Prognostic Meteorological Discussion
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FXUS10 KWNH 201844
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
243 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 MODEL EVALUATION WITH FINAL 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 / 12Z 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 12Z GEFS BY WED EVENING. A BLEND OF
THE 12Z GFS AND 12Z ECMWF REPRESENTS THE MIDDLE OF THIS SPREAD AT
500 MB ALONG WITH AT THE SURFACE AND 850 MB CONSIDERING LOWS AT
THESE LEVELS. THE 12Z ECMWF/UKMET/CMC ARE ALL A BIT STRONGER WITH
THE MAIN VORT MAX / SPEED MAX TRANSLATING JUST OFF OF THE NRN
MID-ATLANTIC COAST DURING THE DAY ON WED WHICH TRANSLATES TO A
STRONGER LOW AT THE SURFACE...WITH THE 12Z GFS LIKELY A BIT WEAK
WITH THE SURFACE LOW...BUT POSITION-WISE...THE 12Z GFS/ECMWF ARE
SIMILAR. THE 12Z UKMET/CMC ARE ON EITHER SIDE OF THE GFS/ECMWF.


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 12Z ECMWF
CONFIDENCE: BELOW AVERAGE

POOR RUN TO RUN CONTINUITY MAKES FOR LOWER THAN AVERAGE CONFIDENCE
IN ANY GIVEN SOLUTION. HOWEVER...THE 12Z GFS AND 12Z ECMWF ARE
CURRENTLY IN THE MIDDLE OF THE LATEST SPREAD WITH MODEL TRENDS
SHOWING TOWARD THIS COMPROMISE. THE 12Z ECMWF TRENDED NORTH WITH
THE MAIN VORT MAX...BUT A COMPROMISED GFS/ECMWF SOLUTION STILL
FITS WITHIN THE MIDDLE OF THE MODEL SPREAD WITH SIMILARITY TO THE
ENSEMBLE MEANS. THE 12Z UKMET/CMC ARE A BIT FASTER THAN THE
GFS/ECMWF.


LONGWAVE TROF ANCHORING THE NORTHEASTERN PACIFIC TUESDAY THROUGH
THURSDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: AVERAGE

DIFFERENCES HERE ARE SOMEWHAT SMALL IN 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
UKMET/ECMWF/CMC ARE A BIT FLATTER WITH TROUGHING INTO THE WEST
COAST...WHILE THE NAM/GFS ARE SLIGHTLY MORE AMPLIFIED. WHILE NO
SINGLE MODEL STANDS OUT AS AN OUTLIER...THERE APPEARS TO BE NCEP
AND NON NCEP CAMPS. GIVEN THE SHIFT IN THE UKMET TOWARD A SLIGHTLY
MORE FLATTENED FLOW ACROSS THE WEST COAST...THE FINAL MODEL
PREFERENCE FOR THIS SYSTEM WILL BE FOR A GENERAL MODEL BLEND
BETWEEN THE TWO CAMPS.


...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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