583
FXUS10 KWNH 090708
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
307 AM EDT THU JUL 09 2020
VALID JUL 09/0000 UTC THRU JUL 12/1200 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH FINAL PREFERENCES/CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...CLOSED LOW MOVING EAST ACROSS SOUTH-CENTRAL CANADA THROUGH
FRIDAY...
...ASSOCIATED COLD FRONT CROSSING THE NORTHERN PLAINS
WEDNESDAY/THURSDAY AND THE GREAT LAKES FRIDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/UKMET/12Z ECMWF MEAN
CONFIDENCE: AVERAGE
..07Z UPDATE
THE 00Z ECMWF REMAINED SIMILAR TO ITS PREVIOUS 12Z CYCLE AND THE
00Z UKMET ADJUSTED SIMILAR TO THE ECMWF. HOWEVER, THE 00Z CMC
REMAINS A BIT SLOWER AND DEEPER WITH THE BASE OF THE TROUGH AXIS
WHICH MOVES EAST TOWARD THE APPALACHIANS INTO SATURDAY MORNING
WHICH IS LARGELY UNSUPPORTED.
..PREVIOUS DISCUSSION FOLLOWS
SOUTH OF A MID-LEVEL CLOSED LOW TRACKING ACROSS SOUTHERN CANADA, A
SHORTWAVE TROUGH WILL ORGANIZE AND MOVE EAST ACROSS THE
MISSISSIPPI RIVER THROUGH FRIDAY MORNING. DIFFERENCES WITH THE
EVOLUTION OF THIS FEATURE IMPACT PLACEMENT OF A RELATED COLD FRONT
AT THE SURFACE. THE 12Z CMC IS THE MOST AGGRESSIVE AND SLOWEST
WITH THE MID-LEVEL SHORTWAVE WHILE THE 00Z GFS APPEARS TO BE THE
FASTEST. THE 00Z NAM IS ALSO A BIT SLOW WHILE THE 12Z UKMET IS
LESS DEFINED BY THE END OF THE WEEK. MESOSCALE CONVECTIVE DETAILS
MAKE FOR DIFFERENCES WITH RESPECT TO SYNOPTIC EVOLUTION IN EACH
MODEL WHICH IS TYPICAL THIS TIME OF YEAR AND KEEPING CONFIDENCE
AVERAGE AT BEST.
...LOW PRESSURE MOVING NORTHEAST ALONG EASTERN SEABOARD INTO THIS
WEEKEND...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/00Z ECMWF/12Z ECMWF MEAN BLEND
CONFIDENCE: AVERAGE
..07Z UPDATE
THE 00Z ECMWF'S MID-LEVEL CENTER OF THE EAST COAST LOW SHIFTED
FARTHER AWAY FROM THE COAST COMPARED TO ITS PREVIOUS 12Z CYCLE,
WITH ITS SURFACE REFLECTION ALSO MOVING FARTHER OFFSHORE, BUT WITH
LESS DISPLACEMENT COMPARED TO THE UPPER LEVELS. THE 00Z UKMET
ADJUSTED IN THE DIRECTION OF THE 00Z ECMWF BUT REMAINS A BIT
FARTHER SOUTH WITH ITS 850-500 MB LOW, AS DOES THE 00Z CMC. THE
PREFERENCE IS TO BE NEAREST TO THE AVERAGE OF THE GEFS/ECMWF MEAN
POSITIONS, WHICH IS IN BETWEEN THE 00Z NAM AND 00Z ECMWF, BUT
CLOSER TO THE ECMWF POSITION...OR BETWEEN THE 12Z AND 00Z ECMWF
CYCLES.
..PREVIOUS DISCUSSION FOLLOWS
THE 00Z NAM AND 00Z GFS ARE QUICKER TO BRING A SURFACE LOW
NORTHWARD ALONG THE EAST COAST THROUGH THE END OF THE WEEK. THE
00Z GFS IS THE FASTEST TO MOVE THE LOW NORTHWARD AND DEVIATES FROM
THE RELATIVELY GOOD RUN TO RUN CONSISTENCY SEEN IN THE PAST 4
CYCLES OF THE ECMWF/GEFS/CMC ENSEMBLE SCATTER LOW PLOTS. THE
SOMEWHAT SLOWER 12Z ECMWF/CMC ARE A BETTER MATCH TO THE ENSEMBLE
CLUSTERING OVER THE NEXT 36-60 HOURS WHILE THE 12Z UKMET BECOMES
SLOWER THAN MOST GUIDANCE. WHILE THE MODELS ARE WELL INITIALIZED
WITH THE CURRENT SURFACE FEATURE AT 00Z, WITH MID-LEVEL RIDGING TO
THE NORTH OF THE ADVANCING LOW, THERE IS SOME QUESTION WITH HOW
QUICKLY THE LOW WILL ADVANCE. THERE ARE ALSO UNCERTAINTIES WITH
THE UPSTREAM (OH VALLEY) TROUGH EVOLUTION AND SUBSEQUENT
INFLUENCES ON THE MID-UPPER LEVEL FLOW WHICH KEEPS CONFIDENCE IN
THE PREFERENCE ONLY NEAR AVERAGE.
...TROUGH MOVING INTO THE PACIFIC NORTHWEST THURSDAY NIGHT,
OVER-TOPPING THE RIDGE INTO THE UPPER MIDWEST BY SAT AND DIVING
INTO THE OH VALLEY BY SUNDAY MORNING...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THE MODELS SHOW SIMILARLY WITH THIS SYSTEM WITH ONLY MINOR
ADJUSTMENTS NOTED IN THE 00Z ECMWF/UKMET/CMC COMPARED TO THEIR
PREVIOUS 12Z CYCLES.
..LARGER SCALE TROF DROPPING INTO PACIFIC NW SATURDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE
..07Z UPDATE
NO SIGNIFICANT ADJUSTMENTS WERE NOTED IN THE 00Z ECMWF/UKMET/CMC
COMPARED TO THEIR PREVIOUS 12Z CYCLES.
..PREVIOUS DISCUSSION FOLLOWS
MINOR TIMING DIFFERENCES EXIST WITH THE 00Z NAM AND GEFS MEAN
SLIGHTLY SLOWER TO ADVANCE THE TROUGH AXIS EASTWARD INTO THE
PACIFIC NORTHWEST WHILE THE 12Z UKMET/CMC ARE FASTER. HOWEVER,
THESE DIFFERENCES IN TIMING ARE SMALL ENOUGH THAT A MIDDLE GROUND
OR GENERAL MODEL BLEND APPEARS REASONABLE ACROSS THIS AREA OF THE
COUNTRY.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
THIS PRODUCT WILL TERMINATE AUGUST 15, 2020 WITH THE 21Z ISSUANCE:
WWW.WEATHER.GOV/MEDIA/NOTIFICATION/PDF2/SCN20-58PMDHMD_TERMINATION.
OTTO
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