954
FXUS10 KWNH 090715
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
214 AM EST SUN FEB 09 2020
VALID FEB 09/0000 UTC THRU FEB 12/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH LATEST PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..DIGGING TROUGH OVER THE GREAT BASIN/SOUTHWEST ON SUNDAY
..ENERGY EJECTING EAST TOWARD THE SOUTHERN PLAINS BY TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z ECMWF/GEFS AND 12Z ECENS
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
A SPLIT IN THE UPPER FLOW DEVELOPING ACROSS THE WESTERN U.S. WILL
ALLOW FOR A SUBSTANTIAL AMOUNT OF SHORTWAVE ENERGY TO DIG
SOUTHWARD OVER THE GREAT BASIN AND INTO THE SOUTHWEST U.S. ON
SUNDAY AROUND THE EASTERN SIDE OF A STRONG DEEP LAYER RIDGE
DEVELOPING OFFSHORE OF THE THE WEST COAST. ALL OF THE GUIDANCE
SHOWS A WELL-DEFINED AND FAIRLY ROBUST UPPER LOW DEVELOPING AND
DROPPING SOUTH THROUGH CALIFORNIA BY SUNDAY EVENING. ON MONDAY,
THE ENERGY IS EXPECTED TO BEGIN MOVING EAST, AND BY TUESDAY SHOULD
BE EJECTING OUT ACROSS THE SOUTHERN PLAINS. THE 00Z GFS HAS
TRENDED SLOWER WITH ITS HEIGHT FALL EVOLUTION WITH THIS SYSTEM
COMPARED TO ITS LAST 12 TO 24 HOURS WORTH OF CYCLES, AND IS
GETTING CLOSER TO THE NON-NCEP MODEL CONSENSUS. HOWEVER, IT STILL
ULTIMATELY ENDS UP BEING THE MOST PROGRESSIVE SOLUTION AFTER ABOUT
48 HOURS AS THE HEIGHT FALLS EJECT OUT ACROSS THE SOUTHERN PLAINS
TUESDAY THROUGH EARLY WEDNESDAY AND IS STILL AN OUTLIER AS A
RESULT. THE 00Z NAM HAS MADE A DRAMATIC SHIFT IN TIMING AND IS
MUCH FASTER THAN 24 HOURS AGO WITH ITS HEIGHT FALL TIMING, WITH
THE NAM NOW OVERALL A LITTLE SLOWER THAN THE GFS, BUT FASTER THAN
THE NON-NCEP MODEL SUITE AS THE ENERGY REACHES THE SOUTHERN
PLAINS. OF THE NON-NCEP MODELS, THE 00Z ECMWF IS A LITTLE FASTER
THAN THE 00Z UKMET/CMC SOLUTIONS. ENSEMBLE CLUSTERING AT THIS
POINT FROM THE 00Z GEFS AND YESTERDAY'S 12Z ECENS SUITES STRONGLY
FAVOR THE 00Z ECMWF UPPER TROUGH EVOLUTION AND THUS A BLEND OF
THESE SOLUTIONS WILL BE PREFERRED AT THIS TIME.
..NORTHERN STREAM TROUGHING OVER THE NORTHERN PLAINS BY SUNDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
A PORTION OF THE UPPER TROUGH CURRENTLY OVER THE NORTHWEST U.S.
WILL QUICKLY EJECT DOWNSTREAM ACROSS THE NORTHERN ROCKIES,
NORTHERN PLAINS AND TOWARD THE UPPER MIDWEST GOING THROUGH SUNDAY.
ON MONDAY, THE ENERGY SHOULD BE SHEARING ACROSS THE GREAT LAKES
AND NORTHEAST. THE MODEL SPREAD IS MINIMAL, SO A GENERAL MODEL
BLEND WILL BE PREFERRED WITH THIS ENERGY.
..NORTHERN STREAM TROUGH/FRONT OVER THE MIDWEST BY TUESDAY
..ENERGY CROSSING THE GREAT LAKES/NORTHEAST ON WEDNESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THE GUIDANCE INDICATES A NORTHERN STREAM TROUGH AND ATTENDANT COLD
FRONT DROPPING SOUTHEAST FROM CANADA AND CROSSING THE NORTHERN
PLAINS LATE MONDAY AND ARRIVING ACROSS THE MIDWEST ON TUESDAY. ON
WEDNESDAY, THIS ENERGY WILL CROSS THE GREAT LAKES, OH VALLEY AND
THE NORTHEAST. THE MODELS OVERALL SHOW GOOD AGREEMENT WITH THIS
SYSTEM NOW, SO A GENERAL MODEL BLEND WILL BE FAVORED WITH THIS
FEATURE AS WELL.
..QUASI-STATIONARY FRONT OVER THE GULF COAST STATES BY TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND...00Z ECMWF/GEFS AND 12Z ECENS WEIGHTED
CONFIDENCE: AVERAGE
THE MODELS ALL AGREE IN PLACING A QUASI-STATIONARY FRONT ACROSS
THE GULF COAST STATES BY LATE MONDAY AND EARLY TUESDAY, WHICH IS
EXPECTED TO PLAY A KEY ROLE IN INITIATING A MULTI-DAY EXCESSIVE
RAINFALL EVENT (SEE LATEST QPFERD) FOR A LARGE PART OF THE SOUTH.
THERE WILL BE PASSAGE OF A JET-STREAK AND ASSOCIATED SURFACE WAVE
MONDAY NIGHT AND EARLY TUESDAY FROM THE TN VALLEY TO THE
MID-ATLANTIC REGION WHICH SHOULD HELP DRIVE THE FIRST ROUND OF
EXCESSIVE RAINFALL POTENTIAL. HOWEVER, IN THE WAKE OF THIS FIRST
WAVE, THE FRONT SHOULD SETTLE A LITTLE FARTHER SOUTH DOWN ACROSS
THE GULF COAST STATES AHEAD OF THE STRONGER AND MORE PRONOUNCED
HEIGHT FALLS ENCROACHING ON THE REGION FROM THE UPSTREAM SOUTHWEST
U.S. TROUGH. THE GLOBAL MODELS TEND TO HAVE DECENT AGREEMENT WITH
THE MASS FIELD EVOLUTION ACROSS THE GULF COAST STATES AND TN
VALLEY THROUGH EARLY TUESDAY, ALTHOUGH THE 00Z UKMET APPEARS TO BE
A BIT TOO STRONG WITH ITS FIRST SURFACE WAVE AND ALSO A LITTLE
FARTHER NORTH WITH IT WHICH PROMOTES SOMEWHAT HEAVIER RAIN ACROSS
PARTS OF THE TN VALLEY AND EVEN THE OH VALLEY.
FROM TUESDAY INTO EARLY WEDNESDAY, THE 00Z NAM IS SEEN AS PLACING
ITS FRONT A BIT FARTHER NORTH COMPARED TO THE GLOBAL MODELS OVER
THE LOWER MS AND TN VALLEY REGION WHICH RESULTS IN A NORTHWARD
DISPLACEMENT OF ITS HEAVIER QPF SWATH COMPARED TO THE GLOBAL
MODELS. THE SLOWER TREND OF THE 00Z GFS WITH ITS UPSTREAM HEIGHT
FALL EVOLUTION ACROSS THE SOUTHWEST AND SOUTHERN PLAINS FAVORS ITS
FARTHER SOUTH FRONTAL PLACEMENT IN CONCERT WITH THE NON-NCEP SUITE
OF GUIDANCE. ASIDE FROM THE FRONTAL PLACEMENT, THERE IS EXPECTED
TO BE AN AREA OF LOW PRESSURE THAT DEVELOPS NEAR THE UPPER
SOUTHEAST TX COASTAL PLAIN BY EARLY WEDNESDAY IN RESPONSE TO THE
STRONGER HEIGHT FALLS APPROACHING FROM THE WEST. THE 00Z GFS IS
SEEN AS BEING A TAD TOO STRONG WITH THIS DEVELOPMENT AT LEAST
THROUGH EARLY WEDNESDAY (POSSIBLY DUE TO SOME CONVECTIVE
FEEDBACK). REGARDLESS, A SECOND WAVE OF HEAVY TO EXCESSIVE
RAINFALL IS EXPECTED TO DEVELOP OVER THE LOWER MS VALLEY INCLUDING
EAST TEXAS AND THE ARKLATEX REGION FOR THIS PERIOD. THE MODEL
PREFERENCE AT THIS TIME FOR THE LOWER MS VALLEY/TN VALLEY AND
ENTIRE GULF COAST REGION IS WEIGHTED TOWARD A NON-NAM CONSENSUS
GIVEN CONCERNS ABOUT THE NAM FRONTAL PLACEMENT, BUT WITH STRONG
WEIGHTING TOWARD THE ECMWF AND THE GEFS/ECENS MEANS GIVEN THE
UPSTREAM PREFERENCES OVER THE SOUTHWEST U.S. THIS ALSO WILL AT
LEAST DAMPEN THE STRONGER UKMET OVER THE TN VALLEY WITH THE FIRST
SURFACE WAVE, AND ALSO THE STRONGER GFS OVER EASTERN TX WITH THE
SECOND SURFACE WAVE AT THE END OF THE PERIOD.
..SHORTWAVE CROSSING BRITISH COLUMBIA MONDAY NIGHT
..ENERGY DROPPING SOUTHEAST ACROSS THE NORTHERN ROCKIES TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND
CONFIDENCE: AVERAGE
UNCERTAINTY STILL EXISTS WITH A SHORTWAVE THAT WILL ADVANCE EAST
ACROSS THE GULF OF AK ON MONDAY AND THEN VERY QUICKLY SOUTHEAST
ACROSS BRITISH COLUMBIA MONDAY NIGHT. THE ENERGY IS EXPECTED TO
SLIDE DOWN ACROSS THE NORTHERN ROCKIES ON TUESDAY WITHIN STRONG
DEEP LAYER NORTHWESTERLY FLOW. THE 00Z NAM BY FAR IS A VERY SLOW
OUTLIER WITH THIS PROGRESSION OF THIS FEATURE. THE GLOBAL MODELS
HAVE COME INTO BETTER AGREEMENT/CLUSTERING WITH THE 00Z CYCLE, SO
A NON-NAM BLEND WILL BE PREFERRED AT THIS POINT.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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