599
FXUS10 KWNH 081714
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1213 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 NAM/GFS EVALUATION WITH PRELIMINARY 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 00Z 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 00Z ECMWF/UKMET/CMC ARE
SUPPORTED BY THE 00Z EC MEAN THROUGH MONDAY. 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 00Z
ECMWF/UKMET BLEND, EXCLUDING THE 00Z CMC AS ITS SURFACE LOW
DEVIATES FROM THE REMAINING MODEL GUIDANCE LATER SUNDAY NIGHT NEAR
THE LOWER GREAT LAKES REGION.
...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, 00Z ECMWF, 00Z 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, AND IS NOW ON THE SLOWER SIDE OF THE
DETERMINISTIC GUIDANCE. 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 (SLIGHTLY FASTER) BLENDED WITH THE 00Z ECMWF/CMC ARE
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: NON 12Z NAM BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
TIMING DIFFERENCES SHOW UP WITH THE 500 MB REFLECTION OF THIS
SHORTWAVE EARLY ON TUESDAY WITH THE 12Z NAM FASTEST FOLLOWED BY
THE 00Z UKMET AND 00Z CMC. THE 12Z GFS IS SLOWEST WHILE THE 00Z
ECMWF IS IN THE MIDDLE. DIFFERENCES THROUGH THE END OF THE SHORT
RANGE PERIOD (00Z/12) ARE RELATIVELY MINOR SO A GENERAL MODEL
BLEND WILL BE PREFERRED FOR THIS SYSTEM.
..QUASI-STATIONARY FRONT OVER THE GULF COAST STATES BY TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z 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 00Z 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 AND 00Z CMC. 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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