380
FXUS10 KWNH 171658
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1157 AM 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 00Z CMC BECOMES A BIT OF A SLOWER AND DEEPER OUTLIER WITH THE
TROUGH AS IT MOVES INTO THE EASTERN U.S. BY THURSDAY. THE 00Z
ECMWF AND 00Z ECENS MEAN ARE ALSO SOMEWHAT ON THE SLOWER SIDE OF
THE GUIDANCE, BUT FOR NOW, WILL SUGGEST A NON-CMC BLEND GIVEN THAT
THERE IS SOME SUPPORT FOR THE SLOWER ECMWF-LED GUIDANCE FROM THE
06Z GEFS ENSEMBLE SUITE.
..LINGERING ENERGY OVER THE CENTRAL ROCKIES/HIGH PLAINS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS AND 00Z 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, 00Z ECMWF AND 00Z CMC AGREE IN TAKING THIS
ENERGY MORE PROGRESSIVELY DOWNSTREAM. HOWEVER, THE 12Z NAM AND 00Z
UKMET 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 UKMET SUGGESTS A CLOSED LOW
PUSHING EAST ACROSS SD/NE. 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: BLEND OF THE 12Z NAM AND 00Z ECMWF
CONFIDENCE: BELOW 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 AND
00Z CMC FAVOR THE ENERGY DIGGING SOUTH OFFSHORE THE PACIFIC
NORTHWEST AND ATTEMPTING TO CLOSE OFF. THE 12Z NAM AND ESPECIALLY
THE 00Z UKMET ARE MORE PROGRESSIVE AND SHOW THE SYSTEM REMAINING
MORE CLOSELY DOMINATED BY THE STRONG PACIFIC FLOW FARTHER NORTH.
THE 00Z ECMWF GENERALLY SPLITS THE DIFFERENCE BETWEEN THE SLOWER
AND FASTER CAMPS. THE ENSEMBLE MEANS ARE GENERALLY SPLIT AS WELL,
WITH THE GEFS SLOWER AND MORE OFFSHORE WITH THE ENERGY, AND THE
ECENS SUITE FASTER AND CLOSE TO A BLEND OF THE NAM AND ECMWF. THE
00Z CMCE SUITE IS ALSO VERY CLOSE TO THIS CAMP AS WELL, SO A BLEND
OF THE NAM AND ECMWF WILL BE PREFERRED. CONFIDENCE IS LIMITED
GIVEN THE COLLECTIVE MASS FIELD SPREAD WITH THE GUIDANCE.
..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
00Z CMC IS A BIT 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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