068  
FXUS10 KWNH 220700  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
300 AM EDT SUN OCT 22 2017  
 
VALID OCT 22/0000 UTC THRU OCT 25/1200 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z MODEL EVALUATION...WITH LATEST MODEL PREFERENCES/CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..UPPER TROUGH CROSSING THE NORTHERN PLAINS/UPPER MS VALLEY SUN
 
   
..COLD FRONT CROSSING THE REGION
 
   
..SURFACE LOW DEEPENING OVER SOUTHERN CANADA
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL CONSENSUS  
CONFIDENCE: ABOVE AVERAGE  
 
THE MODELS ARE IN VERY GOOD AGREEMENT WITH THE MASS FIELD DETAILS  
OF THIS SYSTEM...SO A GENERAL MODEL CONSENSUS WILL BE PREFERRED.  
 
   
..SOUTHERN STREAM LOWER MS VALLEY CLOSED LOW DEVELOPMENT BY MON
 
   
..SURFACE COLD FRONT SWEEPING ACROSS THE MS/TN VALLEYS
 
   
..SURFACE LOW DEVELOPMENT OVER THE TN VALLEY
 
   
..DEEP PHASED CYCLONE OVER THE GREAT LAKES REGION BY TUES
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF THE 00Z UKMET/CMC/ECMWF  
CONFIDENCE: SLIGHTLY BELOW AVERAGE  
 
THE MODELS BREAK AWAY THE SOUTHERN PORTION OF THE LONGER WAVE  
TROUGH EJECTING OUT OF THE WEST AND INTO THE PLAINS STATES ON  
SUNDAY...WITH THIS ENERGY DIGGING SOUTHEAST INTO THE LOWER MS  
VALLEY SUNDAY NIGHT AND RESULTING IN A CLOSED LOW FORMATION BY  
MONDAY. ALREADY THE LATEST NON-OPERATIONAL GOES-16 WV SUITE SHOWS  
A ROBUST VORT MAX AMPLIFYING INTO THE BASE OF THE TROUGH OVER  
NORTHERN TX WHICH IS THE FIRST STAGE OF THIS SOUTHERN STREAM  
SEPARATION. THIS ENERGY WILL STILL BE INTERACTING WITH THE  
SOUTHERN PORTION OF A N/S ORIENTED FRONTAL ZONE AND THE MODELS  
SUGGEST A WAVE OF LOW PRESSURE WILL DEVELOP ALONG THE BOUNDARY  
ACROSS THE TN VALLEY ON MONDAY.  
 
BY MONDAY NIGHT...THE LOW CENTER WILL LIKELY BEGIN TO DEEPEN MORE  
AGGRESSIVELY AND BEGIN LIFTING QUICKLY NORTH TOWARD THE OH VALLEY  
IN RESPONSE TO A STRONG INTRUSION OF NORTHERN STREAM SHORTWAVE  
ENERGY WHICH WILL BE AMPLIFYING SOUTHEAST ACROSS THE MIDWEST. THE  
NORTHERN STREAM TROUGH WILL AMPLIFY INTO THE OH VALLEY AND GREAT  
LAKES REGION AND SHOULD GRADUALLY PHASE WITH THE SOUTHERN STREAM  
CLOSED LOW AS IT ADVANCES TOWARD THE TN VALLEY. THE GUIDANCE HAS  
TRENDED FASTER OVER THE LAST DAY WITH THE PHASING OF ENERGY AND  
THE NORTHWARD ADVANCE OF SURFACE LOW PRESSURE ULTIMATELY ACROSS  
THE OH VALLEY AND INTO THE GREAT LAKES REGION. HOWEVER...THERE ARE  
SUBSTANTIAL DIFFERENCES WITH THE DEPTH OF LOW PRESSURE OVER THE  
GREAT LAKES REGION BY MONDAY NIGHT AND CONTINUING THROUGH TUESDAY  
AND WEDNESDAY. THE 00Z UKMET/CMC AND ECMWF ARE ALL CONSIDERABLY  
STRONGER VERSUS THE 00Z NAM AND GFS. THE NAM IS OVERALL THE  
WEAKEST...BUT THE GFS IS NOT MUCH STRONGER AND IS ALSO A LITTLE  
FARTHER EAST WITH THE SURFACE WAVE EVOLUTION LIKE THE NAM. OVERALL  
THE NON-NCEP GUIDANCE HAS BEEN MORE CONSISTENT OVER THE LAST FEW  
MODEL CYCLES AND TENDS TO HAVE RATHER STRONGER EURO AND CANADIAN  
ENSEMBLE SUPPORT. A FEW GEFS MEMBERS ALSO SUPPORT THE STRONGER  
CONSENSUS. CONFIDENCE IS SLIGHTLY LIMITED...BUT THE STRONGER  
UKMET/CMC/ECMWF CONSENSUS WILL BE PREFERRED.  
 
   
..SHORTWAVE CROSSING B.C./PACIFIC NORTHWEST
 
   
..ATMOSPHERIC RIVER OVER THE PACIFIC NORTHWEST THROUGH SUN
 
   
..UPPER TROUGH SWEEPING ACROSS THE NORTHERN PLAINS/MIDWEST MON
 
   
..WEST COAST RIDGE/SANTA ANA WIND DEVELOPMENT MON/TUES
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL CONSENSUS  
CONFIDENCE: ABOVE AVERAGE  
 
THE MODELS ARE IN GOOD AGREEMENT THROUGH SUNDAY IN TAKING A  
SHORTWAVE ACROSS THE PACIFIC NORTHWEST AND THEN WELL OUT INTO THE  
NORTHERN PLAINS BY MONDAY ALONG WITH A COLD FRONT. THIS ENERGY  
WILL THEN BEGIN TO AMPLIFY SHARPLY ACROSS THE MIDWEST BY LATER  
MONDAY AND TUESDAY WHICH WILL LEAD TO THE EVOLUTION OF THE STRONG  
DEEP LAYER TROUGH OVER THE EASTERN U.S. BY WEDNESDAY. THE INITIAL  
SURGE OF ENERGY ACROSS THE PACIFIC NORTHWEST SHOULD MAINTAIN  
ATMOSPHERIC RIVER CONDITIONS ACROSS THIS AREA THROUGH EARLY SUNDAY  
BEFORE THEN TAPERING OFF AS THE ENERGY ADVANCES WELL OFF TO THE  
EAST AND THE ONSHORE FLOW SLACKENS. A LARGER SCALE RIDGE WILL  
DEVELOP ALONG THE WEST COAST MONDAY AND TUESDAY WHICH WILL SET THE  
STAGE FOR STRONGER SURFACE HIGH PRESSURE TO SETTLE OVER THE GREAT  
BASIN. THIS WILL LEAD TO THE DEVELOPMENT OF A RATHER STRONG SANTA  
ANA WIND SET-UP FOR CALIFORNIA. WILL PREFER A GENERAL MODEL  
CONSENSUS THROUGH THE PERIOD GIVEN GOOD LARGE SCALE MASS FIELD  
AGREEMENT.  
 
   
..SHORTWAVE DIGGING TOWARD THE NORTHERN PLAINS TUES NIGHT
 
   
..ASSOCIATED SURFACE LOW OVER SOUTHERN CANADA
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF THE 00Z UKMET/ECMWF  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE MODELS HAVE ANOTHER NORTHERN STREAM SHORTWAVE AND ASSOCIATED  
LOW CENTER DIGGING SOUTHEAST ACROSS SOUTHERN CANADA AND TOWARD THE  
NORTHERN PLAINS AND UPPER MS VALLEY BY TUESDAY NIGHT AND WEDNESDAY  
AS THE LARGE SCALE PATTERN BECOMES HIGHLY AMPLIFIED OVER THE  
U.S...WITH A DEEP TROUGH OVER THE EAST AND A LARGE SCALE RIDGE  
GENERALLY OVER THE WEST. THIS ADDITIONAL ENERGY WILL BE ATTEMPTING  
TO DIG SOUTH DOWN THE BACK SIDE OF THE EASTERN U.S. TROUGH. THE  
MODELS ARE NOT IN TOO BAD OF AGREEMENT WITH THIS FEATURE...BUT THE  
00Z ECMWF APPEARS TO BE A LITTLE TOO FAST...AND THE 00Z CMC A BIT  
TOO SLOW. THE 00Z GFS/UKMET SOLUTIONS ARE PRETTY WELL CLUSTERED  
AND ARE CLOSE TO THE MODEL CONSENSUS...SO A GFS/UKMET BLEND WILL  
BE PREFERRED WITH THIS FEATURE.  
 
   
..SHORTWAVE TROUGH APPROACHING THE PACIFIC NORTHWEST BY WED
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF THE 00Z GFS/ECMWF  
CONFIDENCE: AVERAGE  
 
THE MODELS HAVE ANOTHER SHORTWAVE APPROACHING THE PACIFIC  
NORTHWEST ON WEDNESDAY WHICH WILL DRIVE SURFACE LOW PRESSURE INTO  
BRITISH COLUMBIA AND A TRAILING COLD FRONT THAT WILL APPROACH  
WESTERN WA. THE 00Z UKMET/CMC AND ECMWF ARE ALL GENERALLY A LITTLE  
FASTER THAN THE 00Z NAM/GFS SOLUTIONS WITH THIS SYSTEM. WILL  
PREFER A COMPROMISE BETWEEN THE TWO CAMPS BY SUGGESTING A  
GFS/ECMWF CONSENSUS AT THIS POINT.  
 
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ORRISON  
 

 
 
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