Prognostic Meteorological Discussion
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000
FXUS10 KWNH 141642
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1235 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 NAM/GFS EVALUATION AND PRELIMINARY PREFERENCES
==================================================
NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO
SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT.
==================================================

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

PREFERENCE: 12Z GFS...06Z GEFS MEAN AND 00Z ECMWF

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.

MODELS ARE NOW VERY SIMILAR IN PREDICTING THE PATH OF HURRICANE
ODILE...WHICH IS FORECAST BY THE NATIONAL HURRICANE CENTER TO
REMAIN AT LEAST AT TROPICAL STORM STRENGTH THROUGH THE SHORT RANGE
PERIOD ENDING 18/00Z. THE EXCEPTION IS THE NAM WHICH DEVIATES TO
THE SOUTH AND WEST OFF BAJA CALIFORNIA TOWARD THE END OF THE
PERIOD. THE NAM IS OTHERWISE COMPARABLE WITH THE GLOBAL MODELS IN
ITS DEPICTION OF AN AMPLIFIED NORTHERN STREAM PATTERN OVER THE
EASTERN PACIFIC AND WESTERN U.S. 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.


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

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

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 00Z GFS/ECMWF

AN EASTERLY WAVE IN THE GULF OF MEXICO...AND A WESTERLY SHORTWAVE
EMANATING FROM TEXAS WILL PASS ONE ANOTHER TO EITHER SIDE OF A
THIN RIDGE AXIS. BOTH WAVES WILL CONTRIBUTE TO SWATHS OF
PRECIPITATION TO AFFECT THE SOUTHERN STATES FROM INTERSTATE 40
SOUTHWARD. RECENT UKMET RUNS HAVE STRAYED FROM CONSENSUS REGARDING
THE DEPTH OF THE WESTERLY SHORTWAVE AS IT NEARS THE SOUTHERN
ATLANTIC COAST. THE 00Z CANADIAN SUFFERED FROM CONVECTIVE
FEEDBACK. THE GFS/ECMWF AND NAM SHOW BETTER AGREEMENT WITH EACH
OTHER AND WITH ENSEMBLE CONSENSUS. THE
GFS/ECMWF...HOWEVER...BETTER AGREE WITH WPC QPF CONTINUITY. THE
NAM APPEARED TOO RESTRICTIVE WITH THE NORTHERN EXTENT OF
PRECIPITATION...ESPECIALLY ON DAY 3 OVER THE SOUTHERN ATLANTIC
COASTAL STATES.

...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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