Prognostic Meteorological Discussion
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FXUS10 KWNH 240629
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
128 AM EST FRI FEB 24 2017

VALID FEB 24/0000 UTC THRU FEB 27/1200 UTC

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

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

SOUTHERN STREAM CLOSED LOW FEATURE OVER S FL LIFTING NE/WEAKENING
OFF THE SOUTHEAST COAST THROUGH SAT BEFORE ABSORBING INTO NORTHERN
STREAM SUN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

MODELS SHOW STRONG ENOUGH AGREEMENT IN STRENGTH/TIMING/PLACEMENT
TO SUPPORT AN ABOVE AVERAGE CONFIDENCE GENERAL MODEL BLEND.

07Z UPDATE: CONTINUED AGREEMENT WAS NOTED WITH THE 00Z NON-NCEP
SOLUTIONS AND AS SUCH WILL CONTINUE TO PREFER A GENERAL MODEL
BLEND AT ABOVE AVERAGE CONFIDENCE.


BROAD LONGWAVE TROF EXITING THE INTERMOUNTAIN WEST FRI WITH
DEVELOPING CLOSED LOW AND SURFACE LOW OVER MIDWEST LATE FRI INTO
SAT...AND THROUGH THE CENTRAL GREAT LAKES INTO ONTARIO BY EARLY
SUN...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

MODEL GUIDANCE CONTINUES TO CONSOLIDATE THE MASS FIELDS AROUND A
COMMON SOLUTION VERY NEAR THE 00Z GFS/12Z ECMWF SOLUTION.  THE 12Z
UKMET AND CMC MASS FIELDS ARE A BIT SLOWER MAINLY IN THE LOWER
LEVELS/SURFACE LOW INITIALLY AND THEN FAVOR A DEEPER TROF THROUGH
THE MIDDLE ATMOSPHERE AND STRONGER SFC REFLECTION OF THE SECONDARY
FRONTAL ZONE/BENT BACK OCCLUDED FRONT CROSSING THE GREAT LAKES.
THIS WOULD BE OPPOSED TO THE 00Z GFS WHICH SHOWED A TYPICAL
SLIGHTLY FASTER SOLUTION.  THIS SEEMS FAIRLY MINOR WITHIN TIGHT
SPREAD TO SUPPORT A GENERAL MODEL BLEND WHICH WOULD COUNTERACT THE
SMALL DIFFERENCES TOWARD A MORE COMMON SOLUTION.  CONFIDENCE
CONTINUES TO GROW THOUGH THIS MINOR SPREAD DOES NOT SUPPORT FULL
CONFIDENCE JUST YET.   PLEASE REFER TO WPC QPF (QPFPFD) AND WINTER
WEATHER (QPFHSD) DISCUSSIONS FOR ADDITIONAL DETAILS AND MODEL
PREFERENCES FOR NON-MASS PREFERENCES.

07Z UPDATE: A SLIGHT FASTER SHIFT OF THE 00Z UKMET BRINGS IT INTO
BETTER OVERALL ALIGNMENT WITH THE 00Z NAM/GFS AND ECMWF.  HOWEVER
THE 00Z CMC TRENDED A BIT SOUTH WITH THE TRACK AND GENERALLY A BIT
TOO SLOW CROSSING THE GREAT LAKES INTO ONTARIO TO FAVOR IT WITHIN
THE PREFERRED BLEND.  AS SUCH A NON-CMC BLEND IS WPC PREFERENCE AT
SLIGHTLY ABOVE AVERAGE CONFIDENCE.


PAIR OF SHORTWAVES DROPPING ALONG THE WESTERN CANADIAN COAST
INTERACTING WITH DEEP CYCLONE NORTH OF HAWAII AND BEFORE
PROGRESSING INTO THE SOUTHWEST SUN/MON  (LOWER MS VALLEY RETURN
FLOW TIMING INTO MON)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM/ECMWF BLEND.
CONFIDENCE: BELOW AVERAGE

THE PATTERN REMAINS IN VERY LOW PREDICTABILITY ALONG THE WEST
COAST THROUGH THE BULK OF THE FORECAST PERIOD GIVEN SMALL
DIFFERENCES IN TIMING/STRENGTH OF SHORTWAVES AND THEIR INTERACTION
WITH THE DEEPER CLOSED LOW NORTH OF HAWAII.  THE LEAD SHORTWAVE IS
TIGHTENING THE GRADIENT WITH THE DEEP UPPER LOW IN GOES-W WV
SUPPORTING INCREASED SUBTROPICAL FLOW/JET ALONG 30N.   IT IS THE
AMOUNT OF THIS ENERGY COMING OUT OF THE SUBTROPICS THAT WILL
DETERMINE THE MAGNITUDE OF IMPACT FOR THE WEST COAST/CALIFORNIA
THROUGH THE WEEKEND.   THE ENSEMBLE SUITE SHOWS INCREASED
CONVERGENCE OF SOLUTIONS BUT THERE REMAIN MULTIPLE QUITE DISPARATE
CAMPS.  THE 00Z GFS/18Z GEFS CONTINUE TO SHOW LITTLE TO NO
INTERACTION WITH THE DEEPER WESTERN UPPER LOW AND THEREFORE ARE
VERY PROGRESSIVE WITH THE SECOND SHORTWAVE DESCENDING OUT OF BC
TODAY.  THIS LEADS TO A DEEPER MORE CONSOLIDATED SHORTWAVE
PROGRESSING THROUGH THE SOUTHWEST SUPPORTING DEEPER/STRONGER
RETURN FLOW OUT OF THE WESTERN GULF BY MONDAY THOUGH THE 00Z RUN
HAS SLOWED WITH RESPECT TO THE 12Z/18Z OPERATIONAL RUNS AND THE
12Z/18Z GEFS MEANS.  AND WHILE PLAUSIBLE...GUIDANCE AND CURRENT
OBSERVATIONS FROM SATELLITE SUGGEST THIS IS BECOMING LESS LIKELY
AS THERE SHOULD BE SOME FORM OF INTERACTION MAKING THIS CAMP LESS
FAVORABLE AT THIS TIME.

ON THE OTHER SIDE OF THE SPECTRUM...THE 12Z UKMET AND CMC ARE VERY
AGGRESSIVE IN SHEARING THE UPPER LOW EASTWARD SUPPORTING A
CONSOLIDATION OF THE WAVE INTO A DEEPER/CONCENTRIC UPPER LOW THAT
WOULD BE VERY SLOW TO PROGRESS EASTWARD AND SETUP DEEP MOISTURE
STREAM INTO THE WEST COAST. WHILE THIS MODELS HAVE BEEN FAIRLY
CONSISTENT IN THIS SOLUTION...THERE HAS BEEN VERY FEW ENSEMBLE
MEMBERS TO SUPPORT THIS INCLUDING QUITE A FEW CMCE MEMBERS BEING A
BIT MORE PROGRESSIVE CLOSER TO THE ECMWF/ECENS MEAN.

THE 00Z NAM HAS TRENDED A BIT DEEPER/SLOWER WITH GREATER
INTERACTION WITH THE WESTERN UPPER LOW/SUBTROPICAL MOISTURE
STREAM...THIS BRINGS IT CLOSER TO THE 12Z ECMWF AND CLOSER TO
YESTERDAY`S 00Z ECMWF RUN.  BOTH THE ECMWF/NAM DO NOT LINGER WITH
THE SHORTWAVE LIKE THE UKMET/CMC AND TRANSLATES THROUGH THE
SOUTHWEST LEADING TO A SLOWER BREAK OUT OF QPF IN THE LOWER MS
VALLEY BY MONDAY.  SO A 00Z NAM/12Z ECMWF BLEND SEEMS BE A FAIR
COMPROMISE OF ALL AVAILABLE POSSIBILITIES.  THOUGH WITH LARGE
SPREAD AND LOW PREDICTABILITY OF THE PATTERN (ESPECIALLY IN THE
DATA SPARSE EASTERN PACIFIC) CONFIDENCE REMAINS BELOW AVERAGE IN
THE BLEND.

07Z UPDATE: THE 00Z UKMET CONTINUES TO SUPPORT THE DEEPEST MOST
CONCENTRIC SOLUTION THOUGH THERE WAS SOME EASTWARD/MORE
PROGRESSIVE TREND TOWARD THE INITIAL PREFERENCE HAVING A BIT LESS
INTERACTION WITH THE CYCLONE NORTH OF HAWAII...STILL THIS SOLUTION
REMAINS A BIT TOO AGGRESSIVE/STRONG AND THEREFORE SLOW TO CURRENT
THINKING/PREFERENCE.  THE 00Z CMC DID TREND TOWARD A LESS
ROBUST/DEEP SHORTWAVE OFF THE WEST COAST...AND WHILE THE AMPLITUDE
OF THE WAVE WAS MORE ON PAR WITH THE ECMWF/NAM...THE TIMING
REMAINS SLIGHTLY SLOWER THAN THE ECMWF MORE ON PAR WITH THE LESS
FAVORABLE UKMET.  THE 00Z ECMWF HAS SHIFTED FASTER THAN ITS 12Z AS
WELL AS YESTERDAY`S 00Z RUN YET STILL NOT AS FAST AS THE 00Z GFS.
THIS RUN TO RUN VARIATION CONTINUES TO BELAY THE CONCERN OF LOW
CONFIDENCE IN ANY SPECIFIC DETERMINISTIC RUN WITHIN THIS PATTERN.
THIS WOULD NORMALLY BE A GOOD TIME TO UTILIZE ENSEMBLE SOLUTIONS
BUT GIVEN THE WIDE VARIATION IN TIMING THE MEANS HAVE GENERALLY
WASHED OUT THE SIGNAL OF THE TROF (SEE 12Z ECENS MEAN) RENDERING
THEM LESS DESIRABLE AS WELL.  THOUGH THE ECMWF TRENDED FASTER IT
REMAINS IN FAIRLY GOOD PLACEMENT IN TIMING WITH THE 00Z NAM...AND
AS SUCH WILL KEEP A 00Z NAM/ECMWF BLEND PREFERENCE BUT CONTINUE TO
HAVE WELL BELOW AVERAGE CONFIDENCE IN THE SOLUTION.


NEXT SHORTWAVE DROPPING OUT OF COASTAL BC TO NW US COAST SUNDAY
INTO MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-GFS BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE TRAIN OF FAST MOVING BUT STRONG SHORTWAVES CONTINUES INTO THE
END OF THE PERIOD...WITH MODELS CONTINUING TO DEPICT SHORTWAVE
ENERGY PUSHING OVER TOP THE STRONG ANTICYCLONE DOMINATING THE GULF
OF ALASKA...ACROSS THE PACIFIC NORTHWEST SUN/SUN NIGHT.
CONSIDERING TIMING ISSUES WITH THE AMPLIFYING UPPER LOW ABOVE...IT
IS SURPRISING THAT MODELS ARE IN REASONABLY GOOD ACCORD WITH THIS
NEXT SHORTWAVE DROPPING ACROSS THE PAC NW SUN/SUN NIGHT.
HOWEVER...DUE TO DECREASING SPACING WITH WHATEVER EVOLVES ACROSS
THE CA COAST.  THE DEEPER/CLOSED SOLUTIONS DOWNSTREAM IN THE
CMC/UKMET WILL PRESENT A CONVERGENCE OF THE WAVES INTO A DEEPER
WAVE EVOLUTION/COMBINATION ACROSS N CA...MAKING THEM LESS
FAVORABLE AFTER 26/12Z.   THE 00Z GFS HAVING A FASTER PROGRESSIVE
SHORTWAVE...THE MEAN TROF IS SHIFTED EASTWARD AND AS SUCH THIS
NEXT WAVE IS SHIFTED A BIT INLAND THAN THE 00Z NAM/12Z ECMWF
EVOLUTION BUT NOT DRAMATICALLY SO TO FULLY DISREGARD IT AT THIS
POINT.   THOUGH THE 00Z GFS ALSO HAVING LITTLE INTERACTION WITH
THE CLOSED LOW NORTH OF HAWAII IS ALSO LESS PHASED WITH IT
SHIFTING EASTWARD TOWARD SW CA AS PRESENTED BY THE NAM/ECMWF AS
WELL.   AS SUCH WPC PREFERENCE WILL SUPPORT A GENERAL MODEL BLEND
AT SLIGHTLY ABOVE AVERAGE CONFIDENCE UP TO 26/12Z BUT SHIFT TO
HEAVILY FAVOR THE 00Z NAM AND 12Z ECMWF IN THE BLEND WITH SOME 00Z
GFS INCLUSION AT LOWER WEIGHTING TO ACCOUNT FOR SOME OF THE
SPREAD/POSSIBILITIES FOR THE LAST 24 HRS OF THE PERIOD.

07Z UPDATE: AS DISCUSSED IN PRIOR SECTION...WITH THE 00Z UKMET/CMC
BOTH KICKING THE CLOSED UPPER LOW OFF THE WEST COAST INTO S
CA/DESERT SOUTHWEST A BIT FASTER...THE EVOLUTION OF THIS SHORTWAVE
SHOWS LESS INTERACTION AND SIMILAR EVOLUTION TO THE NAM/ECMWF.  IN
SUCH A MANNER THAT FURTHER HIGHLIGHTS THE EASTWARD SHIFT OF THE
00Z GFS...MAKING THE GFS THE CLEAR OUTLIER WITH RESPECT TO THIS
WAVE.   AS SUCH FINAL WPC PREFERENCE WILL BE A NON-GFS BLEND AT
SLIGHTLY ABOVE AVERAGE CONFIDENCE THROUGHOUT THE 84HR FORECAST
PERIOD.


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

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

GALLINA

$$





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