931
FXUS10 KWNH 250629
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
228 AM EDT SUN AUG 25 2019
VALID AUG 25/0000 UTC THRU AUG 28/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...STRONG CLOSED LOW TRACKING ACROSS NORTHERN TIER/SOUTHERN
CANADA...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND WEIGHTED TOWARD 00Z ECMWF/GFS/CMC
CONFIDENCE: ABOVE AVERAGE BECOMING SLIGHTLY ABOVE AVERAGE BY DAY 3
07Z UPDATE: THE 00Z UKMET SHOWED SIGNIFICANT IMPROVEMENT SHIFTING
NORTH; HOWEVER, IT IS A DEEPER SOLUTION AND THEREFORE TUCKED WEST
WITH THE SURFACE WAVE RELATIVE TO THE ECMWF/GFS. THIS IS A MINOR
DIFFERENCE THAT WOULD BE FINE BLENDING OUT AND SUPPORTING A
GENERAL MODEL BLEND WEIGHTED TO THE NEW 00Z ECMWF/CMC AND THE GFS.
---PRIOR DISCUSSION---
THE TIGHTLY PACKET DETERMINISTIC GUIDANCE THAT HAD BEEN CONSISTENT
FOR THE PAST FEW DAYS WITH THE LARGE/HIGH-AMPLITUDE NORTHERN
STREAM TROF DIGGING ACROSS THE PLAINS INTO LOWER MS VALLEY HAS
BECOME A BIT LESS AGREEABLE, MORE TYPICAL OF THE SPREAD GIVEN THE
PATTERN, ESPECIALLY AT INTERSECTIONS WITH OTHER STREAMS (LIKE OUT
OF THE WESTERN GULF), WHERE PHASING/TIMING IS TRICKY. THE
DISAGREEMENT IN THE NORTHERN MOST PORTION OF THE TROF, WITH THE
CLOSED LOW, IN SOUTHERN CANADA AND THE NORTHERN TIER, CONTINUES TO
BE MOSTLY A DISPLACEMENT SOUTH OF THE UKMET. THE 18Z GFS JOINED
THE UKMET, BUT THE 00Z GFS SHIFTED BACK NORTH UNTIL THE LOW
BECOMES QUITE MATURE INTO LATE TUES/WED. THE ECMWF/ECENS ARE WELL
NORTH OF THE GFS BUT STILL SHOW BEST CONSISTENCY AND AGREEMENT,
THOUGH THE 18Z GEFS SHOWED SOME MORE SIMILARITIES TO SUGGEST THE
GFS/ECMWF AND THEIR ENSEMBLES, AS WELL AS INCLUSION OF THE 00Z NAM
IS PREFERRED FOR THIS PORTION OF THE SYSTEM.
...SHORTWAVE CROSSING KS, LIFTING THROUGH GREAT LAKES AND PRESSING
COLD FRONT INTO UPPER OHIO VALLEY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
07Z UPDATE: THE ISSUES WITH CMC HAVE BECOME BETTER RESOLVED,
WHILE STILL PRESENTING A STRONGER TRIPLE POINT (LIKE THE UKMET),
IT DOES NOT APPEAR TO HAVE A NEGATIVE RESULT ON THE SENSIBLE
WEATHER, SO A GENERAL MODEL BLEND COULD BE EMPLOYED FOR THIS
PORTION OF THE WAVE. THIS ALSO INCLUDES THE SLOWLY SINKING TAIL
END TO THE COLD FRONT AND QPF AXIS ACROSS THE CENTRAL THEN
SOUTHERN PLAINS (RED RIVER) BY 12Z WED.
---PRIOR DISCUSSION---
FURTHER SOUTH, THROUGH THE CENTRAL PLAINS, AS THE MCV/SHORTWAVE
CURRENTLY IN KS STARTS TO SHEAR AND LIFT BACK THROUGH IL INTO THE
GREAT LAKES LATE MONDAY INTO TUESDAY; THE 12Z CMC SHOWS SOME
NEGATIVE OVER AMPLIFICATION BIAS AS THE SYSTEM DEEPENS THROUGH THE
GREAT LAKES AND EVEN DOMINATES THE CLOSED LOW FURTHER WEST,
SHIFTING THE WHOLE CYCLONE EAST, WELL DEPARTED FROM THE ENSEMBLE
SUITE/REMAINING GUIDANCE. THE 00Z NAM IS A BIT STRONGER AND
DELAYS THE FRONTAL ZONE PUSH EASTWARD RELATIVE TO THE OTHER
GUIDANCE BUT NOT SIGNIFICANTLY AND BLENDED WITH THE TYPICAL FAST
BIAS OF THE GFS SUGGESTS, A NON-CMC BLEND IS PREFERABLE HERE.
...WESTERN GULF TROPICAL WAVE/PHASING WITH BASE OF NORTHERN STREAM
TROF...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND WEIGHT SLIGHTLY MORE TO 00Z GFS
CONFIDENCE: AVERAGE
07Z UPDATE: THE 00Z ECMWF TRENDED A BIT LESS ACTIVE WITH THE
TROPICAL WAVE AND THEREFORE IS MUCH WEAKER. WHILE IT IS STILL A
BIT DEEPER THAN THE GFS/NAM AND CMC, IT HAS A PARTNER IN THE UKMET
WHICH SEEMS EQUALLY PLAUSIBLE. THE TIMING OF THE ECMWF WITH THE
OTHER GUIDANCE PRESSING THE PHASED TROF THROUGH THE SOUTHEAST FITS
WELL WITH A GENERAL MODEL BLEND, BUT STILL FAVORING THE GFS A BIT
MORE IN THE BLEND OVERALL.
---PRIOR DISCUSSION---
THE BASE OF THE TROF, SHOWS THE GREATEST SPREAD IN ITS INTERACTION
WITH THE TROPICAL WAVE LIFTING THROUGH THE WESTERN GULF INTO LA
LATER TODAY. THE 12Z ECMWF, SHOWS VERY STRONG CONVECTIVE
DEVELOPMENT OF THE WAVE EVEN WITH A SURFACE INFLECTION THAT LIFTS
NORTH INTO TN/CUMBERLAND PLATEAU, WHICH IS TOO INTENSE AND DEPICTS
A VERY STRONG QPF RESPONSE THAT IS OVERDONE AS WELL. THE 00Z NAM
ALONG WITH THE 12Z UKMET AND CMC SUPPORT GREATER STRENGTH IN THE
SHEARED TROF ALONG THE GULF COAST AS THE TWO STREAMS MELD BY
TUESDAY. THE 00Z GFS ALSO TRENDED THIS DIRECTION BUT ARE WEAKER
THAN THE NAM/UKMET. CONTINUITY AND TRENDS WOULD FAVOR THE GFS
SLIGHTLY IN A NON-ECMWF BLEND FOR THIS TROPICAL WAVE.
...TROPICAL/SUBTROPICAL WAVE OFF FLORIDA, LIFTING ALONG GULF
STREAM...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND
CONFIDENCE: AVERAGE
07Z UPDATE: THE 00Z ECMWF TRENDED A BIT SLOWER AND WEAKER AND
LOOKS VERY SIMILAR TO THE GFS EVEN DEPICTING A SLIGHT WESTWARD JOG
TOWARD 12Z WED DUE TO THE APPROACHING HEIGHT FALLS AND CONNECTING
TO THE OLD FRONTAL ZONE. THE 00Z UKMET AND CMC BOTH START A BIT
EAST OF THE GFS/ECMWF AND MEANDER SIMILAR TO THE GFS/ECWMF PAIR
BUT SLIGHTLY EAST THROUGH EACH FORECAST STEP, WITH THE UKMET A BIT
FASTER THAN THE CMC. A GFS/ECMWF BLEND COULD BE EMPLOYED BUT TO
COVER THE MODEST SPREAD A NON-NAM SOLUTION IS PREFERRED AT AVERAGE
CONFIDENCE.
---PRIOR DISCUSSION---
ALONG FL EAST COAST THROUGH THE GULF STREAM, THE TROPICAL INVEST
AREA CONTINUES TO SHOW SOLID CONTINUITY OF A DEEPENING SURFACE
WAVE, HOWEVER, THE DEPTH OF THE WAVE CONTINUES TO TREND SLIGHTLY
WEAKER AND SLOWER LIFTING EAST-NORTHEAST. THE 00Z GFS MATCHES
PLACEMENT AND TIMING WITH PRIOR RUN, ALONG WITH THE WEAKER
UKMET/CMC, BUT THE 12Z ECMWF IS CLEARLY STILL FASTEST AND
EVENTUALLY DEEPER BY 12Z WED TOO. THE 00Z NAM ALSO CONTINUES TO
BE VERY SLOW...SO WOULD PREFER A 00Z GFS/UKMET/CMC BLEND FOR THIS
WAVE AT AVERAGE CONFIDENCE.
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML
GALLINA
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