Prognostic Meteorological Discussion
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000
FXUS10 KWNH 050443
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1143 PM EST WED MAR 04 2015

VALID MAR 05/0000 UTC THRU MAR 08/1200 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.


...STRONG HEIGHT FALLS MOVING FROM THE CENTRAL U.S. TOWARD THE
NORTHEASTERN STATES...
...WAVY FRONTAL ZONE EXITING THE EASTERN SEABOARD...

PRELIMINARY PREFERENCE: A NON-12Z CMC MODEL COMPROMISE
FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE

WATER VAPOR IMAGERY TONIGHT SHOWED A BROAD POSITIVELY-TILTED TROF
MOVING FROM THE CENTRAL U.S. TOWARD THE MS RIVER VALLEY. IN
ADVANCE OF THIS FEATURE...THE 500-MB HEIGHT ANALYSIS AND
BLENDED-TPW GRAPHIC SHOWED STRONG MID-LEVEL CONFLUENCE DOWNSTREAM
COLLOCATED WITH AN AREA OF ENHANCED GULF INFLOW. THIS PATTERN HAS
BEEN RESPONSIBLE FOR AN EXPANSIVE AREA OF MIXED PRECIPITATION FROM
THE SOUTHERN PLAINS UP TO THE MID-ATLANTIC. OVERALL...THE MODELS
HAVE COME INTO DECENT AGREEMENT REGARDING THE PASSAGE OF THE
MID-LEVEL TROF. THERE IS A LITTLE MORE UNCERTAINTY WITH THE
STRENGTH AND LOCATION OF THE COLD FRONT WHICH SAGS SOUTHWARD
TOWARD THE SOUTHEASTERN U.S. BY LATE THURSDAY. THE 12Z CMC IS THE
ONE OF THE STRONGER SOLUTIONS ATTEMPTING TO DEVELOP A MORE
PRONOUNCED AREA OF LOW PRESSURE OFFSHORE OF GA. WILL STEER AWAY
FROM THIS IDEA AND FAVOR A NON-12Z CMC MODEL COMPROMISE.


...SECONDARY SHORTWAVE CROSSING THE MIDDLE MS VALLEY BY LATE
THURSDAY...

PRELIMINARY PREFERENCE: BLEND OF THE 12Z ECMWF/UKMET
FORECAST CONFIDENCE: AVERAGE

IN THE WAKE OF THE PRONOUNCED UPPER TROF EXITING THE EASTERN
SEABOARD WILL BE A LOWER AMPLITUDE SYSTEM CROSSING THE MIDDLE MS
VALLEY BY 06/06Z. GENERAL AGREEMENT IS NOTED WITH THE EXCEPTION OF
THE 12Z CMC WHICH IS FARTHER SOUTH WITH THE POSITION OF THE
SHORTWAVE. BY LATE FRIDAY EVENING...THE 00Z NAM/GFS BEGIN TO
MIGRATE AHEAD OF THE OTHER SOLUTIONS WHICH BRINGS THE REINFORCING
SHOT OF COLD AIR IN MORE QUICKLY. PLAN ON LEANING ON THE CONSENSUS
OF THE OTHER CLUSTERED SOLUTIONS FEATURING THE 12Z ECMWF/UKMET.


...ADDITIONAL SHORTWAVES REACHING THE NORTHERN TIER THIS WEEKEND...
...WEAK SURFACE LOW MOVING ACROSS THE GREAT LAKES...

PRELIMINARY PREFERENCE: BLEND OF THE 12Z ECMWF ENSEMBLE/21Z SREF
MEANS
FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE

BROAD UPPER CYCLONIC FLOW WILL CONTINUE THROUGHOUT THE PERIOD AS
ADDITIONAL SHORTWAVES MOVE FROM CENTRAL CANADA TOWARD THE NORTHERN
TIER OF THE U.S. THERE ARE QUITE A FEW TIMING DIFFERENCES IN NOTED
IN THE MODEL SOLUTIONS. ON THE SLOWER SIDE OF THE EQUATION ARE THE
00Z NAM/GFS AND 18Z GEFS MEAN WHILE THE REMAINING MODELS SUGGEST A
FASTER SOLUTION. THE GUIDANCE DOES SEEM TO BE STRUGGLING WITH THE
STRENGTH OF THE APPROACHING SHORTWAVES ALONG WITH THE TIMING. THE
12Z ECMWF SUITE IS EMPHATIC ABOUT A DEEPER SURFACE SOLUTION
RELATIVE TO SOME OF THE OTHER FLATTER SOLUTIONS. GIVEN THE
INHERENT SPREAD...WILL FAVOR A COMBINATION OF ENSEMBLE MEANS UNTIL
THE DETERMINISTIC MODELS SHOW A BIT MORE CONSISTENCY. WPC
RECOMMENDS A COMBINATION OF THE 12Z ECMWF ENSEMBLE/21Z SREF MEANS.


...SLOW MOVING CLOSED LOW IN THE VICINITY OF NORTHERN BAJA CA...

PRELIMINARY PREFERENCE: BLEND OF THE 12Z ECMWF/CMC
FORECAST CONFIDENCE: AVERAGE

SOME FORM OF A REX BLOCK IS NOTED IN THE GUIDANCE ACROSS THE
WESTERN U.S. AS THE PERSISTENT UPPER RIDGE REMAINS IN PLACE ACROSS
THIS SIDE OF THE COUNTRY. BOUNDED TO ITS SOUTH WILL BE A COMPACT
CLOSED LOW WHICH IS FORECAST TO SLIDE EASTWARD ACROSS NORTHERN
BAJA CA BY MIDDAY FRIDAY. THE GUIDANCE VARY WITH HOW QUICKLY TO
EJECT THIS SYSTEM TOWARD THE SOUTHERN HIGH PLAINS. AT THIS
TIME...THE 00Z NAM/GFS ARE THE FASTER SIDE OF THE SPREAD WHICH IS
NOT SUPPORTED GIVEN WOULD RATHER STAY ON THE SLOWER SIDE WITH A
CLOSED LOW IN THE FORECAST. THE PLAN IS TO STAY AT THE CENTER OF
THE SOLUTION SPREAD BOUNDING THE QUICKER 00Z NAM/GFS AND THE
SLOWER 12Z UKMET. THE RECOMMENDATION IS A BLEND OF THE 12Z
ECMWF/CMC AT THIS TIME.


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

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

RUBIN-OSTER

$$





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