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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