627
FXUS10 KWNH 231830
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
129 PM EST SAT NOV 23 2019
VALID NOV 23/1200 UTC THRU NOV 27/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...PHASING NORTHERN/SOUTHERN SHORTWAVES ACROSS GREAT LAKES AND
ASSOCIATED WESTERN APPALACHIAN SURFACE LOW TRANSFERRING TO COASTAL
LOW BY SUNDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
19Z UPDATE: LATE ARRIVING 12Z GUIDANCE CONTINUES TO LOOK GOOD AND
ARE EVEN TIGHTER CLUSTERED TOWARD A COMMON SOLUTION THAN THE NAM
OR GFS. SO NO REAL CHANGE IN THINKING/PREFERENCES.
---PRIOR DISCUSSION---
THE PIECES ALL APPEAR TO BE ON THE BOARD, IE WITHIN THE RAOB
NETWORK, THAT DIFFERENT DATA ASSIMILATION SCHEMES APPEAR TO HAVE
RESOLVED DETAIL DIFFERENCES TO COME INTO A MUCH STRONGER CONSENSUS
IN THE DETERMINISTIC, AS WELL AS WITHIN THE ENSEMBLE SUITES. THE
TREND TOWARD A STRONGER, MORE WESTWARD TRACK HAS BECOME MUCH MORE
EVIDENT STARTING WITH THE 00Z SUITE. THIS SHOULD BRING HIGHER
MOISTURE WHILE DEEPENING ALLOWING FOR INCREASED WINTRY MIX THROUGH
THE NORTHERN MID-ATLANTIC INTO NEW ENGLAND. THE CONSENSUS BRINGS
HIGHER CONFIDENCE IN A GENERAL MODEL BLEND, BUT GIVEN THE DYNAMIC
DEEPENING/COOLING AND RATHER BROAD SHIFT WEST, CONFIDENCE IS NOT
ABSOLUTE. THE KEY ON DURATION, AND DEEPENING APPEARS TO BE THE
WELL UPSTREAM SHORTWAVE/JET SPEED MAX CROSSING SOUTHERN CANADA
INTO THE GREAT LAKES SATURDAY. THIS IS MUCH FASTER/SHARPER WITH
THE INTERACTION, WHICH MAY STILL NOT BE FULLY RESOLVED. STILL,
CONFIDENCE IS SLIGHTLY ABOVE AVERAGE GIVEN THE EVOLUTION PRESENTED
IN A GENERAL MODEL BLEND.
...SHORTWAVE RACING THROUGH CANADIAN ROCKIES SUNDAY BEFORE
SUPPORTING NORTHERN TIER SURFACE WAVE MON...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND
CONFIDENCE: AVERAGE
19Z UPDATE: VERY LITTLE VARIATION FROM THE 00Z RUNS WITH THIS
SYSTEM WERE NOTED IN THE ECMWF/CMC/UKMET AND 12Z GEFS. AS SUCH NO
CHANGE IN INITIAL PREFERENCE/CONFIDENCE.
---PRIOR DISCUSSION---
THE FAST PACIFIC FLOW CONTINUES TO PRESS THE PARADE OF LOW
AMPLITUDE SHORTWAVE/JET SPEED MAXIMA THROUGH SAT INTO EARLY
SUNDAY. THE LAST WILL HELP BREAK THE ZONAL FLOW PATTERN AS IT
AMPLIFIES ACROSS THE SOUTHERN PRAIRIES OF CANADA INTO THE NORTHERN
TIER BY EARLY MONDAY. THIS WILL SUPPORT A STRONG CLIPPER SYSTEM.
GIVEN THE FLAT/ZONAL FLOW, THERE IS EXPECTED SMALL TIMING
DIFFERENCES THAT LEAD TO LATITUDINAL DIFFERENCES AS IT AMPLIFIES.
THE IS MOST NOTED IN THE NAM AND GFS A BIT FURTHER NORTH THAN THE
CMC/ECMWF/UKMET. HOWEVER, THE NAM BEING A BIT STRONGER AND SLOWER
IS EFFECTIVELY WELL ON THE NORTHERN FRIDGE OF SOLUTIONS,
PARTICULARLY WITH EH SURFACE LOW TRACK AND QPF SWATH. ALL
CONSIDERED, A NON-NAM BLEND APPEARS APPROPRIATE AT AVERAGE
CONFIDENCE (GIVEN FAST/FLAT FLOW REGIME).
..DEVELOPING BROAD GLOBAL TROF OVER NORTHWESTERN NORTH AMERICA
...LEAD SHORTWAVE IN GREAT BASIN MONDAY, SHIFTING TO CENTRAL
PLAINS BY TUESDAY...
..SECONDARY BROAD SHORTWAVE DIGGING ALONG WEST COAST TUES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND
EXCEPTION: EXCLUDE THE CMC IN THE ROCKIES/GREAT PLAINS ON TUES.
CONFIDENCE: BELOW AVERAGE
19Z UPDATE: A SHIFT IN THINKING IS LIKELY REQUIRED WITH THIS
UPDATE. THE 12Z UKMET WHILE SLIGHTLY WEAKER WITH THE UPSTREAM
(2ND) WAVE OFF THE WEST COAST, IT IS STILL QUITE STRONG/COMPACT
AND LINE WITH THE PRIOR 00Z RUN AND THE 12Z GFS. THE GEFS ALSO
PRESENTED A VAST MAJORITY OF THE MEMBERS NEAR OR VERY CLOSE TO THE
OPERATIONAL GFS WITH SIMILAR INTENSITY. THE CMC ALSO SLOWED WITH
THIS SYSTEM AND IN DOING SO, FURTHER AMPLIFIED ITS MIDDLE GROUND
SOLUTION BY DAY 3. THIS LEAVES THE 12Z ECMWF AND 00Z ECENS MEAN
ALONG WITH AN UNCHARACTERISTICALLY WEAK 12Z NAM AS THE WEAKER
SOLUTIONS FOR THE WEST COAST.
INTERESTINGLY, THE LEAD WAVE ALL TRENDED SLOWER TOWARD THE 00Z
UKMET/12Z GFS AS WELL, INCLUDING THE 12Z ECMWF, THOUGH IS FAVORING
A SLIGHTLY NORTHWARD TRACK (LIKELY DUE TO BEING A BIT SLOWER
OVERALL. THE CMC IS FURTHER SOUTH, BUT ALSO WEAKER THAN IT WAS.
THIS WOULD SUGGEST SLOWING TOWARD THE GFS/UKMET AND ECMWF MAY BE
BETTER IN THE CO ROCKIES INTO PLAINS ON TUESDAY.
GIVEN THESE SHORTWAVE FEATURES ARE STILL CLOSER TO ASIA CURRENTLY
IN A STRONG PACIFIC FLOW, THERE IS TREMENDOUS UNCERTAINTY AND SO
CONFIDENCE REMAINS WELL BELOW AVERAGE WITH THE EXCEPTION THAT THE
LARGER SCALE BROAD TROF WILL EXIST WITH TWO EMBEDDED SHORTWAVES.
THE TIMING/STRENGTH AND LATITUDE VARIATION IS MUCH TO HIGH TO HAVE
ANY SIGNIFICANT (PRECISE LOCATION CONFIDENCE)...SO A NON-NAM BLEND
SEEMS APPROPRIATE WITH THE CAVEAT OF FURTHER PREFERENCE CHANGES
ARE LIKELY.
---PRIOR DISCUSSION---
IN THE WAKE OF THE LAST ZONAL SHORTWAVE, THE OVERALL LARGE SCALE
PATTERN STARTS ITS PHASE OF AMPLIFICATION CENTERED AROUND ALBERTA
AFTER MIDDAY MONDAY. A STRONG LEADING JET AND ASSOCIATED
SHORTWAVE RIPS THROUGH THE GREAT BASIN AND BY 12Z TUESDAY IS
SHARPENING OVER THE CO ROCKIES, DEVELOPING A STRONG CENTRAL PLAINS
SURFACE LOW. UPSTREAM, ANOTHER BROAD SHORTWAVE HUGGING THE
PANHANDLE OF AK WILL DROP SOUTH ALONG THE COAST, STARTING TO
BUCKLE INTO A LARGER CLOSED LOW FEATURE JUST AFTER THE PERIOD.
THE MODEL SPREAD IS DRIVEN MAINLY BY THE SPACING BETWEEN SYSTEMS.
THE UKMET IS MOST DRAMATIC WITH THE SHORTEST WAVE LENGTH/SPACING.
THIS ALSO ALLOWS FOR GREAT UPPER LEVEL DIFFLUENCE TO SUPPORT RAPID
CYCLOGENESIS ALONG THE LEADING EDGE OF THE SECONDARY WAVE, EVEN
SUPPORTING A SUB 976MB LOW BY 27.00Z. THIS SOLUTION IS ENHANCED
BY THE 12Z GFS, WHICH HAS FLIP-FLOPPED WITH EVOLUTION BETWEEN THE
00Z, 06Z AND BACK ON THE 12Z RUN. THOUGH THE 12Z GFS IS A BIT
FASTER WITH THE LEAD WAVE COMPARED TO THE UKMET. BOTH PROVIDE
REDUCED CONFIDENCE IN THE OVERALL SOLUTION, AS IT IS CLEARLY
PLAUSIBLE FOR THESE SOLUTIONS TO MANIFEST (BASED MAINLY ON THE
DOWNSTREAM SHORTWAVE RIDGING/DIVERGENCE ALOFT). THE GEFS/ECENS
AND CMCE SOLUTIONS WOULD SUGGEST THAT THE STRONGER SOLUTIONS MAY
BE A BIT TOO FAR OUT OF TOLERANCE AT THIS POINT. THE ECMWF/CMC
ALONG WITH THE GEFS APPEAR TO BE A MORE CONSISTENT SOLUTION FOR
PREFERENCE.
THE 12Z NAM, IS QUITE AGREEABLE FOR THE LEAD WAVE, THROUGH THE
ROCKIES INTO THE PLAINS, BUT THE SECONDARY SHORTWAVE IS VERY WEAK
AND MORE DRIVEN THROUGH THE NORTHERN STREAM ENERGY/COLD PUSH
THROUGH THE WESTERN STATES THAN THE SHORTWAVE EVOLUTION OUT OF THE
PACIFIC STREAM. AS SUCH THERE IS HESITATION FOR ITS INCLUSION IN
THE BLEND ALONG THE PACIFIC COAST ON DAY 3.
WHILE THE 00Z CMC SHOWS THE NEXT SHORTEST WAVELENGTH, IT IS ONLY
ON THE EDGE OF THE REMAINING ENSEMBLE SUITE TO SUPPORT A STRONGER
WAVE. SO, IT IS SOLID TO INCLUDE IT IN THE BLEND TO HELP ACCOUNT
FOR THE STRONGER/DEEPER SOLUTION. SO ALL CONSIDERED BOTH
SHORTWAVES, A 00Z ECMWF/CMC BLEND WITH INCLUSION OF THE GEFS/ECENS
IS PREFERRED. THE 12Z NAM COULD BE BLENDED IN THE LEADING
SHORTWAVE, BUT SHOULD BE EXCLUDED ALONG THE PACIFIC COAST WITH THE
SECOND SYSTEM. CONFIDENCE IS BELOW AVERAGE, PARTICULARLY FOR THE
SECOND WAVE.
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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