THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


MODEL DIAGNOSTIC DISCUSSION


[Abbreviations and acronyms used in this product]
Geographic boundaries:    Map 1- [Color] [B/W Print Version]      Map 2 - [Color] [B/W Print Version]



MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
238 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 MODEL EVALUATION INCLUDING THE UKMET/CMC/ECMWF ALONG WITH
FINAL 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/00Z 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 CLOSE
TO THE TIMING OF THE 00Z ECMWF WITH RESPECT TO THIS SHORT WAVE.
THE 00Z 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 00Z
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/UKMET/00Z 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.
THE 00Z UKMET DROPPED INTO THE MIDDLE OF THE CONSENSUS...PERHAPS
JUST A BIT DEEPER. THE 00Z GFS HAS BEEN SHOWING BETTER CONSISTENCY
WITH RESPECT TO TIMING WITH THE SHORT WAVE...SO A BLEND OF THE 00Z
GFS/00Z ECMWF/UKMET IS A PLAUSIBLE SOLUTION FOR DAY 1.

DURING DAY 2...THE 00Z NAM BECOMES FASTER WITH TIME (AND FASTER
THAN THE 21Z SREF MEAN) THAN THE CONSENSUS. THE 00Z GFS IS STILL
IN STEP WITH THE 00Z ECMWF...BUT THE 00Z GFS SPEEDS UP ON DAY 3...
PLACING IT ON THE EASTERN EDGE OF THE CONSENSUS ENVELOPE. THE 00Z
UKMET ALSO BECOMES FASTER WITH TIME (THOUGH SLOWER THAN ITS
PREVIOUS RUNS)...AND FASTER THAN THE 00Z GFS/00Z ECMWF BLEND.


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

BOTH THE 00Z GFS AND 00Z ECMWF HAVE TRENDED A BIT FURTHER NORTH
WITH THE SHORT WAVE...WHICH PLACES THE 00Z ECMWF CLOSER TO THE 00Z
GFS POSITION...AND INCREASING CONFIDENCE IN THIS BLEND FOR THE
PREFERENCE. THE 00Z NAM/UKMET/OFFER FLATTER SOLUTIONS. AT THIS
POINT...GIVEN ITS A DAY 3 SOLUTION IN A FAST FLOW...A BLEND OF THE
00Z GFS/00Z ECMWF OFFERS THE BEST SOLUTION...THOUGH THE 00Z ECMWF
MAY END UP BEING TOO AMPLIFIED WITH SHORT WAVE.


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

THE 00Z GFS/00Z ECMWF REMAIN IN THE MIDDLE OF THE MOST RECENT
DETERMINISTIC SPREAD...AND CLOSER TO THE CONSENSUS OF THE LATEST 
SREF/GEFS/ECMWF SOLUTIONS. THE 00Z UKMET/CMC DID NOT OFFER MUCH TO
BETTER DELINEATE A MODEL PREFERENCE. 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 00Z ECMWF IS FASTER AND NOT
AS AMPLIFIED WITH ITS LONG WAVE TROUGH POSITION ..BRINGING IT
CLOSER TO THE CONSENSUS. BOTH THE 00Z UKMET/CMC WERE FASTER WITH
THE SHORT WAVE COMING ASHORE ACROSS THE PACIFIC NORTHWEST (AND
FASTER THAN THE CONSENSUS). THE 00Z NAM/GFS APPEAR TO BE CLOSEST
TO THE 00Z ECMWF SOLUTION...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





Last Updated: 238 AM EDT SAT MAR 28 2015