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
104 PM EDT MON SEP 26 2016

VALID SEP 26/1200 UTC THRU SEP 30/0000 UTC

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

12Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GFS/NAM INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT
RANGE FORECASTS.


DEEP UPPER LEVEL DROPPING TOWARDS THE OH VALLEY BY THU MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF GEFS/EC MEANS
CONFIDENCE: SLIGHTLY BELOW AVERAGE

THERE CONTINUES TO BE SOME CONVERGENCE SEEN IN THE ENSEMBLE
GUIDANCE WITH THE MAIN UPPER LOW SINCE THIS TIME YESTERDAY...ALONG
WITH TRENDS TOWARD THE WEST...BUT THE 12Z GFS REMAINS TOWARD THE
EASTERN SIDE OF THE SPREAD WHILE THE 00Z ECMWF IS WEST OF THE
ENSEMBLE BETTER CLUSTERING. THE ENSEMBLE MEANS FROM THESE MODELS
IS TOWARD THE CENTER...AND GIVEN THE GROWING CONVERGENCE...A
POSITION IN THE MIDDLE IS CONSIDERED MOST LIKELY TO VERIFY.


FRONTAL WAVE MOVING OFFSHORE EASTERN SEABOARD
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z NAM...00Z EC MEAN BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE

THE ENSEMBLE SCATTER LOW PLOTS HAVE SHOWN BETTER CONVERGENCE OF
LOW STAMPS COMPARED TO YESTERDAY WITH THIS LOW...CLUSTERING OFF OF
THE NC COAST TUE EVENING. THE FEATURE APPEARS TO SPARK FROM THE
PLACEMENT OF AN UPPER LOW JUST OFF OF THE GA COAST THIS
MORNING...BEING LATER INFLUENCED BY THE AMPLIFICATION OF A LARGE
UPPER LOW SINKING SOUTH FROM THE GREAT LAKES. BY WED
EVENING...ENSEMBLE SPREAD INCREASES WITH THE 12Z GFS NEARLY
OUTSIDE OF THE ERN EDGE OF THE ENVELOPE OF LOW TRACKS WHILE THE
00Z ECMWF WAS TOWARD THE SERN EDGE. THE 12Z NAM IS TOWARD THE
MIDDLE OF THE SPREAD...BUT PERHAPS TOO CLOSE TO THE COAST WITH ITS
LOW TRACK GIVEN ENSEMBLE PLACEMENT. HOWEVER...WHEN BLENDED WITH
THE 00Z EC MEAN...THE TWO FORM A DECENT COMPROMISE. GIVEN THE
LARGER THAN AVERAGE SPREAD AND RUN TO RUN CHANGES...CONFIDENCE IS
LOWER THAN AVERAGE.


UPPER LOW WEAKENING NORTHWARD INTO SRN CA AND THE GREAT BASIN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: AVERAGE

THE MODELS SHOW SIMILARLY WITH THIS FEATURE.


COLD FRONT ENTERING THE PACIFIC NORTHWEST TONIGHT AND MT LATE TUE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MODELS SHOW SIMILARLY WITH THIS FEATURE.


UPPER TROUGH AMPLIFYING OFFSHORE THE PACIFIC NORTHWEST WED/THU
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 00Z CMC COMPROMISE
CONFIDENCE: AVERAGE

OUTSIDE OF THE 00Z CMC WHICH IS DISPLACED WESTWARD...THE MODELS
SHOW SIMILARLY WITH THIS FEATURE.


WEAKENING MID-UPPER LEVEL LOW LOCATED SOUTH OF THE FL PANHANDLE
  THIS MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE MODELS HANDLE THIS FEATURE SIMILARLY WITH GRADUAL WEAKENING
AND TRACKING EWD ACROSS THE NRN FL PENINSULA.


SHORTWAVE MOVING BY MAINE/ATLANTIC CANADA TUE/TUE NIGHT
LOW MOVING OFFSHORE NEW ENGLAND TUE NIGHT/WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE 00Z CMC IS A BIT SLOWER...CLOSER TO THE COAST THAN THE
REMAINING DETERMINISTIC CONSENSUS BUT A DETERMINISTIC MODEL BLEND
IS NEAREST TO THE LATEST AGREEABLE ENSEMBLE MEANS.


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

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

OTTO





Last Updated: 104 PM EDT MON SEP 26 2016