880
FXUS10 KWNH 240801
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EST SUN NOV 24 2019
VALID NOV 24/0000 UTC THRU NOV 27/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...NEGATIVE TILTED SHORTWAVE MID-ATLANTIC / NORTHEAST AND
ASSOCIATED SURFACE LOW...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
CURRENT WV IMAGERY SHOWS SHORTWAVE TROUGH OVER THE OHIO VALLEY
WITH THE LATEST SURFACE ANALYSIS HAVING THE PARENT LOW OVER WEST
VIRGINIA. THE EARLIER 12Z GUIDANCE AND NOW THE INCOMING 00Z
GUIDANCE ALL IS IN GOOD AGREEMENT THROUGH 36-48 HOURS WITH THE
EVOLUTION OF THIS SYSTEM. THE PARENT LOW WILL BE REPLACED WITH A
SECONDARY LOW OFF THE MID-ATLANTIC COAST AND AS THE SHORTWAVE
DEEPENS/TILTS MORE, THE LOW WILL TAKE A NORTH/NORTHEAST TURN UP
THE COAST. THE GLOBAL DETERMINISTIC GUIDANCE IS IN VERY GOOD
AGREEMENT WITH LITTLE SPREAD. GIVEN THE HIGHER THAN NORMAL
CONFIDENCE AND LITTLE SPREAD SEEN IN THE MODELS, A GENERAL MODEL
BLEND SHOULD SUFFICE FOR THIS SYSTEM.
...SHORTWAVE RACING THROUGH CANADIAN ROCKIES SUNDAY BEFORE
SUPPORTING NORTHERN TIER SURFACE WAVE MONDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
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 GFS IS A BIT FLATTER AND A TAD FASTER COMPARED TO THE REST OF
THE GUIDANCE WHILE THE CMC IS A TOUCH SLOWER/DEEPER. THE
ECMWF/UKMET LIES IN BETWEEN AND IS A GOOD PROXY, AND WITH A
GENERAL MODEL BLEND, A REASONABLE SOLUTION SHOULD BE APPROPRIATE
FOR SLIGHTLY ABOVE AVERAGE CONFIDENCE.
..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, NON-CMC BLEND
CONFIDENCE: BELOW AVERAGE
08Z UPDATE: LATEST TRENDS STILL SHOW A SLIGHTLY SLOWING PATTERN
WITH THE NEW 00Z GUIDANCE, SUCH THAT THE GFS AND NAM ARE FAST
SOLUTIONS, WITH PERHAPS THE NAM BEING AN OUTLIER AT THIS POINT
FROM THE WEST COAST TOWARD THE CENTRAL PLAINS AND UPPER MIDWEST BY
DAY 3. THE 00Z CMC STILL IS A SLOWER SOLUTION, BUT IS NOT OUT OF
THE ENSEMBLE SPREAD AS MUCH AS BEFORE. THEREFORE THE INITIAL
PREFERENCE IS AMENDED TO INCLUDE NON-NAM ACROSS THE BOARD.
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.
FOR THE CENTRAL PLAINS, UPPER MIDWEST, AND GREAT LAKES CYCLONE,
THE MODEL GUIDANCE HAS COME INTO SLIGHTLY BETTER AGREEMENT IN THE
OVERALL, SYNOPTIC PATTERN AND NOW HAS REASONABLE SPREAD FOR DAY 3.
THE EXCEPTION IS THE 12Z CMC, AS IT IS TOO DEEP/AMPLIFIED/FAST
WITH THE SHORTWAVE TROUGH BY 84 HOURS, AND THUS ITS SURFACE LOW IS
FURTHER EAST. THE REST OF THE GUIDANCE SHOWS SOME TYPICAL BIASES
BUT OVERALL THE SPREAD IS WITHIN THE ENSEMBLE SPREAD, SO A NON-CMC
BLEND SHOULD BE APPROPRIATE FOR THE LARGE SCALE MASS FIELDS.
THE STRONGER, MORE ANOMALOUS CLOSED LOW THAT ARRIVES ON DAY 3
ALONG THE WEST COAST HAS MORE SIGNIFICANT MODEL SPREAD. THE NAM IS
CONSIDERABLY STRONGER WITH THE CLOSED LOW AND SUBSEQUENTLY HAS A
MUCH DEEPER SURFACE LOW OFF THE NORTHERN CA COAST BY 84 HOURS.
THERE IS ALSO SOME LATITUDINAL DIFFERENCES (ECMWF SOUTH, GFS
NORTH) BUT OVERALL THE SETUP IS LARGELY THE SAME AND WITHIN THE
ENSEMBLE SPREAD. THE ECENS MEAN AND ECMWF ARE TIGHTLY CLUSTERED
AND THE 18Z GEFS MEAN AND 00Z GFS SHOW FAIRLY GOOD AGREEMENT. SO
ALL THINGS CONSIDERED, A NON-CMC BLEND OVERALL IS PREFERRED (ALSO
NON-NAM WEST COAST DAY 3) FOR THIS CYCLE.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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