282
FXUS10 KWNH 300438
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1138 PM EST SUN DEC 29 2019
VALID DEC 30/0000 UTC THRU JAN 02/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH PREFERENCES/CONFIDENCE INTERVALS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...DOMINANT CENTRAL PLAINS THROUGH GREAT LAKES AND NORTHEAST
CLOSED LOW/SURFACE CYCLONE(S) INCLUDING COASTAL LOW TUES/WED...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
MATURE/VERTICALLY STACKED LOW OVER THE UPPER MIDWEST CURRENTLY
WILL CONTINUE TO PIVOT AROUND THE GREAT LAKES THE NEXT COUPLE OF
DAYS, WITH SEVERAL IMPULSES ROUNDING THROUGH THE LOW. MODEL
AGREEMENT IS VERY TIGHT AND WELL CLUSTERED THROUGH 48 HOURS WITH
SOME DIFFERENCES BEGINNING TO CREEP UP AS THE LOW PICKS UP SPEED
AND MOVES EAST OVER THE NORTHEAST U.S. AND NEW ENGLAND. THE GFS
ENDS UP BEING ON THE FASTER SIDE OF THE MODEL ENVELOPE BY 48
HOURS, BUT THE DIFFERENCES ARE FAIRLY MINOR ENOUGH TO GO WITH A
GENERAL MODEL BLEND THROUGH THE FORECAST PERIOD.
..PACIFIC SHORTWAVE DIVING ALONG THE WEST COAST SUN-WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH 01.00Z; ECMWF/CMC BLEND
THEREAFTER
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THROUGH ABOUT 01.00Z, MODEL AGREEMENT IS VERY STRONG/HIGH WITH THE
COMPACT CLOSED LOW THAT IS CURRENTLY JUST OFF THE CA COAST. THIS
SYSTEM WILL FURTHER DROP SOUTH/SOUTHEAST REACHING THE BAJA REGION
TUESDAY. BEYOND 01.00Z, THERE ARE SOME DIFFERENCES ON HOW QUICKLY
AND HOW MUCH ENERGY IS SHEARED NORTHEASTWARD WITH A NORTHERN
STREAM SHORTWAVE TROUGH DROPPING THROUGH THE CENTRAL PLAINS. THE
ECMWF IS THE FURTHEST SOUTH WITH THE INITIAL CLOSED LOW AND
THEREFORE KEEPS MOST OF THE ENERGY REMOVED FROM THE NORTHERN
STREAM. MEANWHILE, THE 00Z NAM AND THE GFS TO SOME DEGREE ALLOW
FOR MORE ENERGY TO PHASE AND SHOW A QUICKER/MORE OPEN SOLUTION.
THE UKMET, WHILE INITIALLY SLOW AND SUPPRESSED, PICKS UP ITS
EVOLUTION BY 02.00Z WITH A FASTER SOLUTION SIMILAR TO THE GFS.
FINALLY, THE CMC OFFERS A MIDDLE GROUND SOLUTION BETWEEN THE ECMWF
AND GFS/NAM. FOR NOW, WILL SIDE FOR A SLOWER SOLUTION AND PREFER A
ECMWF/CMC BLEND AFTER 01.00Z THROUGH THE END OF THE PERIOD.
..ATMOSPHERIC RIVER SINKING INTO PAC NW BY LATE TUES
...AMPLIFYING INTO BROAD TROF ACROSS NORTHERN ROCKIES/NORTHERN
PLAINS BY LATE WED...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
IN THE WAKE OF THE CLOSED LOW NEAR THE COAST CURRENTLY, VERY
VIGOROUS PACIFIC FLOW, NOTED UPSTREAM IN THE GOES-WEST WV SUITE,
BECOMES VERY ZONAL INTO THE PACIFIC NW BUT IS VERY STRONG WITH
INTERNAL SMALLER SCALE WAVES RIPPLING FAST THROUGH IT. COMBINE
THIS WITH DEEP ANOMALOUS MOISTURE TAPPED FROM THE WARM CENTRAL
PACIFIC AIDS A STRONG ATMOSPHERIC RIVER THAT SLOWLY DROPS SOUTH
INTO THE CONUS BY EARLY TUESDAY. IN THE LAST 2-3 MODEL CYCLES,
AGREEMENT HAS TRENDED HIGHER AND NOW MOST OF THE DETERMINISTIC
MODELS OFFER SIMILAR LARGE SCALE SOLUTIONS WELL WITHIN THE
ENSEMBLE SPREAD AS WELL. THIS PUTS FORECAST CONFIDENCE UP TO
AVERAGE/SLIGHTLY ABOVE AVERAGE. THE ECMWF DOES SHOW A SLIGHT FAST
BIAS WITH THE SURFACE REFLECTION (AND ~ 10 MB WEAKER) IMPACTING
THE COAST BY 01.00Z, EVEN AHEAD OF THE GFS AND OTHER DETERMINISTIC
MODELS. BUT OVERALL THE DIFFERENCES ARE FAIRLY MINIMAL, SO WILL GO
WITH A GENERAL MODEL BLEND AT THIS POINT.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
TAYLOR
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