Prognostic Meteorological Discussion
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000
FXUS10 KWNH 150459
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1258 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 PRELIMINARY PREFERENCES
==================================================
NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO
SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT.
==================================================

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

PREFERENCE: BLEND OF 00Z GFS/12Z ECMWF

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...BUT ARE STILL RATHER SIGNIFICANT IN THE NORTHERN TIER
OF STATES. SOLUTIONS AT THE SURFACE SHOW LESSER SPREAD...BUT
SIMILAR TO THE SOLUTIONS ALOFT...THE GREATEST DIFFERENCES ARE OVER
THE MIDWEST/GREAT LAKES. AN IDEAL OPERATIONAL BLEND IS DIFFICULT
TO FIND GIVEN THE RUN TO RUN CHANGES IN THE SMALL SCALE DETAILS.
ONE COULD RECOMMEND A BLEND OF THE GEFS MEAN AND ECMWF ENSEMBLE
MEAN TO GET TOWARD SOMETHING REPRESENTATIVE OF CONSENSUS. A BLEND
OF THE OPERATIONAL GFS/ECMWF MAY ACCOMPLISH THE SAME FEAT WHILE
PRESERVING SOME OF THE SHORTWAVE DETAILS ALOFT.


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

PREFERENCE: BLEND OF 00Z NAM WITH 12Z ECMWF/UKMET

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. ASIDE GFS BEING SLIGHTLY FAST AND THE CANADIAN SLIGHTLY
FLAT...THE MODELS SHOW STRONG AGREEMENT.


...PACIFIC NORTHWEST THURSDAY...

PREFERENCE: BLEND OF 12Z ECMWF/UKMET

MODELS PREDICT SIMILAR STRENGTH AND STRUCTURE TO THE NEXT PACIFIC
SHORTWAVE TO ARRIVE THURSDAY. EAST TO WEST VARIATION IN TIMING OF
THE SYSTEM IS THE MAIN DIFFERENCE IN THE MODELS...ALTHOUGH THE 12Z
CANADIAN WAS SOMETHING OF A FLAT OUTLIER. THE UKMET SUPPORTS THE
SLOWER ECMWF AND ECMWF ENSEMBLE MEAN...SO WE SIDE WITH THOSE
MODELS GIVEN THE OFTEN OBSERVED FAST BIAS IN THE NCEP GUIDANCE.
THE NAM IS SLOWER THAN THE GFS AND BETTER DEFINED WITH THE WAVE.
THE NAM COULD PERHAPS BE USED WITH AN ADJUSTMENT TOWARD THE
ECMWF/UKMET TIMING.


...SOUTHERN CALIFORNIA THURSDAY...

PREFERENCE: BLEND OF 00Z NAM/GFS WITH 12Z ECMWF

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...AND THE
NAM/GFS/ECMWF ARE THE OPERATIONAL SOLUTIONS WHICH BEST FIT THE
MEANS.


...EASTERN U.S TODAY...

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

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.

...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...
...500 MB FORECASTS AT www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

BURKE
$$





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