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
305 PM EDT TUE JUL 26 2016

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

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

12Z PRELIMINARY MODEL EVALUATION AND PREFERENCES


...MULTIPLE SHORTWAVES MOVING EAST OVER THE SOUTHWEST
RIDGE...DROPPING SOUTHEAST INTO A DEVELOPING EAST COAST TROUGH...
...SHORTWAVE ENERGY MOVING NORTH OUT OF THE GULF OF MEXICO...ALSO
BEING ABSORBED INTO THE EAST COAST TROUGH...

PREFERENCE: CONSENSUS OF THE 12Z GFS/ECMWF/UKMET/GEM
CONFIDENCE: SLIGHTLY BELOW AVERAGE

COMPLEX PATTERN OVER THE CONUS FOR THE SHORT TERM PERIOD. FORECAST
IS LARGELY DRIVEN BY SMALL SCALE CONVECTIVE FEATURES...WHICH ARE
DIFFICULT TO TRACK AND FORECAST. IN THE LARGE SCALE THERE IS
PRETTY GOOD AGREEMENT AMONGST THE MODELS...WITH A SOUTHWESTERN
U.S. UPPER RIDGE...AND A DEVELOPING EAST COAST TROUGH. ALSO GOOD
AGREEMENT THAT WE WILL SEE MULTIPLE SHORTWAVES RIDE UP AND OVER
THE RIDGE INTO THE TROUGH...WITH ENERGY IN THE GULF OF MEXICO ALSO
MOVING NORTH AND BEING ABSORBED INTO THE TROUGH.

THE DISAGREEMENT COMES FROM THE TIMING/STRENGTH OF BOTH THE
SHORTWAVES MOVING OVER THE RIDGE ACROSS THE PLAINS AND THE GULF OF
MEXICO ENERGY...AND HOW THESE TWO END UP INTERACTING OVER THE
EAST. THE GFS HAS CONSISTENTLY BEEN THE QUICKEST SOLUTION IN THE
PROGRESSION OF THE TROUGH EASTWARD...WITH THE ECMWF THE SLOWEST.
THINK THE GFS MAY BE ON TO SOMETHING WITH HOW IT IS INITIALLY
HANDLING THE GULF OF MEXICO ENERGY...WITH THE ECMWF TAKING TOO
LITTLE ENERGY INTO MS/LA TODAY AND TOMORROW. HOWEVER THINK THE GFS
THEN ENDS UP SHEARING THINGS OFF TO THE NORTHEAST TOO QUICKLY. IN
GENERAL THE 0Z UKMET/GEM ARE SOMEWHERE BETWEEN THE GFS AND
ECMWF...SO THINK THE GFS AND ECMWF MOST LIKELY REPRESENT THE
BOOKENDS OF POSSIBLE SOLUTIONS...WITH THE MOST PROBABLE OUTCOME IN
BETWEEN...CLOSER TO EITHER THE 0Z UKMET OR GEM. THE 12Z NAM IS A
DEEP AND NORTH OUTLIER...AND APPEARS TO FALL OUTSIDE THE BEST
MODEL CLUSTERING...AND THUS WILL NOT BE PREFERRED AT THIS TIME.
CONFIDENCE REMAINS LOW GIVEN THE MODEL SPREAD AND LACK OF SIGNAL
IN THE ENSEMBLES...HOPEFULLY THE REMAINDER OF THE 12Z GUIDANCE
WILL CONTINUE TO CONVERGE ON A SOLUTION.

19Z UPDATE:

THE 12Z ECMWF DID INDEED TREND CLOSER TO THE GFS WITH ITS HANDLING
OF THE SHORTWAVE ENERGY MOVING NORTH OUT OF THE GULF OF
MEXICO...AND IN TURN IS ALSO QUICKER WITH THE TROUGH PROGRESSION
ACROSS THE EAST. THE GFS REMAINS THE MOST PROGRESSIVE
SOLUTION...BUT NOT BY MUCH. THE TREND HAS ALSO BEEN FOR A FURTHER
NORTH WAVE AND SURFACE LOW TRACK THURSDAY INTO FRIDAY. THE NAM
STILL APPEARS TOO STRONG WITH ENERGY ON THE NORTHERN EDGES OF THE
TROUGH IN THE LOWER GREAT LAKES. THE 12Z UKMET IS THE SLOWEST
SOLUTION...BUT STILL WITHIN THE RANGE OF PLAUSIBLE SOLUTIONS. THE
GFS IS NOW THE FURTHEST SOUTH SOLUTION. THE 12Z GEFS MEAN IS A BIT
NORTH AND SLOWER THAN THE DETERMINISTIC RUN...ABOUT HALFWAY
BETWEEN THE DETERMINISTIC 12Z ECMWF AND GFS WITH REGARDS TO TIMING
AND CLOSER TO THE LATITUDE OF THE ECMWF. THUS STILL BELIEVE A
CONSENSUS SOLUTION IS MOST LIKELY...WHICH IS PROBABLY BEST
REPRESENTED BY THE 12Z ECMWF. ALTHOUGH SOME INCORPORATION OF THE
12Z GFS/GEM AND UKMET IS STILL PREFERRED AS WELL.

CHENARD


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

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





Last Updated: 305 PM EDT TUE JUL 26 2016