Prognostic Meteorological Discussion
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000
FXUS10 KWNH 301623
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1223 PM EDT THU OCT 30 2014

VALID OCT 30/1200 UTC THRU NOV 03/0000 UTC

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

==================================================
12Z NAM/GFS EVALUATION AND PRELIMINARY PREFERENCES
==================================================
NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO
SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT.
==================================================

...TROUGH AMPLIFYING ACROSS EASTERN NORTH AMERICA...

PREFERENCE: 00Z ECMWF

COASTAL CYCLOGENESIS IS FORECAST TO START RAMPING UP LATE FRIDAY.
OVER THE WEEKEND THIS INITIAL LOW LIFTS TOWARD COASTAL NORTHERN
NEW ENGLAND...WHILE A SECOND LOW FORMS BENEATH A STRONGLY
ANOMALOUS VORTICITY MAXIMUM THAT DIVES TOWARD THE CAROLINA COAST.
THE TWO SYSTEMS MAY CONSOLIDATE BY SUNDAY EVENING. GEFS STANDARD
ANOMALIES FOR 500 MB HEIGHTS REACH AN IMPRESSIVE 4.5 DEVIATIONS
FROM CLIMATOLOGY OVER SOUTH CAROLINA ON SATURDAY.

THERE IS FAIRLY GOOD MODEL CLUSTERING ON A LARGE SCALE...BUT A
NUMBER OF SMALLER SCALE DIFFERENCES. VARIABILITY WITHIN THE GEFS
IS EVEN A LITTLE GREATER THAN USUAL...ESPECIALLY TOWARD NORTHERN
NEW ENGLAND ON DAYS 2/3. THE 12Z GFS MOVED SIGNIFICANTLY LEFT OF
THE PREVIOUS 00Z/06Z GFS RUNS. THE NEW 12Z VERSION IS CERTAINLY
WITHIN A REASONABLE SPREAD...BUT HAS ONLY A FEW GEFS MEMBERS
SUPPORTING IT. WITHOUT HAVING SEEN THIS NORTHWESTWARD TREND IN ANY
OTHER GUIDANCE...WE ARE HESITANT TO GIVE IT MUCH WEIGHT. GENERALLY
THE 00Z ECMWF FITS MORE NICELY INTO THE CONSENSUS SOLUTION
SUPPORTED BY THE VARIOUS ENSEMBLE MEANS...SO WE RECOMMEND MAJORITY
WEIGHT ON IT.

THE 12Z NAM IS SIMILAR TO THE ECMWF...ASIDE FROM BEING EVEN MORE
ROBUST/DEEP WITH THE ANOMALOUS SHORTWAVE INTO THE CAROLINAS ON DAY
2...RESULTING IN A MORE ROBUST SURFACE CYCLONE. THE NAM IS ALSO
PARTICULARLY AGGRESSIVE AT RAISING HEIGHTS ON THE BACK SIDE OF THE
TROUGH BY DAY 3. THE MODELS HAVE TRENDED TOWARD NARROWING THE
BREADTH OF THE TROUGH...BUT THE AMPLIFYING PATTERN ACROSS NORTH
AMERICA WOULD ARGUE TOWARD MORE PERSISTENT CYCLONIC FLOW ALONG THE
EAST COAST...MORE LIKE THE NON-NAM SOLUTIONS.


...AMPLIFIED TROUGH/CLOSED LOW MOVING INTO THE WEST...

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

THE MODELS CLUSTER FAIRLY WELL HERE...ESPECIALLY AS THE NAM/GFS
TRENDED SLOWER WITHIN THE BASE OF THE POSITIVELY TILTED TROUGH
OVER THE SOUTHWEST U.S. ON DAY 3. REGARDING THE LEAD SHORTWAVE
THAT EJECTS INTO MT/ND...THE GFS MAY BE SLIGHTLY FAR TO THE
EAST...BUT IS CLOSE ENOUGH TO BE GROUPED WITH THE NAM/ECMWF/UKMET.
THE 00Z CANADIAN APPEARED TOO FAR SOUTH WITH THIS LEAD WAVE.

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

BURKE
$$





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