Prognostic Meteorological Discussion
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FXUS10 KWNH 201639
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1239 PM EDT MON OCT 20 2014

VALID OCT 20/1200 UTC THRU OCT 24/0000 UTC

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

12Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 12Z
NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS.


CLIPPER-LIKE SYSTEM RACING THROUGH THE OHIO VALLEY TODAY
UPPER LOW CLOSING OFF OVER THE NRN MID-ATLANTIC WED/THU
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS / 00Z ECMWF
CONFIDENCE: AVERAGE

THERE CONTINUES TO BE CONVERGENCE SEEN IN THE 500 MB ENSEMBLE
SPAGHETTI HEIGHTS LOOKING OVER THE PAST THREE 12/00Z CYCLES
LOOKING AT THE 552 AND 564 DM LINES OFF OF THE NRN MID-ATLANTIC
COAST TOWARD WED/THU. THE LATEST SPREAD SHOWS 00Z EC MEMBERS
CLUSTERED A BIT SOUTH OF THE 06Z GEFS BY WED EVENING. A BLEND OF
THE 12Z GFS AND 00Z ECMWF REPRESENT THE MIDDLE OF THIS SPREAD AT
500 MB ALONG WITH AT THE SURFACE AND 850 MB CONSIDERING LOWS AT
THESE LEVELS. IT APPEARS THE 00Z UKMET IS AN OUTLIER AT THIS TIME
WHILE THE 12Z NAM COULD BE TOO FAR SOUTH/WEST GIVEN THE REMAINING
MODELS NORTH/EAST WITH THIS SYSTEM.


CLOSED LOW GRADUALLY SHEARING ACROSS NEW MEXICO THROUGH TUE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE MODELS SHOW SIMILARLY WITH THIS SYSTEM.


NEGATIVELY TILTED MID-LEVEL TROUGH TACKING ACROSS THE NRN ROCKIES
TUE...REACHING THE NRN PLAINS BY WED EVENING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS AND 00Z ECMWF
CONFIDENCE: BELOW AVERAGE

POOR RUN TO RUN CONTINUITY MAKES FOR LOWER THAN AVERAGE CONFIDENCE
IN ANY GIVEN SOLUTION. HOWEVER...THE 12Z GFS AND 00Z ECMWF ARE
CURRENTLY IN THE MIDDLE OF THE LATEST SPREAD WITH MODEL TRENDS
SHOWING TOWARD THIS COMPROMISE.


LONGWAVE TROF ANCHORING THE NORTHEASTERN PACIFIC TUESDAY THROUGH
THURSDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z NAM/GFS
CONFIDENCE: AVERAGE

DIFFERENCES HERE ARE SOMEWHAT SMALL WITH TIMING AND AMPLITUDE WITH
MANY SMALLER SCALE FEATURES AT WORK. BROAD CYCLONIC FLOW OVER THE
NORTHEASTERN PACIFIC WILL ALLOW A MYRIAD OF SHORTWAVES TO RACE
TOWARD THE PACIFIC NORTHWEST AND BRITISH COLUMBIA THIS WEEK. THE
ECMWF/CMC ARE A BIT FLATTER WITH TROUGHING INTO THE WEST
COAST...WHILE THE NAM/GFS/UKMET SLIGHTLY MORE AMPLIFIED. WHILE NO
SINGLE MODEL STANDS OUT AS AN OUTLIER...THE NAM/GFS COMBO APPEARS
MOST REASONABLE GIVEN THE CURRENT MODEL SPREAD AND TRENDS SEEN
SINCE YESTERDAY.


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

OTTO

$$




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