865
FXUS10 KWNH 051853
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
153 PM EST SUN JAN 05 2020
VALID JAN 05/1200 UTC THRU JAN 09/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...SHORTWAVE TROUGH TRACKING ACROSS THE GREAT LAKES/NORTHEAST
THROUGH LATE MON...
..WEAK SURFACE LOW MOVING THROUGH SOUTHERN CANADA
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THE MODELS SHOW SIMILARLY WITH THIS SYSTEM. NO SIGNIFICANT CHANGES
WERE NOTED IN THE 12Z ECMWF/UKMET/CMC COMPARED TO THEIR PREVIOUS
00Z CYCLES.
..SPLIT-FLOW TROUGH NEAR THE PACIFIC NORTHWEST TODAY
..ENERGY REACHING THE GREAT LAKES/NORTHEAST TUE/WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z NAM, 12Z ECMWF AND 12Z UKMET BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
..19Z UPDATE
WHILE SMALL TIMING CHANGES WERE NOTED, NO SIGNIFICANT CHANGES
OCCURRED IN THE 12Z ECMWF/UKMET/CMC COMPARED TO THEIR PREVIOUS 00Z
CYCLES.
..PREVIOUS DISCUSSION FOLLOWS
AS SHORTWAVE ENERGY MAKES ITS WAY EAST INTO THE GREAT LAKES REGION
ON TUESDAY, THERE ARE DIFFERENCES WITH THE HANDLING OF THE 500 MB
TROUGH. THE 12Z GFS IS DISPLACED NORTH WITH THE CORE OF THE BASE
OF THE TROUGH IN THE VICINITY OF WESTERN ONTARIO NOTED MID-DAY
TUESDAY. THE 00Z CMC IS DISPLACED SLIGHTLY SOUTH AND SLOWER THAN
THE REMAINING CONSENSUS. FAIRLY GOOD AGREEMENT IN THE ENSEMBLES
EXISTS FOR A BLEND NEAR THE 12Z NAM, 00Z ECMWF AND 00 UKMET.
..SOUTHERN STREAM TROUGH/LOW NEAR THE TN VALLEY BY TUE
..SURFACE LOW IMPACTING THE MID-ATLANTIC/NORTHEAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z NAM AND 12Z ECMWF
CONFIDENCE: AVERAGE
..19Z UPDATE
THERE WAS A SUBTLE TREND FOR MORE SEPARATION BETWEEN THE NORTHERN
AND SOUTHERN STREAM COMPONENTS OF THE EASTWARD MOVING TROUGH AXIS
DESCRIBED BELOW IN THE 12Z ECMWF/UKMET/CMC COMPARED TO THEIR
PREVIOUS 00Z CYCLES. THE RESULT IS A SURFACE LOW TRACK A LITTLE
FARTHER SOUTH AND OFFSHORE AS THE LOW TRACKS NORTH OFF OF NEW
ENGLAND. A BLEND OF THE 12Z NAM/CMC (MORE WEST) AND 12Z
ECMWF/UKMET (MORE EAST) PLACES A LOW CLOSEST TO THE CENTER OF MOST
ENSEMBLE SCATTER LOW PLOTS VALID 12Z/08. A BLEND OF THE 12Z
NAM/ECMWF IS SILL PREFERRED WHICH REPRESENTS A SMALL SHIFT FROM
CONTINUITY. THE 12Z GFS IS STILL CONSIDERED TOO FAST.
..PREVIOUS DISCUSSION FOLLOWS
WHILE MODEL DIFFERENCES ARE RATHER MINOR WITH THIS SYSTEM, A
MODEST AMOUNT OF SPREAD REMAINS IN THE ENSEMBLES AND RUN TO RUN
CONSISTENCY IN THE GUIDANCE HAS NOT BEEN GREAT. THE 12Z GFS STANDS
OUT FIRST WITH A FASTER 500 MB TROUGH PROGRESSION TOWARD THE EAST
COAST, PERHAPS DUE TO MORE SEPARATION IN THE FLOW WITH THE
NORTHERN COMPONENT OF THE LARGER SCALE TROUGH AXIS TRACKING
THROUGH SOUTHERN CANADA.
AMONG THE NON 12Z GFS GUIDANCE, SPECIFICALLY CONCERNING THE 850 MB
LOW, FROM LATE TUESDAY INTO WEDNESDAY, THE 12Z NAM IS ON THE SOUTH
SIDE OF THE DETERMINISTIC GUIDANCE WHILE THE 00Z ECMWF/UKMET/CMC
ARE NORTH. THE 12Z GFS IS ALSO SOUTH LIKE THE NAM, BUT AGAIN IS
FASTER THAN IDEAL. A BLEND BETWEEN THE 12Z NAM AND 00Z ECMWF IS
CONSIDERED BEST FOR THIS SYSTEM AT THIS TIME, BUT ADJUSTMENTS IN
FUTURE CYCLES APPEAR POSSIBLE GIVEN THE CHANGES SEEN LEADING TO
TODAY'S RUNS.
...SHORTWAVE/FRONTS APPROACHING THE PACIFIC NORTHWEST MON AND
TUE...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 12Z UKMET BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
..19Z UPDATE
WHILE THE 12Z UKMET ADJUSTED A LITTLE SLOWER WITH ITS TROUGH
PROGRESSION, IT IS STILL THE FASTEST OF THE LATEST DETERMINISTIC
GUIDANCE WITH THIS SYSTEM. IN FACT, A SMALL SHIFT TO BE SLOWER WAS
NOTED IN THE 12Z ECMWF/CMC, SO A NON 12Z UKMET BLEND WILL STILL BE
PREFERRED AT THIS TIME.
..PREVIOUS DISCUSSION FOLLOWS
YET ANOTHER IN A SERIES OF SHORTWAVE TROUGHS WILL ARRIVE ACROSS
THE PACIFIC NORTHWEST LATE MONDAY INTO TUESDAY. INITIALLY A WARM
FRONT WILL CROSS THE REGION AHEAD OF THIS ENERGY, WITH THE MAIN
TROUGH CROSSING BY LATE TUESDAY. MODEL AGREEMENT WITH THE WARM
FRONT IS NOW GOOD, BUT THE 00Z UKMET IS FASTER WITH THE MID-LEVEL
SHORTWAVE ALONG THE WEST COAST. THE FASTER TIMING OF THE 00Z UKMET
CARRIES OVER DOWNSTREAM INTO INTERIOR PORTIONS OF THE WEST AND IS
A NOTABLE FASTER SOLUTION IN THE 500 MB ENSEMBLE SPAGHETTI PLOTS
THROUGH WEDNESDAY. WHILE NOT A COMPLETE OUTLIER, PREFER TO STICK
NEARER TO THE BETTER ENSEMBLE/DETERMINISTIC CLUSTERING AWAY FROM
THE 00Z UKMET. TIMING DIFFERENCES AMONG THE NON 00Z UKMET
GUIDANCE ARE PRESENT (00Z ECMWF A BIT FASTER) BUT ARE RELATIVELY
MINOR.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
OTTO
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