Prognostic Meteorological Discussion
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000
FXUS10 KWNH 280443
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1243 AM EDT SAT MAR 28 2015

VALID MAR 28/0000 UTC THRU MAR 31/1200 UTC

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

00Z NAM/GFS EVALUATION ALONG WITH PRELIMINARY PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 00Z
NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS.


LONGWAVE TROUGH MOVING ACROSS THE EAST COAST SAT
DEEPENING SURFACE LOW TRACKING UP EAST OF NOVA SCOTIA
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z GFS/12Z ECMWF
CONFIDENCE: AVERAGE

THERE IS STILL SOME MODEL SPREAD CONCERNING THE HOW THE SHORT WAVE
TRACKING OUT OF THE BOTTOM OF THE LONG WAVE TROUGH AFFECTS
DEVELOPING LOW PRESS OF THE MID ATLANTIC COAST DURING DAY 1. THE
00Z NAM LOOKS TOO FAST/TOO FAR NORTH WITH THE SURFACE LOW...AND
THIS IS TIED TO THE FASTER SHORT WAVE TIMING. THE 00Z GFS IS
CLOSER TO THE TIMING OF THE 12Z ECMWF WITH RESPECT TO THIS SHORT
WAVE...THOUGH THE 12Z ECMWF IS STILL A BIT FURTHER WEST WITH THE
LOW TRACK (AS WAS ITS ENSEMBLE MEAN POSITION). THE 12Z UKMET
REMAINS FURTHER SOUTHWEST/SLOWER WITH THE SURFACE LOW DURING THE
DAY 1 TIME FRAME.

AFTER DAY 1...THE 00Z GFS SPEEDS UP (WHEN COMPARED WITH THE 12Z
ECMWF AND ITS OWN 18Z SOLUTION...BUT STILL NOT AS FAST AS THE 00Z
NAM). HOWEVER...AT THIS POINT...THE SENSIBLE WEATHER EFFECTS
SHOULD BE WELL NORTHEAST OF NEW ENGLAND.


SHORTWAVE TRACKING FROM THE PACIFIC NORTHWEST SAT INTO NEW ENGLAND
DURING MON
COLD FRONT REACHING THE EAST COAST MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z GFS/12Z ECMWF
CONFIDENCE: AVERAGE

DURING DAY 1...AS THE SHORT WAVE TRACKS FROM THE PACIFIC NORTHWEST
INTO NORTHERN PLAINS...THE 00Z NAM/GFS ARE CLOSE TO THE 12Z
ECMWF...WITH THE 12Z UKMET JUST A BIT FURTHER WEST AND DEEPER. THE
00Z GFS HAS BEEN SHOWING BETTER CONSISTENCY WITH RESPECT TO TIMING
WITH THE SHORT WAVE...SO A BLEND OF THE 00Z GFS/12Z ECMWF/UKMET IS
A PLAUSIBLE SOLUTION FOR DAY 1.

DURING DAY 2...THE 00Z NAM BECOMES FASTER WITH TIME (AND A BIT
FASTER THAN ITS 18Z SOLUTION) THAN THE CONSENSUS. THE 00Z GFS IS
STILL IN STEP WITH THE 12Z ECMWF (AND THE 12Z ECMWF ENSEMBLE
POSITION FOR THE SHORT WAVE)...AND THIS TIMING REMAINS IN PLACE
FOR DAY 3 AS WELL. THE 12Z UKMET ALSO BECOMES FASTER WITH TIME
(THOUGH SLOWER THAN ITS PREVIOUS RUNS)...AND FASTER THAN THE 00Z
GFS/12Z ECMWF BLEND.


SHORTWAVE CROSSING THE UPPER MS VALLEY/GREAT LAKES MON...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/12Z ECMWF
CONFIDENCE: SLIGHTLY BELOW AVERAGE

BOTH THE 00Z GFS AND 12Z ECMWF HAVE TRENDED A BIT FURTHER NORTH
WITH THE SHORT WAVE...THOUGH THE 12Z ECMWF REMAINS ON THE SOUTHERN
EDGE OF THE CONSENSUS ENVELOPE (EVEN THE 12Z ECMWF POSITION IS
FURTHER NORTH THAN THE 12Z ECMWF OPERATIONAL RUN). THE 00Z NAM/12Z
UKMET/12Z CMC OFFER FLATTER...FASTER SOLUTIONS. AT THIS
POINT...GIVEN ITS A DAY 3 SOLUTION IN A FAST FLOW...A BLEND OF THE
00Z GFS/12Z ECMWF OFFERS THE BEST SOLUTION...THOUGH THE 12Z ECMWF
MAY END UP BEING TOO AMPLIFIED WITH SHORT WAVE.


WEAK MID LEVEL TROUGH NEAR BAJA CA ON SUNDAY/MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z GFS/12Z ECMWF
CONFIDENCE: BELOW AVERAGE

THE 00Z GFS/12 ECMWF REMAIN IN THE MIDDLE OF THE MOST RECENT
DETERMINISTIC SPREAD...AND CLOSER TO THE CONSENSUS OF THE LATEST
SREF/GEFS/ECMWF SOLUTIONS. HOWEVER....GIVEN THE LACK OF RUN TO RUN
CONSISTENCY AMONG THE MODELS...FORECAST CONFIDENCE IS BELOW
AVERAGE.



SOUTHWEST FLOW AHEAD OF A LONG WAVE TROUGH OFF THE PACIFIC
NORTHWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM/00Z GFS/00Z ECMWF BLEND
CONFIDENCE: BELOW AVERAGE

THERE IS REASONABLY GOOD MODEL AGREEMENT THROUGH DAY 2 CONCERNING
THE TIMING AND PLACEMENT OF THE LONG WAVE TROUGH APPROACHING THE
PACIFIC NORTHWEST/BRITISH COLUMBIA. THE MODEL SPREAD DEVELOPS
DURING DAY 3...AS MODELS HANDLE THE SHORT WAVE AT THE BOTTOM OF
THE LONG WAVE TROUGH DIFFERENTLY. THE 12Z ECMWF IS
DEEPEST/FURTHEST WEST WITH THE LONG WAVE TROUGH POSITION (A
DEPARTURE FROM ITS PREVIOUS TWO SOLUTIONS)...AND APPEARS TO BE THE
ODD MODEL OUT HERE. THE 00Z NAM/GFS APPEAR TO BE CLOSEST TO THE
00Z ECMWF SOLUTION (WHICH ENJOYED A BETTER MODEL CONSENSUS)...AND
THEY ARE CLOSE WITH THE FRONTAL POSITION BY THE END OF DAY 3.


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

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

HAYES

$$




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