662
FXUS10 KWNH 290811
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
310 AM EST SUN DEC 29 2019
VALID DEC 29/0000 UTC THRU JAN 01/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH PREFERENCES/CONFIDENCE INTERVALS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..CENTRAL PLAINS TO GREAT LAKES CLOSED LOW/SURFACE CYCLONE(S)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-GFS BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
LARGE TROUGHING OVER THE CENTRAL ROCKIES AND A SURFACE LOW
DEEPENING IN THE CENTRAL PLAINS WILL TRACK TOWARD THE UPPER MS
RIVER VALLEY THROUGH SUNDAY. IN THE NEAR TERM, THERE IS
EXCELLENT/ABOVE AVERAGE FORECAST CONFIDENCE IN THE LARGE SCALE
SYNOPTIC SETUP HOWEVER THERE REMAINS SOME DIFFERENCES IN THE
TIMING/STRENGTH OF INDIVIDUAL SHORTWAVES EMBEDDED IN THE CLOSED
LOW. THE GFS CONTINUES TO SHOW A WEAKER INNER CORE DISSOLVING
FASTER THAN THE REST OF THE MODELS. THIS OVERALL PUTS THE LOW
PRESSURE FURTHER NORTH/EAST BY EARLY NEXT WEEK, MAKING IT LESS
FAVORABLE. OTHERWISE, THE REST OF THE GUIDANCE IS SUFFICIENT
ENOUGH TO INCLUDE SO WILL CONTINUE TO PREFER A NON-GFS BLEND.
...REMAINS OF CLOSED LOW/DEVELOPMENT OF COASTAL LOW INTO NORTHEAST
MON-WED...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE
08Z UPDATE: THE REMAINING 00Z GUIDANCE SHOWED A TREND TOWARD THE
00Z GFS, WITH A FASTER SURFACE LOW PROGRESSING OFF THE NORTHEAST
AND NEW ENGLAND COASTS IN THE MON/TUES TIME FRAME. AS A RESULT,
WILL MAKE A CHANGE TO THE PREFERENCE AND GO WITH GENERAL MODEL
BLEND THROUGH THE PERIOD.
UPSTREAM DEEP CLOSED LOW WILL CONTINUE TO BREAK DOWN ACROSS THE
GREAT LAKES BY LATE MON INTO TUESDAY AND THE FORMER PIVOT/INNER
CORE CENTER ACCELERATES EASTWARD UNDER THE NEWER MATURE CENTER.
THROUGH ABOUT 31.06Z, THE LATEST MODEL GUIDANCE SHOWS HIGH ENOUGH
AGREEMENT TO GO WITH A GENERAL MODEL BLEND. BEYOND THAT TIME
FRAME, THE GFS ACCELERATES THE MID/UPPER LEVEL LOW (AND SURFACE
LOW) MUCH FASTER THAN THE REST OF THE GUIDANCE AND BECOMES
UNUSABLE BEYOND 01.00Z ACROSS THE NORTHEAST US. FORECAST
CONFIDENCE DOES DROP OFF BEYOND THAT TIME FRAME AS WELL, BUT GIVEN
THE RELATIVELY GOOD AGREEMENT WITH THE REST OF THE MODELS, WILL
SIDE WITH A NON-GFS BLEND BEYOND 31.06Z.
..PACIFIC SHORTWAVE DIVING ALONG THE WEST COAST SUN-TUES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
08Z UPDATE: NO BIG CHANGES SEEN WITH THE REST OF THE 00Z GUIDANCE
NOW AVAILABLE. WITH THE ABOVE AVERAGE AGREEMENT AND GOOD RUN TO
RUN CONSISTENCY, THE GENERAL MODEL BLEND IS STILL REASONABLE.
THE PACIFIC CONTINUES TO BE VERY ACTIVE BUT PROGRESSIVE AND WITH
AN UPSTREAM SHARP RIDGE THAT BLOCKS THE FLOW AND RAPIDLY STRETCHES
IT SOUTHWARD ALONG THE ENTIRE WEST COAST OF THE US. THERE IS
GROWING CONSENSUS IN THE TIMING AND SHAPE/EVOLUTION OF THE WAVE
INCLUDING THE TIMING OF THE WAVE AS IT CLOSES ALOFT AND SPINS UP A
SURFACE LOW NEAR SAN FRANCISCO BAY LATE SUNDAY INTO MONDAY.
OVERALL, THE GUIDANCE IS VERY STRONG THAT A GENERAL MODEL BLEND IS
SUPPORTED AT ABOVE AVERAGE CONFIDENCE.
..ATMOSPHERIC RIVER SINKING INTO PAC NW BY LATE TUES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/CMC
CONFIDENCE: SLIGHTLY BELOW AVERAGE
08Z UPDATE: THE 00Z ECMWF/CMC SHOW A SLOWING TREND WITH THE
ARRIVAL OF THE SHORTWAVE AND ATMOSPHERIC RIVER, WHICH PUTS THE GFS
EVEN MORE OF A FASTER OUTLIER (ALONG WITH THE UKMET). GIVEN ITS
TYPICAL FAST BIAS, WILL CONTINUE TO SIDE TOWARD THE SLOWER
ECMWF/CMC SOLUTIONS SEEN IN THE 00Z RUNS.
A NORTHERN PACIFIC STREAM / ATMOSPHERIC RIVER WILL PUSH INTO THE
PACIFIC NORTHWEST LATE IN THE FORECAST PERIOD (TUES/WED) ON THE
SOUTHERN PERIPHERY OF A STRONG GULF OF ALASKA CLOSED LOW. IN THE
BIG PICTURE SENSE THE LATEST DETERMINISTIC MODELS SHOW FAVORABLE
SIMILARITIES. ONCE THE SYSTEM MOVES ONSHORE, MORE NOTABLE
DIFFERENCES DEVELOP. THE ECMWF DIVES THE SHORTWAVE ENERGY FURTHEST
SOUTH AS A LONGWAVE TROUGH IS CARVED OUT OVER THE ROCKIES. THIS IS
SUPPORTED BY THE ECENS MEAN AS WELL AS THE 12Z CMC. THE GFS SHOWS
THIS SETUP AS WELL BUT IS SHALLOWER WITH THE DEPTH OF THE TROUGH
THAT DEVELOPS. THE UKMET IS CONSIDERABLY STRONGER WITH THE ENTIRE
SYSTEM AS IT MOVES ONSHORE. OVERALL, LEANING ON THE PREVIOUS
PREFERENCE, WILL CONTINUE TO SUGGEST A ECMWF/CMC 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
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