259
FXUS10 KWNH 221946
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
345 PM EDT TUE OCT 22 2019
VALID OCT 22/1200 UTC THRU OCT 26/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z FINAL MODEL EVALUATION WITH PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
CENTRAL U.S. CYCLONE; SECONDARY LOW FROM CAROLINAS TO NEW ENGLAND
TODAY-WEDNESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
19Z UPDATE: MODELS REMAIN IN FAIRLY GOOD AGREEMENT ACROSS THE
CONUS DURING THE FIRST HALF OF THE FORECAST PERIOD. NO ADJUSTMENTS
NEEDED TO THIS PORTION OF THE EVALUATION.
PREVIOUS DISCUSSION: A SURFACE LOW WILL CONTINUE TO LIFT INTO
ONTARIO THROUGH THE NEXT COUPLE OF DAYS WITH AN ASSOCIATED COLD
FRONT TRAVERSING THE EAST COAST. THE TROUGH AXIS WILL PIVOT
THROUGH NEW ENGLAND WEDNESDAY INTO EARLY THURSDAY. AS MUCH OF THE
CONUS WILL BE UNDER TROUGHING, NORTHWEST FLOW ACROSS THE NORTHERN
ROCKIES WILL ALLOW MID-LEVEL IMPULSES TO QUICKLY MOVE SOUTH AND
EAST INTO THE NORTHERN PLAINS. HIGH PRESSURE WILL QUICKLY BUILD
BEHIND THE APPARENT COLD FRONT ACROSS THE EAST THROUGH WEDNESDAY
WITH RIDGING IN THE WEST.
THE NCEP/NON-NCEP MODELS INCLUDING ENSEMBLE MEANS ARE IN GOOD
AGREEMENT WITH THE TIMING AND INTENSITY DURING THIS TIME.
STRONGER SHORTWAVE DROPPING THROUGH ROCKIES INTO THE SOUTHERN
PLAINS WEDNESDAY PM-SATURDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/ECMWF MEAN/CMC/UKMET
CONFIDENCE: BELOW AVERAGE
1930Z UPDATE: THERE IS NO CHANGE TO THE PRELIM PREFERENCES GIVEN
THE MODEL DIFFERENCES CONTINUE. THE 12Z GFS/NAM IS STILL FASTER
AND MORE AMPLIFIED WHILE THE EC/UK/CMC IS SLOWER AND DEEPER WITH
THE CLOSED LOW IN THE SOUTHERN PLAINS - THOUGH A NOTED ADJUSTMENT
TO THE EAST WITH THE MID-LEVEL CLOSED LOW AND ASSOCIATED QPF. THE
12Z NCEP GUIDANCE SEEMS A BIT TOO FAST AND THE NON-NCEP SEEMS A
BIT MORE REASONABLE AS THE MODELS HAVE SPED UP A BIT.
PREVIOUS DISCUSSION: MODELS CONTINUE TO BE IN DISAGREEMENT WITH
REGARDS TO THE PATTERN CHANGES SET FOR LATE WEDNESDAY INTO THE
WEEKEND. THERE IS A CLEAR DICHOTOMY BETWEEN THE NCEP AND NON-NCEP
MODELS THAT HAS LED TO VASTLY DIFFERENT SYNOPTIC FEATURES AND THUS
QPF PLACEMENT AND INTENSITY.
NCEP MODEL (GFS/NAM) OUTPUT CONTINUES TO PROGRESS A TROUGH EAST
WITH MID-LEVEL VORTICITY CLEANLY ROUNDING THE TROUGH AXIS.
MEANWHILE, THE NON-NCEP MODELS (EC/UKMET/CMC) CALVES OFF A
SHORTWAVE FROM THE MAIN TROUGH AXIS WHICH IS GENERATING A
MID-LEVEL LOW INTO THE DESERT SOUTHWEST. AS A RESULT, THE NCEP
MODELS ARE PRODUCING A MORE AMPLIFIED TROUGH PATTERN THAT WILL
GENERATE A MORE PROGRESSIVE COLD FRONT THROUGH THE CENTRAL US AND
SURFACE LOW OFF THE GULF COAST REGION BY EARLY FRIDAY. CONVERSELY,
THE NON-NCEP MEMBERS ARE DEVELOPING A STRONG SURFACE LOW ACROSS
NM/TX WHICH IS SLOW TO PROGRESS EASTWARD THROUGH THE PERIOD. THIS
PIECE OF ENERGY BREAKING OFF THE MAIN TROUGH WILL LEAD TO A
QUICKER NORTHERN JET STREAM AND SURFACE FRONT THROUGH THE GREAT
LAKES AND NORTHEAST DURING THE DAY FRIDAY.
IN OBSERVING THE RUN-TO-RUN CONTINUITY AMONG THE MODELS, IT
APPEARS THEY ARE ALL FAIRLY CONSISTENT. THIS IS MAKING IT A
CHALLENGE IN DETERMINING WHICH MODEL MAY BE THE BEST CHOICE
THROUGH DAY 3. HOWEVER, WHEN DIVING INTO THE ENSEMBLE MEANS, IT
APPEARS THE 00Z/12Z GEFS ILLUSTRATES A TREND TOWARD THE NON-NCEP
SOLUTIONS, SLOWING THE PROGRESSION OF THE TROUGH WITH A BIT MORE
INTERACTION WITH THE MID-LEVEL IMPULSES. ALSO, THE 12Z GFS
COMPARED TO THE 06Z SHOWS SOME SIGNS OF SLOWING AS WELL, WHICH HAS
BEEN QUITE SUBTLE OVER THE PAST COUPLE OF RUNS. THE 12Z NAM ALSO
SLOWED. BASED ON THIS AND THE FACT THE THE 00Z ECMWF HAS DEEPENED
THE SURFACE/MID-LEVEL LOW OVER THE PAST COUPLE OF CYCLES, WITH THE
EC MEAN STAYING VERY CONSISTENT, FEEL THERE IS NO EVIDENCE TO
CHANGE THE BLEND AT THIS POINT.
THE WPC PREFERENCE REMAINS FOR A HEAVY WEIGHT TOWARD THE NON-NCEP
GUIDANCE, WITH MOST OF THE WEIGHT TOWARD THE ECENS MEAN WHICH IS A
GOOD COMPROMISE UNTIL FORECAST CONFIDENCE INCREASES AND MODEL
SPREAD LOWERS.
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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