091
FXUS10 KWNH 241829
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
128 PM EST SUN NOV 24 2019
VALID NOV 24/1200 UTC THRU NOV 28/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...MID-ATLANTIC/NORTHEAST SHORTWAVE(S) AND ASSOCIATED SURFACE
LOW...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
19Z UPDATE: NO SIGNIFICANT CHANGES WERE NOTED WITH THE LATE
ARRIVING MODELS, SO WILL CONTINUE WITH INITIAL
PREFERENCE/CONFIDENCE LEVELS.
---PRIOR DISCUSSION---
THE LAST VESTIGES OF THE NOR'EASTER ACROSS NEW ENGLAND OCCUR
THROUGH THE REST OF SUNDAY. THE CMC IS A BIT WEAKER INITIALLY,
BUT OVERALL ITS SLOWER DEVELOPMENT REACHES THE LEVEL OF THE OTHER
GUIDANCE WITHIN 3 TO 6 HOURS BY EARLY MONDAY, THAT IS NOT A MAJOR
DIFFERENCE. SO A GENERAL MODEL BLEND CAN BE SUPPORTED AT ABOVE
AVERAGE CONFIDENCE FOR ITS REMAINDER IN THE CONUS.
...SHORTWAVE RACING THROUGH CANADIAN ROCKIES SUNDAY BEFORE
SUPPORTING NORTHERN TIER SURFACE WAVE MONDAY AND SHEARING OUT
ALONG THE GREAT LAKES/SW QUEBEC BY TUES...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
19Z UPDATE: NO SIGNIFICANT CHANGES WERE NOTED WITH THE LATE
ARRIVING MODELS, SO WILL CONTINUE WITH INITIAL
PREFERENCE/CONFIDENCE LEVELS.
---PRIOR DISCUSSION---
GOES-W WV STARING TO SHOW THE AMPLIFICATION OF THE NORTHERN STREAM
SHORTWAVE OVER BC AT THIS TIME IN PREPARATION FOR CROSSING THE
CANADIAN ROCKIES. THE GUIDANCE SUITE HAS TIGHTENED OVER THE LAST
24HRS THOUGH THERE REMAINS A SMALL LATITUDE DIFFERENCE IN THE QPF
SWATH WITH THE NCEP GUIDANCE A BIT NORTH AND THE UKMET/CMC/ECMWF
SUITE A TAD SOUTH (ALONG/JUST SOUTH OF THE BORDER MON INTO EARLY
TUES). THIS IS FAIRLY MINOR AND IN LINE WITH TYPICAL BIASES...TO
SUPPORT AN EQUAL BLEND OF THE GUIDANCE TO SPLIT THE DIFFERENCE,
ESPECIALLY AS THE GUIDANCE REMAINS AGREEABLE THROUGH THE SHEARING
PHASE THROUGH THE GREAT LAKES INTO QUEBEC. CONFIDENCE IN A
GENERAL MODEL BLEND IS SLIGHTLY ABOVE AVERAGE.
...LEAD SHORTWAVE IN DEVELOPING GLOBAL-SCALE TROF IN FOUR CORNERS
BY 00Z TUESDAY...
...DEVELOPMENT OF STRONG/BROAD SURFACE LOW IN PLAINS TUESDAY AND
GREAT LAKES BY WED...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/ECMWF BLEND
CONFIDENCE: AVERAGE
19Z UPDATE: THE 12Z UKMET CONTINUED TO BE A BIT SLOWER THAN THE
REMAINING GUIDANCE, BUT ALSO ADDED A SOUTHWARD SHIFT WITH THIS
ITERATION. THE 12Z CMC TRENDED A BIT STRONGER AND THEREFORE
CLOSER TO THE INITIAL PREFERENCE/GREATER CLUSTERING BUT STILL
FALLS A BIT TOO FAR SOUTH, GIVEN CONTINUED STRONGER AGREEMENT
BETWEEN THE GFS AND THE 12Z ECMWF. SO ONLY CHANGE WAS TO ADD THE
12Z ECMWF IN PLACE OF THE 00Z RUN IN THE PREFERENCE.
---PRIOR DISCUSSION---
PATTERN CHANGING SHORTWAVE/JET SPEED MAX OVER-TOPPING THE CENTRAL
PACIFIC RIDGE IS EXPECTED TO DIVE SOUTHEAST INTO THE GREAT BASIN
BY 25.18Z. IN THE WEAK, BROAD CYCLONIC FLOW, THIS WAVE STARTS TO
BUCKLE THROUGH THE CENTRAL ROCKIES AND START TO SPIN UP A BROAD
SURFACE CYCLONE ACROSS THE CENTRAL HIGH PLAINS MONDAY INTO
TUESDAY. THE ECMWF IS A BIT SLOWER WITH THIS AND SHOWS A BIT
GREATER RIDGE AMPLIFICATION ACROSS THE ROCKIES INCREASING UPSLOPE
MOISTURE FLOW. WHILE THE 12Z GFS IS IN A TYPICALLY SLIGHTLY
FASTER TRANSITION MATCHING VERY CLOSELY THE CENTROID OF THE ECENS
AND GEFS MEANS. WHILE THE 12Z NAM IS IN FAIRLY GOOD AGREEMENT,
THERE IS GREATER DEPTH AND MORE CONCENTRIC APPEARANCE TO THE
DEVELOPING CLOSED LOW BY WED AND IS ABOUT 40-60DM DEEPER THAN THE
ECMWF/GFS. WHILE ON THE OPPOSITE SIDE, THE 00Z CMC IS VERY WEAK
AND THE SURFACE WAVE IS A BIT SOUTH INITIALLY. THE 00Z UKMET
WHILE ALSO FAIRLY AGREEABLE TO THE ECMWF, IS EVEN SLOWER WITH THE
WAVE MOVING OUT OF THE ROCKIES (ATYPICAL) BUT THEN RAPIDLY
ACCELERATES TO MATCH THE GFS BY THE END OF THE FORECAST PERIOD.
OVERALL, THERE IS GROWING CONFIDENCE WITH THE EVOLUTION OF THE
SYSTEM, BUT WITH IMPORTANCE OF TIMING AND ANGLE OF AMPLIFICATION
TO THE ORIENTATION OF THE TERRAIN IN THE ROCKIES, WILL UTILIZE THE
ENSEMBLE CENTROID AND SUGGEST A 12Z GFS/00Z ECMWF BLEND AS A BEST
REPRESENTATION, THOUGH CONFIDENCE IS AVERAGE IN THIS BLEND.
...STRONG SECONDARY SHORTWAVE SUPPORTING WITH VERY DEEP SURFACE
LOW NEAR N CA TUES, EXPANDING
ACROSS NORTHERN CA/N GREAT BASIN BY 00Z THURS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/UKMET AND ECMWF BLEND
CONFIDENCE: AVERAGE
19Z UPDATE: THE CMC SAW A MARKED IMPROVEMENT WITH THE EVOLUTION OF
THE VERY STRONG SHORTWAVE AND DEVELOPMENT OF THE CLOSED LOW BY
WED. SO THIS SAW A SOUTH AND WESTWARD SHIFT COMPARED TO THE 00Z
RUN; WHILE THIS IS CLOSER TO THE INITIAL PREFERENCE IT WAS STILL
WELL NORTH. HOWEVER, THE 12Z ECMWF TRENDED A BIT NORTH,
PARTICULARLY AT LANDFALL OF THE SURFACE CYCLONE, WHICH WAS TURNING
MORE WEST AND NORTH WITH STRONGER NORTHERN STREAM INFLUENCE/BINARY
INTERACTION INTO LATE WED. THE UKMET, SLOWED A BIT INITIALLY BUT
CONTINUES TO HAVE THE GREATEST CONTINUITY OVER THE LAST FEW DAYS
WITH THE VERY STRONG CYCLONE. IT IS PAIRED WELL WITH THE GFS TO
PROVIDE BETTER OVERALL AGREEMENT. THE 12Z GEFS ALSO MATCHES THE
OPERATIONAL CLOSE. THIS PLACES THE SLOWER AND SOUTHWARD NAM
FURTHER FROM CONSENSUS... SO FOR BEST BLEND THAT KEEPS THE
STRONGEST SIGNAL, THE PREFERENCE WILL BE A 12Z GFS/UKMET WITH SOME
BUT LOWER WEIGHTING TO THE 12Z ECMWF; WITH NO WEIGHTING TO THE NAM
OR CMC. CONFIDENCE IS INCREASING SLIGHTLY BUT STILL AVERAGE
OVERALL GIVEN THIS WOULD BE NEAR AN ALL-TIME PRESSURE RECORD FOR
NOVEMBER AT EUREKA, CA AND PERHAPS AN ALL-TIME (JANUARY 2010) LOW
SURFACE PRESSURE RECORD AS WELL.
---PRIOR DISCUSSION---
THE NEXT SHORTWAVE QUICK ON THE HEELS OF THE PRIOR, OVER-TOPS THE
CENTRAL PACIFIC RIDGE BY 00Z TUES. HOWEVER, BEING A BIT STRONGER,
IT TAMPS DOWN THE RIDGE, AND AS IT SLIDES SOUTHEAST ALONG THE
EASTERN PORTION OF THE RIDGE, A SMALL FRACTION OF NORTHERN STREAM
ENERGY AIDS IN A BROADER WAVE DEVELOPMENT EVENTUALLY TOWARD A
CLOSED LOW. THE CMC IS THE ONLY GUIDANCE, THAT SUGGESTS GREATER
INFLUENCE FROM THE NORTHERN STREAM WHICH LEADS TO IT BEING FURTHER
EAST AND WEAKER OVERALL BY THE END OF THE FORECAST PERIOD, AND IS
NOT PREFERRED IN THE PREFERENCE.
THE REMAINING GUIDANCE, ALL NOW SUPPORT A VERY STRONG/COMPACT
LEADING EDGE TO THE SHORTWAVE REACHING THE N CA COAST 00Z WED
(LATE TUESDAY), WITH A VIGOROUSLY DEEPENING SURFACE CYCLONE.
AFTER LANDFALL, THE UPPER LOW, BROADENS AND SLIDES SOUTH. THE
GREATEST AGREEMENT EXISTS WITH THE 12Z GFS/00Z ECMWF BUT THE 12Z
NAM AND 00Z UKMET ARE SOLID ENOUGH IN THE ENSEMBLE SUITE TO HAVE
GOOD AGREEMENT TO INCORPORATE INTO A PREFERRED BLEND. THE NAM IS
A BIT SLOW ON WED, THAT WOULD REDUCE/REMOVE THE WEIGHTING WITH
TIME ON DAY 3. WHILE THERE IS GOOD ALIGNMENT OF THE WAVE
DEVELOPMENT TO PROVIDE CONFIDENCE, ITS CURRENT LOCATION/SOURCE AND
INFLUENCES OF THE RIDGE AND NORTHERN STREAM STILL PROVIDE SOME
REDUCED ABSOLUTE CERTAINTY TO THIS BLEND. SO, WHILE THE
CONFIDENCE HAS IMPROVED SUBSTANTIALLY SINCE YESTERDAY, IT IS STILL
AVERAGE.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
GALLINA
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