665
FXUS10 KWNH 231904
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
304 PM EDT WED OCT 23 2019
VALID OCT 23/1200 UTC THRU OCT 27/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
19Z UPDATE: NO CHANGES TO THE MODEL PREFERENCES AS THE 12Z EC HAS
ONLY SUBTLE DIFFERENCES FROM ITS PREVIOUS RUN. THE 12Z CMC IS NOT
AS SLOW WITH THE CLOSED LOW ACROSS THE SOUTHERN PLAINS AND IS WELL
CLUSTERED WITH THE REST OF THE MODEL GUIDANCE. HOWEVER, IT IS
STILL THE SLOWEST DETERMINISTIC SOLUTION AND THUS WILL NOT BE
ADDED TO THE BLEND AT THIS TIME.
CENTRAL U.S. CYCLONE THROUGH EARLY THURSDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
A POSITIVELY TILTED TROUGH DIGGING SOUTH FROM THE UPPER MID-WEST
INTO THE CENTRAL ROCKIES IS IN GOOD AGREEMENT AMONG THE MODELS.
IN RESPONSE, MID-LEVEL IMPULSES ROUNDING THE TROUGH WITH INTERACT
WITH SURFACE FEATURES THAT WILL CONTINUE TO PRODUCE PRECIPITATION
FROM THE NORTHERN ROCKIES ACROSS THE NORTHERN PLAINS. MEANWHILE,
AN ASSOCIATED COLD FRONT WILL CONTINUE TO TREK NORTHEAST OFF OF
MAINE.
AS A SHORTWAVE DIVES SOUTH FROM THE CENTRAL ROCKIES OVERNIGHT INTO
THE SOUTHERN PLAINS, CYCLOGENESIS WILL DEVELOP. IT WAS AT THIS
POINT WHERE MODELS STRUGGLED TO DETERMINE THE EVOLUTION OF THIS
PIECE OF ENERGY WITH THE GFS TOO FAST. HOWEVER, THE LATEST 12Z
GFS IS COMING INTO BETTER AGREEMENT, THUS FEEL A GENERAL MODEL
BLEND ACROSS THE CONUS WILL SUFFICE.
STRONGER SHORTWAVE DROPPING THROUGH ROCKIES; CLOSING OFF ACROSS
THE SOUTHERN PLAINS THROUGH SATURDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF, ECENS MEAN, UKMET, GEFS (LESSER WEIGHT)
BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
THE AFOREMENTIONED SHORTWAVE WILL CALVE OFF THE MAIN TROUGH,
SPLITTING FROM THE NORTHERN STREAM. NOW ALL MODELS ARE
ILLUSTRATING A CLOSED MID-LEVEL LOW DROPPING SOUTH INTO THE
SOUTHERN PLAINS. THOUGH THE DIFFERENCES AMONG THE MODELS CONTINUE
WITH POSITION, TIMING AND INTENSITY. THE 12Z GFS TRENDED SLOWER
AND IS COMING MORE IN LINE WITH THE MODEL DIAGNOSTIC PREFERENCES
OVER THE PAST SEVERAL DAYS: EC/EC MEAN/UKMET. THE 00Z CMC
CONTINUES TO BE THE SLOWEST SOLUTION, ALONG WITH THE LATEST SREF
MEAN; THUS WILL NOT USE WITHIN THE BLEND. A LOT DEPENDS ON THE
SHORTWAVE INTERACTION WITH BOTH THE DEPARTING TROUGH AXIS MOVING
EAST FRIDAY AND ALSO THE APPROACHING TROUGH IN THE WEST. THE
PREVIOUS RUNS OF THE GFS HAD THE SHORTWAVE BEING CARRIED BY THE
DEPARTING TROUGH, WHILE THE NON-NCEP MEMBERS HAD THE APPROACHING
TROUGH CARRY THE EXISTING SHORTWAVE/CLOSED LOW NORTHEAST. IT WOULD
SEEM THAT A SLOWER SOLUTION WITH RESPECT TO THE CLOSED LOW IS MOST
FITTING GIVEN THE ANOMALOUSLY HIGH HEIGHTS INTO ALASKA (RIDGING BY
LATE IN THE PERIOD) AND THE COOLER TEMPERATURE DIVING INTO THE
ROCKIES. IN ADDITION, THE STRENGTHENING JET AXIS TO THE NORTH ALSO
FAVORS A SLOWER PROGRESSION. SO WITH THE GFS COMING INTO BETTER
AGREEMENT WITH THE EC/EC MEAN/UKMET, COULD FEASIBLY INCORPORATE
THIS MODEL INTO THE BLEND. HOWEVER, FOR NOW, SINCE THE GFS IS
STILL TOO FAST, WILL USE THE GEFS MEAN. AGAIN, THE POSITION AND
TIMING OF THE SHORTWAVE AND HOW IT INTERACTS WITH THE APPROACHING
TROUGH WILL ULTIMATELY DETERMINE THE TRACK/INTENSITY OF THE
SURFACE LOW.
SHORTWAVE TROUGHING ACROSS PACIFIC NORTHWEST FRIDAY-SATURDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE
THE ANOMALOUS RIDGE OVER THE EASTERN PACIFIC AND WESTERN U.S. MID
TO LATE WEEK WILL BE SHUNTED AND BROKEN DOWN SOME AS ANOTHER
STRONG SHORTWAVE TROUGH APPROACHES FROM THE GULF OF ALASKA. WHILE
THE PREVIOUS MODEL RUNS SHOWED A BIT BETTER AGREEMENT AMONG THE
GFS/EC WITH THIS FEATURE, THE EC/ECMEAN AND NOW THE THE 12Z GFS IS
SHOWING A SHARPENING OF THE TROUGH AS IT MOVES THROUGH THE
NORTHERN ROCKIES. THIS DIFFERS FROM THE REST OF THE MODEL
GUIDANCE. REGARDLESS OF THIS VARIABILITY, THE QPF DIFFERENCES ARE
NEGLIGIBLE. THUS WITH A GENERAL MODEL BLEND, THIS SHOULD TAKE
CARE OF ANY SUBTLE DIFFERENCE THAT EXIST WITHIN THE MASS FIELDS
THIS LATE IN THE FORECAST PERIOD.
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML
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