492
FXUS10 KWNH 070628
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
227 AM EDT MON OCT 07 2019
VALID OCT 07/0000 UTC THRU OCT 10/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...UPPER TROUGH CROSSING THE GREAT LAKES THROUGH MONDAY WITH
PROGRESSIVE COLD FRONT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
07Z UPDATE: THE 00Z ECMWF TRENDED FASTER, BUT REMAINS SLIGHTLY
SLOWER THAN THE REMAINING GUIDANCE. SUGGEST THE ECMWF'S INCLUSION
TO THE BLEND AT THIS POINT, BUT PERHAPS AT LOWER WEIGHTING GIVEN
THE OTHERWISE VERY STRONG AGREEMENT.
---PRIOR DISCUSSION---
THE MODELS SHOW VERY GOOD AGREEMENT WITH THE DETAILS OF THE UPPER
TROUGH AND ASSOCIATED SHORTWAVE ENERGY THAT WILL BE CROSSING THE
UPPER MIDWEST AND GREAT LAKES REGION THROUGH MONDAY. HOWEVER, THE
12Z ECMWF SHOWS SOME SLOW BIAS BREAKING FROM THE REMAINING
CONSENSUS EXITING THE GREAT LAKES A BIT SLOWER THAN THE OTHER
GUIDANCE MONDAY; DELAYING THE PROGRESS ON TUESDAY THROUGH NEW
ENGLAND. THE 12Z ECENS MEAN HAS SOME SUPPORTING MEMBERS, BUT THAT
NUMBER IS WELL BELOW HALF; SO IT SEEMS PRUDENT TO KEEP THE
NON-ECMWF BLEND PREFERENCE WITH THIS SYSTEM. NOTE: THIS APPEARS
TO NEGATIVELY AFFECT THE LINGERING TROF IN THE APPALACHIANS AND
NORTHWARD TRACK OF THE TROPICAL WAVE (SEE BELOW).
...LINGERING SHORTWAVE ENERGY AMPLIFYING OVER CENTRAL APPALACHIANS
INTO THE MID-ATLANTIC...
...DEEPENING SURFACE LOW PRESSURE OFF THE EAST COAST WITHIN
ELONGATED COASTAL TROF BACK TO FL...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GEFS/GFS/NAM AND UKMET BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
07Z UPDATE: WITH A SLIGHTLY FASTER EXIT OF THE NORTHERN STREAM
SHORTWAVE, THE PLACEMENT/TIMING OF THE REMAINING SHORTWAVE IN THE
APPALACHIANS AND ORIENTATION OF THE TROPICAL MOISTURE
STREAM/SURFACE STREAM CLOSER TO THE COAST WITH THE NEW 00Z ECMWF.
IT IS STILL A BIT SLOWER WITH THE EMBEDDED SHORTWAVE ENERGY IN THE
TROPICAL STREAM RELATIVE TO THE GFS/NAM/CMC, SO CYCLOGENESIS
REMAINS SOUTH OF THOSE GUIDANCE MEMBERS BUT THE SHIFT IS MUCH
BETTER TOWARD THE CENTROID OF GEFS/CMCE AND ECENS ENSEMBLE
SOLUTIONS, BUT STILL SOUTH OF THE INITIAL PREFERENCE. THE CMC
TRENDED NORTH AS WELL AS THE UKMET. THIS PLACED THE CMC WELL
NORTH OF THE OVERALL GUIDANCE/ENSEMBLE SUITE AND A SHADE DEEPER
AND THE UKMET VERY CLOSE TO THE NAM. THE 00Z GEFS WAS VERY
SIMILAR TO THE 18Z RUN AND SO IS STILL THE MOST PREFERABLE
SOLUTION. CONFIDENCE IS INCREASED A BIT IN THE OVERALL FORECAST
TO SLIGHTLY BELOW AVERAGE IN A GEFS/GFS/NAM/UKMET BLEND.
---PRIOR DISCUSSION---
CONTINUED UNCERTAINTY REMAINS WITH THE EVOLUTION OF COMBINING
STREAMS ALONG THE EASTERN US COAST. AS MENTIONED ABOVE, THE 12Z
ECMWF IS SLOW EXITING WITH THE MAIN NORTHERN STREAM WAVE; THIS
ALLOWS THE LINGERING BASE OF THE TROF TO BE TUGGED EASTWARD A BIT
MORE THAN OTHER GUIDANCE SUGGESTS. THIS MAY INCREASE SOME RIDGING
JUST OFF SHORE, AS THE OPERATIONAL ECMWF IS THE ONLY MAIN
DETERMINISTIC GUIDANCE MEMBER TO DEFLECT THE TROPICAL RETURN WARM
CONVEYOR BELT, ALONG THE WESTERN PERIPHERY OF THE SUBTROPICAL
RIDGE, OUT TO SEA FARTHER. AS THE TROPICAL WAVE AND SURFACE
CYCLOGENESIS LIFTS NORTH AND IS ENHANCED BY THE BAROCLINIC FLOW
ALOFT, THE ECMWF PRESSES THE WAVE SOUTH INTO AN ANTICYCLONIC LOOP
AND IS ON THE EASTERN-SOUTHERN SIDE OF THE ECENS GUIDANCE
SOLUTIONS. WHILE THE ECENS SOLUTIONS ARE STILL FURTHER SOUTH THAN
GEFS/CMCE MEMBERS, THE OPERATIONAL SOLUTION IS ON THE OUTSIDE
PERIPHERY OF THE GUIDANCE. THE 12Z UKMET IS VERY WEAK ACROSS THE
CUMBERLAND PLATEAU INTO THE CENTRAL APPALACHIANS, AND FAVORS A
SLOWER EMERGENCE OF THE TROPICAL-STREAM CYCLOGENESIS, IN THE
CENTER OF THE ECENS CLUSTER.
THE 00Z NAM/GFS AND 12Z CMC, MUCH LIKE THE UKMET/ECMWF ARE
STARTING TO FAVOR STRONGER SHORTWAVE ENERGY EMERGING ALONG THE
WARM CONVEYOR BELT ALONG THE EAST COAST SURFACE TROF. SO WHILE,
THERE IS A TREND TOWARD A WEAKENING OR SMALLER LINGERING SHORTWAVE
OUT OF THE CENTRAL APPALACHIANS HELPING TO BUILD SOME WEAK FORM OF
REX BLOCK IN THE NORTHEAST, THERE IS REDUCTION OF BAROCLINIC
INFLUENCES RELATIVE TO THE TROPICAL SURGE. THE COOL CONVEYOR
REMAINS STRONG AND ACTIVE SOUTH OF LONG ISLAND, BUT THE SURFACE
CYCLOGENESIS IS A BIT FURTHER SOUTH AND EAST WITH THE 00Z RUNS
RELATIVE TO THE 12Z/18Z SOLUTIONS. THIS PLACES THE 00Z GFS VERY
CLOSE TO A FAVORABLE 18Z GEFS SOLUTION. THE 00Z NAM IS VERY
AGGRESSIVE WITH TROPICAL ENERGY LIFTING NORTH, AND AS IT
INTERSECTS WITH THE FORMING COOL CONVEYOR, VERY STRONG
RESPONSE/CYCLOGENESIS OCCURS. THE CMC HAS BEEN SIMILAR AND MORE
CONSISTENT OVERALL TOWARD THIS SOLUTION. SO WHILE THERE IS
REMAINING HIGH UNCERTAINTY (GIVEN SMALL TIMING/DEPTH DIFFERENCE
LEAD TO LARGE EVOLUTION OUTCOME DIFFERENCES, WPC IS FAVORING
SOMETHING CLOSER TO THE 18Z GEFS/00Z GFS WITH SOME 12Z CMC AND 00Z
NAM WEIGHTING AND EVEN LOWER 12Z ECENS MEAN INPUT TO ACCOUNT FOR
THIS UNCERTAINTY. CONFIDENCE AND MORE INCLUSION OF THE
ECMWF/UKMET INTO PREFERENCE OCCURS TOWARD FLORIDA/BAHAMAS, GIVEN
LESS MODEL SPREAD AND BETTER CONSISTENCY OF THE MOISTURE/FLOW
REGIME AXES.
..DEEP UPPER TROUGH/CLOSED LOW AMPLIFYING OVER THE WEST
..HIGH PLAINS CYCLOGENESIS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
BROAD LARGE SCALE TROUGH CURRENTLY OVER AK AND THE NORTHERN GULF
OF AK WILL DROP SOUTHEAST AND SUPPORT STRONG COLD AIR SURGE DOWN
BOTH SIDES OF THE TERRAIN. THIS WILL SUPPORT A SHARPER, BUT
ELONGATING POSITIVE TILT TROUGH TO DOMINATE THE NORTHWESTERN CONUS
TO NORTHERN CANADA BY LATE TUESDAY. THE TROF WILL SUPPORT A
STRONG COMPACT SHORTWAVE SHIFTING EAST THROUGH BOREAL CANADA AS
THE SOUTHWESTERN PORTION STARTS TO TAKE SHAPE AND SPUR CENTRAL
HIGH PLAINS CYCLOGENESIS BY WED WITH COLD FRONT EXTENDING THROUGH
THE NORTHERN PLAINS AHEAD OF THE COLD SURGE. GUIDANCE IS
REMARKABLY IN GOOD AGREEMENT WITH THE EVOLUTION OF THE ENTIRE
TROUGH, WITH ONLY SMALL DEPTH ISSUES NEAR THE CENTERS OF EACH
DEVELOPING INTERNAL CORES. THE 00Z NAM SHOWS THIS THE MOST IN A
TYPICAL LATE DAY 3, OVER-DEEPENING SOLUTION. THIS HELPS TO
SHARPEN THE NORTHEASTWARD EXTENDING DEFORMATION ZONE AND QPF AXIS
RELATIVE TO OTHER GUIDANCE AS WELL AS GREATER CONVECTIVE
DEVELOPMENT IN THE WARM SECTOR FROM NE KS TO MN. THE UKMET/ECMWF
ARE ON THIS MORE AGGRESSIVE SIDE COMPARED TO THE SLIGHTLY WEAKER
00Z GFS. HOWEVER, THIS IS FAIRLY MINOR AND IN LINE WITH TYPICAL
BIASES THAT ARE ACCOUNTED FOR IN A GENERAL MODEL BLEND. AS SUCH
THE GENERAL MODEL BLEND REMAINS WPC PREFERENCE AT ABOVE 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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