Prognostic Meteorological Discussion
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000
FXUS10 KWNH 280636
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
135 AM EST TUE FEB 28 2017

VALID FEB 28/0000 UTC THRU MAR 03/1200 UTC

...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...

00Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

BROAD LONGWAVE TROUGH OVER THE WEST (CONFLUENCE OF THREE
SHORTWAVES) TRACKS INTO THE PLAINS TUES/WED WITH ASSOCIATED
SURFACE LOW(S) ACROSS THE GREAT LAKES/NORTHEAST WED INTO THURS
WITH TRAILING COLD FRONT IN THE MS RIVER VALLEY WED AND INTO THE
MID-ATLANTIC/SOUTHEAST BY LATE WED/EARLY THURS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC BLEND (WEIGHTED TOWARD 12Z ECMWF)
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

GOES WV MOSAIC SHOWS THE CONFLUENCE OF SHORTWAVES INTO A WELL
FORECAST LARGER SCALE TROF ACROSS THE WEST...WITH THE LEAD
NORTHERN SHORTWAVE CENTERED AROUND YELLOWSTONE STARTING TO TREK
INTO THE N CENT PLAINS LATER TODAY WITH THE SURFACE LOW ALREADY
OVER NE CO/SE WY.   MODELS HAVE SHOWN AN OVERALL BETTER AGREEMENT
TO THIS WAVE AND ASSOCIATED SURFACE WAVE THAT LIFTS INTO THE GREAT
LAKES WITH THE TRAILING FRONT/SFC TROF EXTENDING BACK TO THE NEXT
WAVE/HEIGHT FALLS AS THE MAIN TROF AXIS EJECTS LATE TUESDAY INTO
WED.  OVERALL MODEL TRENDS HAVE BEEN SUPPRESSING THE LEAD WAVE
WITH EVENTUAL STALLING ACROSS THE WESTERN GREAT LAKES WITH THE
EXCEPTION OF THE GFS.  THE 00Z GFS HAS ONCE AGAIN DEEPENED THE
WAVE BUT ALSO CONTINUES TO SHIFT IT OUT FASTER...AND AS SUCH
PRESENTS THE FASTEST SURFACE WAVE IN THE MOST RECENT SUITE OF
GUIDANCE...YET THERE CONTINUES TO BE A TREND TOWARD A COMMON
SOLUTION WITH THE SLOWER SOLUTIONS TOO.

AS THE MAIN HEIGHT FALLS OF THE HIGH AMPLITUDE TROF EJECT INTO
WED...THE BASE/SOUTHERN STREAM SHORTWAVE SWINGS SLIGHTLY IN
ADVANCE OF THE NORTHERN KICKER WAVE THAT HAS TAKEN ROOT ACROSS THE
NORTHERN ROCKIES/N CENTRAL PLAINS...AND BEGINS TO CONSOLIDATE/WRAP
UP ACROSS THE MIDWEST AND OHIO VALLEY INTO THE EASTERN GREAT LAKES
LATE WED INTO THURSDAY...THIS TIMING LOOKS MUCH MORE AGREEABLE
THROUGH THE ENSEMBLE SUITE AND GLOBAL DETERMINISTIC RUNS GENERALLY
CENTERED AROUND THE 12Z ECMWF.  THE 12Z CMC APPEARS  BIT SLOWER
AND NORTHWEST OF THE TROF PRESENTED BY THE ECMWF/ECENS
MEAN...WHILE THE 00Z GFS IS A BIT FASTER WITH THE MEAN PIVOT/TROF
IN SE ONT/SW QUEBEC INSTEAD OF NY.   THE 00Z NAM LOOKS TO BE A BIT
SLOWER AND SHARPER WITH THE TROF AXIS..WHILE THE 12Z UKMET LOOKS
QUITE SIMILAR.   ALL IN ALL...MINUS THE 12Z CMC...THE MASS FIELDS
ARE QUITE SIMILARLY SHAPED SURFACE PATTERN BRINGING MUCH HIGHER
CONFIDENCE IN THE MODEL SUITE AS A WHOLE.  HOWEVER...THE REMAINING
SPREAD IN THE SURFACE PATTERN EXISTS WITH THE EXACT PLACEMENT OF
THE SURFACE LOW(S) ALONG THE SURFACE TROF AND THE PRECISE TIMING
OF THE COLD FRONT THROUGH THE SOUTH INTO THE SOUTHEAST.   THE 00Z
NAM/12Z UKMET SEEM TO CONTINUE TO LAG THE COLD FRONT COMPARED TO
THE ECMWF AND FASTER GFS.  STILL THIS MAY BE TOO PICKY GIVEN
OVERALL PATTERN AND SMALL SCALE INTERACTIONS/CONVECTIVE FEEDBACK
THAT IS LIKELY TO EXIST CURRENTLY AND CONTINUE TO VARY WITH EACH
DETERMINISTIC RUN.   AS SUCH A NON-CMC BLEND IS PREFERRED THOUGH
WEIGHTED QUITE HEAVILY TOWARD THE 12Z ECMWF AND LOWEST TO THE 00Z
GFS (SINCE IT REMAINS A SHADE TOO FAST TO THE MEAN TIMING).
CONFIDENCE REMAINS SLIGHTLY ABOVE AVERAGE IN THIS BLEND.   ALSO OF
NOTE: THERE ARE SOME QPF ISSUES WITHIN THIS BLEND SO PLEASE REFER
TO THE QPFPFD AND QPFHSD (SNOW) DISCUSSIONS FOR ADDITIONAL MODEL
PREFERENCES.

07Z UPDATE: LITTLE CHANGES FROM 12Z TO 00Z RUNS OF THE ECMWF/UKMET
AND CMC.  THE SUBTLE CHANGES THAT DID HAPPEN WAS A SLIGHT DELAY OF
THE UPSTREAM SHORTWAVE ENERGY IN THE SOUTHERN STREAM SUPPORTING A
DEEP AND FURTHER WEST SURFACE WAVE FIRST PRESENTED BY THE 00Z GFS
MOVING THROUGH THE ONTARIO PENINSULA LATE WED INTO S QUEBEC EARLY
THURSDAY.  THIS WAS ALSO REPRESENTED IN THE 00Z UKMET AND CMC
(THOUGH THE CMC WAS LIKE THE PRIOR WAVE A BIT FURTHER NORTH AND
WEST.   AS SUCH WPC PREFERENCE WILL CONTINUE TO BE NON-CMC BLEND
AT SLIGHTLY ABOVE AVERAGE CONFIDENCE.


LOW AMPLITUDE SHORTWAVE CLIPPING THE NRN ROCKIES WED MORNING INTO
NORTHERN PLAINS AMPLIFYING INTO DEEPER TROF IN GREAT LAKES TOWARD
N MID-ATLANTIC FRI
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/ECMWF/UKMET BLEND
CONFIDENCE: AVERAGE

A DEEP UPPER LEVEL LOW CRASHES INTO THE AK PANHANDLE/NW BC LATE
TUESDAY...WITH SOME DAMPENING SHORTWAVE ENERGY EJECTING DOWNSTREAM
AS A LOW AMPLITUDE WAVE THAT CLIPS THE NORTHERN ROCKIES/NW
MT...BEFORE DROPPING ACROSS THE DAKOTAS INTO THE UPPER MIDWEST
THURSDAY SPURRING A WEAK SURFACE REFLECTION.  BY LATE THURS/EARLY
FRIDAY THE WAVE INCREASED IN AMPLITUDE AT THE BASE OF LARGER
GLOBAL TROF/VORTEX CENTERED IN JAMES BAY BEFORE SHIFTING THROUGH
THE MID-ATLANTIC FRI.   THERE IS MINOR SPREAD IN THESE SOLUTIONS;
THE 00Z GFS CONTINUES TO BE MOST AMPLIFIED THROUGH THE NORTHERN
PLAINS SUPPORTING A NORTHWARD TRACK OF THE SURFACE WAVE FOLLOWED
BY THE 00Z NAM AND 12Z UKMET.   THE SOUTHERN SOLUTIONS CONTINUE TO
BE THE FLATTER 12Z ECMWF AND 12Z CMC WHICH ALSO SLIGHTLY OUTPACES
THE ECMWF.   BY LATE THURSDAY AS THE SOLUTIONS REACH THE BASE OF
THE TROF...THE NAM/UKMET AND CMC ALSO APPEAR TO SHARPEN A BIT MORE
THAN THE ECMWF/GFS AND THE BULK OF THE GEFS/ECENS MEMBERS.  THIS
GENERALLY SLOWS THE UKMET/NAM AS WELL BREAKING FROM CONTINUITY AND
SHOWING LESS METEOROLOGICAL REASONING THAN THE GFS/ECMWF.  LITTLE
BREAK IN CONTINUITY WITH THE DEEPER GFS/GEFS AND THE ECMWF/ECENS
CAMPS WITHOUT THE WAVE EVEN STARTING TO MANIFEST THROUGH THE HIGH
TERRAIN IN NW CANADA...MAKES IT HARD TO SUPPORT ONE OVER THE OTHER
ESPECIALLY WITH SMALL DIFFERENCES IN LATITUDE/MAGNITUDE AT THIS
POINT.  AS SUCH WILL FAVOR A 00Z GFS/12Z ECMWF BLEND BUT ONLY AT
AVERAGE CONFIDENCE GIVEN THE REMAINING POSSIBILITIES BEFORE
FRUITION.

07Z UPDATE: THE 00Z UKMET TRENDED A BIT FASTER THAN THE 12Z RUN
MAINLY DUE TO THE FACT IT DID NOT SHARPEN OVER THE MID TO UPPER
OHIO VALLEY FRIDAY. THIS ALLOWED IT TO NICELY SPLIT THE DIFFERENCE
OF THE GFS/ECMWF SOLUTIONS (ESPECIALLY AS THE 00Z ECMWF IS NEARLY
IDENTICAL TO THE 12Z RUN).  THE 00Z CMC ALSO SEEMS QUITE SIMILAR
BEING FURTHER SOUTH AND FAST THROUGH THE MID-ATLANTIC.  AS SUCH
WILL INCLUDE THE UKMET IN THE INITIAL GFS/ECMWF BLEND.


BROAD UPPER LOW IN GULF OF ALASKA...ONSHORE FLOW TO PACIFIC
NORTHWEST AND EMBEDDED SHORTWAVES WITHIN THE FLOW LATE THURS AND
MIDDAY FRIDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/UKMET/ECMWF BLEND
CONFIDENCE: AVERAGE

THE DEEP UPPER LOW OVER THE GULF OF AK WILL SLOWLY RETROGRADE
TUES/WED AFTER INJECTING THE PRIOR WAVE (SEE ABOVE) INTO CANADA
BUT WILL ALSO CONSOLIDATE AND BEGIN TO PUMP UP THE RIDGE OVER THE
NORTHEAST PACIFIC BRINGING IN WESTERLY/WSWLY FLOW ACROSS S BC INTO
THE PACIFIC NW.  AS THE CONSOLIDATION EVOLVES WITH SLIGHT
SOUTHEASTWARD DRIFT BY LATE THURS...AN UNDERCUTTING
SHORTWAVE/SPEED MAX RAPIDLY ADVANCES TO THE COAST.  MODELS ARE ALL
OVER THE PLACE IN TIMING OF THIS WAVE.  THE 00Z NAM BREAKING THE
WAVE INTO TWO SMALLER PARTS BUT DELAYING THE MORE POTENT ONE TO
ENTER JUST PRIOR TO THE MAIN HEIGHT FALLS OF THE DEEPER LOW LATE
THURSDAY NIGHT INTO EARLY FRIDAY WELL SLOWER THAN OTHER GUIDANCE.
THE 12Z CMC IS UNCHARACTERISTICALLY THE FASTEST SOLUTION...WHILE
THE UKMET/00Z GFS/12Z ECMWF ARE CLOSEST IN TIMING BRING IT ASHORE
AROUND 03-06Z ON FRIDAY.   OVERALL THE UKMET/GFS AND ECMWF ARE
ALSO WELL SHAPED AND TIMED WITH THE MAIN UPPER LOW/HEIGHT FALLS
APPROACHING THE PACIFIC NORTHWEST BY THE END OF THE FORECAST
PERIOD.  AS SUCH WILL FAVOR THESE 3 IN THE WPC PREFERENCE AT
AVERAGE CONFIDENCE.

07Z UPDATE: THE 00Z UKMET TRENDED A BIT BROADER WITH THE EMBEDDED
SHORTWAVE BUT OVERALL DIDN`T AFFECT THE OVERALL MASS FIELDS TOO
MUCH.  THE 00Z ECMWF DID HOWEVER TREND A BIT SLOWER BUT MORE
IMPORTANTLY AMPLIFIED THE DOWNSTREAM RIDGE ACROSS SW CANADA/NW US
IN ADVANCE OF THE SHORTWAVE...LEADING TO A SLIGHT SOUTHWARD SHIFT
OF THE WAVE AS WELL.  STILL OVERALL MATCHES WELL WITH THE
UKMET/GFS.


www.wpc.ncep.noaa.gov/html/model2.shtml...

www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

GALLINA


$$





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