990
FXUS10 KWNH 171922
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
220 PM EST MON FEB 17 2020
VALID FEB 17/1200 UTC THRU FEB 21/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH LATEST PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..PAIR OF SHORTWAVES CROSSING THE GREAT LAKES/NORTHEAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
A SHORTWAVE AND ASSOCIATED SURFACE LOW WILL CROSS THE GREAT LAKES
REGION ON TUESDAY AND THEN ADVANCE EAST-NORTHEAST AND CLIP
PORTIONS OF NORTHERN NEW ENGLAND THROUGH EARLY WEDNESDAY. IN THE
WAKE OF THIS INITIAL SHORTWAVE, THERE WILL BE ANOTHER NORTHERN
STREAM SHORTWAVE THAT WILL FOLLOW WITH ABOUT 12 HOURS WORTH OF
SEPARATION. ALL OF THIS ENERGY BY LATE WEDNESDAY WILL BE EXITING
NORTHERN NEW ENGLAND AND LIFTING THROUGH EASTERN CANADA. THE
MODELS AT THIS POINT SHOW MINIMAL MASS FIELD SPREAD AT THE SURFACE
AND ALOFT, SO A GENERAL MODEL BLEND WILL BE PREFERRED WITH BOTH
SHORTWAVES.
..BROAD LONGWAVE TROUGH OVER THE PLAINS/MIDWEST WEDNESDAY
..ENERGY REACHING THE GREAT LAKES/NORTHEAST BY THURSDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC BLEND
CONFIDENCE: AVERAGE
AS A TRANSIENT DEEP LAYER RIDGE MOVES INTO SOUTHWEST CANADA AND
ACROSS THE PACIFIC NORTHWEST BY WEDNESDAY, THERE WILL BE A
POSITIVELY TILTED AND BROAD LONGWAVE TROUGH DOWNSTREAM THAT WILL
CROSS THE NORTHERN PLAINS AND A LARGE AREA OF THE MIDWEST. BY
THURSDAY, THIS TROUGHING WILL CROSS THE GREAT LAKES AND NORTHEAST.
THE 12Z CMC BECOMES A BIT OF A SLOWER AND DEEPER OUTLIER WITH THE
TROUGH AS IT MOVES INTO THE EASTERN U.S. BY THURSDAY. THE 12Z
ECMWF IS ALSO SOMEWHAT ON THE SLOWER SIDE OF THE GUIDANCE, BUT
DOES TEND TO HAVE AT LEAST SOME SUPPORT FROM THE 00Z ECENS SUITE.
FOR NOW, WILL CONTINUE TO FAVOR A NON-CMC BLEND.
..LINGERING ENERGY OVER THE CENTRAL ROCKIES/HIGH PLAINS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS AND 12Z ECMWF
CONFIDENCE: AVERAGE
THE GUIDANCE SUGGESTS A TRAILING TAIL OF ENERGY ASSOCIATED WITH
THE AFOREMENTIONED LONGWAVE TROUGH BECOMING DETACHED AND LINGERING
OVER THE CENTRAL ROCKIES AND HIGH PLAINS LATE WEDNESDAY INTO
THURSDAY. THE 12Z GFS AND 12Z ECMWF AGREE IN TAKING THIS ENERGY
MORE PROGRESSIVELY DOWNSTREAM. THE 12Z UKMET HAS TRENDED MUCH
WEAKER AND MORE PROGRESSIVE WITH THE ENERGY AND IT ACTUALLY WEAKER
THAN THE GFS/ECMWF CAMP. HOWEVER, THE 12Z NAM AND 12Z CMC HOLD
BACK A CONSIDERABLE AMOUNT OF ENERGY BY COMPARISON. ON WEDNESDAY,
THE NAM IS THE STRONGEST SOLUTION WITH ITS ENERGY OVER WY/CO, BUT
THEN BY THURSDAY THE CMC SUGGESTS AN ELONGATED CLOSED LOW PUSHING
CENTERED NEAR THE BLACK HILLS. THE BETTER ENSEMBLE SUPPORT AND
DETERMINISTIC CLUSTERING WOULD FAVOR A SOLUTION TOWARD THE GFS AND
ECMWF, SO A BLEND OF THOSE TWO SOLUTIONS WILL BE PREFERRED.
..SHORTWAVE CLIPPING THE PACIFIC NORTHWEST THURSDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-GFS BLEND
CONFIDENCE: AVERAGE
A NORTHERN STREAM SHORTWAVE MAY CLIP THE PACIFIC NORTHWEST ON
THURSDAY AS THE PATTERN TRANSITIONS TO VERY STRONG PACIFIC FLOW
CROSSING FROM THE GULF OF AK THROUGH MUCH OF WESTERN AND CENTRAL
CANADA. THE GUIDANCE IS A BIT SPLIT ON WHETHER THIS SHORTWAVE WILL
SEPARATE OUT FROM THE STRONG NORTHERN STREAM FLOW. THE 12Z GFS
FAVORS THE ENERGY DIGGING SOUTH OFFSHORE THE PACIFIC NORTHWEST AND
ATTEMPTING TO CLOSE OFF. THE REMAINING GUIDANCE IS A BIT WEAKER
AND FLATTER, AND SUGGESTS THE SYSTEM REMAINING MORE CLOSELY
DOMINATED BY THE STRONG PACIFIC FLOW FARTHER NORTH. THE LATEST
ENSEMBLE MEANS FROM THE GEFS AND ECENS DO NOT FAVOR THE
DETERMINISTIC GFS, AND ARE GENERALLY ALIGNED WITH THE FLATTER
SOLUTIONS. SO, FOR NOW, A NON-GFS BLEND WILL BE PREFERRED.
..UPPER TROUGH/CLOSED LOW OFFSHORE CALIFORNIA BY THURSDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THE MODELS SHOW A STRONG SPLIT IN THE UPPER FLOW PATTERN BY
THURSDAY WITH A SUBSTANTIAL SOUTHERN STREAM TROUGH AND CLOSED LOW
FOCUSING OFFSHORE OF CALIFORNIA AS STRONG NORTHERN STREAM PACIFIC
FLOW ADVANCES THROUGH WESTERN CANADA. OVERALL, THERE IS DECENT
MODEL AGREEMENT WITH THE SOUTHERN STREAM ENERGY AS ALL OF THE
MODELS SHOW A NEGATIVE HEIGHT ANOMALY ASSOCIATED WITH A CLOSED LOW
JUST OFFSHORE OF CENTRAL CALIFORNIA BY THE END OF THE PERIOD. THE
12Z CMC IS A BIT DEEPER AND FARTHER EAST WITH THE PLACEMENT OF THE
CLOSED LOW AND IS GENERALLY AN OUTLIER COMPARED TO THE SUITE OF
DETERMINISTIC AND ENSEMBLE GUIDANCE. SO, A NON-CMC BLEND WILL BE
PREFERRED WITH THIS SOUTHERN STREAM TROUGHING ON THURSDAY.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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