364
FXUS10 KWNH 211624
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1123 AM EST THU NOV 21 2019
VALID NOV 21/1200 UTC THRU NOV 25/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...WEAKENING CLOSED LOW CROSSING THE FOUR CORNERS INTO THE PLAINS
FRIDAY/SATURDAY, PHASING WITH POTENT NORTHERN STREAM SHORTWAVE
ACROSS GREAT LAKES SAT INTO SUN...
...SURFACE LOW MOVING FROM THE LOWER MISSISSIPPI VALLEY INTO THE
CENTRAL APPALACHIANS FRIDAY NIGHT INTO SATURDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND
CONFIDENCE: AVERAGE
THE COLD CLOSED LOW IN THE SOUTHWEST CONTINUES TO BREAK DOWN AND
STRETCH ACROSS THE LOWER MS VALLEY BY THE END OF THE WEEK, BEFORE
A SHARP NORTHERN STREAM SHORTWAVE AIDS IN CYCLOGENESIS THROUGH THE
TENNESSEE VALLEY INTO THE APPALACHIANS BEFORE TRANSFERRING TO
COASTAL LOW BY SUNDAY MORNING IN THE NEW YORK BIGHT. THE GUIDANCE
IS COMING INTO SOME AGREEMENT IN THE EVOLUTION. HOWEVER, THE 12Z
NAM HAS BROKEN FROM THIS TREND, LEADING TO A SLOWER, SOUTHWARD
EMERGENCE OF THE SOUTHERN STREAM SHORTWAVE AND A DIFFERENCE IN THE
NORTHERN STREAM BY DEFLECTING THE ENERGY NORTH; THIS LEADS TO A
MUCH WEAKER AND FURTHER EAST SURFACE EVOLUTION. WHILE THE PIECES
MAY BE HINTING AT A LEGITIMATE POSSIBILITY IN EVOLUTION (IE
GREATER VERTICAL CONVECTION CLOSER TO THE GULF COAST, WEAKENING
THE TROF OVERALL)...THERE IS VERY LITTLE SUPPORT ELSEWHERE TO
INCLUDE IT IN A BLEND AT THIS POINT. OTHERWISE, THE GUIDANCE IS
IN A TYPICAL SPREAD, GFS FAST, PERHAPS A TAD TOO MUCH, WITH A MORE
REASONABLE GEFS MEAN NOTED, WHILE THE CMC IS SLOWER. THE ECMWF
ALSO SHOWS SOME NEGATIVE BIAS, WITH A VERY SMALL BUT COMPACT
SHORTWAVE IN THE NORTHERN STREAM; IT DOES NOT'T SEEM TO NEGATIVELY
AFFECT THE LOWER ATMOSPHERE MASS FIELDS/EVOLUTION BUT IT CLEARLY
LOOKS ODD IN MASS FIELDS ALOFT. STILL, THIS IS GOOD TO SUGGEST A
NON-NAM BLEND, HEDGING TOWARD THE GEFS MEAN AND THE UKMET/ECMWF.
CONFIDENCE IS RISING, BUT MODERATE VARIATION IN TIMING STILL MAY
LEAD TO A DIFFERENT EVOLUTION OF THE SYSTEM TO HAVE ONLY AVERAGE
OVERALL CONFIDENCE.
...EMBEDDED SHORTWAVES WITHIN STRONG ZONAL NORTHERN PACIFIC JET
INTO THE NORTHWEST...
..ASSOCIATED SURFACE WAVE ACROSS THE NORTHERN TIER BY 00Z MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH 24.00Z
AFTERWARD: NON-NAM/ECMWF BLEND FAVORING GEFS/ECENS MEAN
CONFIDENCE: SLIGHTLY BELOW AVERAGE AFTER 24.00Z
A GLOBAL-SCALE TROF IS EVOLVING ACROSS THE BERING SEA INTO W AK,
BUT ALONG THE SOUTHERN PERIPHERY A VERY STRONG JET WITH TIGHT
HEIGHT PACKING IS DEVELOPING IN THE FAR NORTHEAST PACIFIC/SOUTHERN
GULF OF AK, TAPPING SOME SOLID MOISTURE. THIS IS TO BE DIRECTED
INTO THE COASTAL RANGES OF BC WITH SLOW SOUTHWARD DRIFT BY EARLY
SUNDAY. AN EMBEDDED SHORTWAVE/JET SPEED MAX WILL REACH THE
CENTRAL BC COAST, EARLY SAT FOLLOWED QUICKLY BY ANOTHER WAVE BY
LATE SAT INTO EARLY SUN. WITH ITS PASSAGE ON SUNDAY, THE FRONTAL
ZONE/MOISTURE STREAM WILL DROP SOUTH INTO THE PACIFIC NW. BOTH
WAVES WILL PROGRESS ACROSS THE CANADIAN ROCKIES AND AMPLIFY
SLIGHTLY ON THE EASTERN SIDE OF THE LARGER SCALE RIDGE. AS IS
TYPICAL WITH SUCH VERY FAST AND LOW AMPLITUDE WAVE PACKS, THE
GUIDANCE IS AGREEABLE UNTIL IT PASSES THE RIDGE AND SO THE SMALL
VARIATIONS IN TIMING LEAD TO LARGE DOWNSTREAM DIFFERENCES IN
TRACK/INTENSITY TO THE DEVELOPING CLIPPER SURFACE WAVE. THIS IS
NO DIFFERENT, THOUGH THE VAST MAJORITY OF GUIDANCE FAVORS A MORE
NORTHERN TRACK REPRESENTED BY THE 12Z GFS, 00Z UKMET/CMC, GEFS AND
ECENS MEAN. WHILE THE ECMWF, PRESENTS A NORTHERN WAVE, IT
PRESENTS SECOND SHORTWAVE IS A BIT STRONGER AND SLOWER AND
THEREFORE A BIT SOUTH. THIS WOULD PRESENT MORE QPF, SENSIBLE
WEATHER FOR THE NORTHERN TIER STATES RELATIVE TO THE
AFOREMENTIONED PACKING. GIVEN THE ECENS MEAN IS FURTHER NORTH,
NEAR THE GEFS...THINK TRENDING TOWARD THE MEANS IN PREFERENCE IS
FAVORED AFTER THE SPREAD RAPIDLY INCREASES (24.12Z). THE 12Z NAM
APPEARS ON TRACK WITH THE CYCLONE BUT AGAIN BY THE END OF DAY 3,
LOOKS A BIT TOO AMPLIFIED GIVEN THE FLOW REGIME...SO WILL HEDGE
AWAY FROM THE NAM AS WELL. AS SUCH, FAVOR THE GEFS/ECENS MEAN
INSIDE A NON-NAM/ECMWF BLEND, BUT CONFIDENCE IN THIS BLEND IS
SLIGHTLY BELOW 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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