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Model Diagnostics Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1859Z Oct 30, 2014)
 
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MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 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 MODEL EVALUATION AND PREFERENCES
==============================================
NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO
SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT.
==============================================

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

PREFERENCE: BLEND OF 12Z ECMWF/CANADIAN
CONFIDENCE: AVERAGE

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. RUN TO RUN 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. NOT TOO SURPRISINGLY...THE
12Z GEFS MEAN SHOWED THE SAME TREND. EVIDENCE IN THE VALIDITY OF
THIS TREND IS STRENGTHENED...HOWEVER...BY THE UKMET AND CANADIAN
SHOWING SOMETHING SIMILAR...ALTHOUGH TO A LESSER DEGREE. THIS
ALLOWS US TO HEDGE A LITTLE TOWARD A TRACK FARTHER TO THE
LEFT...AND PERHAPS AN INCREASE TO THE AMOUNT OF PRECIPITATION
REACHING NORTHERN NEW ENGLAND...ESPECIALLY EASTERN MAINE...ON DAYS
2/3. THE OPERATIONAL GFS...THOUGH...APPEARS TO SPIN UP THE INITIAL
LOW MORE STRONGLY AND FARTHER LEFT THAN MOST GUIDANCE...SO WE
STILL RECOMMEND SOLUTIONS OTHER THAN THE 12Z GFS.

THE 12Z NAM WAS SIMILAR TO THE ECMWF...BUT THE NAM WAS 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/ECMWF/CANADIAN
CONFIDENCE: AVERAGE

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...AND THE UKMET SLIGHTLY FAST TO LIFT NORTHWARD.

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

BURKE