130
FXUS10 KWNH 161831
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
131 PM EST MON DEC 16 2019
VALID DEC 16/1200 UTC THRU DEC 20/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH PREFERENCE AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..EASTERN CONUS
~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
19Z UPDATE: THE 12Z UKMET SOLUTION SHIFTED SLOWER AND THEREFORE
WELL WITHIN THE MEAN SPREAD TO SUGGEST A FULL SUITE BLEND,
PARTICULARLY WITH LITTLE VARIATION IN THE 12Z GEFS/ECMWF OR CMC.
CONFIDENCE IS ABOVE AVERAGE.
---PRIOR DISCUSSION---
LARGE SCALE SYNOPTIC STRETCHING OF THE SHORTWAVE CURRENTLY
EMERGING INTO THE SOUTHERN PLAINS, IS IN FULL AFFECT BY LATE
TUESDAY IN A LONG POSITIVE TILT ORIENTATION FROM NEW ENGLAND TO
CENTRAL TX AND IS FAIRLY WELL PLACED IN TIMING/STRENGTH. A
COMPACT ARCTIC SHORTWAVE BREAKS FROM THE GLOBAL SCALE VORTEX OVER
THE NW TERRITORIES BY MIDDAY TUESDAY AS IT ROLLS JUST NORTH OF THE
GREAT LAKES WED. THE INTERACTION SHOWS THE 00Z UKMET A TAD
FASTER/WEAKER THAN ECMWF/CMC MORE COMPACT, SLIGHTLY SLOWER AND A
TAD SOUTH RELATIVE WITH THE 12Z GFS/NAM IN BETWEEN HEDGING TOWARD
THE SLOWER ECMWF/CMC. THIS IS VERY MINOR DIFFERENCES FROM A
SYNOPTIC PERSPECTIVE, BUT WOULD SUGGEST LESSER WEIGHTING TO THE
UKMET IN A GENERAL MODEL BLEND. CONFIDENCE IS SLIGHTLY ABOVE TO
ABOVE AVERAGE EVEN WITH THE TAIL END OF THE TROF AS IT SKIRTS
THROUGH THE SOUTHEAST BY FRI.
..WESTERN CONUS INTO CENTRAL PLAINS FRI
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND (GREATEST WEIGHTING TOWARD GEFS
MEAN)
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
19Z UPDATE: THE 12Z UKMET SLOWED SIGNIFICANTLY IN THE NORTHERN
STREAM AND WHILE IT STILL OUTPACES THE REMAINING GUIDANCE IT IS
JUST A TAD FASTER THAN THE GFS AND LOOKS QUITE SIMILAR INCLUDING
IN THE SOUTHERN STREAM. THE 12Z CMC IS A BIT SLOWER IN THE
NORTHERN STREAM BUT AGAIN MATCHES THE ECMWF FAIRLY WELL. SO
TIMING WILL BE THE REMAINING PROBLEM AS THE EVOLUTION OF THE
FEATURES LOOK QUITE SIMILAR. THIS TIMING ISSUE WILL CONTINUE TO
AFFECT THE QPF MOST, GIVEN THE TIMING OF THE MOISTURE RETURN NORTH
AND WHICH SECTION OF THE WEST COAST IT HITS BEFORE THE AR STARTS
IN EARNEST AT THE VERY END OF THE FORECAST PERIOD. THE 12Z GEFS
CONTINUES TO BE THE MOST MIDDLE GROUND SOLUTION, SO WILL SUPPORT A
GENERAL MODEL BLEND BUT WEIGHT HEAVIEST TO THE GEFS FOLLOWED BY
THE ECMWF THEN GFS/UKMET. THE NAM, PARTICULARLY IN THE SOUTHERN
STREAM INTO THE GREAT BASIN/FOUR CORNERS IS MOST OUT OF PHASE
(THOUGH NOT DRAMATICALLY SO). CONFIDENCE REMAINS SLIGHTLY ABOVE
AVERAGE FOR THE MASS FIELDS...BUT AVERAGE FOR QPF.
---PRIOR DISCUSSION---
AN ELONGATED, NARROWING TROF WILL APPROACH THE WEST COAST TUESDAY
WHICH IS EXPECTED TO FULLY SEVER AND RE-CONSOLIDATE INTO A CLOSED
LOW ALONG THE CA COAST BY 00Z WEDNESDAY, WITH SOME REMAINING
ENERGY PROVIDING DPVA AT THE LEADING NOSE OF THE DEVELOPING
WESTERLY JET BY THURSDAY. THE 00Z UKMET IS STRONGEST WITH THE
REMAINING VORTICITY STRIP AT THE NOSE OF A TIGHTER/FASTER JET
STREAM WHICH ACCELERATES THE NORTHERN STREAM ACROSS THE ROCKIES
WELL FASTER THAN THE REMAINING GUIDANCE AND ENSEMBLE SUITE
(INCLUDING ITS TRENDS). THIS IN TURN, SLOWS THE SOUTHERN STREAM
CLOSED LOW THROUGH THE FOUR CORNERS AT THE ANTICYCLONIC ROTOR.
THE 12Z NAM, WHICH TENDS TO BE STRONGER BY DAY 3, IS VERY SIMILAR
JUST A BIT SLOWER IN THE NORTHERN STREAM, MORE IN LINE WITH THE
GEFS SUITE. THE 12Z GFS REMOVED SOME OF THE STRONGER VORTICITY
STRIP BUT WITH A SLIGHTLY FASTER EVOLUTION IS ABLE TO TAP A MORE
SOUTHERLY WARM ADVECTION ALONG THE WEST COAST/OR CONSOLIDATING
MOISTURE FLUX COMPARATIVE TO THE ECMWF. WHILE THE ECMWF, IS WEAK
WITH THE LOW FLOW AND THE DIGGING SHORTWAVE RELATIVE TO THE
GFS/NAM ALLOWING FOR A BROADER QPF SWATH (OR DELAYED FOCUS FOR
HEAVY RAIN). THE 00Z CMC,WILL FAVOR THE CMC BUT MATCHES THE MASS
FIELD WELL WITH THE GFS/GEFS TOO, PROVIDING AVERAGE TO SLIGHTLY
ABOVE AVERAGE CONFIDENCE IN THE EVOLUTION OVERALL. THIS PLACES
THE GEFS MEAN AS A NICE MIDDLE GROUND OVERALL, AND SO WILL GLEAN
THE GREATEST WEIGHT IN A NON-UKMET BLEND. CONFIDENCE IS SLIGHTLY
ABOVE AVERAGE IN THE MASS FIELDS, BUT REDUCES WITH THE
MOISTURE/QPF AXIS TO AVERAGE.
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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