Prognostic Meteorological Discussion
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000
FXUS10 KWNH 300549
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
148 AM EDT SAT APR 30 2016

VALID APR 30/0000 UTC THRU MAY 03/1200 UTC

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

00Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET

...WEAKENING UPPER LOW OVER LOWER MI...
...EXITING SURFACE LOW FROM THE MID-ATLANTIC REGION...

PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: AVERAGE

THERE IS MINIMAL MASS FIELD SPREAD WITH THE WEAKENING UPPER LOW
AND ITS SHEARING ENERGY ACROSS THE MID-ATLANTIC REGION THROUGH
LATE SATURDAY. WEAK LOW PRESSURE NEAR THE MID-ATLANTIC COAST IS
AGREED UPON BY THE GUIDANCE TO QUICKLY EXIT OUT TO SEA DURING THE
DAY TODAY.


...UPPER LOW EJECTING OUT OF THE FOUR CORNERS...
...ENERGY EJECTING OUT ACROSS THE MIDWEST
...EVENTUAL SURFACE LOW DEVELOPMENT BY SUNDAY...

PREFERENCE: BLEND OF THE 30/00Z GFS/UKMET AND 29/12Z ECMWF THROUGH
SAT NIGHT
            BLEND OF THE 29/21Z SREF AND 30/00Z NCEP MODELS SUNDAY
AND BEYOND
CONFIDENCE: AVERAGE

THE 30/00Z NCEP MODELS TENDED TO HOLD ON TO THE MID LEVEL
CIRCULATION CENTER COMING OUT OF THE ROCKIES ABOUT 12 TO 18 HOURS
LONGER THAN IN PREVIOUS RUNS.  THE 30/00Z ECMWF HAD A SIMILAR IDEA
BUT EVEN LOST THE MID LEVEL CENTER BEFORE THE NCEP GUIDANCE.  THIS
ULTIMATELY KEEPS LOWER HEIGHTS OVER THE MIDWEST INTO THE GREAT
LAKES REGION FOR AN EXTRA PERIOD OR SO.

BY SUNDAY THOUGH...MODEL CONTINUITY FALLS APART ON SUNDAY AS THE
NCEP GUIDANCE WANTS TO DEVELOP A SURFACE LOW TO THE LEE OF THE
GREAT LAKES WHILE THE 29/12Z MODEL RUNS WERE MORE INCLINED TO TAKE
THE SURFACE LOW EASTWARD TOWARDS THE MID ATLANTIC.  THE 29/21Z
SREF MEANS WERE CLEARLY IN THE CAMP WITH THE 30/00Z NCEP/UKMET
GUIDANCE...WHILE THE GEFS AGREEMENT WAS NOT QUITE AS STRONG BUT
EVEN IT TENDED TO FAVOR THE LOW CLOSER TO THE LAKES.

...LOW OVER THE WESTERN U.S. ON TUESDAY...

PREFERENCE: NON ECMWF/UKMET
CONFIDENCE: BELOW AVERAGE

THE SHORT RANGE MODELS ARE HAVING TROUBLES RESOLVING THE EVOLUTION
OF THE PATTERN OVER THE WESTERN STATE BY LATE MONDAY AND TUESDAY.
THE ECMWF IDEA OF FORMING A DEEP CLOSED SYSTEM ON THE EAST SIDE OF
A PROGRESSIVE CLOSED HIGH...THEN DROPPING THE LOW ALONG THE FRONT
RANGE WAS AT ODDS WITH ITS OWN MEAN.  THE UKMET IDEA WAS NOT A LOT
BETTER.  AFTER CHATTING WITH WPC MEDIUM RANGE...WE THINK THAT THE
30/00Z GFS WAS MOST USABLE OF THE AVAILABLE 00Z GUIDANCE AND WOULD
CONTINUE TO BE SO BEYOND 12Z ON TUESDAY.

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

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

BANN

$$




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