Prognostic Meteorological Discussion
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946
FXUS10 KWNH 220449
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1249 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 12Z 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 12Z 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 TROUGH APPROACHING THE PACIFIC NORTHWEST BY WED...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z GFS/12Z 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 12Z CMC/ECMWF SOLUTIONS ARE A LITTLE FASTER THAN
THE 00Z NAM/GFS AND 12Z UKMET. WILL PREFER A COMPROMISE BETWEEN
THE TWO CAMPS BY SUGGESTING A GFS/ECMWF CONSENSUS AT THIS POINT.


www.wpc.ncep.noaa.gov/html/model2.shtml
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml

ORRISON

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