Prognostic Meteorological Discussion
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FXUS10 KWNH 191850
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
250 PM EDT TUE AUG 19 2014

VALID AUG 19/1200 UTC THRU AUG 23/0000 UTC

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

...AN EVALUATION OF THE 12Z CMC/UKMET/ECMWF ALONG WITH FINAL
PREFERENCES/FORECAST CONFIDENCE...

THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 12Z
NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS.


...UPPER TROF SLIDING FROM THE UPPER GREAT LAKES TOWARD THE
NORTHEASTERN U.S...

FINAL PREFERENCE: NON-12Z NAM MODEL COMPROMISE
FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE

A BROAD UPPER TROF INITIALLY OVER THE UPPER GREAT LAKES HAS BEEN
RESPONSIBLE FOR MULTIPLE ROUNDS OF CONVECTION THE PAST 24 HOURS.
THIS CLOSED LOW WILL MIGRATE EASTWARD TOWARD THE LOWER GREAT LAKES
THROUGH WEDNESDAY WITH THE 12Z NAM BECOMING MORE AMPLIFIED THAN
THE ENSEMBLE MEANS WHICH INCLUDES THE 09Z SREF MEAN WHICH WAS
FLATTER. IT SEEMS LIKE THE REMAINING MODELS HAVE A DECENT GRASP ON
THE PATTERN SO WILL FAVOR A NON-12Z NAM MODEL COMPROMISE.


...SHORTWAVES LIFTING FROM THE CENTRAL ROCKIES INTO THE UPPER
MIDWEST THROUGH THURSDAY...

FINAL PREFERENCE: BLEND OF THE 12Z ECMWF/UKMET
FORECAST CONFIDENCE: BELOW AVERAGE

A MYRIAD OF SHORTWAVES MOVING THROUGH THE CENTRAL ROCKIES WILL
NUDGE THE SHORTWAVE RIDGE EASTWARD AS HEIGHTS BEGIN TO FALL ACROSS
THE HIGH PLAINS. AS WAS THE CASE YESTERDAY...THE 12Z NAM IS
FARTHER NORTH WITH THE ENERGY ALLOWING IT TO BECOME ABSORBED INTO
THE SYNOPTIC-SCALE TROF ACROSS WESTERN/CENTRAL CANADA. THE OTHER
MODELS WHICH INITIALLY HAD FAVORED CARRYING MORE OF THE SHORTWAVE
ENERGY EASTWARD ABOVE THE MS RIVER VALLEY RIDGE HAVE BACKED OFF
SOMEWHAT. A MAJORITY OF THE 12Z MODELS SHOW SOME OF THE ENERGY
LIFTING INTO ONTARIO WHILE THE REMAINS OF THE SYSTEM CROSS THE
GREAT LAKES. WILL TEND TO FAVOR A SOLUTION WHICH FAVORS SPLITTING
THE REMNANT ENERGY INTO CANADA AS WELL AS THE GREAT LAKES. THE 12Z
GFS SEEMS TO FOLLOW THE 12Z NAM SO WILL STAY A LITTLE MORE TOWARD
THE 12Z ECMWF/UKMET. THE CONFIDENCE HAS DIMINISHED THOUGH BEING
BELOW AVERAGE NOW.


...CLOSED LOW GRADUALLY DROPPING DOWN THE CA COAST...

FINAL PREFERENCE: 12Z/00Z ECMWF
FORECAST CONFIDENCE: AVERAGE

WATER VAPOR IMAGERY SHOWED A TIGHTLY WOUND CLOSED LOW SLIDING DOWN
THE CENTRAL CA COAST. IT SHOULD EVENTUALLY REACH THE SOUTHERN CA
COAST BY MIDDAY WEDNESDAY. THE 09Z SREF MEAN FAVORS A LITTLE MORE
RETROGRESSION OF THE SYSTEM BY LATE WEDNESDAY. ADDITIONALLY...THE
12Z GFS LOOKS VERY SIMILAR TO ITS RUN YESTERDAY WHICH WAS FASTER
AND DEPICTING A MORE AGGRESSIVE SOLUTION. THE ENSEMBLE MEANS FAVOR
SOMETHING SLOWER EXCEPT FOR THE 12Z GEFS MEAN WHICH APPEARS TO
HAVE FOLLOWED THE DETERMINISTIC GFS. ONE ISSUE THAT ARISES IS THE
POSSIBLE INTERACTION WITH TROPICAL STORM LOWELL. THE 12Z CMC HAS
TRENDED AWAY FROM THE MORE AGGRESSIVE 00Z RUN BUT STILL DOES NOT
FOLLOW THE FORECAST TRACK. 12Z/00Z ECMWF FOLLOW THEIR TRACK MOST
CLOSELY AND OBEYS THE WELL CLUSTERED ENSEMBLE MEANS. WPC WILL
RECOMMEND THE 12Z/00Z ECMWF.


...MEAN TROF ANCHORING THE NORTHWESTERN CONUS...

FINAL PREFERENCE: BLEND OF THE 12Z GFS/ECMWF WITH THE 12Z GEFS/00Z
ECMWF ENSEMBLE MEANS
FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE

A LONGWAVE TROF ACROSS WESTERN/CENTRAL CANADA WILL BE MAINSTAY
FEATURE FOR THE WEEK AS ADDITIONAL HEIGHT FALLS DROP DOWN INTO THE
PACIFIC NORTHWEST FOR THE END OF THE PERIOD. WILL NOT INCLUDE THE
12Z NAM INTO THE PREFERENCE AS IT WAS QUICK IN LIFTING SHORTWAVE
ENERGY INTO THE EASTERN EXTENT OF THE TROF AS PREVIOUSLY
DISCUSSED. THE ENSEMBLE MEANS ARE IN VERY GOOD AGREEMENT FOR AN 84
HOUR FORECAST WITH THE OVERALL STRUCTURE OF THE UPPER TROF. THE
12Z/00Z ECMWF FOLLOW THESE MEANS VERY CLOSELY WHILE THE 12Z GFS
SHOWS THIS BUT WITH MORE ENERGY DISPLACED TOWARD THE WEST. THE 12Z
UKMET ALSO FOLLOWS THE GFS A BIT BUT WITH MORE AMPLITUDE. WILL
MAINTAIN THE PREVIOUS PREFERENCE BUT WHILE INCORPORATING THE NEWER
MODELS.


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

RUBIN-OSTER

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