Prognostic Meteorological Discussion
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FXUS10 KWNH 191701
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
100 PM EDT TUE SEP 19 2017

VALID SEP 19/1200 UTC THRU SEP 23/0000 UTC

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

12Z MODEL EVALUATION...WITH PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...UPPER TROUGH SWEEPING ACROSS THE NORTHWEST THROUGH TONIGHT...
...ASSOCIATED COLD FRONT EJECTING ACROSS THE NORTHERN PLAINS
THROUGH WED...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

THE MODEL DIFFERENCES ON THIS FEATURE HAVE CONTINUED TO DECREASE
WITH THE 12Z GFS NOW IN LINE WITH 00Z ECMWF/UKMET/CMC CONSENSUS AS
THE COLD FRONT MOVES ACROSS THE NORTHERN PLAINS TO LAKE SUPERIOR
WEDNESDAY. THEREFORE A GENERAL MODEL BLEND IS PREFERRED.


...SHORTWAVE ENTERING THE PACIFIC NORTHWEST TONIGHT...DEEPENING
THE TROUGH OVER THE WEST WED THROUGH FRI...
...SURFACE WAVE DEVELOPMENT OVER THE PLAINS THURS NIGHT/FRI...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC CONSENSUS
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

CONSENSUS IS IN THE TROUGH OVER THE WEST AMPLIFYING AS A SHORTWAVE
RIDES FROM THE PACIFIC NORTHWEST TONIGHT TO SOUTHERN CALIFORNIA
THURSDAY NIGHT. MOVEMENT OF THE EXISTING LOW EAST OF THE SOUTHERN
CANADIAN ROCKIES IS NOW LESS...PARTICULARLY IN THE 12Z GFS WHICH
HAS TRENDED TO MUCH SLOWER EAST MOVEMENT OF THE LOW CENTER. THIS
HAS BROUGHT THE 12Z GFS INTO BETTER CONSENSUS WITH THE 00Z
ECMWF/UKMET. THE 00Z CMC IS THE ONLY OUTLIER WITH THE CANADIAN LOW
EJECTED MUCH FARTHER EAST BY THURSDAY EVENING. WILL SEE IF THE CMC
REMAINS AN OUTLIER WITH THE 12Z CYCLE. SLIGHT DIFFERENCES EXIST IN
THE POSITION OF THE SURFACE LOW AND TROUGH THAT DEVELOPS OVER THE
NORTHERN GREAT PLAINS THURSDAY NIGHT INTO FRIDAY OWING TO SLIGHT
DIFFERENCES IN THE POSITION OF MID-LEVEL FORCING FROM THE UPPER
TROUGH OVER THE WEST AND SOUTHERN CANADIAN PRAIRIE UPPER LOW. THE
GREATEST DIFFERENCE IS WITH THE 00Z CMC THAT IS SLOWER WITH THE
PLAINS LOW/TROUGH DEVELOPMENT GIVEN THE MORE PROGRESSIVE MOVEMENT
TO THE CANADIAN LOW. AT THIS TIME A NON-CMC CONSENSUS IS
RECOMMENDED.


...HURRICANE JOSE...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC CONSENSUS
CONFIDENCE: REFERENCE NHC PRODUCTS

THE LATEST (15Z) NHC TRACK OF HURRICANE JOSE IS CLOSE TO A NON-00Z
CMC CONSENSUS WITH MINIMAL MODEL SPREAD THROUGH 00Z THURSDAY.
SPREAD THEN INCREASES WITH THE CLOCKWISE RECURVE OF JOSE
SOUTH/WEST. THE 12Z NAM/GFS TAKE A TIGHTER CURVE WHILE THE 00Z
ECMWF IS BROADER/FARTHER EAST. THE OFFICIAL FORECAST LIES BETWEEN
THESE CURVES.


...BROAD UPPER TROUGH OVER THE SOUTHEAST AND GULF COAST REGION...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

THE MODELS ALLOW FOR A BROAD AND WEAK UPPER TROUGH TO BE LEFT
BEHIND OVER THE SOUTHEAST AND THE GULF COAST STATES IN THE WAKE OF
HURRICANE JOSE TRACKING NORTH UP OFF THE EAST COAST. THE MODELS
ARE IN GOOD AGREEMENT WITH THE BROADER DETAILS OF THE TROUGH...SO
A GENERAL MODEL BLEND WILL BE PREFERRED.


www.wpc.ncep.noaa.gov/html/model2.shtml
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml

JACKSON/CHENARD

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