724
FXUS10 KWNH 061648
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1147 AM EST THU FEB 06 2020
VALID FEB 06/1200 UTC THRU FEB 10/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH LATEST MODEL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..FULL LATITUDE TROUGH IMPACTING THE CENTRAL/EASTERN U.S
..EMBEDDED VIGOROUS SHORTWAVE TROUGH LIFTING NORTHEAST
..CONSOLIDATING LOWS FROM THE TN VALLEY TO THE NORTHEAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-GFS BLEND
CONFIDENCE: ABOVE AVERAGE
NORTHERN STREAM SHORTWAVE IS STARTING TO INTERACT WITH THE BASE OF
THE POSITIVE-TILT FULL LATITUDE TROF ACROSS THE MS VALLEY,
ALLOWING FOR THE KICK/AMPLIFICATION AS IT LIFTS NORTH THROUGH THE
SOUTHEAST AND EAST COAST BY FRIDAY. THIS WILL ALLOW FOR A
CONSOLIDATION OF THE SURFACE LOW THROUGH THE MID-ATLANTIC TOMORROW
MORNING WITH A WEAK WAVE THAT CONTINUES TO RAPIDLY DEEPEN THROUGH
DOWNEAST MAINE FRIDAY EVENING. GUIDANCE HAS COME INTO VERY STRONG
AGREEMENT WITH THE MASS FIELDS, INCLUDING THE SURFACE TROF/WEAK
WAVE ALONG THE COAST PRECURSORY TO THE MAIN SYSTEM.
TROWAL/COMMAHEAD SNOW AREAS ALSO CONTINUE TO CLIMB IN QPF BUT WITH
SOLID AGREEMENT IN ORIENTATION AND SMALL VARIATION IN QPF TO HAVE
ABOVE AVERAGE CONFIDENCE IN GOING WITH A GENERAL MODEL BLEND FOR
THE DURATION OF THE SYSTEM.
..SHORTWAVE CROSSING THE PLAINS AND OH VALLEY BY SATURDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND
CONFIDENCE: ABOVE AVERAGE
STRONG FLOW WILL CONTINUE TO OVER-TOP A BROAD BUT DOMINANT EASTERN
PACIFIC/WEST COAST RIDGE AXIS THROUGH THE REMAINDER OF THE WEEK.
THIS WILL ALLOW SUBTLE SHORTWAVE ENERGY CRESTING THE RIDGE TO DIVE
SOUTHEAST ACROSS THE CENTRAL/NORTHERN PLAINS ON FRIDAY AND THEN
TOWARD THE OH VALLEY ON SATURDAY. A WEAK AREA OF SURFACE LOW
PRESSURE AND A FRONT WILL BE ASSOCIATED WITH THIS ENERGY. THE 00Z
UKMET CONTINUES TO BE A BIT FAST, BUT NOT TERRIBLY OUT OF POSITION
IN AMPLIFICATION/DEPTH, SO JUST A TAD FASTER THAN THE GFS WHICH OF
COURSE IS FASTER THAN THE ECMWF/CMC. THE 12Z NAM WHILE MUCH
BETTER STILL SEEMS TO HAVE A BIT GREATER AMPLIFICATION ACROSS THE
TN VALLEY ON SAT, BUT THIS MAY BE GETTING TOO PICKY, BUT FOR
HIGHEST CONFIDENCE A NON-NAM BLEND IS SUPPORTED.
..DEEP TROUGH/CYCLONE CROSSING THE PACIFIC NORTHWEST SATURDAY
...DIGGING ENERGY OVER THE GREAT BASIN/SOUTHERN CALIFORNIA BY
SUNDAY...
..DOWNSTREAM TROUGHING OVER THE NORTHERN PLAINS BY SUNDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-UKMET BLEND, REMOVE 12Z NAM AFTER 78HRS
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
A WELL ADVERTISED COMPACT SHORTWAVE/CLOSED LOW EVOLVES IN THE GULF
OF AK OUT OF THE LARGER SCALE BERING SEA LOW. EVEN EARLY IN THE
FORECAST PERIOD, THE 00Z UKMET IS GENERALLY SOUTH AND SLIGHTLY
FASTER WITH THIS SYSTEM IN AN OTHERWISE TIGHT CLUSTERING. AS THE
LOW ENTERS THE PACIFIC NORTHWEST, THE FLOW BEGINS TO SPLIT...THIS
DRAWS THE SURFACE LOW INTO THE NORTHERN HIGH PLAINS (PLEASE SEE
SECTION BELOW), THOUGH THE MAJORITY OF MID TO UPPER LEVEL ENERGY
BEGINS TO OPEN WITH THE UPSTREAM ENERGY DIGGING A DEEP TROF
THROUGH OR INTO THE GREAT BASIN, AND EVENTUALLY INTO S CA BY 00Z
MONDAY AS AN "INSIDE SLIDER". THE ECMWF IS A BIT SLOWER AND
ALLOWS FOR GREATER ENERGY WEST OF THE SPINE OF THE SIERRA NEVADA
(SO NOT A 'SLIDER' PER SE), BUT IT MAY JUST BE A TAD TOO SLOW
(TYPICAL OF ANY POTENTIAL NEGATIVE BIAS) AS THE GFS/GFS/CMC ARE
MORE EAST. THE 12Z NAM, ABOUT MID-WAY THROUGH THE EVOLUTION
PROCESS REMAINS STRONG (AS IT TYPICALLY DOES) BUT ALSO BECOME
QUITE FAST, EVEN OUT PACING THE GFS, AND NEARS THE UKMET. THIS IS
LESS FAVORED OVERALL AND SO THE NON-UKMET BLEND WILL TRANSITION TO
A 12Z GFS AND 00Z ECMWF/CMC BLEND AT 78-84HRS. CONFIDENCE IS
SLIGHTLY ABOVE AVERAGE
...SEPARATING SHORTWAVE ENERGY;SURFACE LOW TRACKING OUT OF
NORTHERN HIGH PLAINS INTO UPPER MIDWEST SUN...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-UKMET, HEDGE WEIGHTING TO 00Z ECMWF/12Z GFS
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
AS DESCRIBED ABOVE, AS THE STRONG SHORTWAVE ENTERS THE PACIFIC NW,
BROADENING GLOBAL TROUGH ACROSS CANADA, ALLOWS FOR THE LEADING
EDGE/INNER CORE OF THE CLOSED LOW TO SPLIT EASTWARD ALONG THE
SPINE OF THE NORTHERN US ROCKIES. THE UKMET IS ALREADY TOO FAST
AND SOUTH, BUT ALSO SHEDS THE LEAST AMOUNT OF ENERGY EASTWARD AND
THEREFORE THE SURFACE LOW WEAKENS AND SLOWS AS THE UPPER LEVEL
CORE SHEARS THROUGH TO THE FAR NW GREAT LAKES BY 00Z MON. THE
OTHER GUIDANCE IS FAIRLY SOLIDLY AGREEING THROUGH MUCH OF THE
EARLY WEEKEND; HOWEVER, THE TYPICAL LATE DAY 3 BIASES MANIFEST.
THE 12Z NAM WHILE CENTRALLY LOCATED IS A BIT
DEEPER/AMPLIFIED...THE GFS IS A TAD WEAKER AND FASTER, THE ECMWF
IS A BIT SLOWER BUT SLIGHTLY STRONGER THAN THE EQUALLY SLOW CMC.
SO OVERALL, A NON-UKMET BLEND IS SUPPORTED BUT WILL HEDGE TOWARD A
MORE TRADITIONAL ECMWF/GFS BLEND WITH LOWER WEIGHTING OF THE
NAM/CMC.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
GALLINA
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page