Prognostic Meteorological Discussion
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FXUS10 KWNH 260406
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1206 AM EDT SUN APR 26 2015

VALID APR 26/0000 UTC THRU APR 29/1200 UTC

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

00Z MODEL EVALUATION...INCLUDING THE NAM AND GFS

...DEEP TROUGH/CLOSED LOW DIGGING INTO SOUTHWEST U.S....
...LOW PRESSURE DEVELOPING OVER THE SOUTHERN PLAINS BY MON...

PREFERENCE: GENERAL MODEL COMPROMISE...THROUGH 60 HOURS
            BLEND OF THE 00Z GFS/12Z ECMWF AND 12Z GEM...AFTER 60
HOURS
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

VERY GOOD MASS FIELD AGREEMENT IS SEEN IN THE GUIDANCE THROUGH
ABOUT 60 HOURS WITH THE DETAILS OF THE DEVELOPING CLOSED LOW OVER
THE FOUR CORNERS REGION WHICH WILL EJECT EAST ACROSS THE SOUTHERN
PLAINS AND FOSTER THE DEVELOPMENT OF SURFACE LOW PRESSURE OVER THE
TX HIGH PLAINS. THEREAFTER...ALL OF THIS ENERGY WILL SHIFT EAST
ACROSS THE LOWER MS VALLEY AND GULF COAST STATES...BUT THERE ARE
SOME NOTABLE TIMING DIFFERENCES. THE 12Z UKMET AND 00Z NAM
GRADUALLY BECOME MORE PROGRESSIVE THAN THE GLOBAL MODEL
CONSENSUS...WITH THE 00Z GFS/12Z ECMWF AND 12Z GEM CLUSTERED
TOGETHER AND A BIT SLOWER. THE 12Z ECENS MEAN FAVORS THE
GFS/ECMWF/GEM CLUSTER...WITH THE 18Z GEFS MEAN APPEARING TO BE TOO
SLOW. A CONSENSUS OF THE GFS/ECMWF AND GEM WILL BE PREFERRED AFTER
60 HOURS WITH A GENERAL MODEL COMPROMISE PRIOR TO THIS.

...SOUTHERN STREAM TROUGH SHEARING THROUGH THE MID-ATLANTIC...
...SURFACE LOW EXITING OFFSHORE ON SUN...

PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE MODELS ARE NOW IN VERY GOOD AGREEMENT WITH THE MASS FIELD
DETAILS OF THIS SYSTEM AS IT EXITS THE MID-ATLANTIC EARLY ON SUN.
A GENERAL MODEL COMPROMISE WILL BE PREFERRED.


...DEEP CLOSED LOW REMAINING ACROSS NEW ENGLAND...

PREFERENCE: NON-GEM CONSENSUS
CONFIDENCE: ABOVE AVERAGE

OUTSIDE OF THE 12Z GEM...WHICH IS SLOWER MON NIGHT WITH A
SHORTWAVE PINWHEELING AROUND THE SLOWLY DEPARTING CLOSED LOW
CENTERED OFF OF NEW ENGLAND...THE MODELS SHOW REASONABLE AGREEMENT
HERE. DETAIL DIFFERENCES WITH INDIVIDUAL SHORTWAVES ARE BEST
BLENDED WITH A NON-GEM CONSENSUS.


...TROUGH/FRONT CROSSING THE NORTHERN PLAINS/UPPER MIDWEST THROUGH
TUES...

PREFERENCE: GENERAL MODEL COMPROMISE...THROUGH 60 HOURS
            NON-GEM CONSENSUS...AFTER 60 HOURS
CONFIDENCE: ABOVE AVERAGE

VERY GOOD MASS FIELD AGREEMENT IS SEEN WITH THIS FEATURE THOUGH
ABOUT 60 HOURS. THEREAFTER...THE 12Z GEM BECOMES MORE AMPLIFIED
WITH ENERGY DROPPING SOUTH THROUGH THE MIDWEST. A GENERAL MODEL
COMPROMISE WILL BE PREFERRED...BUT MINUS THE GEM AFTER 60 HOURS.


...TROUGH/FRONT APPROACHING THE PACIFIC NORTHWEST BY TUES
MORNING...

PREFERENCE: NON-UKMET CONSENSUS
CONFIDENCE: AVERAGE

THE 12Z UKMET IS SIGNIFICANTLY SLOWER WITH A SHORTWAVE APPROACHING
THE PACIFIC NORTHWEST EARLY ON TUE...WHILE THE REMAINING
DETERMINISTIC MODELS AND ENSEMBLE MEANS ARE FASTER WITH REASONABLE
AGREEMENT. A NON-UKMET CONSENSUS WILL REMAIN THE PREFERENCE FOR
NOW.

...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...

...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

ORRISON

$$





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