769
FXUS10 KWNH 030637
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
237 AM EDT FRI APR 03 2020
VALID APR 03/0000 UTC THRU APR 06/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..WESTERN ATLANTIC CLOSED LOW AND OFFSHORE SURFACE LOW
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND AFTER 04.00Z
CONFIDENCE: ABOVE AVERAGE
07Z UPDATE: A SMALL ADJUSTMENT TOWARD A DEEPER, EASTWARD SOLUTION
OF THE 00Z UKMET/CMC BRING THEM VERY CLOSE TO THE 00Z ECMWF AND
JUST A TAD WEAKER/SLOWER THAN THE GFS. THIS LEAVES THE NAM AS THE
CLEAR OUTLIER AND THEREFORE A NON-NAM BLEND IS PREFERRED AT ABOVE
AVERAGE CONFIDENCE.
---PRIOR DISCUSSION---
LARGE NW ATLANTIC CLOSED LOW HAS ONE STRONGER DEEP STACKED LOW
WITH SURFACE CENTER EAST OF CAPE COD CURRENTLY, WHILE AN
UNDERCUTTING SHORTWAVE CURRENTLY IS EXITING THE MID-ATLANTIC COAST
PER GOES-WV SUITE. THE BINARY INTERACTION WILL CONTINUE TO BE
DOMINATED BY THE DEEPER CYCLONE THAT WILL RETROGRADE TOWARD THE
CAPE BY EARLY THIS MORNING, BEFORE DRIFTING SOUTHEAST TOWARD
BERMUDA BY LATE SAT/SUNDAY. THE SPREAD HERE WILL BE MAINLY
OFFSHORE BY THE TIME IT REACHES BERMUDA, WITH THE 00Z NAM AND
LESSER SO THE 12Z UKMET FOLLOWED BY THE CMC FAVORING GREATER
ELONGATION IN THE BINARY INTERACTION AND THEREFORE FURTHER
SOUTHWEST BY THE END OF THE FORECAST PERIOD. THE 00Z GFS, 12Z
ECMWF AND THE BULK OF THE ENSEMBLE SUITE ARE A TAD
STRONGER/STACKED AND CYCLONICALLY ROTATE EASTWARD EARLIER (NORTH
OF BERMUDA). SO WILL FAVOR A GENERAL MODEL BLEND THROUGH 24HRS
BUT SHIFTING MORE GFS/ECMWF HEAVY THEREAFTER AT SLIGHTLY ABOVE
AVERAGE CONFIDENCE.
...NORTHERN ROCKIES/W CANADA GYRE BREAKING DOWN AND SLIDING
THROUGH NORTHERN PLAINS FRI/SAT INTO GREAT LAKES/NORTHEAST BY
MON...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-GFS BLEND AFTER 05.12Z
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
07Z UPDATE: A SIGNIFICANT ADJUSTMENT TO THE 00Z UKMET BRINGS ITS
EVOLUTION IN LINE WITH THE REST OF THE GUIDANCE AND IS VERY CLOSE
TO THE NON-GFS SOLUTION AFTER 05.12Z...SO A GENERAL MODEL BLEND
CAN BE AFFORDED THROUGH 05.12Z MOVING TOWARD NON-GFS THEREAFTER.
CONFIDENCE IS INCREASED SLIGHTLY TO SLIGHTLY ABOVE AVERAGE
THROUGHOUT THE FORECAST PERIOD.
---PRIOR DISCUSSION---
VERY ANOMALOUS LARGE SCALE GYRE SET UP OVER NORTHERN ALBERTA HAS
AN ELONGATED EXTENSION/TROF CROSSING OUT OF THE NORTHERN HIGH
PLAINS ACROSS ACROSS THE NORTHERN PLAINS TODAY. A SECONDARY
INTERNAL SHORTWAVE WILL FOLLOW LATE SAT INTO SUN. THE OVERALL
GYRE WILL CONTINUE TO BREAKDOWN AND THESE SHORTWAVES WILL SHEAR
UNDER THE STRONG CLOSED ANTICYCLONE OVER NUNAVUT, WITH THE
SECONDARY WAVE ACCELERATING ACROSS THE NORTHERN GREAT LAKES
CLIPPING INTERIOR NEW ENGLAND LATE SUNDAY INTO MONDAY. THE UKMET
BECOMES AN SIGNIFICANT OUTLIER WITHIN THE SUITE BY SAT, WITH A
WEAKER/FASTER LEADING WAVE SLIDING UP INTO BOREAL CANADA, ALLOWING
FOR A STRONGER MORE AMPLIFIED SECONDARY WAVE. THIS IS NOT LIKELY.
THE REMAINING UNCERTAINTY IN THE GUIDANCE WILL BE THE STRENGTH OF
THE DEVELOPING CLOSED LOW/REX BLOCK ACROSS NUNAVUT/ONTARIO AND THE
AMPLITUDE OF THE WAVE INTO THE NORTHEAST. HERE THE 00Z GFS IS
FASTER TOWARD THE CLOSED LOW OVER N MANITOBA AND MORE CONCENTRIC
HAVING LESS INFLUENCE ON THE UNDERCUTTING WAVE...SO THAT WAVE
REMAINS WELL SOUTH SUPPORTING A SURFACE LOW NEAR THE ROOFTOP OF
MAINE BY EARLY MONDAY. THE 12Z ECMWF IS A BIT WEAKER THROUGH THE
ENTIRE LENGTH OF THE WAVE, PERHAPS TOO MUCH, WHILE THE 00Z NAM AND
12Z CMC ARE CENTRAL IN THE OVERALL ENSEMBLE SUITE AS A NICE
COMPROMISE WHILE DEPICTING SENSIBLE EVOLUTION. SO WILL SUPPORT A
NON-UKMET BLEND WITH REDUCING INFLUENCE OF THE GFS PARTICULARLY
AFTER 05.12Z. CONFIDENCE IS SOLID THOUGH THE PATTERN MAY BE LESS
PREDICTABLE IN VORTEX BREAKDOWN STAGES; SO IT IS SLIGHTLY ABOVE
AVERAGE BECOMING AVERAGE BY MONDAY.
..SOUTHERN PLAINS/LOWER MS VALLEY --- SUBTROPICAL STREAM
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM AFTER 05.00Z
CONFIDENCE: SLIGHTLY BELOW AVERAGE
07Z UPDATE: THE 00Z ECMWF BACKED OFF THE MORE AMPLIFIED
SUBTROPICAL STREAM SHORTWAVE, FLATTENING TOWARD THE INITIAL
PREFERENCE. IT STILL REMAINS SLIGHTLY SLOWER IN EVOLUTION THAN
THE FASTER GFS, BUT THE 00Z UKMET/CMC SPLITTING THE DIFFERENCE
(PERHAPS A TAD CLOSER TO THE GFS) A NON-NAM BLEND IS NOW PREFERRED
AFTER 05.00Z, WHEN THE NAM MOVES OUT OF PHASE, STILL THE
IMPORTANCE OF MESOSCALE BOUNDARIES, MOISTURE RETURN AND
CLEARING/CLOUD COVER FOR INSTABILITY DEVELOPMENT; STILL PROVIDE
AMPLE UNCERTAINTY AND REDUCED CONFIDENCE IN THE BLEND COMING TO
FRUITION, AND REMAINS SLIGHTLY BELOW AVERAGE IN CONFIDENCE.
---PRIOR DISCUSSION---
SIGNIFICANT MOISTURE/INSTABILITY RETURN ACROSS THE SOUTHERN PLAINS
MAY PRESENT THE POTENTIAL FOR HEAVY RAINFALL/FLASH FLOODING
CONDITIONS THROUGH THE WEEKEND. THIS WILL BE DRIVEN MAINLY BY
MESOSCALE FORCING/WEAK BOUNDARIES FOR A DIFFICULT MASS FIELD
PREFERENCE. STILL, A VERY ACTIVE/STRONG SUBTROPICAL JET WILL
EXIST AND SLIDE THROUGH NORTHERN OLD MEXICO INTO TEXAS AND THE
LOWER MS VALLEY THROUGH THE FORECAST PERIOD. THE COLD FRONT
CURRENTLY DROPPING SOUTH OF THE RED RIVER WILL CONTINUE TO
PROGRESS TOWARD THE COAST, BUT WITH SIGNIFICANT UNCERTAINTY IN THE
POSITION OF THE BOUNDARY DUE TO THE UNKNOWN DEPTH OF THE COLD AIR
(IE SLOPE OF THE FRONTAL ZONE ACROSS TX). THIS IS CRITICALLY
IMPORTANT ON DAY 2 AND EVEN MORE SO ON DAY 3.
THE MAIN MASS FIELD "CERTAINTIES" AND INFLUENCES ARE UPSTREAM IN
CA (SEE SECTION BELOW). THE 00Z NAM IS QUITE STRONG AND SOUTH
WITH THIS FEATURE AND PUMPS THE DOWNSTREAM RIDGE ACROSS THIS AREA;
AS IT IS UNFAVORED ACROSS THE WEST, THE NAM WILL BE INCREASINGLY
LESS PREFERRED BY THE END OF DAY 2 INTO DAY 3 ACROSS THE SOUTHERN
PLAINS. THE OTHER DIFFERENCES, NOTED WAS THE SLOWER BUT ALSO MORE
AMPLIFIED SUBTROPICAL WAVE IN THE 00Z ECMWF; THIS WAVE HELPS TO
BACK LOW LEVEL FLOW THROUGH THE RIO GRANDE VALLEY INCREASING
MOISTURE FLUX OFF THE WESTERN GULF, WHILE THE OVERALL PATTERN
SHOULD SUPPORT BETTER SOUTHERLY FLOW (THAN SOUTHEASTERLY), THE GFS
WHILE SHOWING SOME TYPICAL DAY 3 SPEED(FAST) BIAS, IS PAIRED WITH
THE UKMET AND CMC AS WELL AS GEFS TO HAVE SOME CONFIDENCE TOWARD
THIS EVOLUTION UNFOLDING OVER THE 00Z ECMWF. WHILE CONFIDENCE IS
ALWAYS POOR WITH THE POSITION OF SUBTROPICAL SHORTWAVES AND
SUBTROPICAL JET ORIENTATION, A 00Z GFS AND 12Z UKMET/CMC BLEND IS
PREFERRED BY DAY 3 AT SLIGHTLY BELOW AVERAGE CONFIDENCE.
...PAIR OF SHORTWAVES ALONG WEST COAST BECOMING DOMINANT CLOSED
LOW SUN/MON...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND FOR INITIAL SHORTWAVE
00Z GFS/ECMWF BLEND OVERALL
CONFIDENCE: AVERAGE
07Z UPDATE: LITTLE CHANGE IN THE PREFERENCE WITH THE ECMWF
SHIFTING A BIT SOUTH OF THE 12Z RUN, BUT STILL QUITE ALIGNED WITH
THE GFS (IF PERHAPS A TAD SLOWER AND A TAD STRONGER). THE 00Z
UKMET/CMC BOTH SHOW VERY STRONG AGREEMENT IN PLACEMENT WITH THE
00Z NAM THOUGH STILL NOT AS STRONG, THEY ARE TRENDING DEEPER...AND
AWAY FROM THE PREFERRED SOLUTIONS. THIS BRINGS A BIT OF
UNCERTAINTY BACK INTO THE PREFERENCE GIVEN BETTER ALIGNMENT
OVERALL INTO TWO CLUSTERS OF EVOLUTION, SO CONFIDENCE IS AVERAGE
IN A 00Z GFS/ECMWF BLEND ESPECIALLY AS THE 00Z GEFS SHOWS SOME
TRENDS TOWARD THE DEEPER SOLUTIONS TOO.
---PRIOR DISCUSSION---
A COMPACT CLOSED LOW CURRENTLY SIT ATOP OF THE LARGER SCALE
PACIFIC RIDGING ACROSS THE S GULF OF AK CURRENTLY, THIS WAVE IS
EXPECTED TO DROP SOUTH ON THE BACKSIDE OF THE DEEP
CANADIAN/NORTHERN ROCKIES GYRE REACHING THE NORTHERN CA COAST SAT.
UPSTREAM JET ENERGY WILL SUPPORT A DEVELOPING SHORTWAVE QUICK ON
ITS HEELS THAT WILL DIG/AMPLIFY ALONG THE BC COAST AT THE SAME
TIME. MODELS ARE IN SOLID AGREEMENT ON THE LEAD WAVE AS IT STALLS
UNDER THE UPSTREAM DEVELOPMENT AND EVENTUALLY SWINGS EASTWARD
THROUGH THE NORTHERN GREAT BASIN/SNAKE RIVER PLAIN BY SUNDAY,
RAPIDLY WEAKENING. PERHAPS THE 00Z NAM IS A BIT STRONGER AND
FASTER (ALONG WITH A WEAKER BUT FAST GFS) BUT IS SMALL TO HAVE
HIGHER THAN NORMAL CONFIDENCE IN A GENERAL MODEL BLEND FOR THIS
FEATURE.
HOWEVER, AS THE WAVE WEAKENS AND SLIDES EAST-NORTHEAST; IT LEAVING
THE PACIFIC MOISTURE STREAM DIRECTED ACROSS THE NORTHERN/CENTRAL
CA COAST AHEAD OF THE SECONDARY WAVE. HERE THE 00Z NAM IS A CLEAR
OUTLIER BEING A BIT STRONGER AND FURTHER WEST (HAVING LESS OF AN
INNER CORE, LESS CYCLONIC SHEAR, MORE SPEED SHEAR). THE 12Z
UKMET BECOMES A BIT UNRULY AS AN UPSCALE FEEDBACK RAPIDLY TIGHTENS
AND DEEPENS THE CORE OF THE DEVELOPING/EXPANDING CLOSED LOW OFF
THE CENTRAL CA COAST...A NEGATIVE BIAS WHEN IT MANIFESTS WITH THIS
MODEL. THE 00Z GFS REMAINS SOLID AGREEMENT WITH THE 12Z
ECMWF/ECENS MEAN AND 18Z GEFS SOLUTIONS...GIVEN THIS TIGHTNESS OF
AGREEMENT/CONTINUITY WILL FAVOR THEM HEAVILY. THE 12Z CMC SEEMS
OK WITHIN THIS BLEND IF A TAD WEAKER/SOUTH, BUT WOULD BE VIABLE IF
DESIRED IN A BLEND. CONFIDENCE IS SLIGHTLY ABOVE AVERAGE IN A
GFS/ECMWF BLEND.
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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