Prognostic Meteorological Discussion
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000
FXUS10 KWNH 041643
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1242 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 MODEL EVALUATION...INCLUDING THE NAM/GFS ALONG WITH
PRELIMINARY 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/00Z 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 FASTER THAN THE CONSENSUS. 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. THE
PREFERENCE IS FOR A BLEND OF THE 12Z GFS/00Z ECMWF...BUT GIVEN THE
SPREAD AMONG THE MODELS (AND THEIR ENSEMBLE MEAN
POSITIONS)...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: 12Z GFS/00Z ECMWF BLEND
CONFIDENCE: AVERAGE

THE 12Z NAM WAS CLOSE TO THE CONSENSUS WITH THE SHORT
WAVE...THOUGH ITS HAS SLOWED COMPARED TO ITS PREVIOUS RUNS. THE
12Z GFS REMAINS CLOSE TO THE MULTI MODEL CONSENSUS...AS WELL AS
ITS PREVIOUS SOLUTIONS AND THE 06Z GEFS MEAN. BOTH OF THESE
SOLUTIONS ARE CLOSE TO THE 00Z ECMWF...SO A BLEND OF THE 12Z
GFS/00Z ECMWF IS PREFERRED.


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

PREFERENCE: BLEND OF THE 12Z GFS/00Z 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 GFS REMAINS CLOSE TO THE CONSENSUS (AND IS
CONSISTENT WITH ITS PREVIOUS SOLUTIONS). THE 00Z ECMWF SOLUTION
REMAINS CLOSE TO THE 12Z GFS...SO A BLEND OF THESE SOLUTIONS WAS
PREFERRED.


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

PREFERENCE: 12Z NAM/00Z 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 IS FASTER THAN THE CONSENSUS WITH THIS SYSTEM (AND
SLOWER THAN ITS EARLIER MODEL SOLUTIONS...SUGGESTING A SLOWING
TREND). THE 00Z UKMET WAS TOO FAST WITH THIS SYSTEM AS WELL...AND
THE 00Z CMC NEVER DEEPENS THE SHORT WAVE AS IT APPROACHES THE
SOUTHERN PLAINS. THE 12Z NAM IS CLOSE TO THE 00Z ECMWF...SO THIS
COMBINATION WAS PREFERRED WITH THIS SYSTEM.


...EASTERN PACIFIC UPPER LOW APPROACHING CALIFORNIA BY TUES...

PREFERENCE: BLEND OF THE 12Z NAM/12Z GFS/00Z ECMWF
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 00Z ECMWF
SOLUTION. 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

$$





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