Prognostic Meteorological Discussion
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000
FXUS10 KWNH 300440
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1240 AM EDT THU MAR 30 2017

VALID MAR 30/0000 UTC THRU APR 02/1200 UTC

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

00Z GUIDANCE EVALUATION INCLUDING MODEL PREFERENCE AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

CLOSED LOW CROSSING OUT OF THE PLAINS TODAY INTO THE OH/TN VALLEYS
THU/FRI AND MID-ATLANTIC/COASTAL SOUTHEAST LATE FRI INTO SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF AND 00Z NAM(ONLY UP TO 02/00Z)
CONFIDENCE: AVERAGE

OVERALL GUIDANCE CONTINUES TO TIGHTEN AROUND A COMMON
SOLUTION...VERY CLOSE TO THE MORE CONSISTENT ECMWF/ECENS MEAN
SOLUTIONS.  STILL THE OVERALL TREND CONTINUES TO MAINTAIN A
STRONGER/MORE CONSOLIDATED UPPER LOW TRACKING ACROSS THE OHIO
VALLEY INTO THE MID-ATLANTIC WHEN COMPARING THE LAST 3-4 CYCLES OF
THE ENSEMBLE SPAGHETTI ANALYSIS.   MOST OF THE GUIDANCE IS FAIRLY
COMPARABLE UP UNTIL SAT WHEN THE SPREAD INCREASES.  THE 12Z CMC IS
FIRST TO GO BUT ALSO SHOWS GREATEST DIVERGENCE IN EVOLUTION
UNCHARACTERISTICALLY WEAKENING THE INNER CORE OF THE UPPER LOW AND
BROADENING THE OVERALL TROF.   THE 12Z UKMET AND 00Z GFS ARE
CONSOLIDATED BUT ARE A BIT FASTER THAN THE ECENS MEAN AND MUCH
FURTHER SOUTHEAST.  THIS MANIFESTS GREATEST AS THE SOUTHERN STREAM
SURFACE LOW TAKES OVER OUT OF THE LOWER MID-ATLANTIC/N CAROLINAS
EARLY SAT ON THE SOUTHEAST SIDE OF THE 12Z ENSEMBLE CLUSTER (WITH
MANY GEFS MEMBERS).  THE 00Z NAM TRACKS CLOSEST TO THE
ECMWF/ECENS/CONTINUITY BUT MAY FAVOR THE DEEPENING NORTHERN STREAM
ACROSS NEW ENGLAND LATE SAT A BIT MORE AGGRESSIVELY THAN EXPECTED.
  LIKE THE NAM...THE 12Z ECMWF SHOWED A NORTHWARD SHIFT TO THE
SURFACE TRACK WITH GREATER NORTHERN STREAM AFFECTS BUT THIS IS
MINOR.  AS SUCH WILL CONTINUE TO FAVOR THE 12Z ECMWF AT AVERAGE
CONFIDENCE THOUGH INCREASING BLEND WITH THE 00Z NAM MAY BE
BENEFICIAL PARTICULARLY BEFORE 00Z SUN WHEN THE NORTHERN STREAM
DOMINATES.


VIGOROUS WESTERN TROF DIGGING THU BEFORE BECOMING A STRONG CLOSED
LOW OVER THE FOUR CORNERS BY FRI/SAT BEFORE STRETCHING/OPENING UP
INTO THE HIGH PLAINS EARLY SUN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF
CONFIDENCE: AVERAGE

ALL GUIDANCE HAS COME TO AGREEMENT OF DIGGING THE SHORTWAVE ENERGY
ENTERING THE PACIFIC NW CURRENTLY AND QUITE VIGOROUSLY SO. ONLY
MINOR DIFFERENCES IN PLACEMENT (EAST/WEST) EXIST AT PEAK INTENSITY
AS A CLOSED LOW NEAR THE FOUR CORNERS LATE FRIDAY.  THE 12Z
NAM/GFS CONTINUE TO BE FURTHER EAST AND WHILE THE THE CMC/ECMWF
ARE FURTHER WEST.  AS THE LOW VERTICALLY STACKS AND LOSES FORCING
TO MAINTAIN IT...SHEARING FORCES ALLOW FOR THE NORTHWARD
STRETCHING AS THE TROF EXITS THE WEST INTO THE CENTRAL PLAINS.
THE FASTER GFS/NAM INITIALLY CONTINUE FURTHER COMPOUNDING SPREAD
AND FAVOR A LIFTING THE INNER CORE NORTH AND EAST INTO NEB/KS BY
THE END OF THE FORECAST PERIOD WITH THE NAM REMAINING MORE
CONSOLIDATED WITH ITS KNOWN NEGATIVE VERIFYING BIAS TOWARD DAY 3.
 THE 00Z GFS EVEN SHIFTED MUCH FASTER WITH THE LINGER BASE OF THE
TROF AWAY FROM THE 06Z OPERATIONAL AND GEFS MEAN (AS WELL AS THE
VAST MAJORITY OF ENSEMBLE MEMBERS...MAKING IT A CLEAR OUTLIER
ACROSS THE CAP ROCK/SOUTHWESTERN PLAINS.

THE OVERALL PATTERN ALSO SEEMS TO FAVOR THE 12Z ECMWF/ECENS
MEAN...GIVEN LIMITED SHEARING INFLUENCES OR KICKER FEATURES...THE
EVOLUTION TOWARD FAVORING A DIGGING/SOUTHWARD SHIFT OF THE
WEAKENING INNER CORE TO THE UPPER LOW SLOWING THE EASTWARD
ADVANCEMENT SEEMS METEOROLOGICALLY LOGICAL AT THIS POINT AS WELL.
THE 00Z CMC HAS SIMILAR PLACEMENT/TIMING OF THE TROF BUT SHOWS
SOME TYPICAL DEEP/CONSOLIDATED VORT FEATURES AT 5H TO FEEL
CONFIDENT ITS INCLUSION IN THE PREFERENCE AT THIS TIME.   WPC WILL
FAVOR A 12Z ECMWF PREFERENCE.  THOUGH THE ECMWF EVOLUTION IS SOUND
WITH GOOD CONTINUITY THE LACK OF ADDITIONAL SUPPORT FROM NON-EC
SOLUTIONS PROVIDES SOME LACK IN OVERALL CONFIDENCE.


NORTHERN STREAM TROUGH/FRONT CLIPPING THE NORTHERN PLAINS FRI
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE NEXT NORTHERN STREAM TROUGH WILL CROSS THE NORTHERN PLAINS BY
FRI ALONG WITH A WEAK FRONTAL PASSAGE. THERE IS SUFFICIENT MASS
FIELD CLUSTERING TO CONTINUE TO SUPPORT A GENERAL MODEL BLEND.


NORTHERN STREAM SHORTWAVES TRACKING INTO INCREASINGLY ZONAL FLOW
ACROSS SW CANADA SAT INTO SUN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: AVERAGE

STRENGTHENING PACIFIC FLOW EVENTUALLY KNOCKS DOWN THE MEAN RIDGE
ACROSS THE PACIFIC NORTHWEST INTO LATE SATURDAY ALLOWING EMBEDDED
SHORTWAVES TO ADVANCE ACROSS SOUTHWEST CANADA.  THE 12Z ECMWF/CMC
CONTINUE TO BE A BIT FASTER AND ALLOW FOR EARLIER AMPLIFICATION OF
THE WAVE EXITING THE SOUTHERN CANADIAN ROCKIES EVENTUALLY LEADING
TO A CLOSED SURFACE WAVE IN S ALBERTA/SASKATCHEWAN INTO EARLY
SUNDAY.  THE 12Z UKMET IS EQUALLY QUICK BUT LOADS THE TROF A BIT
FURTHER NORTH IN COMPARISON. THE 00Z GFS/NAM HAVE TRENDED SLIGHTLY
SLOWER AND NOW LAG THE NON-NCEP GUIDANCE ACROSS THE NORTHERN TIER
SLIGHTLY...THE 00Z GFS APPEARS A BIT MORE AMPLIFIED THAN THE NAM
LIKELY WITH SOME INFLUENCE OF THE ELONGATING UPPER LOW/TROF ACROSS
THE CENTRAL AND SOUTHERN PLAINS.  WHILE THE GFS/NAM ARE NOT
FAVORED WITH THAT PORTION OF THE FLOW...WILL CONTINUE TO SUPPORT
THEM IN THIS NORTHERN STREAM BLEND GIVEN SMALL TIMING DIFFERENCES
WOULD BE LIKELY AT THIS TIME IN THE FUTURE (ALLOWING FOR FURTHER
CONSENSUS AS WE APPROACH THE 00HR TIME).  CONFIDENCE REMAINS
AVERAGE IN A GENERAL MODEL BLEND.


www.wpc.ncep.noaa.gov/html/model2.shtml...

www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

GALLINA

$$





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