Prognostic Meteorological Discussion
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000
FXUS10 KWNH 141908
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
308 PM EDT SUN SEP 14 2014

VALID SEP 14/1200 UTC THRU SEP 18/0000 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.
==============================================

...WESTERN U.S. INCLUDING HURRICANE ODILE...

PREFERENCE: 12Z GFS/ECMWF AND 06Z GEFS MEAN
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE SYNOPTIC PATTERN IS SETTING UP TO SUPPORT A POTENTIALLY
ANOMALOUS HEAVY RAINFALL EVENT IN ADVANCE OF HURRICANE ODILE...TO
BEGIN IN THE DESERT SOUTHWEST LATE TUE OR WED...WITH MOISTURE
LATER MOVING DOWNSTREAM TO THE NORTH AND EAST/SEE WPC MEDIUM RANGE
DISCUSSION FOR DETAILS/. SOME RUN TO RUN VARIABILITY LIMITS
CONFIDENCE AS TO SMALLER SCALE TIMING AND PLACEMENT...BUT A NUMBER
OF MODEL AND ENSEMBLE SOURCES PREDICT UNUSUALLY RICH
MOISTURE...PRECIPITABLE WATER OF 0.75 INCHES UP TO IDAHO AND 2.0
INCHES OVER SOUTHERN CA/AZ...REPRESENTING 3 TO 5 STANDARD
DEVIATIONS FROM CLIMATOLOGY.

THE GFS AND ECMWF HAVE BEEN FAIRLY STEADY IN PREDICTING THE PATH
OF HURRICANE ODILE...FORECAST TO REMAIN AT LEAST AT TROPICAL STORM
STRENGTH THROUGH THE SHORT RANGE PERIOD ENDING 18/00Z. THE NAM
DEVIATES TO THE SOUTH AND WEST OFF OF BAJA CALIFORNIA TOWARD THE
END OF THE PERIOD. THE CANADIAN HAS SHOWN MORE VARIABILITY...BUT
IS CLOSE TO THE MORE EASTERLY TRACK SEEN IN THE UKMET...WHICH
WOULD TAKE THE CYCLONE INTO THE NORTHERN GULF OF CALIFORNIA. THE
12Z GEFS ACTUALLY TRENDED IN THAT DIRECTION...WITH THE ENSEMBLE
MEAN SHOWING A CLOSED MSLP CONTOUR OVER THE GULF AT 18/00Z. THIS
NOTION WAS NOT SUPPORTED BY THE OPERATIONAL GFS...AND IS ONLY
EVIDENT IN 5 OF THE 50 ECMWF ENSEMBLE MEMBERS FROM THE 00Z CYCLE.
FOR NOW THE MAJORITY OF EVIDENCE POINTS TOWARD A TRACK CLOSE TO
THE OFFICIAL FORECAST FROM THE NATIONAL HURRICANE CENTER.

OTHERWISE THE MODELS AGREE IN DEPICTING AN AMPLIFIED NORTHERN
STREAM PATTERN OVER THE EASTERN PACIFIC AND WESTERN NORTH AMERICA.
GIVEN THE STRONG MOISTURE ANOMALIES SEEN IN THE MODELS...AND AMPLE
HEATING LIKELY TO TAKE PLACE DURING SEPTEMBER...THE MODEL
PREFERENCE HERE MAY BE A MATTER OF LOOKING FOR THOSE THAT ARE MORE
GENEROUS WITH PRECIPITATION COVERAGE AND INTENSITY. THE 06Z GEFS
MEAN AND 00Z ECMWF FIT THIS DESCRIPTION. THE OPERATIONAL GFS HAS
ALSO BEEN TRENDING WETTER...AND IMPROVED ITS NORTHERN STREAM
SOLUTION RELATIVE TO THE 00Z RUN. WE SHIED AWAY FROM THE 12Z GEFS
MEAN GIVEN THE MORE EASTERLY TRACK OF THE TROPICAL CYCLONE
DISCUSSED ABOVE.


...NORTHERN AND EASTERN U.S...

PREFERENCE: BLEND OF 12Z GFS/ECMWF/UKMET/CANADIAN
CONFIDENCE: ABOVE AVERAGE

WE COULD VERY NEARLY RECOMMEND A BLEND OF ALL THE OPERATIONAL
MODELS HERE...AS THERE IS VERY LITTLE SEPARATION. THE
NAM...HOWEVER...GETS SLIGHTLY AHEAD OF THE PACK BY DAY 3...WITH A
SLIGHTLY QUICKER AND COLDER SOLUTION OVER THE GREAT LAKES AND NEW
ENGLAND.


...GULF COAST AND THE SOUTHERN ATLANTIC SEABOARD...

PREFERENCE: BLEND OF 12Z GFS/ECMWF/UKMET
CONFIDENCE: AVERAGE

AN EASTERLY WAVE IN THE GULF OF MEXICO...AND A WESTERLY SHORTWAVE
EMANATING FROM TEXAS WILL PASS ONE ANOTHER...BOTH CONTRIBUTING TO
SWATHS OF PRECIPITATION TO AFFECT THE SOUTHERN STATES FROM
INTERSTATE 40 SOUTHWARD. RECENT UKMET RUNS HAD STRAYED FROM
CONSENSUS REGARDING THE DEPTH OF THE WESTERLY SHORTWAVE AS IT
NEARS THE SOUTHERN ATLANTIC COAST. THE 12Z
RUN...HOWEVER...IMPROVED. THE 00Z CANADIAN SUFFERED FROM
CONVECTIVE FEEDBACK. THE 12Z RUN IMPROVED...BUT STILL SPREADS
PRECIPITATION WELL OUTSIDE OF THE CONSENSUS AXIS...ESPECIALLY OVER
THE WESTERN GULF STATES EARLY IN THE PERIOD. ALTHOUGH THERE ARE NO
MARKED OUTLIERS...THE GFS/ECMWF/UKMET SHOW BETTER AGREEMENT WITH
WPC QPF CONTINUITY.

...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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