689
FXUS10 KWNH 251643
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1242 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 AND 00Z UKMET/ECMWF BLEND THEREAFTER
CONFIDENCE: SLIGHTLY ABOVE AVERAGE UNTIL 28.00Z
AVERAGE TO SLIGHTLY BELOW AVERAGE THEREAFTER
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 AND 00Z ECMWF BLEND THEREAFTER
CONFIDENCE: SLIGHTLY ABOVE TO ABOVE AVERAGE
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: 12Z GFS(1/3RD)/00Z ECMWF (2/3RD)
CONFIDENCE: AVERAGE
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 NAM/00Z ECMWF BLEND
CONFIDENCE: AVERAGE
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
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