652
FXUS10 KWNH 020656
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
256 AM EDT SAT MAY 02 2020
VALID MAY 02/0000 UTC THRU MAY 05/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION INCLUDING FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...SHORTWAVE/SURFACE LOW TRACKING NEAR THE U.S./CANADIAN BORDER
THROUGH SUNDAY, FRONTAL ZONE THROUGH OHIO VALLEY; NORTHEAST
REINFORCEMENT/SURFACE REDEVELOPMENT SUNDAY TO MONDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM/ECMWF/CMC BLEND
CONFIDENCE: AVERAGE
..07Z UPDATE
NO SIGNIFICANT CHANGES NOTED IN THE 00Z ECMWF/CMC COMPARED TO
THEIR 12Z CYCLES, BUT THE 00Z UKMET DID MAKE SOME FASTER
ADJUSTMENTS TO THE TIMING OF THE NORTHERN PORTION OF THE SHORTWAVE
TROUGH REACHING THE NORTHEAST SUNDAY NIGHT. THE 00Z GFS CONTINUES
TO LOOK TOO FAST OVERALL THOUGH WITH A 00Z NAM/ECMWF/CMC BLEND
APPEARING BEST FOR THIS PART OF THE COUNTRY.
..PREVIOUS DISCUSSION FOLLOWS
THE MODELS ARE IN FAIR AGREEMENT WITH TIMING, BUT THE 00Z GFS
BECOMES FASTER WITH THE SHORTWAVE AS IT NEARS THE NORTHEAST. THIS
IS REFLECTED IN ENSEMBLE SPAGHETTI PLOTS AND COMPARISONS OF THE
00Z GFS TO THE LATEST DETERMINISTIC CONSENSUS. WHILE THERE ARE
SOME DIFFERENCES WITH FRONTAL PLACEMENT ACROSS THE MS VALLEY AND
TO THE WEST...WITH THE 12Z UKMET SLOWER IN THE SOUTHERN PLAINS, A
NON-00Z GFS BLEND OF GUIDANCE APPEARS REASONABLE AT THIS POINT IN
TIME.
...DEEP TROUGH OFFSHORE THE WEST COAST TODAY WITH REMNANT
SHORTWAVE ENERGY MOVING THROUGH THE NORTHERN ROCKIES SUNDAY
MORNING, NORTHERN HIGH PLAINS SURFACE LOW...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/UKMET/CMC/12Z ECMWF MEAN
CONFIDENCE: BELOW AVERAGE
..07Z UPDATE
THERE APPEARS TO BE SOME BETTER AGREEMENT WITH MODEL CONVERGENCE
BASED ON ADJUSTMENTS IN THE 00Z ECMWF/UKMET/CMC COMPARED TO THEIR
PREVIOUS CYCLES. THE 00Z ECMWF ADJUSTED TOWARD THE CONSISTENT
UKMET/CMC WITH THE REMNANT SHORTWAVE ACROSS SOUTHERN ALBERTA AND
SASKATCHEWAN AND ALL THREE MODELS (ECMWF/UKMET/CMC) LOOK BETTER
WITH VORTICITY IN THE ZONAL FLOW RUNNING FROM THE INTERMOUNTAIN
WEST INTO THE GREAT PLAINS. WILL CONTINUE TO FAVOR AGAINST THE 00Z
NAM/GFS GIVEN THE LATEST AVAILABLE GUIDANCE.
..PREVIOUS DISCUSSION FOLLOWS
LARGE SPREAD AND POOR RUN TO RUN CONSISTENCY MAKE FOR BELOW
AVERAGE FORECAST CONFIDENCE. INITIALLY, THERE IS GOOD AGREEMENT
WITH THE UPPER TROUGH AXIS REACHING WASHINGTON AND OREGON BUT
DIFFERENCES GROW THROUGH SUNDAY WITH THE REMNANT SHORTWAVE AS IT
MOVES INLAND ACROSS THE NORTHERN ROCKIES AND SOUTHWESTERN CANADA.
THERE ARE ALSO EMBEDDED SHORTWAVES WITHIN ZONAL FLOW ACROSS THE
INTERMOUNTAIN WEST WITH POOR MODEL AGREEMENT.
THE PREFERENCE IS TO STAY NEAR THE MIDDLE, AWAY FROM OUTLIERS,
WHILE CONSIDERING TRENDS. THIS TAKES OUT THE 00Z NAM AND 00Z GFS
WHICH ARE FASTER WITH THE UPPER TROUGH INTO SOUTHERN
ALBERTA/SASKATCHEWAN. THE 12Z ECMWF IS SLIGHTLY MORE ELONGATED
WITH THE TROUGH AXIS TOWARD THE EAST BY MONDAY MORNING, BUT THE
12Z ECMWF MEAN IS MORE IN LINE WITH A MIDDLE GROUND. THE 12Z UKMET
IS ALSO MIDDLE GROUND BUT IT LACKS A MORE ROBUST SHORTWAVE TO THE
SOUTH AS SEEN IN THE ENSEMBLES. THE 12Z CMC IS ALSO A REASONABLE
SOLUTION NEAR THE ECMWF AND ITS MEAN.
...NEXT EMBEDDED SHORTWAVE IN GULF OF AK GYRE, CLIPPING NW
MONDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
..07Z UPDATE
ADJUSTMENTS FROM THE 00Z ECMWF/UKMET/CMC FAVORED A SLOWER AND MORE
WESTWARD PLACEMENT TO THE SHORTWAVE TROUGH CLIPPING THE PACIFIC
NORTHWEST MONDAY NIGHT. THE 00Z GEFS MEAN AND 12Z ECMWF MEAN NOW
ARE IN GENERAL AGREEMENT WITH THE 00Z DETERMINISTIC MODEL SUITE,
WITH THE 00Z UKMET/CMC REMAINING A BIT MORE AGGRESSIVE/FASTER WITH
THE SHORTWAVE TROUGH AXIS COMPARED TO THE 00Z NAM/GFS/ECMWF.
..PREVIOUS DISCUSSION FOLLOWS
ENSEMBLE SPAGHETTI HEIGHTS SHOW THE 12Z UKMET AS A FAST OUTLIER
WITH THE TROUGH AXIS CLIPPING THE PACIFIC NORTHWEST MONDAY NIGHT.
THE 12Z CMC ALSO APPEARS A BIT FAST WHILE THE 00Z NAM/GFS APPEAR
SLOW. OVERALL TRENDS IN THE ENSEMBLES OVER THEIR PAST FOUR 12/00Z
CYCLES SUPPORT SOME SLOWING VALID TUESDAY MORNING WHICH WOULD
LEAVE THE FASTER GUIDANCE OUT OF THE PREFERENCE. WHILE THERE IS
SOME POTENTIAL FOR FURTHER SLOWING, PREFER TO STAY TOWARD THE
MIDDLE OR THE 12Z ECMWF/ECMWF MEAN. THIS SOLUTION IS ALSO
CONSISTENT WITH OTHER SYSTEMS DOWNSTREAM ACROSS THE CONUS.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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