433
FXUS10 KWNH 081852
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
151 PM EST SAT FEB 08 2020
VALID FEB 08/1200 UTC THRU FEB 12/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...WEAK SHORTWAVE CROSSING THE OH VALLEY/APPALACHIANS
TODAY/TONIGHT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THE MODELS SHOW SIMILARLY WITH THIS SYSTEM.
..DEEP TROUGH/CYCLONE CROSSING THE NORTHWEST TODAY
...DOWNSTREAM TROUGHING OVER THE NORTHERN PLAINS BY SUNDAY WITH
RELATED SURFACE LOW TRACKING INTO THE UPPER MIDWEST WITH TRAILING
COLD FRONT ACROSS THE MISSISSIPPI VALLEY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 12Z CMC BLEND
CONFIDENCE: AVERAGE
THE 12Z GFS SHOWS UP AS STRONGEST WITH THE 850 MB REFLECTION OF
THIS SYSTEM SUNDAY MORNING WITH THE 12Z NAM A CLOSE SECOND. THE
GEFS SUPPORTS THE STRONGER GFS WHILE THE 12Z ECMWF/UKMET/CMC ARE
SUPPORTED BY THE 00Z EC MEAN THROUGH MONDAY. THE 12Z NON-NCEP
GUIDANCE TRENDED SLIGHTLY STRONGER BUT GIVEN THE NEARLY EVEN SPLIT
AND SHORT TERM NATURE OF THE FORECAST, A BLEND OF THE TWO CAMPS IS
RECOMMENDED. THIS EQUATES TO A 12Z NAM/GFS AND 12Z ECMWF/UKMET
BLEND, EXCLUDING THE 12Z CMC AS ITS SURFACE LOW DEVIATES FROM THE
REMAINING MODEL GUIDANCE LATER SUNDAY NIGHT NEAR THE LOWER GREAT
LAKES REGION WITH A SOMEWHAT SLOWER PROGRESSION.
...DIGGING MID-LEVEL TROUGH OVER THE GREAT BASIN/SOUTHWEST BY
SUNDAY, EVOLVING INTO A STRONG CLOSED LOW NEAR SOUTHERN CALIFORNIA
ON MONDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z NAM/ECMWF/CMC BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
SIMILAR DIFFERENCES EXIST WITH THIS SYSTEM AS WHAT WAS SEEN ON
FRIDAY WITH THE 12Z GFS FASTER THAN ALL OF THE DETERMINISTIC
GUIDANCE AND ALMOST ALL OF THE LATEST ENSEMBLE GUIDANCE. THE 00Z
UKMET TRENDED SLOWER HOWEVER COMPARED TO YESTERDAY, AND IS ON THE
SLOWER SIDE OF THE DETERMINISTIC GUIDANCE. THE 12Z ECMWF/UKMET/CMC
TRENDED A LITTLE FASTER COMPARED TO THEIR PREVIOUS 00Z CYCLES.
ENSEMBLE SPAGHETTI HEIGHTS FROM 500 MB AT 558 DAM SUPPORT A MIDDLE
GROUND BUT THE ENVELOPE OF SOLUTIONS HAS TRENDED QUICKER COMPARED
TO ITS PREVIOUS 3 CYCLES VALID TUESDAY. THE 12Z NAM/ECMWF/CMC ARE
RATHER SIMILAR TO ONE ANOTHER AND THE 3-WAY BLEND IS RECOMMENDED
FOR THIS SYSTEM AT THIS TIME WITH THE 12Z GFS CONSIDERED VERY
UNLIKELY TO VERIFY.
..NORTHERN STREAM TROUGH/FRONT OVER THE MIDWEST BY TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/CMC BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
TIMING DIFFERENCES SHOW UP WITH THE 500 MB REFLECTION OF THIS
SHORTWAVE EARLY ON TUESDAY WITH THE 12Z NAM AND 12Z UKMET FASTEST
FOLLOWED BY THE 12Z ECMWF AND 12Z CMC. THE 12Z GFS IS SLOWEST WITH
THIS SYSTEM BY TUESDAY EVENING. GIVEN SOME OF THESE MINOR
DIFFERENCES THROUGH THE END OF THE SHORT RANGE PERIOD (00Z/12)
COULD IMPACT THE ORIENTATION OF THE FRONTAL BOUNDARY/MOISTURE
TOWARD THE GULF COAST STATES, A MIDDLE GROUND 12Z ECMWF/CMC BLEND
WILL BE PREFERRED AT THIS TIME FOR THE NORTHERN STREAM TROUGH.
..QUASI-STATIONARY FRONT OVER THE GULF COAST STATES BY TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z CMC/ECMWF BLEND
CONFIDENCE: AVERAGE
SOME LATITUDE DIFFERENCES DEVELOP WITH THIS FRONTAL BOUNDARY DUE
TO SOME DIFFERENCES ALOFT WITH THE POSITION OF A STRONG RIDGE OVER
THE WESTERN CARIBBEAN AND AN UPSTREAM CLOSED LOW OVER THE
SOUTHWEST. AS DISCUSSED ABOVE, THE 12Z GFS IS CONSIDERED TOO FAST
WITH THE EJECTION OF THE SOUTHWESTERN CLOSED LOW AND THIS IMPACTS
THE ORIENTATION OF THE FRONT DOWNSTREAM BY TUESDAY. THE 12Z NAM
SHOWED SOME DIFFERENCES IN WIND CONVERGENCE OVER THE GULF COAST
STATES ON TUESDAY BUT THE 12Z CMC/ECMWF APPEAR SIMILAR ENOUGH TO
EACH OTHER AND ARE PREFERRED WITH SURROUNDING SYNOPTIC SCALE
FEATURES TO WARRANT USE FOR THE NEARLY STATIONARY FRONT ACROSS THE
GULF COAST STATES THROUGH TUESDAY.
...MID-LEVEL SHORTWAVE POTENTIALLY REACHING THE BRITISH COLUMBIA
COAST MONDAY NIGHT AND ADVANCING INTO THE NORTHWEST FOR TUESDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS
CONFIDENCE: BELOW AVERAGE
LARGE UNCERTAINTY EXISTS WITH A SHORTWAVE ANALYZED SOUTH OF THE
WESTERN ALEUTIAN ISLANDS AT 12Z THIS MORNING, AND HOW IT INTERACTS
AND EVOLVES DOWNSTREAM TOWARD NORTH AMERICA MONDAY AND TUESDAY.
THE 00Z ECMWF WAS FASTEST WITH THIS FEATURE. TRENDS HAVE BEEN
INCONCLUSIVE WITH THE DETERMINISTIC GUIDANCE AND ENSEMBLE GUIDANCE
SHOWS ONLY WEAK SUPPORT FOR A STRONGER COMPACT SHORTWAVE AS SEEN
IN THE 12Z NAM. THE 12Z CMC WEAKENED THIS FEATURE FROM ITS
PREVIOUS 00Z CYCLE AND THE 12Z ECMWF SLOWED DOWN A BIT WHICH
APPEARS TO BE STEPS IN THE RIGHT DIRECTION. THE 12Z GFS APPEARS TO
BE A FAVORABLE MIDDLE GROUND REGARDING TIMING AND STRENGTH WITH
THIS FEATURE BUT POOR RUN TO RUN CONSISTENCY AND POOR MODEL
AGREEMENT LEADS TO BELOW AVERAGE CONFIDENCE.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
OTTO
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