298
FXUS10 KWNH 111841
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
141 PM EST SAT JAN 11 2020
VALID JAN 11/1200 UTC THRU JAN 15/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH FINAL PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..OVERALL PATTERN ACROSS THE CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/12Z ECMWF BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
..19Z UPDATE
THE 12Z UKMET SPED UP RELATIVE TO ITS PREVIOUS 00Z CYCLE WITH THE
EXITING EAST COAST SYSTEM ON SUNDAY AND THE WEAK SYSTEM
APPROACHING THE GREAT LAKES EARLY MONDAY. OUTSIDE OF THIS CHANGE
IN THE UKMET, ONLY MINOR CHANGES WERE NOTED WITH THE 12Z
ECMWF/UKMET/CMC RELATIVE TO THEIR PREVIOUS 00Z CYCLES. THERE WAS
SOME CONVERGENCE WITH THE AMPLITUDE OF THE WESTERN TROUGH FOR
TUESDAY, BUT TIMING DIFFERENCES INCREASED SLIGHTLY. A 12Z
GFS/ECMWF BLEND STILL LOOKS REPRESENTATIVE OF THE MIDDLE OF THE
MODEL SPREAD FOR THE CONUS.
..PREVIOUS DISCUSSION FOLLOWS
A POWERFUL MID-LEVEL TROUGH OVER THE SOUTHERN PLAINS THIS MORNING
IS FORECAST TO TRACK NORTHEASTWARD ATOP AN ANOMALOUS RIDGE
CENTERED JUST OFF OF THE EAST COAST. THE ACCOMPANYING SURFACE
CYCLONE WILL QUICKLY TRACK FROM THE OHIO VALLEY ACROSS NEW ENGLAND
WITH GOOD MODEL AGREEMENT. HOWEVER, THE 00Z UKMET WAS SLIGHTLY
SLOWER TO EXIT THE CYCLONE EASTWARD RELATIVE TO THE REMAINING
AVAILABLE DETERMINISTIC/ENSEMBLE GUIDANCE.
AFTER THE DEPARTURE OF THE SYSTEM CROSSING THE NORTHEAST EARLY
SUNDAY, THE UPPER LEVEL PATTERN WILL FEATURE A BROAD TROUGH
CENTERED OVER THE WESTERN 2/3 OF THE NATION WITH THE
AFOREMENTIONED RIDGE OVER THE WESTERN ATLANTIC. A SERIES OF
SHORTWAVES WILL TRACK ACROSS THE WESTERN U.S. INTO THE GREAT
PLAINS FOLLOWED BY WEAKENING TOWARD THE GREAT LAKES. THE WESTERN
PORTION OF THE FRONT EXITING THE EAST COAST ON SUNDAY WILL BE LEFT
DRAPED FROM ENSEMBLE AGREEMENT IS FAIR TO GOOD FOR THE SHORT
RANGE PERIOD (ENDING TUESDAY EVENING) WITH THE OVERALL PREFERENCE
TO BE NEAR THE MIDDLE OR 00Z ECMWF MEAN GIVEN CONSISTENCY FROM RUN
TO RUN AND ITS POSITIONING TOWARD THE MIDDLE OF THE LATEST
DETERMINISTIC/ENSEMBLE SPREAD.
THE 00Z UKMET WAS NOTED TO BE SLIGHTLY SLOWER THAN IDEAL WITH THE
FIRST OF THE SHORTWAVES EXPECTED TO REACH THE GREAT LAKES REGION
LATE SUNDAY NIGHT/EARLY MONDAY MORNING. REGARDING THE SECOND
SHORTWAVE, MODEL CONSENSUS SHOWS THE 12Z GFS TO BE A LITTLE SLOW
AS A SURFACE LOW NEARS THE GREAT LAKES ON TUESDAY, WITH THE 12Z
NAM AND 00Z ECMWF IN BETTER ALIGNMENT WITH THE MODEL CONSENSUS.
HOWEVER, THE 12Z NAM DEVELOPS TIMING ISSUES WITH A SYSTEM UPSTREAM
WHICH IMPACTS THE FLOW DOWNSTREAM OVER THE EASTERN HALF OF THE
NATION. A TRANSITION TOWARD A 12Z GFS/00Z ECMWF BLEND IS
RECOMMENDED FROM MONDAY NIGHT INTO TUESDAY.
THE LAST SHORTWAVE TO MENTION FOR THE SHORT RANGE WILL REACH THE
WEST COAST TUESDAY MORNING. OUTSIDE OF THE MUCH FLATTER 12Z NAM,
AMPLITUDE DIFFERENCES SHOW THE 12Z GFS/00Z UKMET FLATTER COMPARED
TO THE DEEPER 00Z ECMWF/CMC. A BLEND TOWARD THE MIDDLE (12Z
GFS/00Z ECMWF) IS RECOMMENDED HERE AND WILL WORK FOR MOST OF THE
REMAINDER OF THE CONUS THROUGH TUESDAY EVENING.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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