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Model Diagnostics Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0441Z Aug 31, 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
1241 AM EDT SUN AUG 31 2014

VALID AUG 31/0000 UTC THRU SEP 03/1200 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.
==================================================

...LOW AMPLITUDE TROUGH PASSING THROUGH THE EASTERN U.S...

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

A PROGRESSIVE NORTHERN STREAM FLOW PATTERN WILL FERRY LOW
AMPLITUDE TROUGHING ACROSS THE EASTERN AND NORTHEASTERN U.S. BY
MONDAY MORNING. LOCAL EMBEDDED VORTICITY MAXIMA WILL PASS FROM THE
GREAT LAKES THROUGH NEW ENGLAND AND FROM THE LOWER OHIO VALLEY
THROUGH THE MID ATLANTIC. THE NAM/GFS/ECMWF AGREE AS TO THE TIMING
AND STRENGTH OF THESE FEATURES. THE 12Z UKMET TRAILED CONSENSUS
OVER THE OHIO VALLEY...AND SEVERAL RUNS OF THE CANADIAN HAVE SPUN
UP A BETTER DEFINED SURFACE REFLECTION AS THIS TROUGHING REACHES
THE ATLANTIC. GIVEN A DE-AMPLIFYING WAVE AND CONSENSUS
SOLUTION...THE CANADIAN LOOKS JUST SLIGHTLY OVERLY DEVELOPED AT
THE SURFACE.


...TROUGH SWEEPING THROUGH CENTRAL NORTH AMERICA...

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

SURFACE LOW PRESSURE IN THE DAKOTAS THIS MORNING WILL LIFT INTO
CANADA WHILE CYCLOGENESIS TAKES PLACE AHEAD OF A MEDIUM WAVELENGTH
TROUGH. THIS IS THE TYPE OF WELL DEFINED SYSTEM THAT IS USUALLY
HANDLED WELL BY THE OPERATIONAL MODELS...AND THE ENSEMBLE SPREAD
IS SMALL HERE. WE RECOMMEND THE NAM/GFS/ECMWF...WHEREAS THE 12Z
CANADIAN WAS SOMEWHAT OUT OF PHASE...AND THE 12Z UKMET WAS THE
ONLY MODEL EMPHASIZING DEVELOPMENT OF A SECOND FRONTAL WAVE AND
STRONG LOW PRESSURE OVER THE WESTERN GREAT LAKES.


...AMPLIFYING TROUGH REACHING THE NORTHWEST U.S. ON TUESDAY...

PREFERENCE: BLEND OF THE OPERATIONAL MODELS

IN ITS 00Z RUN THE GFS SPED UP...AND ALTHOUGH IT STILL LAGS BY A
SMALL AMOUNT...IT IS VERY NEAR THE DAY 3 POSITION OF THE OTHER
OPERATIONAL MODELS...INCLUDING THE 00Z NAM.


...EASTERLY WAVES AFFECTING TEXAS AND FLORIDA...

PREFERENCE: BLEND OF THE OPERATIONAL MODELS...EXCLUDING THE NAM

THE MODELS SHOW FAIRLY GOOD AGREEMENT IN DEPICTING WHAT ARE
SOMEWHAT BROAD EASTERLY WAVES / INVERTED TROUGHS...ONE APPROACHING
SOUTH TEXAS AND ONE APPROACHING FLORIDA ON DAY 3. THE MAIN OUTLIER
IS THE NAM. NEAR FLORIDA IT DEPICTS A NARROWER...SHARPER LOW LEVEL
TROUGH AXIS WITH INCREASED WINDS RELATIVE TO CONSENSUS...WHILE
ALSO BEING MORE EXPANSIVE WITH DEPRESSION OF THE MID LEVEL HEIGHTS
AROUND THIS WAVE. FARTHER WEST THE NAM IS SPINNING UP A TROPICAL
SYSTEM OVER THE BAY OF CAMPECHE. THE NATIONAL HURRICANE CENTER
DOES GIVE 40 PERCENT ODDS OF THIS SYSTEM BECOMING A TROPICAL
CYCLONE WITHIN 5 DAYS. THE NAM SOLUTION...HOWEVER...IS ONE OF THE
MORE AGGRESSIVE ONES. IT BEGINS INTENSIFYING THE CYCLONE EVEN AS
IT IS CROSSING THE YUCATAN PENINSULA. FOR NOW A CONSERVATIVE
APPROACH IS TO SET THE NAM SOLUTION ASIDE AS A LESS LIKELY
OUTCOME...ALTHOUGH IT IS ONE THAT CANNOT BE ENTIRELY DISCOUNTED.

www.wpc.ncep.noaa.gov/html/model2.shtml...
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

BURKE