403
FXUS10 KWNH 041621
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1221 PM EDT WED SEP 04 2019
VALID SEP 04/1200 UTC THRU SEP 08/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION, CONFIDENCE, AND PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..OVERALL PATTERN ACROSS THE CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-UKMET BLEND
EXCEPTION: 12Z GFS/00Z ECMWF NORTHWEST AND NORTHERN HIGH PLAINS
INTO DAY 3.
CONFIDENCE: AVERAGE TO SLIGHTLY ABOVE AVERAGE
THE SHORTWAVE, INCREASINGLY POSITIVE TILT TROF, CROSSES NEW
ENGLAND TODAY. AS SUCH, THE OVERALL GRADIENT TIGHTENS AND A
COUPLED POLAR/SUBTROPICAL JET CORE DEVELOPS OVER THE NORTHEAST,
FED BY THE STRONGER POLAR BUT ALSO THE APPROACH/OUTFLOW FOR
DORIAN. THE DIFFERENCE IN GUIDANCE HERE, IS MAINLY IN THE
PLACEMENT AND ORIENTATION OF THE SOUTHERN BRANCH ACROSS THE
MID-ATLANTIC AND EVEN INTO THE EASTERN SLOPES OF THE APPALACHIANS.
STRONGER, BETTER ANTICYCLONICALLY CURVED ENTRANCES TO THE JET
CONTINUE WITH THE 12Z NAM/NAM CONEST SUPPORTING STRONGER DRAW OF
THE QPF SWATH TO THE NORTH AND WEST ACROSS THE COASTAL NC/SE VA.
THE 12Z GFS FOLLOWS THIS, BUT CONTINUES TO VARY OVER THE LAST 4-5
CYCLES ON STRENGTH/PLACEMENT AND SO THE TIGHT QPF GRADIENT VARIES,
BUT HAS SPED UP COMPARED TO THE 00Z RUN AND IS EVER SO SLIGHTLY
SOUTHEAST OF THE 06Z RUN.
UPSTREAM, GUIDANCE IS COMING INTO BETTER ALIGNMENT IN STRENGTH AND
TIMING OF THE PRECEDING SHORTWAVE AS WELL AS THE NOSE OF THE
DEVELOPING NORTHWEST FLOW/PACIFIC JET THAT ENTERS THE GREAT LAKES
00Z FRI. THE SOLID TIMING/SHAPE ALSO PROVIDES A SIMILAR EVOLUTION
OF THE SURFACE WAVE AND QPF FORECAST THROUGH THE NORTHERN TIER
INTO THE GREAT LAKES. HOWEVER, AFTERWARD, THE UKMET IS A BIT
FLATTER AND WEAKER AS IT DIGS THROUGH THE GREAT LAKES AND PRESSES
DORIAN OFF THE COAST. WHILE THE SLIGHTLY MORE AMPLIFIED AND
STRONGER SOLUTIONS OF THE GFS/ECMWF AND CMC PHASE WITH THE
CIRCULATION OF DORIAN. THEREAFTER THE SHORTWAVE/LEFT ROTOR OF AT
THE TAIL OF THE JET STREAK, WILL AMPLIFY AND DIG SOUTHEAST INTO
QUEBEC AND TURN DORIAN LEFT TOWARD NOVA SCOTIA AND THE UKMET IS
WEAK HERE AS WELL...SO START TO SHIFT PREFERENCE AWAY FROM THE
UKMET AFTER 06/00Z AT SLIGHTLY ABOVE AVERAGE CONFIDENCE.
BROAD CLOSED LOW OFF THE WEST COAST, WILL CONTINUE TO LIFT
NORTHEAST INTO THE PACIFIC NORTHWEST BEING KICKED BY A
STRONGER/FULL LATITUDE CLOSED LOW/TROF OVER GULF OF AK/NORTHERN
PACIFIC. AS IT LIFTS IT WILL WEAKEN INTO THE LARGER SCALE RIDGE
IN THE ROCKIES BUT MAINTAIN SUFFICIENTLY TO EMERGE INTO THE
NORTHERN HIGH PLAINS BY EARLY SAT, WITH SURFACE WAVE IN WY. THIS
SURFACE WAVE WILL WEAKEN FROM THE STRONG NORTHERN HIGH BUILDING
IN. HERE THE UKMET AND NAM ARE SLIGHTLY TOO FAST AND BECOME FLAT
IN THE WAKE OF INCREASED TROUGHING DOWNSTREAM. THE 12Z GFS SLOWED
A BIT, AND IS TIMED WELL WITH THE CMC/ECMWF. HOWEVER, THE CMC IS
VERY OUT OF PHASE WITH THE UPSTREAM TROF ELONGATING ALONG THE
COAST BY DAY 3 AND HAS SOME SUBTLE ISSUES WITH WAVE CROSSING THE
ROCKIES AS WELL. SO GIVEN STRONG AGREEMENT/PLACEMENT AND TIMING
THINK A BLEND OF THE 12Z GFS AND 00Z ECMWF WILL WORK BEST FOR THE
NORTHERN HIGH PLAINS, NORTHERN ROCKIES, GREAT BASIN AND PACIFIC
NORTHWEST WITH THESE TWO SYSTEMS. THE NAM AND UKMET ARE NOT TOO
FAR OUT OF PHASE SO CONFIDENCE IN A GFS/ECWMF BLEND IS AVERAGE TO
SLIGHTLY ABOVE AVERAGE.
..HURRICANE DORIAN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PLEASE REFER TO THE OFFICIAL NATIONAL HURRICANE CENTER FORECAST
TRACK
FOR THE NEXT DAY OR SO, THE GUIDANCE IS WELL PACKED AROUND THE
OFFICIAL 15Z FORECAST, BUT BY 36HRS THE 12Z NAM AND GFS START
PICKING UP PACE AND SLIDE A SHADE NORTH AND EAST OF THE ECWMF/CMC
AND UKMET. AS IT PARALLELS THE CAROLINA COAST LATE THURS INTO
FRI, THE GFS AND NAM CONTINUE TO LIFT A BIT FASTER THAN THE
REMAINING GUIDANCE ALSO WITH GREATER BAROCLINIC SUPPORT (JET
ENTRANCE SEE FIRST SECTION), QPF AXIS IS NORTH AND WEST. AS
DORIAN, ACCELERATES UP THE COAST, THERE IS A GENERAL LEFT TURN IN
THE GUIDANCE TOWARD NOVA SCOTIA GIVEN STRONGER BINARY INTERACTION
WITH NORTHERN STREAM GLOBAL TROF DIGGING INTO NW QUEBEC FROM JAMES
BAY. ONLY THE UKMET DEVIATES WELL EAST, ALSO THE SLOWER GUIDANCE
DOES EVENTUALLY CATCH UP WITH THE NAM/GFS. OVERALL, THE BEST
PROXY TO THE 15Z FORECAST CONTINUES TO BE THE GFS, WITH THE 12Z
GFS EVEN BETTER ALIGNED THAN THE 06Z RUN.
..TROPICAL STORM FERNAND.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PLEASE REFER TO THE OFFICIAL NATIONAL HURRICANE CENTER FORECAST
TRACK
THE MID-LEVEL CENTER OF FERNAND IS TRACKING FAIRLY WELL AND TIGHT
THROUGH THE MEXICAN PLATEAU WITH SOLID MODEL AGREEMENT FOR THE
REMAINDER OF THE OFFICIAL NHC TRACK. THE SURFACE WAVE IS
CURRENTLY ALONG THE COAST OF NE MEXICO AND LIKELY TO SWIRL INTO
EXTINCTION AS THE MID-LEVEL CIRCULATION MOVES AWAY. BEST PROXY TO
THE OFFICIAL NHC FORECAST IS CLOSE TO A GENERAL MODEL BLEND
THROUGH TOMORROW...THOUGH BOTH THE 12Z GFS AND 00Z ECMWF AND TO A
LESSER EXTENT THE 12Z NAM SHOW A STRONG REMAINING MID-LEVEL
SHORTWAVE THAT WILL CROSS S SONORA/N SINALOA UNDER THE BUILDING
RIDGE IN THE US SOUTHWEST.
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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