903
FXUS10 KWNH 071658
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1158 AM EST FRI FEB 07 2020
VALID FEB 07/1200 UTC THRU FEB 11/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..POWERFUL SURFACE LOW EXITING FROM THE NORTHEAST FRIDAY NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THE MODELS SHOW SIMILARLY WITH THIS SYSTEM AS A DEEPENING SURFACE
LOW QUICKLY RACES OFF TOWARD THE NORTHEAST, AWAY FROM THE NEW
ENGLAND COAST.
...WEAK SHORTWAVE CROSSING THE OH VALLEY AND MID-ATLANTIC
THROUGHOUT THE DAY/NIGHT ON SATURDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THERE ARE ONLY MINOR AMPLITUDE/TIMING DIFFERENCES WITH THIS
SYSTEM, BUT A GENERAL MODEL BLEND LOOKS REASONABLE FOR THIS SYSTEM.
..DEEP TROUGH/CYCLONE CROSSING THE PACIFIC NORTHWEST SATURDAY
...DOWNSTREAM TROUGHING OVER THE NORTHERN PLAINS BY SUNDAY AND
RELATED SURFACE LOW TRACKING THROUGH THE UPPER MIDWEST WITH
TRAILING COLD FRONT INTO THE LOWER MISSISSIPPI VALLEY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 12Z NAM BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
AS A POTENT MID-LEVEL SHORTWAVE REACHES THE PACIFIC NORTHWEST LATE
FRIDAY, IT WILL TRACK INTO INTERIOR PORTIONS OF THE NORTHWEST
BREAKING INTO TWO COMPONENTS. A SOUTHERN COMPONENT OF THIS SYSTEM
WILL TRACK SOUTHWARD ALONG THE WEST COAST, LIKELY CLOSING OFF A
LOW NEAR SOUTHERN CALIFORNIA. THIS SOUTHERN PORTION OF THE
SHORTWAVE IS DISCUSSED IN THE SECTION BELOW.
THE NORTHERN PORTION OF THE SYSTEM IS EXPECTED TO TRACK THROUGH
THE CENTRAL TO NORTHERN GREAT PLAINS SATURDAY NIGHT INTO THE UPPER
MIDWEST ON SUNDAY. A RELATIVELY WEAK SURFACE LOW WILL ACCOMPANY
THE UPPER SYSTEM ACROSS THE UPPER MIDWEST AND GREAT LAKES, WITH A
TRAILING COLD FRONT INTO THE LOWER MISSISSIPPI VALLEY. THE 12Z
NAM'S SHORTWAVE IS STRONGER THAN THE REMAINING MODEL CONSENSUS AND
ALSO A BIT FASTER. THERE ARE SOME MINOR TIMING DIFFERENCES AMONG
THE REMAINING GUIDANCE WITH THE 00Z ECMWF A BIT SLOWER AND 12Z GFS
A BIT FASTER. A BLEND BETWEEN THE 12Z GFS AND 00Z ECMWF IS
PREFERRED AS IT FITS WELL WITHIN THE MIDDLE OF THE LATEST ENSEMBLE
SPREAD.
...DIGGING MID-LEVEL TROUGH OVER THE GREAT BASIN/SOUTHWEST BY
SUNDAY, EVOLVING INTO A STRONG CLOSED LOW NEAR SOUTHERN CALIFORNIA
ON MONDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z NAM, 00Z ECMWF AND 00Z CMC
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
ENSEMBLE SPAGHETTI PLOTS AT 500 MB FOR THE 558 DAM HEIGHT SUPPORT
THE 12Z NAM, 00Z ECMWF AND 00Z CMC AS ENERGY ALOFT SLIDES DOWN THE
WEST COAST AND ALLOWS A CLOSED LOW TO FORM OVER CALIFORNIA BY
MONDAY MORNING.
THE 12Z GFS DOES NOT AMPLIFY THE POSITIVELY TILTED MID-LEVEL
TROUGH AS FAR BACK TO THE WEST AS THE REMAINING
DETERMINISTIC/ENSEMBLE CONSENSUS SATURDAY NIGHT INTO SUNDAY. THIS
DIFFERENCE IN THE 12Z GFS CONTINUES THROUGH MONDAY EVENING WITH
THE 500 MB ENERGY LESS CLOSED OFF AND SEPARATED FROM THE NORTHERN
STREAM WESTERLIES THAN THE REMAINING MODEL GUIDANCE. THE 00Z UKMET
LOOKS SIMILAR IN THE WAY IT CLOSES OFF THE MID-LEVEL ENERGY TO THE
MODEL CONSENSUS BUT THE ENSEMBLES WOULD SUGGEST THAT THE 00Z UKMET
IS TOO FAST. THIS RESULTS IN THE 00Z UKMET'S POSITION FALLING OUT
OF ALIGNMENT WITH THE PREFERENCE BY MONDAY EVENING.
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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