Prognostic Meteorological Discussion
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000
FXUS10 KWNH 041852
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
251 PM EDT SAT JUL 04 2015

VALID JUL 04/1200 UTC THRU JUL 08/0000 UTC

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

12Z FINAL MODEL EVALUATION...INCLUDING THE UKMET/CMC/ECMWF...AS
WELL FINAL PREFERENCES AND CONFIDENCE

...UPPER TROUGH MOVING THROUGH WESTERN/CENTRAL CANADA SUN AND
MON...
...COLD FRONT CROSSING THE NORTHERN PLAINS TO THE MIDWEST/GREAT
LAKES...

PREFERENCE: BLEND OF THE 12Z GFS/ECMWF
CONFIDENCE: SLIGHTLY BELOW AVERAGE

A LONG WAVE TROUGH CROSSES WESTERN AND CENTRAL CANADA THROUGH
MON...WITH THE SOUTHERN PORTION OF THE LONG WAVE TOUCHING THE
NORTHERN PLAINS. THE LONG WAVE DRIVES A COLD FRONT ACROSS THE
NORTHERN AND CENTRAL PLAINS INTO THE GREAT LAKES DURING THIS TIME.
THE 12Z NAM APPEARS TO BE TOO FAST WITH THE SURFACE FRONT...ENDING
UP SLIGHTLY FASTER THAN THE CONSENSUS ACROSS THE UPPER MS VALLEY
AND GREAT LAKES DURING MON. THE 12Z GFS HAS SLOWED A BIT COMPARED
ITS PREVIOUS SOLUTIONS...AND IS CLOSER TO THE 00Z ECMWF PLACEMENT
OF THE LONG WAVE THROUGH AND SURFACE FRONT...ALL OF WHICH IS
SUPPORTED BY THE 12Z CYCLE CONSENSUS. THE 12Z
ECMWF...HOWEVER...SPED UP NOTICEABLY COMPARED TO ITS PREVIOUS RUN.
THIS WAS ESPECIALLY TRUE ALOFT WHERE IT IS FASTER THAN THE GLOBAL
MODEL CONSENSUS. THE PREFERENCE IS FOR A BLEND OF THE 12Z
GFS/ECMWF...BUT WITH MORE WEIGHT GIVEN TO THE GFS THIS CYCLE. ON
THE LARGE SCALE THE MODELS SHOW DECENT AGREEMENT...BUT GIVEN THE
RUN TO RUN VARIABILITY WITH RESPECT TO DETAILS...CONFIDENCE IS
SLIGHTLY BELOW NORMAL WITH THIS SYSTEM.


...SURFACE WAVE MOVING OFF THE MID ATLANTIC COAST TONIGHT...

PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THERE IS GOOD MODEL AGREEMENT CONCERNING A MID LEVEL SHORTWAVE
TROUGH AND ASSOCIATED WAVE OF LOW PRESSURE OVER THE MID ATLANTIC
REGION...SO A GENERAL MODEL COMPROMISE IS PREFERRED.


...SHORTWAVE CLIPPING THE GREAT LAKES/NORTHERN NEW ENGLAND THROUGH
SUN...

PREFERENCE: BLEND OF THE 12Z OPERATIONAL MODELS...DROPPING THE
CANADIAN AT LATER TIMES
CONFIDENCE: ABOVE AVERAGE

THE MODELS SHOW GOOD AGREEMENT IN HANDLING THIS
PROGRESSIVE...MEDIUM WAVELENGTH TROUGH. THE NAM IS JUST SLIGHTLY
COOLER THAN CONSENSUS AT THE BASE OF THE TROUGH AS MEASURED BY THE
MID LEVEL HEIGHTS. OTHERWISE ITS PROGRESSION WAS CLOSE TO THE
CONSENSUS. THE 12Z GFS REMAINS CLOSE TO THE MULTI MODEL
CONSENSUS...AS WELL AS ITS PREVIOUS SOLUTIONS AND THE 06Z GEFS
MEAN. THE 12Z UKMET AND CMC WERE CLOSE TO THE 12Z GFS/NAM IN
TIMING AND PLACEMENT OF THE TROUGH...SO A GENERAL CONSENSUS IS
PREFERRED WITH THIS SYSTEM. THE CANADIAN BECOMES SLOW BY DAY
2...BUT AT THAT TIME THE SYSTEM WILL BE OVER OPEN WATERS IN THE
NORTH ATLANTIC.


...UPPER TROUGH CROSSING THE GULF COAST STATES/SOUTHEAST SUN AND
MON...

PREFERENCE: BLEND OF THE 12Z GFS/ECMWF
CONFIDENCE: AVERAGE

SHORT WAVE ENERGY DROPPING INTO THE BASE OF THE EASTERN UNITED
STATES TROUGH WILL SLOWLY BECOME DETACHED FROM THE TROUGH AND TRY
TO BECOME A CLOSED MID LEVEL SYSTEM. THE 12Z NAM IS CLOSE TO THE
CONSENSUS EARLY...BUT BECOMES SLOWER AND FLATTER THAN THE
CONSENSUS...AS THE TROUGH ALMOST BECOMES ABSORBED BY THE MID LEVEL
FLOW. THE 12Z UKMET BECOMES FASTER THAN THE
CONSENSUS...PARTICULARLY ON MON...AND THE 12Z CMC IS FASTER AND
FLATTER THAN THE ENSEMBLE BASED CONSENSUS DURING THAT TIME.

THE GFS AND ECMWF REMAINS CLOSEST TO CONSENSUS...AND SHOWED GOOD
RUN TO RUN CONTINUITY...SO A BLEND OF THESE SOLUTIONS WAS
PREFERRED.


...SHORT WAVE CROSSING THE SOUTHWEST AND SOUTHERN PLAINS MON/TUE...

PREFERENCE: 12Z NAM/ECMWF BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE

A SHORT WAVE EJECTED FROM A CLOSED MID LEVEL SYSTEM OFF THE CA
COAST RIDES THROUGH THE MID LEVEL FLOW ACROSS THE SOUTHWEST AND
SOUTHERN ROCKIES BEFORE AMPLIFYING OVER THE SOUTHERN PLAINS TUE.
THE 12Z GFS AND UKMET ARE FASTER THAN THE CONSENSUS WITH THIS
SYSTEM...WITH THE GFS BEING A LITTLE SLOWER THAN IN EARLIER
RUNS...SUGGESTING A SLOWING TREND. THE 12Z CMC DEEPENS THE SHORT
WAVE...BUT REMAINS SLOWER THAN THE 12Z NAM.  THE 12Z NAM IS CLOSE
TO THE ECMWF WHICH REMAINED RELATIVELY UNCHANGED BETWEEN RUNS...SO
THIS COMBINATION WAS PREFERRED.


...EASTERN PACIFIC UPPER LOW APPROACHING CA BY TUE...

PREFERENCE: GENERAL MODEL CONSENSUS
CONFERENCE: ABOVE AVERAGE

ALL MODELS TAKE AN UPPER LOW OVER THE EASTERN PACIFIC CURRENTLY
CENTERED NEAR 33N 130W SLOWLY  EASTWARD INTO EARLY NEXT WEEK. BOTH
THE 12Z NAM AND GFS WERE CLOSE TO THE MODEL CONSENSUS (AS WELL AS
THEIR PREVIOUS RUNS)...WHICH WERE VERY CLOSE TO THE 12Z CMC AND
UKMET POSITIONS. GIVEN THE GOOD MODEL AGREEMENT...CONFIDENCE WITH
THIS SYSTEM IS ABOVE AVERAGE.


...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...

...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

HAYES/BURKE
$$




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