663
FXUS10 KWNH 231842
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
242 PM EDT MON MAR 23 2020
VALID MAR 23/1200 UTC THRU MAR 27/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH PRELIMINARY PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..NOR'EASTER DEVELOPING OFF NEW ENGLAND TONIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
..19Z UPDATE
MINOR CHANGES WERE OBSERVED WITH THE 12Z ECMWF/UKMET/CMC COMPARED
TO THEIR PREVIOUS CYCLES. NO CHANGES ARE RECOMMENDED WITH A
GENERAL MODEL BLEND CONTINUING TO REPRESENT THE BEST OPTION FOR
THIS SYSTEM.
..PREVIOUS DISCUSSION FOLLOWS
MINOR PLACEMENT DIFFERENCES EXIST WITH THIS SYSTEM, PERHAPS THE
12Z GFS STANDS OUT THE GREATEST EARLY TONIGHT WITH ITS SURFACE LOW
TRACK BEING DISPLACED A LITTLE FARTHER OFFSHORE. HOWEVER, THE
DIFFERENCES IN THE GFS DISAPPEAR BEYOND 12Z TUESDAY, WITH A
GENERAL MODEL BLEND FROM START TO FINISH LOOKING FINE FOR THIS
SYSTEM AS THE DIFFERENCES NOTED WITH THE GFS ARE WELL WITHIN THE
TIGHT ENSEMBLE SPREAD.
...MID-LEVEL SHORTWAVE TRACKING FROM THE SOUTHWEST TODAY TO THE
EAST COAST WEDNESDAY MORNING...
...SURFACE LOW TRACKING OFFSHORE OF THE NORTHERN MID-ATLANTIC
COAST WEDNESDAY INTO THURSDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z NAM, 12Z GFS BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
..19Z UPDATE
THE 12Z ECMWF TRENDED SLOWER WITH THE MID-LEVEL SHORTWAVE AND IS
IN BETTER AGREEMENT WITH THE TIMING OF THE OTHER MODELS. HOWEVER,
THE 12Z CMC CONTINUES TO BE SLOWER THAN THE REMAINDER OF THE
GUIDANCE. NO MAJOR TRENDS WERE SEEN IN THE 12Z UKMET. THE 12Z NAM
AND 12Z CMC ARE CLOSEST TO THE COAST WITH THE SURFACE LOW AND THE
12Z GFS/ECMWF/UKMET ARE MORE OFFSHORE. THIS SEEMS TO SUGGEST THE
EARLIER TREND IN THE ENSEMBLES IS THE NEW DIRECTION TO LEAN. BUT
SOME INCORPORATION OF THE 12Z NAM IS STILL PREFERRED TO ACCOUNT
FOR THE CONTINUED MODEL SPREAD. THE 12Z CMC IS CONSIDERED LEAST
LIKELY TO VERIFY WITH A CONTINUED STRONGER AND MORE WESTWARD TRACK.
..PREVIOUS DISCUSSION FOLLOWS
THE 00Z THE TIMING OF THE 00Z ECMWF MID-LEVEL SHORTWAVE IS NOTED
TO BE FASTEST AS IT NEARS THE OHIO VALLEY TUESDAY EVENING AND
OFFSHORE OF THE EAST COAST WEDNESDAY EVENING. THE 00Z ECMWF MEAN
IS NOTED TO BE A LITTLE SLOWER THAN THE DETERMINISTIC ECMWF. THE
REMAINING MODEL SHOW MINOR DIFFERENCES WITH THE SHORTWAVE TIMING
BUT MORE NOTABLE DIFFERENCES SHIFT TO THE RELATED SURFACE LOW.
ENSEMBLE SCATTER LOW PLOTS HAD BEEN CONSISTENT OVER THEIR PAST FEW
CYCLES, VALID 12Z/26, WITH A CENTROID JUST EAST OF THE 40N/70W
BENCHMARK. HOWEVER, THE LATEST (00Z/23) ENSEMBLE CYCLE HAS SHIFTED
THE ECMWF/GEFS/CMC SURFACE LOWS SOUTHEAST OF THE BENCHMARK OR MORE
OFFSHORE. IT IS UNCLEAR IF THIS TREND IS A TEMPORARY SHIFT OR A
NEW DIRECTION THAT THE GUIDANCE WILL ALL SHIFT TOWARD. FOR NOW,
PREFER TO PLAY THE MIDDLE OF THE TWO CAMPS, OR BY BLENDING THE 12Z
NAM AND 12Z GFS. THE 12Z GFS IS SUPPORTED BY THE 00Z UKMET, WHILE
THE 00Z CMC WHICH IS STRONGER AND CLOSEST TO THE COAST IS NOT
CONSIDERED LESS LIKELY TO VERIFY GIVEN LACK OF SUPPORT, ESPECIALLY
WEDNESDAY EVENING.
..LONGWAVE TROUGH OVER THE WESTERN U.S
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/CMC BLEND
CONFIDENCE: AVERAGE
..19Z UPDATE
THE 12Z ECMWF/UKMET/CMC SLOWED THE UPPER TROUGH TIMING INTO THE
WEST COMPARED TO THEIR PREVIOUS CYCLES. THIS MAKES THE FASTER 12Z
NAM/GFS STAND OUT MORE WITH THEIR QUICKER PROGRESSION. THE
PREFERENCE WILL BE UPDATED TO INCLUDE THE 12Z ECMWF/CMC WHICH
REPRESENTS A NUDGE TO THE WEST WITH THE UPPER TROUGH.
..PREVIOUS DISCUSSION FOLLOWS
THE AMPLIFIED PATTERN OVER THE EASTERN PACIFIC WILL END UP
PRODUCING A POSITIVELY TILTED LONGWAVE TROUGH AXIS WHICH WILL WORK
DOWN THE WEST COAST AND EVENTUALLY MOVE INLAND INTO THE SOUTHWEST
FRIDAY MORNING. THERE HAVEN'T BEEN MANY TRENDS IN THE ENSEMBLES
AND THERE IS A MODERATE AMOUNT OF SPREAD WITH THE TIMING BY
THURSDAY EVENING. THE 12Z GFS AND 12Z NAM ARE JUST A LITTLE FASTER
THAN THE MAJORITY OF ENSEMBLE SPAGHETTI HEIGHT PLOTS WHILE THE 00Z
UKMET IS TOWARD THE SLOWER SIDE. PREFER TO STAY TOWARD THE MIDDLE,
OR NEAR THE 00Z ECMWF/CMC AT THIS TIME, WITH THINKING THAT THE 12Z
NAM/GFS ARE LESS LIKELY TO VERIFY WITH A FASTER PROGRESSION WITHIN
THE AMPLIFIED FLOW REGIME.
...NEGATIVELY TITLED MID-LEVEL SHORTWAVE CROSSING SOUTHERN
ONTARIO/QUEBEC ON THURSDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z NAM/ECMWF/UKMET BLEND
CONFIDENCE: AVERAGE
..19Z UPDATE
THE 12Z CMC ADJUSTED FASTER WITH THE SHORTWAVE THURSDAY EVENING
WHILE THE 12Z ECMWF/UKMET ONLY MADE MINOR CHANGES COMPARED TO
THEIR PREVIOUS CYCLES. THINKING REMAINS THE SAME AS THE PREVIOUS
DISCUSSION, WITH THE UPDATED PREFERENCE EXCLUDING THE FASTER 12Z
CMC.
..PREVIOUS DISCUSSION FOLLOWS
THE 12Z GFS APPEARED TO BE A FASTER OUTLIER HERE WHICH IS AN OFTEN
SEEN BIAS IN THE GFS CONCERNING SHORTWAVE TROUGH PROGRESSION.
GIVEN ONLY THE GEFS SUPPORTS THE FASTER TIMING OF THE 12Z GFS BY
LATE THURSDAY, A NON 12Z GFS BLEND WILL BE PREFERRED.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
OTTO
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page