011
FXUS10 KWNH 231852
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
151 PM EST MON DEC 23 2019
VALID DEC 23/1200 UTC THRU DEC 27/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH PREFERENCE AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..CLOSED LOW ACROSS SOUTHEAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
19Z UPDATE: THE 12Z CMC TRENDED A BIT FASTER BUT STILL LAGS THE
SUITE OVERALL BY 25.12Z, SO WILL KEEP WITH INITIAL NON-CMC BLEND.
---PRIOR DISCUSSION---
DEEP, SYMMETRIC CLOSED LOW OVER THE NORTHEAST GULF AND ASSOCIATED
SURFACE LOW WILL CONTINUE TO WOBBLE WITH CONTINUED EASTWARD
PROGRESSION THROUGH THE SHORT-TERM FORECAST PERIOD. THE 12Z NAM
HAS TRENDED BACK INTO THE FOLD, WITH A FASTER EASTWARD TRACK, ON
PAR WITH THE 12Z GFS AND 00Z ECMWF/UKMET. THE 00Z CMC CONTINUES
TO SLOW EJECT EASTWARD, AND SO A NON-CMC BLEND IS FAVORED FOR THE
REMAINDER OF THE SHORT-RANGE. CONFIDENCE IS SLIGHTLY ABOVE
AVERAGE FOR THIS SYSTEM.
...DEEP LATITUDE TROF CROSSING SOUTHWEST, WEAKENING THROUGH THE
PLAINS BEFORE CONSOLIDATING IN RED RIVER VALLEY OF THE NORTH
THURSDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GEFS/ECMWF/UKMET/CMC BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
19Z UPDATE: THE CMC WAS A BIT SLOWER, AND THE UKMET WAS A BIT
DEEPER/SOUTH AND THE ECMWF A TAD WEST TRACKING THROUGH THE PLAINS,
BUT THE END RESULT IN COMING TOGETHER OVER THE RED RIVER VALLEY
INTO SOUTHERN CANADA, WAS ESSENTIALLY SIMILAR TO INITIAL
PREFERENCE. AS SUCH WILL UPDATE PREFERENCE TO 12Z BLEND OF THE
GEFS/ECMWF/UKMET/CMC, BUT STILL SLIGHTLY BELOW AVERAGE GIVEN THE
MODEST SPREAD AND UNCERTAINTY OF MULTIPLE SMALL SCALE PIECES
COMING TOGETHER IS ALWAYS A BIT DIFFICULT TO LOCK DOWN.
---PRIOR DISCUSSION---
CURRENT GOES-WV SUITE DEPICTS A COMPACT SHORTWAVE/SMALL CLOSED LOW
WELL SOUTHWEST OF CA WITH TROF EXTENDING TO ANOTHER SMALL COMPACT
SHORTWAVE OVER NE OREGON. THIS INITIAL SHORTWAVE PAIRING, WILL
GIVE WAY TO THE BROADENING LARGER SCALE TROF THAT EXPANDS ACROSS
THE INTERMOUNTAIN WEST TO 135W BY WED, IN DOING SO, THE OLDER BASE
SHORTWAVE, ELONGATES AND WEAKENS MOVING THROUGH THE SOUTHWEST AND
EVENTUALLY INTO THE CENTRAL PLAINS BY MIDDAY WED. THE NORTHERN
STREAM COMPACT LOW IS RETAINED AND SLOWLY WOBBLES INTO S ALBERTA.
BY THIS POINT, THE GUIDANCE IS STARTING TO DECOUPLE IN SOLUTIONS.
THE 12Z GFS, AS AN INITIAL OMEGA BLOCK, WITH TAIL OF SHORTWAVE
ENERGY LINGERING THROUGH THE SOUTHEAST CANADIAN PRAIRIES AND THAT
ALONG WITH A STRONGER/SLOWER CLOSED LOW IN ALBERTA, ALLOWS FOR THE
SHORTWAVE EMERGING FROM THE PLAINS TO DEVELOP MUCH FURTHER NORTH
AND EAST FROM PRIOR GUIDANCE AND BULK OF GEFS MEMBERS (ENSEMBLE
SUITE AS A WHOLE), WHICH MAY BE A GOOD REPLACEMENT TO THE
OPERATIONAL. THE 12Z NAM, WHILE MORE SENSIBLE IN THE LOCATIONS OF
THE SHORTWAVE PIECES, SHOWS TYPICAL DAY 3 OVER-AMPLIFICATION WITH
MUCH COLDER AIR SURGING THROUGH MT/ND IN ADVANCE OF THE SYSTEM
(AIDING THE INTENSIFICATION). AS SUCH WILL FAVOR AN
ECMWF/UKMET/CMC AND GEFS BLEND BUT AT SLIGHTLY BELOW AVERAGE
CONFIDENCE GIVEN ALL THE UNCERTAINTY IN TIMING, MAGNITUDE OF EACH
OF THESE PIECES COMING TOGETHER OVER THE RED RIVER VALLEY OF THE
NORTH THURSDAY.
..WESTERN SIDE OF LARGE SCALE TROF IN PACIFIC
DEVELOPING SW CA
CLOSED LOW...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM
CONFIDENCE: AVERAGE
19Z UPDATE: THE 12Z CMC TRENDED AWAY FROM TAPPING THE MOISTURE
STREAM WITH THE WEAKENING/STRETCHING VORTICITY STRIP PRIOR TO THE
MAIN HEIGHT-FALLS. WHILE, THE CLOSED LOW IS A TAD SLOWER IT
REMAINS WELL SITUATED WITH THE INITIAL PREFERENCE AND THE 12Z
ECMWF/GEFS ADDITIONS. THE 12Z UKMET ALSO SLOWED SLIGHTLY,
ALLOWING FOR A TIGHTENING OF THE SOLUTION PACKAGE OVERALL, AND
LEAVING THE NAM AS THE MAIN DEPARTURE OF THE WHOLE SUITE. AS SUCH
WILL SWITCH PREFERENCE TOWARD A NON-NAM BLEND, THOUGH FAVORING THE
ECMWF/GFS IN THE WEIGHTING.
---PRIOR DISCUSSION---
BY LATE TUESDAY, A LARGE SCALE GLOBAL TROF WILL BE FORMING FROM
135W INTO THE INTERMOUNTAIN WEST. A NARROW VORTICITY STRIP WILL
SHEAR OUT IN FAVOR OF THE COMPACT SHORTWAVE TRACKING THROUGH THE
SOUTHERN GULF OF AK BY WED. THE 00Z CMC IS THE ONLY SOLUTION THAT
RETAINS THE VORTICITY STRIP THROUGH THE LENGTH OF THE PERIOD WITH
NEGATIVE MOISTURE FLUX TRANSPORT THROUGH S CA, WED INTO EARLY
THURSDAY. THE UPSTREAM SHORTWAVE WILL ENTER THE WESTERN PERIPHERY
OF THE LARGER TROF, ENHANCE WITH STRONG MERIDIONAL 110+ KT 25H
JET, AND SLIDE ALONG THE LENGTH OF CALIFORNIA. MUCH OF THE
GUIDANCE IS IN STRONG AGREEMENT OF THE ENERGY'S EXISTENCE AND
ORIENTATION BUT THE TIMING IS A CLEAR UNCERTAINTY. THE ENSEMBLE
TREND IS TOWARD A CLOSED LOW EVOLUTION AND OVERALL SLOWER. THIS
FAVORS THE MASS FIELDS OF THE ECMWF/CMC AND ECENS MEAN.
INTERESTINGLY, THE 12Z GFS SLOWED BY THE END OF THE FORECAST
PERIOD, BUT BECAUSE IT IS INITIALLY FAST (EARLY TOWARD DEVELOPING
THE CLOSED LOW, FURTHER NORTH) THAN THE ECMWF/ECENS. STILL, THIS
SLOWING AIDS SUPPORT TOWARD THE ECMWF/CMC TIMING OVERALL AND AWAY
FROM THE 12Z NAM AND 00Z UKMET. BOTH WHICH HAVE A TENDENCY TO BE
FASTER WITH CLOSED LOWS. SO OVERALL, A 12Z GFS AND 00Z ECMWF/CMC
BLEND IS PREFERRED THOUGH THE CMC SHOULD BE REMOVED FOR QPF
CONCERNS AS ALLUDED TO INITIALLY.
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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