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Model Diagnostics Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0442Z Mar 26, 2015)
 
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Abbreviations and acronyms used in this product
 
Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1242 AM EDT THU MAR 26 2015

VALID MAR 26/0000 UTC THRU MAR 29/1200 UTC

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

...AN EVALUATION OF THE 00Z NAM/GFS ALONG WITH PRELIMINARY
PREFERENCES/FORECAST CONFIDENCE...

THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 00Z
NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS.


...FULL-LATITUDE TROF CROSSING THE EASTERN U.S. BY EARLY IN THE
WEEKEND...
...STRONG COLD FRONT/ASSOCIATED SURFACE WAVES...

PRELIMINARY PREFERENCE: BLEND OF THE 00Z GFS/12Z ECMWF...WEIGHTED
2/3 TOWARD THE 12Z ECMWF
FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE

THE CURRENT WATER VAPOR IMAGERY SHOWED A PAIR OF STRONG SHORTWAVES
AFFECTING THE OZARKS AND SOUTHERN ONTARIO...RESPECTIVELY. THE
FORMER HAS HELPED IGNITE A LARGE CLUSTER OF SHOWERS AND
THUNDERSTORMS ACROSS OK/AR WHICH HAS BEEN RESPONSIBLE FOR SEVERE
WEATHER REPORTS AND FLASH FLOODING. ALL FEATURES MOVING FORWARD
SHOULD BECOME MORE PROGRESSIVE IN NATURE AS HEIGHT FALLS PROJECT
EASTWARD IN TIME. A COMPLEX ARRAY OF IMPULSES MOVING IN FROM
CENTRAL CANADA WILL HELP DRAG THE UPPER TROF EASTWARD WITH THE
SYSTEM EVENTUALLY REACHING THE WESTERN ATLANTIC BY LATE IN THE
WEEKEND. THE ACCOMPANYING COLD FRONT WILL FEATURE A MULTITUDE OF
SURFACE WAVES WITH THE GUIDANCE GENERALLY DIFFERING WITH REGARD TO
THE POSITION AND INTENSITY OF EACH OF THESE LOWS.

OVERALL...THE 00Z GFS/18Z GEFS MEAN HAVE TENDED TO BE A BIT
QUICKER WITH THE SOUTHERN EXTENT OF THE UPPER TROF ON FRIDAY
EVENING ACROSS THE SOUTHEASTERN U.S. THIS ULTIMATELY LEADS TO THE
GFS SUITE OF SOLUTIONS BEING MORE PROGRESSIVE WITH THE EJECTING
SURFACE LOW OVER THE WESTERN ATLANTIC. LATER IN THE PERIOD...THE
12Z CMC/UKMET STAND OUT AS BEING RATHER SLOW WITH THE BACK EDGE OF
THE UPPER TROF. IN FACT...THE 12Z CMC CLOSES OFF A 534-DM UPPER
LOW ACROSS THE MID-ATLANTIC BY 29/0000Z. THIS LEADS TO A MORE
WRAPPED UP COASTAL SOLUTION WHICH KEEPS PRECIPITATION ACROSS THE
MID-ATLANTIC INTO DAY 3. ENSEMBLE LOW PLOTS SUGGEST SUCH A
SOLUTION IS A MINORITY AT THIS POINT. AS A WHOLE LIKE THE COMBO OF
THE 00Z GFS/12Z ECMWF BUT WILL WEIGHT THE SOLUTION TWO-THIRDS
TOWARD THE LATTER GIVEN THE THOUGHT THAT THE GFS IS TOO FAST INTO
DAY 3.


...PROGRESSIVE SHORTWAVE REACHING THE PACIFIC NORTHWEST BY LATE
FRIDAY...
...WELL-DEVELOPED SURFACE CYCLONE MOVING THROUGH THE NORTHERN TIER
THIS WEEKEND...

PRELIMINARY PREFERENCE: BLEND OF THE 00Z GFS/21Z SREF MEAN
FORECAST CONFIDENCE: BELOW AVERAGE

A STOUT UPPER RIDGE ANCHORING THE WESTERN U.S. WILL QUICKLY GIVE
WAY TO A PROGRESSIVE SHORTWAVE CROSSING THE PACIFIC NORTHWEST BY
FRIDAY NIGHT. THE MODELS ALREADY SHOW SOME DISAGREEMENT WITH THE
PATTERN...PARTICULARLY THE 12Z UKMET WHICH IS SLOWER AND SPREADS
SOME OF THE VORTICITY DOWN TOWARD NORTHERN CA. THIS SOLUTION GIVES
WAY TOO MUCH EMPHASIS ON A SOUTHERN SPLIT WHICH IS NOT VERY
SUPPORTED BY THE GUIDANCE. MANY OF THE 00Z MODELS PLACE MORE
EMPHASIS ON KEEPING THE SHORTWAVE INTACT ACROSS THE NORTHERN TIER
STATES. LOOKING TOWARD DAY 3....THE 12Z ECMWF STARTS TO BECOME
SLOWER THAN THE ENSEMBLE MEANS INCLUDING ITS OWN 12Z ECMWF
ENSEMBLE MEAN. PREFER TO STAY ON THE MORE PROGRESSIVE SIDE AS
SUPPORTED BY THE ENSEMBLE MEANS. WILL FAVOR A COMBINATION OF THE
00Z GFS WITH THE 21Z SREF MEAN. THE 00Z GFS IS ON THE SOUTHERN END
OF THE ENSEMBLE SPREAD REGARDING THE LOW TRACK. SO WILL SPLIT THE
DIFFERENCE BETWEEN THE TWO.



...SHORTWAVES CROSSING THE DESERT SOUTHWEST ON SATURDAY...

PRELIMINARY PREFERENCE: BLEND OF THE 18Z GEFS/12Z ECMWF ENSEMBLE
MEANS
FORECAST CONFIDENCE: BELOW AVERAGE

THIS AREA OF THE COUNTRY IS PLAGUED BY QUITE A BIT OF SPREAD AS
THE REGION WILL BE AFFECTED BY A PAIR OF DISTURBANCES. AS
MENTIONED EARLIER...THE 12Z UKMET IS DISPLACED SOUTHWARD WITH THE
PACIFIC NORTHWEST SYSTEM WHICH BRINGS STRONGER HEIGHT FALLS INTO
THE SOUTHWESTERN STATES. LURKING TO THE WEST ACROSS THE EASTERN
PACIFIC IS ANOTHER SHORTWAVE EXPECTED TO APPROACH THE AREA LATE IN
THE PERIOD. THE 00Z NAM/GFS AND 12Z UKMET ARE MORE EMPHATIC ABOUT
CARRYING THIS ENERGY INTO THE MAP DOMAIN WHILE THE 12Z ECWMF/CMC
SHOW A MORE SHEARED OUT SYSTEM. GIVEN THE SPREAD IN PLACE...WILL
BLEND THE ENSEMBLE MEANS PENDING ADDITIONAL MODEL GUIDANCE.



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RUBIN-OSTER