Prognostic Meteorological Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8
000
FXUS10 KWNH 221838
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
237 PM EDT MON MAY 22 2017

VALID MAY 22/1200 UTC THRU MAY 26/0000 UTC

...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...

12Z MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


...CLOSED LOW OVER THE UPPER MS VALLEY AND GREAT LAKES TODAY...
...COLD FRONT MOVING ACROSS THE CENTRAL AND EASTERN U.S....
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

THE 12Z MODELS REMAIN IN GOOD AGREEMENT WITH THE EVOLUTION OF THIS
LARGE SCALE SYNOPTIC SYSTEM. A GENERAL MODEL BLEND IS PREFERRED.


...SHORTWAVE MOVING INTO MT TODAY THEN AMPLIFYING OVER THE MIDWEST
AND MOVING TOWARDS THE EAST COAST THROUGH THU...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-12Z NAM BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

A WELL-DEFINED SHORTWAVE OVER THE MT HIGH PLAINS TODAY WILL DIG SE
AROUND THE SOUTHWEST QUADRANT OF THE UPPER LOW OVER THE UPPER MS
VALLEY INTO THE CENTRAL PLAINS TUE...WITH THE PATTERN AMPLIFYING
IN THE PROCESS. THE UPPER TROUGH WILL MOVE ACROSS THE MIDDLE/LOWER
MS VALLEY WED AND APPROACH THE MIDDLE ATLANTIC THU.

THE 12Z NAM HAS MOVED CLOSER TO THE MAIN CLUSTER OF MODEL
SOLUTIONS THROUGH WED...BUT IT BEGINS TO DIVERGE WED NIGHT AND THU
MAINLY BY DEPICTING A TIGHTER CLOSED MID LEVEL CIRCULATION AS THE
SYSTEM MAKES ITS WAY EAST OF THE MS VALLEY TOWARD THE MIDDLE
ATLANTIC. IT SHOULD BE NOTED THAT THERE IS GENERALLY MORE SPREAD
IN THE MODEL SOLUTIONS BEGINNING WED NIGHT/THU. HOWEVER THE OTHER
12Z MODELS ARE IN BROAD AGREEMENT THAT THE UPPER TROUGH/LOW WILL
BE A MORE NORTH-SOUTH ELONGATED FEATURE WITH A CONCENTRATION OF
VORTICITY MOVING THROUGH THE BASE OF THE TROUGH OVER THE
SOUTHEAST/MIDDLE ATLANTIC. A MODEL BLEND THAT EXCLUDES THE 12Z NAM
IS RECOMMENDED.


...UPPER SHORTWAVE AND SOUTHERN BRANCH JET OVER SOUTHERN PLAINS
TODAY WITH ADDITIONAL SHORTWAVE ENERGY MOVING ACROSS THE GULF
COAST/SOUTHEAST THROUGH TUE...
...SURFACE LOWS TRAVERSING THE GULF COAST INTO THE SOUTHEAST TUE...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z NAM/12Z ECMWF/12Z CMC
CONFIDENCE: AVERAGE

THE UPPER SHORTWAVE AND SOUTHERN BRANCH JET MOVING ACROSS
TX...ALONG WITH ADDITIONAL ENERGY DROPPING SOUTHEAST AROUND THE
BASE OF THE CENTRAL U.S. TROUGH...IS INTERACTING WITH A STALLED
FRONT THAT EXTENDS FROM THE TX AND LA COAST INTO THE SOUTHEAST.
ONE OR MORE WAVES OF LOW PRESSURE SHOULD DEVELOP ALONG THE FRONT
AND  ADVANCE EAST-NORTHEAST...MOVING JUST INLAND ACROSS THE
CENTRAL GULF COAST AND THEN LIFTING NORTHEAST UP ACROSS THE
INTERIOR SOUTHEAST U.S. AND MID-ATLANTIC THROUGH LATE TUE INTO WED.

THE GFS HAS BEEN EXHIBITING A CONVECTIVE FEEDBACK ISSUE WITH THIS
SYSTEM IN RECENT MODEL RUNS. THE 12Z GFS SOLUTION HAS MOVED CLOSER
TO THE MAIN GROUP OF SOLUTIONS...BUT ON ACCOUNT OF THE FEEDBACK
ISSUE STILL APPEARS TO PROGRESS THE LEAD WAVE EAST-NORTHEAST TOO
QUICKLY. THIS IS BEST SEEN IN THE QPF FIELDS...WHICH SHOW THE MAIN
PRECIPITATION BAND ANOMALOUSLY FAR EAST. OTHERWISE THE 12Z SUITE
OF MODELS ARE IN REASONABLY GOOD AGREEMENT WITH RESPECT TO MASS
FIELDS. THE 12Z CMC HAS COME INTO BETTER AGREEMENT WITH THE MAIN
CLUSTER OF MODEL SOLUTIONS WITH RESPECT TO ITS QPF FIELDS...BUT
THE 12Z UKMET REMAINS AN OUTLIER IN THIS RESPECT. FOR NOW A BLEND
OF THE 12Z NAM...12Z ECMWF AND 12Z CMC WILL PROBABLY GIVE THE MOST
REPRESENTATIVE FORECAST.


...UPPER TROUGH MOVING ACROSS THE PACIFIC NORTHWEST TUE/TUE
NIGHT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

A RATHER STRONG UPPER TROUGH IS EXPECTED TO DIG SOUTHEAST ACROSS
THE PACIFIC NORTHWEST TUE/TUE NIGHT FROM THE GULF OF AK. THIS
ENERGY WILL ADVANCE INLAND SLOWLY...CROSS THE NORTHERN ROCKIES WED
AND MOVING INTO THE WEST PORTION OF THE NORTHERN PLAINS THU. MODEL
CLUSTERING IS GOOD ENOUGH WITH THIS SYSTEM TO RECOMMEND A GENERAL
MODEL BLEND FOR THE TIME BEING.


WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML... /ALL LOWER CASE/
WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML... /ALL LOWER CASE/

MCDONNAL

$$




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.