448
FXUS10 KWNH 271825
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
124 PM EST FRI DEC 27 2019
VALID DEC 27/1200 UTC THRU DEC 31/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH PREFERENCES/CONFIDENCE INTERVALS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..CENTRAL CONUS LARGE CLOSED LOW/SURFACE CYCLONE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM THROUGH 30.00Z; 00Z ECMWF/UKMET/CMC BLEND
THEREAFTER
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
19Z UPDATE: THE 12Z ECMWF TRENDED FAVORABLY TOWARD A MORE
CONCENTRIC SOLUTION INITIALLY NEARLY CENTRALIZED IN THE 00Z ECENS
SUITE AND WITH THE 12Z GEFS SUITE TRENDING TOWARD THE ECMWF, IT
ALONG WITH SLIGHT ADJUSTMENTS OF THE 12Z CMC AND UKMET PROVIDES
INCREASING CONFIDENCE IN A NON-NAM SOLUTION THROUGH 30.00Z THEN
SHIFTING TO A 12Z ECMWF/UKMET/CMC BLEND (FOCUSED ON THE ECMWF).
CONFIDENCE IS RAISED TO SLIGHTLY ABOVE AVERAGE.
CONSOLIDATION OF MULTIPLE SYSTEMS ACROSS THE CENTRAL PLAINS LATER
TODAY INTO TOMORROW, CLOSED LOW IN THE SOUTHWEST LIFTS NORTHWARD,
EXPANDING A HIGH-AMPLITUDE TROF AS NORTHERN STREAM/MERIDIONAL JET
CARVES OUT THE WESTERN PORTION OF THE TROF. TIMING/SHAPE OF THE
SHORT-WAVE FEATURES CONTINUES TO LEAD TO SMALLER SCALE BUT
METEOROLOGICALLY IMPORTANT EVOLUTION DIFFERENCES TO THE DEEP
SURFACE CYCLONE THAT MOVES OUT OF THE CENTRAL PLAINS BEFORE
PIVOTING ACROSS S MN/N IA BY THE END OF THE WEEKEND. HERE THE,
NAM IS A BIT SLOWER WITH THE POLAR JET COMING NORTH AND THE RIGHT
ENTRANCE TO THE EXITING JET ACROSS THE GREAT LAKES/ONTARIO, IS
IDEALLY ORIENTED FOR DUAL JET ENHANCEMENT AND DEVELOPMENT THAT
PRESSES THE ENERGY TOO FAR NORTH ON A STRONGER THAN ENSEMBLE LOW
LEVEL JET. THE 12Z GFS HAS THE SIMILAR STRONGER LLJ RELATIVE TO
THE CMC/ECMWF BUT DOES NOT GO AS FAR NORTH AS THE NAM, BUT STILL
IS ON THE NORTHERN FRINGE OF THE OVERALL ENSEMBLE SUITE. THE 00Z
ECMWF IS ON THE OTHER SIDE OF THE SUITE BY THE MATURE STAGE OF THE
CYCLONE AND IS MUCH MORE CONCENTRIC. THIS HAS BEEN STABLE THROUGH
THE LONGER TERM TRENDS, THOUGHT IS EVEN WEST AND SOUTH OF THE BULK
OF ECENS MEMBERS SUGGESTING A COMPROMISE, WHICH IS WHERE THE
CMC/CMCE AND UKMET ARE GENERALLY THROUGH 30.00Z SO A NON-NAM
SOLUTION IS PREFERRED.
AS THE NORTHERN STREAM SHORTWAVE REACHES THE BASE SUNDAY, IT
SHARPENS A BIT AND SWINGS NEGATIVE TILT THROUGH THE MISSISSIPPI
VALLEY, SUPPORTING A STRONGER TRIPLE POINT SURFACE CYCLONE THAT
WILL BLAST THROUGH THE GREAT LAKES MONDAY. THE NAM BEING
OFF-BALANCE WITH THE INITIAL CENTER HUB IS DISCOUNTED A BIT, BUT
SEEMS TO HAVE SIMILAR TIMING AND PLACEMENT IN THE STREAM
(GEOGRAPHICALLY) TO THE ECMWF/CMC/UKMET...BUT REMAINS TOO FAST AND
THEN NORTH. THE 12Z GFS IS INITIALLY SLOWER BRINGING THE
SHORTWAVE OUT AND SO SHIFTS A BIT EAST BY THE TIME IT ROLLS
THROUGH THE GREAT LAKES AND APPEARS AS AN EASTERN OUTLIER ON DAY 3
IN THE ENSEMBLE SUITE THOUGH BETTER THAN THE 06Z, SO WILL HEDGE
AWAY FROM THE GFS ON DAY3. THE UKMET APPEARS TO HAVE A TYPICAL
WET BIAS THROUGH THE TENNESSEE VALLEY/CUMBERLAND PLATEAU INTO THE
UPPER REACHES OF THE OHIO VALLEY, SO WHILE THE MASS FIELDS ARE
STRONG, IT MAY BE HIGHLY PRUDENT TO TEMPER THE QPF FIELDS AS WELL.
RUN TO RUN VARIANCE AND THE WEST V. EAST DIFFERENCES KEEP THE
CONFIDENCE AT AVERAGE FOR THIS BLEND.
..PACIFIC SHORTWAVE DIVING ALONG THE WEST COAST SUN-TUES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
19Z UPDATE: THE 12Z UKMET TRENDED FAVORABLY TO THE TIMING OF THE
INITIAL PREFERENCE HAVING STRETCHED MORE OF THE SHORTWAVE ENERGY
INTO THE SOUTHERN STREAM VS OVER-TOPPING THE RIDGE, WHILE IT
REMAINS MORE COMPACT/A TAD DEEPER THAN SAY THE MORE BROAD
CMC...THERE IS INCREASING CONFIDENCE TOWARD ITS INCLUSION THE
PREFERENCE. SO A NON-NAM BLEND IS PREFERRED OVERALL AT SLIGHTLY
ABOVE AVERAGE CONFIDENCE.
A NARROW, NORTHEAST ANGLING RIDGE IS BUILDING THROUGH THE
WEST/NORTHWEST THROUGH EARLY SUNDAY MORNING, DEFLECTING THE
INITIAL STRONG SHORTWAVE IMPULSES ROLLING THROUGH THE PACIFIC INTO
BC. THE SQUEEZING FLOW/BLOCKING FORCES THE UPSTREAM SHORTWAVE
ENERGY TO ELONGATE/STRETCH SOUTHWARD AS IT APPROACHES THE PACIFIC
NORTHWEST LATE SUNDAY. HERE THE 12Z NAM IS OUT OF SORTS, SHOWING
A TYPICAL NEGATIVE OVER-AMPLIFICATION BIAS NOTED IN THE ENDING
HOURS OF THE CYCLE RUN. THE UKMET IS CLOSER TO THIS, AND LOSES
MORE ENERGY OVER THE TOP OF THE RIDGE RELATIVE TO THE REMAINING
GUIDANCE SUITE, THIS MAKES THE SHORTWAVE A BIT SMALLER AND THEN
MORE COMPACT AS IT CURLS INTO A CLOSED LOW ALONG THE WEST COAST,
AND GIVEN STRONG FLOW, ACCELERATES FURTHER SOUTH FASTER...SO
THINKING IT SHOULD HAVE LESS INFLUENCE IN THE BLEND AS WELL.
OTHERWISE, THE ECMWF/GFS AND CMC SHOW FAIRLY SIMILAR EVOLUTION
EVEN IN A LOWER PREDICTABILITY FLOW REGIME...TO HAVE SLIGHTLY
ABOVE AVERAGE CONFIDENCE IN A 12Z GFS AND 00Z ECMWF/CMC BLEND.
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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