893
FXUS10 KWNH 050447
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1147 PM EST WED DEC 04 2019
VALID DEC 05/0000 UTC THRU DEC 08/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..OVERALL PATTERN ACROSS THE CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
EXCEPTION: NON-UKMET ACROSS SOUTH INTO EAST COAST AFTER 60HRS
WEST COAST LOW: 12Z ECWMF/00Z GFS AND UKMET NORTH OF 40N, 00Z
NAM EXCEPT IN MT INTO NORTHERN PLAINS
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
MODEL AGREEMENT CONTINUES TO BE STRONG THROUGH THE NEW 00Z NAM/GFS
WITH LOW ENSEMBLE SPREAD THROUGH DAY 2. HOWEVER, BY DAY 3, MODEL
SPREAD CONTINUES TO WAFFLE/VARY AS THE MAIN FEATURES START TO
BREAK DOWN A BIT FASTER/SLOWER OR START ENHANCING OTHER FEATURES
ELSEWHERE.
CURRENT POTENT SHORTWAVE CROSSING THE SOUTHWEST/SOUTHERN GREAT
BASIN, WILL PROGRESS ACROSS THE SOUTHERN STATES WITH FAIRLY GOOD
AGREEMENT. THE 12Z UKMET IS A BIT STRONGER/COMPACT AND EVENTUALLY
LIFTS A BIT NORTH, OFF THE ATLANTIC COAST BY 12Z SAT, WHICH HELPS
TO ELONGATE THE NORTHERN STREAM A BIT MORE, MAKING IT A BIT LESS
FAVORABLE IN ANY BLEND. SO A NON-UKMET BLEND IS FAVORED THROUGH
THE SOUTH AND THEN OFFSHORE OF THE NORTHEAST FOR DAY 3.
ON THE HEELS OF THE SHORTWAVE, A STRONG CLOSED LOW IN THE CENTRAL
PACIFIC PROGRESSES EASTWARD EXPANDING TO MATURITY AROUND 00Z FRI,
UNDER STRONG AGREEMENT. AS THE CLOSED LOW BREAKS DOWN, MODEL
SPREAD INCREASES UNDER TYPICAL BIAS, IE NAM IS STRONGER BY DAY 3,
ECMWF IS SLOWER, GFS IS FASTER. THE 00Z GFS WHILE STILL FASTER,
IS ABLE TO DRAW MORE ENERGY FROM THE NORTHERN STREAM 00Z SUNDAY
INTO THE PACIFIC NORTHWEST, TO SLOW THE WAVE A BIT MORE SENSIBLY
TO THE ENSEMBLE MEAN (INCLUDING THE 18Z GEFS). THE CMC IS
UNCHARACTERISTICALLY FAST DUE TO A WEAKENING OF THE INNER CORE OF
THE LOW ON SAT. THIS LEADS TO THE WAVE PROGRESSING A BIT TOO FAST
INTO THE WEST, WITH GREATER NORTH-SOUTH ORIENTATION OF THE WAVE
AXIS COMPARED TO THE REMAINING GUIDANCE AND ENSEMBLE SUITE (SO IS
NOT FAVORED AFTER DAY 2). THE UKMET LOOKS VERY GOOD WITHIN THE
SUITE, HOWEVER, HAS A VERY WET SUBTROPICAL STREAM COMPARED TO THE
REMAINING GUIDANCE, TAPPING THE TROPICS A BIT MORE THAN OTHER
SOLUTIONS, WHILE THE REMAINING MASS FIELDS ARE STRONG, GIVEN THE
QPF, IT IS NOT FAVORED IN THE SOUTHWEST FOR LATE DAY 2 INTO DAY 3.
THE 00Z NAM IS VERY STRONG WITH THE INNER CORE TO THE CLOSED LOW
WHICH IS ON PAR/FAVORED BUT THE NORTHERN STREAM THAT IS DIGGING
BECOMES A BIT STRONG AS WELL AS FAST, PRESSING THE COLD FRONT
THROUGH THE NORTHERN PLAINS BY SUNDAY BUT ALSO SHARPENING THE TROF
OUT OF ALBERTA/MONTANA. SO THIS MAKES IT LESS USEFUL FOR THOSE
SECTIONS LATE SAT INTO SUNDAY. ALL CONSIDERED, PREFERENCE IS VERY
CLOSE TO THE ECENS/GEFS MEANS WHICH IS BEST REPRESENTED BY THE 12Z
ECMWF/GFS AND UKMET NORTH OF 40N AND 00Z NAM (EXCEPT N ID/MT INTO
THE NORTHERN PLAINS).
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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