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Model Diagnostics Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0657Z Apr 15, 2014)
 
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Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
257 AM EDT TUE APR 15 2014

VALID APR 15/0000 UTC THRU APR 18/1200 UTC

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

==============================================
00Z NAM/GFS EVALUATION AND PREFERENCES
==============================================
NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO
SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT.
==============================================

...CENTRAL U.S. AMPLIFYING TROUGH...

PREFERENCE: BLEND OF 00Z ECMWF/CANADIAN
CONFIDENCE: AVERAGE

A SERIES OF RELATIVELY LOW AMPLITUDE TROUGHS AT SEVERAL LATITUDES
WILL HELP CARVE A DEEPER LARGE SCALE TROUGH IN CENTRAL NORTH
AMERICA BY THURSDAY. TIMING AND DEPTH ISSUES ALOFT HAVE BEEN
DECREASING...AND AS OF THE 00Z CYCLE THESE DIFFERENCES FOLLOW THE
FAMILIAR PATTERN OF A FAST GFS...A NAM THAT IS FAST AT THE SURFACE
BUT MORE VIGOROUS ALOFT...AND THE ECMWF/UKMET/CANADIAN BEGINNING
TO CLUSTER TOGETHER. WE DROP THE UKMET FROM THIS MIX BASED ON ITS
PERFORMANCE AT THE BASE OF THE TROUGH IN THE SOUTHERN
PLAINS...WHERE IT IS NOW A DEEP OUTLIER.


...SUB-TROPICAL JET AMPLIFICATION NEARING FLORIDA THURSDAY...

PREFERENCE: BLEND OF 00Z NAM/ECMWF
CONFIDENCE: AVERAGE

AN ACTIVE SUB-TROPICAL JET IS FORECAST TO REMAIN AT THE LATITUDE
OF THE GULF OF MEXICO. WITHIN THIS BRANCH OF THE JET SOME
AMPLIFICATION OF A WAVE IS EXPECTED SLIGHTLY DOWNSTREAM OF THE
NORTHERN STREAM FLOW RELATED TO AMPLIFIED TROUGHING IN THE CENTRAL
U.S. THE GFS IS SLIGHTLY FAST AND THE CANADIAN SLIGHTLY FLAT. THE
UKMET BECAME A DEEP OUTLIER WITH RESPECT TO AN UPSTREAM SHORTWAVE
EXITING THE SOUTHERN PLAINS...WITH SOME DOWNSTREAM EFFECTS SEEN IN
ITS SOLUTION OVER THE GULF. THEREFORE...WE DROPPED THE UKMET FROM
OUR PREFERENCE.


...PACIFIC NORTHWEST THURSDAY...

PREFERENCE: BLEND OF 00Z UKMET WITH 12Z ECMWF
CONFIDENCE: AVERAGE

MODELS PREDICT RELATIVELY SIMILAR STRENGTH AND STRUCTURE TO THE
NEXT PACIFIC SHORTWAVE DUE TO ARRIVE THURSDAY. THE 00Z
ECMWF...HOWEVER...TRENDED TOWARD A SHARPER/DEEPER TROUGH
AXIS...CERTAINLY ON THE DEEP SIDE OF THE 12Z ECMWF ENSEMBLE MEAN.
SEEING NO SIMILAR TREND IN THE OTHER MODELS...AND KNOWING THE
OPERATIONAL ECMWF HAS A TENDENCY TO ERR ON THE DEEP SIDE...WE
PREFER THE 12Z ECMWF AT THIS TIME. ADDITIONALLY...SOME EAST TO
WEST VARIATION IN TIMING OF THE SYSTEM REMAINS AMONG THE MODELS.
THE UKMET IS SOMEWHAT SLOWER. THE CANADIAN JOINED THE FASTER
NAM/GFS...BUT RUN TO RUN CONTINUITY HAS BEEN POOR IN THE CANADIAN
OVER THIS REGION. GIVEN THE TENDENCY OF THE NAM/GFS TO BE TOO
FAST...WE WILL TAKE A CONSERVATIVE APPROACH TOWARD THE ENSEMBLE
MEANS...BEST REPRESENTED BY THE 00Z UKMET AND 12Z ECMWF. THE NAM
IS CLOSER TO OUR PREFERENCE THAN IS THE GFS...AND THE NAM COULD
PERHAPS BE USED BY APPLYING SOME ADJUSTMENT.


...SOUTHERN CALIFORNIA THURSDAY...
CONFIDENCE: AVERAGE

PREFERENCE: BLEND OF THE 00Z OPERATIONAL MODELS

A SOUTHERN STREAM TROUGH WELL OFFSHORE WILL BE DRAGGED EASTWARD BY
INCREASINGLY ENERGETIC NORTHERN STREAM FLOW. THE AXIS OF A MEDIUM
WAVELENGTH TROUGH IS FORECAST TO REACH SOUTHERN CALIFORNIA BY LATE
THURSDAY...WITH A LEAD SHORTWAVE HEADING INTO THE DESERT SOUTHWEST
AS THE WHOLE PATTERN SHOWS GRADUAL AMPLIFICATION. THE GEFS MEAN
AND ECMWF ENSEMBLE MEAN SHOW GOOD AGREEMENT. THE OPERATIONAL
MODELS TRENDED TOWARD ONE ANOTHER DURING THIS CYCLE...FORMING A
NARROW SPREAD AROUND THE MEANS WITH ONLY SOME SMALL SCALE
DIFFERENCES. CONFIDENCE IS ONLY AVERAGE SINCE THE SMALL SCALE
DIFFERENCES HAVE OPPORTUNITY TO AMPLIFY WITH THIS BEING A DAY 3
SYSTEM...AND ONE THAT IS POTENTIALLY INFLUENCED BY CHANGES TO THE
NORTHERN STREAM SOLUTION.


...EASTERN U.S TODAY...

PREFERENCE: AWAY FROM THE FASTER TREND IN THE 00Z GFS
CONFIDENCE: HIGH

AGREEMENT IN THE MASS FIELDS HAD BEEN EXCELLENT HERE. THE 00Z NAM
MAINTAINED CONTINUITY WITH THE GLOBAL MODEL CONSENSUS. THE 00Z
GFS...HOWEVER...ACCELERATED THE SYSTEM SLIGHTLY...ESPECIALLY THE
SOUTHERN STREAM SHORTWAVE LIFTING OUT OF THE GULF COAST STATES.
GIVEN THAT RAPID PROGRESSION IS A BIAS OF THE GFS...WE PREFER THE
SLOWER 18Z RUN WHICH WAS MORE IN TUNE WITH CONSENSUS.

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

BURKE