOT AS WARM AND MORE IN TOLERANCE TO KEEP IN THE
BLEND, BUT WOULD CONTINUE TO FAVOR THE ECMWF WITH PROFILES OVER
THE GFS WHEN DIGGING DOWN TO P-TYPE INFLUENCES, ETC.
AFTERWARD, AS THE DEEPER CYCLONE IS REINFORCED BY UPSTREAM
SHORTWAVE ENERGY, THE MODEL SPREAD INCREASES DUE TO DIFFERENCES IN
TIMING AND MAGNITUDES OF INTERACTION. THE 12Z NAM MOVES OUT OF
PREFERENCE FIRST GIVEN A STRONGER/MORE CONCENTRIC ORGANIZATION
THAT SHIFTS THE SURFACE CYCLONE TRACK NORTH OF THE ENSEMBLE SUITE.
BY THE END OF THE FORECAST PERIOD, THERE ARE SOME TYPICAL BIASES
STARTING TO MANIFEST WITH THE FASTER 12Z GFS (EVEN RELATIVE TO THE
06Z GEFS SUITE), SLOWER TO WEAKEN THE OCCLUSION WITH THE ECMWF AND
THE UKMET HAVING A STRONGER, NEGATIVE TILT AS IT WEAKENS THE
LARGER SCALE CLOSED LOW OVER NEW YORK/SE CANADA RELATIVE TO THE
OTHER GUIDANCE. THESE ARE SMALL BUT IMPORTANT DETAILS THAT WILL
NEED TO BE DETERMINED IN FUTURE RUNS; BUT FOR NOW A 12Z GFS AND
00Z UKMET/ECMWF BLEND SHOULD BE SOLID AFTER 60HRS AT AVERAGE TO
SLIGHTLY BELOW AVERAGE CONFIDENCE.
TROUGH AXIS AFFECTING THE NORTHWEST INTO THE UPPER MIDWEST/GREAT
LAKES THROUGH MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH 27.12Z
12Z NAM/GFS/ECMWF BLEND THEREAFTER
CONFIDENCE: ABOVE AVERAGE
19Z UPDATE: WITH MORE PREFERABLE EVOLUTION DOWNSTREAM, THE 12Z
UKMET AND CMC BOTH TRENDED BETTER WITH THE BASE SHORTWAVE
UNDER-CUTTING THE BLOCK RIDGE AND SLIDING THROUGH THE GREAT LAKES
BY THE END OF DAY 3. STILL, BOTH ARE GENERALLY MUCH WEAKER WITH
THE UKMET FAST AND THE CMC SLOW. OVERALL, A GENERAL MODEL BLEND
WOULD LIKELY SUFFICE, BUT FOR A STRONGER BLEND...WILL KEEP WITH
INITIAL PREFERENCE OF 12Z NAM/GFS/ECMWF BLEND AFTER 27.12Z; BUT
INCREASE CONFIDENCE TO ABOVE AVERAGE
---PRIOR DISCUSSION---
SHORTWAVE CURRENTLY ENTERING SOUTHWEST BC WILL TRANSLATE ACROSS
SOUTHERN CANADA UNDER SOLID MODEL AGREEMENT THROUGH 48 HOURS AS IT
CLIPS THE NORTHERN TIER OF THE US NORTHERN PLAINS. DOWNSTREAM
BLOCKING RIDGE ACROSS LAKE SUPERIOR WILL LEAD TO A BIFURCATION OF
THE UPPER LEVEL TROF, WHILE THE BULK OF THE ENERGY WILL LIFT
NORTH, THE TRAILING TAIL-END OF THE TROF WILL MOVE UNDER THE RIDGE
AND SHEAR INTO THE CONFLUENT REGION OF THE LARGER SCALE BROAD
CYCLONIC WEAKNESS OVER SE ONTARIO/LOWER LAKES. MUCH OF THE MODEL
DIFFERENCE/SPREAD WITH THIS EVOLUTION IS REALLY RELATED TO THE
BREAKDOWN OF THE DOWNSTREAM CYCLONE. THE UKMET (AS STATED IN THE
SECTION ABOVE) IS QUICK TO WEAKEN AND PRESS THE CYCLONE OUT,
ALLOWING FOR A FASTER EASTWARD TRANSLATION AND HELPS TO
KICK/ENHANCE THE SHORTWAVE IN THE MARITIME. THE CMC IS ON THE
OTHER SIDE IS MUCH STRONGER AND DOMINATES/SHEARS OUT THE ENERGY.
THE 12Z NAM/GFS AND ECMWF ARE ALL MORE CENTRAL AND WHILE THERE ARE
SOME DIFFERENCES, THEY REMAIN SMALL. AS SUCH A GENERAL MODEL
BLEND IS SUPPORTED THROUGH 48 HOURS (27.12Z) MOVING TOWARD A 12Z
NAM/GFS AND 00Z ECMWF BLEND AT SLIGHTLY ABOVE TO ABOVE AVERAGE
CONFIDENCE.
SHORTWAVE ENERGY AFFECTING THE PACIFIC NORTHWEST ON MONDAY INTO
THE PLAINS BY TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 1/3RD GFS; 2/3RD ECMWF BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
19Z UPDATE: THE 12Z UKMET STARTED TO REMOVE THE STRONG CONVECTIVE
FEEDBACK ACROSS THE NORTHERN PLAINS INTO THE UPPER MIDWEST, BUT IT
STILL REMAINS STRONGER AND FASTER WITH THIS FEATURE. THE 12Z
ECMWF TRENDED A BIT STRONGER WITH THIS SOUTHERN CLUSTER BUT MORE
IMPORTANTLY MOVED IT FASTER, LEADING TO GREATER SPACING BETWEEN IT
AND THE MAIN WAVE ENTERING THE NORTHERN PLAINS, THIS ALLOWS FOR A
BROADER (LESS SHARP) BROADENING OF THE LARGER TROF BY 84 HOUR,
WEAKENING THE SURFACE WAVE. THIS INCREASES SPACING WITH THE 12Z
GFS, WHICH DUG FASTER FURTHER SOUTH (THOUGH NOT AS DRAMATIC AS THE
12Z NAM). THE 12Z CMC, APPEARS TO BE A MIDDLE-GROUND SOLUTION
BETWEEN THE UKMET (CONVECTIVE UPSCALE) AND THE ECMWF, SLIGHTLY
SLOWER WITH THE MAIN WAVE. AS SUCH IT AMPLIFIES VERY DEEPLY BY
84HRS OVER S MN AND LOOKS DRAMATICALLY OUT OF PLACE IN DEPTH,
THOUGH SHOWS A SIMILAR PLACEMENT TO THE ECMWF. OVERALL, THIS
SPEAKS MORE TO THE UNCERTAINTY OF TIMING AND INTERACTION OF
INGREDIENTS (INSTABILITY AND MOISTURE) WITH THIS WAVE. THE 12Z
GEFS IS VERY CLOSE TO THE ECENS MEAN, AND BOTH SPLIT THE
DIFFERENCE BETWEEN THE GFS/ECMWF. SO WILL KEEP WITH INITIAL
PREFERENCE OF 1/3RD GFS AND 2/3RD ECMWF BUT REDUCE CONFIDENCE TO
SLIGHTLY BELOW AVERAGE (MAINLY AFTER 72HRS)
---PRIOR DISCUSSION---
THE GENERALLY ZONAL PATTERN OVER-TOPPING A STRONG RIDGE THAT
DOMINATES THE EASTERN PACIFIC INTO THE DESERT SOUTHWEST. THE NEXT
STRONG SHORTWAVE COMES ALONG WITH THE BULK OF ENERGY IN THE CORE
OF THE SYSTEM LIFTING NORTH TO BUILD THE LARGER GULF OF AK VORTEX.
THE TAIL END OF THE TROF AND ASSOCIATED COLD FRONT WILL TRACK
THROUGH SW CANADA CLIPPING THE PACIFIC NORTHWEST. THIS WAVE WILL
BE A BIT WEAKER/FLATTER HAVING LOST MOST OF THE ENERGY NORTH, BUT
WITH A STRONG ASSOCIATED JET IS PROGRESS QUICKLY AND FINDING
WEAKNESS IN THE WAKE OF THE PRIOR SYSTEM, BEGINS TO AMPLIFY/DIG
INTO THE NORTHERN PLAINS BY TUESDAY. THIS SYSTEM, LIKE MANY IN
THIS PATTERN BEFORE IT, BECAUSE OF THE STRONG RIDGE OVER THE WEST,
WILL DIG SHARPLY AND LOADED ON THE UPSTREAM SIDE OF THE TROF.
THE CMC AND UKMET HAVE DOWNSTREAM BLOCKING ISSUES THAT ARE ALREADY
LESS FAVORED AND THIS CONTINUES FOR THIS SYSTEM AFTER TRANSLATING
ACROSS THE NORTHERN US ROCKIES, TO THE POINT THE 00Z UKMET HAS A
SIGNIFICANT FEED-BACK ISSUE ACROSS THE NORTHERN PLAINS IN THE LATE
DAY 3. WHILE THIS CONVECTIVE COMPLEX IS LIKELY TO BE THERE, GIVEN
THE GFS/ECMWF AND THEIR ENSEMBLE SUITES, THE REFLECTION IN THE
UKMET IS TOO MUCH TO CONSIDER AS IT MESSES UP THE ENTIRE MASS
FIELDS. THE 12Z NAM IS A BIT BROADER CROSSING THE CANADIAN
ROCKIES, AND ATYPICAL AS IT IS, DOES NOT HAVE A STRONG
AMPLIFICATION...WHICH SEEMS A BIT LESS LIKELY GIVEN THE LONGER
TERM PATTERN. THE 12Z GFS IS A TAD FASTER THAN THE ECMWF TO THE
POINT THE GEFS IS CLOSER IN LINE TO THE ECMWF THAN THE GFS.
STILL, BOTH ARE SIMILAR IN EVOLUTION, AND WILL PREFER A 1/3 12Z
GFS AND 2/3RD ECMWF BLEND BY THE END OF DAY 3. CONFIDENCE IS
AVERAGE.
COLD FRONT REACHING PACIFIC NORTHWEST LATE TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GEFS/00Z ECENS MEAN
CONFIDENCE: BELOW AVERAGE
19Z UPDATE: THE EFFECTS OF MODEL DIFFERENCE IN THE GULF OF AK AND
THE TIMING OF THE MOISTURE ARRIVAL TO THE PACIFIC NORTHWEST MAY BE
MINOR; BUT SIZABLE MODEL SHIFTS INCREASED THE OVERALL
SPREAD/UNCERTAINTY FOR THE CLOSED LOW/SURFACE CENTER. THE
UKMET/CMC DIDN'T CHANGE TOO MUCH REMAINING SLOW, MORE ELONGATED
BETWEEN TWO SHORTWAVE CENTERS...BUT THE 12Z ECMWF TRENDED SLOWER
NEARLY MATCHING THE TRACK/TIMING OF THE UKMET/CMC. THIS IS AWAY
FROM THE CONSENSUS OF THE 00Z CMCE/ECENS AND THE 06/12Z GEFS. THE
CHANGES ALSO HIGHLIGHT A GLARING FAST/STRONG BIAS OF THE NAM AS
WELL AS IT APPROACHES THE WEST COAST LATE ON TUESDAY. TO KEEP
WITH CONTINUITY, WILL SUPPORT A 12Z GEFS/00Z ECENS MEAN SOLUTION
FOR THIS SETUP AND REDUCE CONFIDENCE TO BELOW AVERAGE
---PRIOR DISCUSSION---
AFTER A SLIGHT DELAY, THE PACIFIC PARADE OF SHORTWAVES CONTINUE
WITH A PAIR OF CLOSELY PACKED SHORTWAVE FEATURES; THE FIRST OF
WHICH APPROACHES TUESDAY. THE LEAD WAVE, IS DELAYED SLIGHTLY DUE
TO THE SPACING OF THE LATER...BUT THE GFS IS CLEARLY VERY FAST AND
WELL NORTH OF THE CLUSTER, PRESSING THE COLD FRONT AND PRECURSORY
MOISTURE FEED INTO THE PACIFIC NORTHWEST AT THE END OF THE
FORECAST PERIOD. THE 12Z NAM AND 00Z ECMWF ARE CENTRAL TO THE
ENSEMBLE SUITE WHILE THE UKMET AND CMC ARE SLOWER, SHOWING NO REAL
DISTINCTION BETWEEN WAVE PACKETS (IE NO SHORT-WAVE RIDGING
BETWEEN) BY THE END OF THE FORECAST PERIOD, WHICH DELAYS THE
FRONTAL ZONE. WILL FAVOR A 12Z NAM/00Z ECMWF BLEND FOR THIS
SYSTEM AT 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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page