556
FXUS10 KWNH 011901
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 PM EDT WED JUL 01 2020
VALID JUL 01/1200 UTC THRU JUL 05/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z FINAL MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...CLOSED LOW EXITING NEW ENGLAND THURSDAY AND BACK DOOR FRONT
DIVING THROUGH LATE FRIDAY...
..DEVELOPING TROUGH NEAR THE GULF COAST FRIDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH FRIDAY
NON UKMET/CMC SATURDAY /D3/
CONFIDENCE: ABOVE AVERAGE THROUGH FRIDAY, AVERAGE SATURDAY
19Z UPDATE: NO CHANGES TO THE PREFERRED BLEND WITH THE 12Z
NON-NCEP SUITE. THE CMC HAS BACKED OFF A BIT ON THE AMPLITUDE OF
THE TROUGH/CLOSED LOW NEAR THE GULF COAST, TRENDING MORE TOWARDS
THE PRIOR PREFERRED CONSENSUS.
PREVIOUS DISCUSSION:
GUIDANCE IS IN EXCELLENT AGREEMENT WITH LITTLE SPREAD IN BOTH THE
SPATIAL AND TEMPORAL EVOLUTION OF THE CLOSED LOW DROPPING E/SE
AWAY FROM NEW ENGLAND LATE IN THE WEEK. BY FRIDAY THE CLOSED LOW
OPENS AND IS WELL REMOVED FROM THE EAST COAST, AND A GENERAL BLEND
IS ACCEPTABLE THROUGH D2.
THEREAFTER, AS A RIDGE TRIES TO BLOSSOM NORTHEAST FROM THE MIDDLE
OF THE COUNTRY, A TROUGH DIGS BACK INTO NEW ENGLAND, WHILE A
SECONDARY TROUGH DEVELOPS BENEATH THE RIDGE AXIS ACROSS THE GULF
COAST. IN NEW ENGLAND, A BACK DOOR FRONT DIGGING SOUTHWARD FRIDAY
NIGHT INTO SATURDAY FEATURES SIMILAR TIMING, ALTHOUGH THE GFS MAY
BE A BIT TOO FAST TO DRIVE THE FRONT SOUTHWEST AS IT ENCOUNTERS A
RIDGE AND MAY GET HUNG UP BY INTERACTION WITH MID-LEVEL IMPULSES.
THE ECMWF ON THE OTHER HAND IS THE WETTEST OF THE GUIDANCE AND
FEATURES THE SUBTLY STRONGEST SHORTWAVE. A BLEND OF THESE FEATURES
SHOULD GET SOMETHING CLOSE TO REALITY, AND IS CLOSER TO THE
ENSEMBLE MEANS. ACROSS THE GULF COAST, THE UKMET SHOWS NO EVIDENCE
OF A TROUGH AS IT BULGES THE RIDGE TOO QUICKLY FROM THE W/SW,
WHILE THE CMC IS A STRONG OUTLIER WITH THE INTENSITY OF THE
TROUGH, CLOSING IT OFF NEAR THE CENTRAL GULF COAST. REMOVING THESE
TWO FEATURES FROM THE BLEND LEAVES A GOOD GENERAL CONSENSUS AMONG
THE REST OF THE GLOBAL MODELS IN A BROAD POSITIVELY TILTED TROUGH
LINGERING NEAR THE GULF COAST SATURDAY. IT SHOULD BE NOTED,
HOWEVER, THAT THIS TROUGH DEVELOPS IN RESPONSE TO RESIDUAL MCVS
DIVING THROUGH THE MS VLY EARLIER IN THE FORECAST PERIOD. THE
POSITION AND INTENSITY OF THESE FEATURES ARE NOTORIOUSLY DIFFICULT
TO PLACE, ESPECIALLY BY D3, SO UNCERTAINTY IN THE BLEND AND THE
EVOLUTION BECOMES MUCH GREATER BY THE WEEKEND.
..DEEP UPPER TROUGH/CLOSED LOW ACROSS THE INTER-MOUNTAIN WEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH FRIDAY
NON NAM/UKMET SATURDAY /D3/
CONFIDENCE: AVERAGE
19Z UPDATE: NO SIGNIFICANT CHANGES WITH THE PREFERENCES AFTER
EXAMINATION OF THE 12Z NON-NCEP SUITE.
PREVIOUS DISCUSSION:
EXPANSIVE CLOSED LOW MEANDERING ACROSS FAR WESTERN CANADA AND THE
PACIFIC NORTHWEST WILL LINGER THROUGH FRIDAY AS MULTIPLE VORT
CENTERS ROTATE AROUND THEMSELVES AND WITHIN THE LARGER GYRE.
SLOWLY, THIS FEATURE IS LIKELY TO GENERALLY LIFT NORTHEAST INTO
CANADA, LEAVING JUST A WEAK TROUGH ACROSS THE PACNW BY FRIDAY. THE
GUIDANCE DOES FEATURE SUBTLE DIFFERENCES IN THE INTENSITY AND
POSITION OF THE INDIVIDUAL VORT CENTERS, BUT THE GENERAL MASS
FIELD SHOWS GOOD AGREEMENT THROUGH 60 HOURS. THEREAFTER, THE NAM
AND UKMET BOTH DIVE A STRONGER SHORTWAVE NEAR THE OR COAST FOR D3,
AMPLIFYING THE TROUGH ONCE AGAIN, BECOMING OUTLIERS COMPARED TO
THE GLOBAL CONSENSUS. WHILE QPF LOOKS MINIMAL ACROSS THE NW DURING
THIS TIME, A DEEPER TROUGH AND A MORE SW TO NE ORIENTED JET STREAK
IN RESPONSE COULD PROVIDE MORE SIGNIFICANT ASCENT LOCALLY D3. THE
REMAINING GUIDANCE INCLUDING THE ENSEMBLE MEANS SHOW A FLATTER
DEPICTION OF THE TROUGH BY THIS TIME WITH A MORE ZONAL JET STREAK,
AND THIS IS PREFERRED FOR THE REGION AT THE END OF THE FORECAST
PERIOD.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
WEISS
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