Prognostic Meteorological Discussion
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FXUS10 KWNH 260644
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
243 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/GFS/UKMET/GEM AND THE
ECMWF

...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/00Z ECMWF...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 TIMING DIFFERENCES. THE 00Z NAM GRADUALLY BECOME MORE
PROGRESSIVE THAN THE GLOBAL MODEL CONSENSUS...WITH THE 00Z GFS/00Z
ECMWF/00Z GEM AND 00Z UKMET ALL A BIT SLOWER. THE STRONGER MODEL
CLUSTERING SUGGESTS A BLEND OF THE GFS AND ECMWF...AND THIS IS
SUPPORTED BY THE 12Z ECENS MEAN AND 00Z GEFS MEAN. A BLEND OF THE
GFS AND ECMWF 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 00Z GEM...WHICH IS STILL A LITTLE SLOWER AND DEEPER
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 48 HOURS
            BLEND OF THE 00Z GFS/00Z UKMET...AFTER 48 HOURS
CONFIDENCE: AVERAGE

VERY GOOD MASS FIELD AGREEMENT IS SEEN WITH THIS FEATURE THROUGH
ABOUT 48 HOURS. THEREAFTER...THE 00Z GEM AND 00Z ECMWF BECOME MORE
AMPLIFIED WITH ENERGY DROPPING SOUTH THROUGH THE MIDWEST...WITH
BOTH MODELS DEVELOPING AN UPPER LOW. THE 00Z NAM ATTEMPTS TO DO
THE SAME AT THE VERY END OF THE PERIOD...BUT HAS ITS UPPER LOW
POSITIONED FARTHER EAST. THE 00Z GFS AND 00Z UKMET ARE
CONSIDERABLY WEAKER...AND THE WEAKER SOLUTIONS ARE FAVORED BY THE
12Z ECENS MEAN AND 00Z GEFS MEAN. A GENERAL MODEL COMPROMISE WILL
BE PREFERRED UP TO 48 HOURS...FOLLOWED BY A GFS/UKMET BLEND.


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

PREFERENCE: NON-UKMET CONSENSUS
CONFIDENCE: ABOVE AVERAGE

THE 00Z UKMET IS REMAINS SLOWER AND MORE AMPLIFIED WITH A
SHORTWAVE APPROACHING THE PACIFIC NORTHWEST EARLY ON TUES...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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