680
FXUS10 KWNH 141836
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
236 PM EDT SAT SEP 14 2019
VALID SEP 14/1200 UTC THRU SEP 18/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..GREAT LAKES INTO NORTHEAST CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
A VERY FLAT BUT TIGHTLY PACKED HEIGHT PATTERN EXISTS ACROSS THE
CONUS, PARTICULARLY THE NORTHERN CONUS AT THE START OF THE
FORECAST PERIOD, WITH A SUBTLE SHORTWAVE CROSSING ND INTO MN
TODAY. THIS WAVE WILL CROSS THE GREAT LAKES AND HELP TO BUILD
SOME BROAD TROUGHING ACROSS THE NORTHEAST. THE 00Z ECMWF IS A BIT
DEEPER THAN OTHER GUIDANCE BUT WITH LITTLE SIGNIFICANCE
WEATHER-WISE TO SUPPORT THE GENERAL MODEL BLEND AT ABOVE AVERAGE
CONFIDENCE.
...DEEP LATITUDE TROF ENTERING THE WEST BY MONDAY; SOUTHWEST
SHORTWAVE...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 1/3RDS 12Z GFS & 2/3RDS 12Z ECMWF
CONFIDENCE: AVERAGE
19Z UPDATE: THE 12Z UKMET SLOWED SIGNIFICANTLY BUT STILL REMAINS
SLIGHTLY FASTER THAN THE REMAINING GUIDANCE, AND WITH LITTLE
CHANGE IN THE ECMWF/CMC WILL KEEP INITIAL PREFERENCE OF GFS/ECMWF
AT AVERAGE CONFIDENCE.
---PRIOR DISCUSSION---
GOES-WV SUITE DENOTES A NICE OUTFLOW TO THE SHORTWAVE ACROSS THE
DESERT SOUTHWEST, THIS WILL MOVE NORTHWARD WITH SIMILAR EVOLUTION
IN THE GUIDANCE SUITE. HOWEVER, TIMING IS GOING TO BE AN ISSUE
BUT THIS IS MOSTLY AFFECTED BY THE TIMING OF THE UPSTREAM DIGGING
LARGE SCALE TROF ENTERING N CA MONDAY. THERE HAS BEEN SOME
GROWING CONSENSUS WITH THE UKMET/GFS SLOWING THROUGH MONDAY, BUT
TYPICAL OF BIAS, BY TUESDAY THE SPLIT IN TIMING INCREASES. THE
UKMET IS WELL OUTPACED OVER THE NAM/GFS FOLLOWED BY THE LAGGING
ECMWF/CMC. THIS APPEARS TO BE A TRADITIONAL TIMING ISSUE, SO A
TYPICAL GFS/ECMWF BLEND WILL LIKELY WORK BEST WITH AVERAGE
CONFIDENCE (GIVEN SPREAD IS MODERATE TO LARGE BY DAY 3). SO
EMPLOYING A 1/3RD GFS AND 2/3RDS ECWMF SOLUTION WORKS OUT WELL
HERE.
..GULF OF MEXICO TUTT AND SURFACE WAVE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z NAM/CMC/ECWMF BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
19Z UPDATE: THE 12Z UKMET TRENDED AWAY FROM THE STRONGER SOLUTION
AND HAS BECOME CLOSER TO THE OTHER GUIDANCE, BUT IS A BIT FURTHER
NORTH AND FASTER TO KEEP INCLUDED. THE 12Z CMC TRENDED FASTER AND
MATCHES TIGHTLY WITH THE 12Z NAM/ECMWF TO SUGGEST THE GFS IS NOW A
BIT TOO FAST AS WELL, SO WILL FAVOR A 12Z NAM/ECMWF/CMC BLEND.
---PRIOR DISCUSSION---
THE TUTT CELL MOVING WEST ACROSS THE GULF CONTINUES TO LOOK
IMPRESSIVE WITH A SOLID TRAILING SURFACE WAVE. THE 12Z NAM AND
ECMWF ARE VERY SIMILAR IN DEPTH AND TIMING OF BOTH FEATURES, WHILE
THE GFS IS IN A SEMI-BIASED WEAKER PHASE RELATIVE TO BOTH BUT
TIMED WELL. THE 00Z UKMET IS TYPICAL BIAS IN TROPICAL SYSTEMS
WITH STRONG CONVECTIVE RESPONSE LEADING TO A COMPACT WAVE THAT
FEEDS BACK ON ITSELF...SLOWING AND SHIFTING NORTH OF THE REMAINING
GUIDANCE. THE 00Z CMC EVOLVES THE SURFACE WAVE WELL, BUT THE TUTT
IS A BIT TOO WEAK AND SLOW, SO THE SURFACE WAVE LAGS. SO WHILE
NOT FAVORED IN A BLEND, IT DOES PROVIDE CONFIDENCE TO THE
EVOLUTION OF THE SYSTEM. SO A 12Z NAM/GFS AND 00Z ECMWF BLEND IS
PREFERRED IN THE GULF AT SLIGHTLY ABOVE AVERAGE CONFIDENCE.
..TROPICAL STORM HUMBERTO
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: OFFICIAL NHC FORECAST
BEST PROXY: 12Z CMC/ECMWF THROUGH 48HRS; 12Z GFS/NAM THEREAFTER
CONFIDENCE: AVERAGE
19Z UPDATE: THE 12Z ECMWF/CMC TRACK QUITE CLOSE TO THE 15Z NHC
FORECAST THROUGH 48HRS, THEREAFTER THE CMC AND ECMWF SLOW
SIGNIFICANTLY WITH THE NAM/GFS PASSING IT ALONG THE NHC TRACK.
THE UKMET IS THE ONLY GUIDANCE MEMBER FASTER THAN NHC FORECAST
TRACK BUT REMAINS VERY STRONG COMPARATIVELY AS WELL. SO THE BEST
PROXY WILL BE THE CMC/ECWMF THROUGH 48HRS AND MORE GFS/NAM
THEREAFTER.
---PRIOR DISCUSSION---
HUMBERTO IS STARTING TO HAVE A STRONGER/DEEPER APPEARANCE AT THIS
TIME. THERE REMAINS A SOLID SPLIT IN THE GUIDANCE WITH THE
ECMWF/UKMET CONTINUING TO BE EAST AND EVENTUALLY SOUTH OF THE NHC
TRACK AFTER THE TURN AT 36 TO 48HRS. THE 12Z GFS/NAM BOTH START
INITIALLY SLOWER AND SLIGHTLY EAST OF THE 00Z GUIDANCE BUT STILL
ARE WEST AND NORTHWEST OVER THE NEXT TWO DAYS BEFORE TURNING EAST.
THE 00Z CMC IS CLOSEST TO THE TRACK THROUGH 48HRS BEFORE
ACCELERATING AFTER THE EASTWARD TURN...MOVING AWAY FROM THE OTHER
GUIDANCE. IT IS AT THIS POINT THE GFS/NAM BOTH MOVE ALONG THE
EASTWARD TRACK AFTER 48HRS WITH BETTER TIMING, PERHAPS A BIT SLOW.
OVERALL, THE BEST PROXY IN A GENERAL MODEL BLEND, BUT TO NOT
BLEND OUT THE FEATURES TOO MUCH; A 00Z CMC THROUGH 48HRS SHIFTING
TO GFS/NAM THEREAFTER WORKS CLOSEST TO THE NHC FORECAST. THERE IS
GROWING CONSENSUS AS THE GUIDANCE ENVELOPE TIGHTENS, AS SUCH
CONFIDENCE IS AVERAGE IN UTILIZING THIS PROXY FOR THE 15Z NHC
FORECAST.
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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